diff options
Diffstat (limited to 'Documentation')
46 files changed, 3797 insertions, 1764 deletions
diff --git a/Documentation/00-INDEX b/Documentation/00-INDEX index 438277800103..7286ad090db7 100644 --- a/Documentation/00-INDEX +++ b/Documentation/00-INDEX @@ -21,6 +21,9 @@ Changes - list of changes that break older software packages. CodingStyle - how the boss likes the C code in the kernel to look. +development-process/ + - An extended tutorial on how to work with the kernel development + process. DMA-API.txt - DMA API, pci_ API & extensions for non-consistent memory machines. DMA-ISA-LPC.txt diff --git a/Documentation/ABI/testing/sysfs-profiling b/Documentation/ABI/testing/sysfs-profiling new file mode 100644 index 000000000000..b02d8b8c173a --- /dev/null +++ b/Documentation/ABI/testing/sysfs-profiling @@ -0,0 +1,13 @@ +What: /sys/kernel/profile +Date: September 2008 +Contact: Dave Hansen <dave@linux.vnet.ibm.com> +Description: + /sys/kernel/profile is the runtime equivalent + of the boot-time profile= option. + + You can get the same effect running: + + echo 2 > /sys/kernel/profile + + as you would by issuing profile=2 on the boot + command line. diff --git a/Documentation/DocBook/Makefile b/Documentation/DocBook/Makefile index 1615350b7b53..fabc06466b93 100644 --- a/Documentation/DocBook/Makefile +++ b/Documentation/DocBook/Makefile @@ -6,7 +6,7 @@ # To add a new book the only step required is to add the book to the # list of DOCBOOKS. -DOCBOOKS := wanbook.xml z8530book.xml mcabook.xml videobook.xml \ +DOCBOOKS := wanbook.xml z8530book.xml mcabook.xml \ kernel-hacking.xml kernel-locking.xml deviceiobook.xml \ procfs-guide.xml writing_usb_driver.xml networking.xml \ kernel-api.xml filesystems.xml lsm.xml usb.xml kgdb.xml \ diff --git a/Documentation/DocBook/procfs-guide.tmpl b/Documentation/DocBook/procfs-guide.tmpl index 8a5dc6e021ff..9eba4b7af73d 100644 --- a/Documentation/DocBook/procfs-guide.tmpl +++ b/Documentation/DocBook/procfs-guide.tmpl @@ -14,17 +14,20 @@ <othername>(J.A.K.)</othername> <surname>Mouw</surname> <affiliation> - <orgname>Delft University of Technology</orgname> - <orgdiv>Faculty of Information Technology and Systems</orgdiv> <address> - <email>J.A.K.Mouw@its.tudelft.nl</email> - <pob>PO BOX 5031</pob> - <postcode>2600 GA</postcode> - <city>Delft</city> - <country>The Netherlands</country> + <email>mouw@nl.linux.org</email> </address> </affiliation> </author> + <othercredit> + <contrib> + This software and documentation were written while working on the + LART computing board + (<ulink url="http://www.lartmaker.nl/">http://www.lartmaker.nl/</ulink>), + which was sponsored by the Delt University of Technology projects + Mobile Multi-media Communications and Ubiquitous Communications. + </contrib> + </othercredit> </authorgroup> <revhistory> @@ -109,18 +112,6 @@ </para> <para> - This documentation was written while working on the LART - computing board (<ulink - url="http://www.lart.tudelft.nl/">http://www.lart.tudelft.nl/</ulink>), - which is sponsored by the Mobile Multi-media Communications - (<ulink - url="http://www.mmc.tudelft.nl/">http://www.mmc.tudelft.nl/</ulink>) - and Ubiquitous Communications (<ulink - url="http://www.ubicom.tudelft.nl/">http://www.ubicom.tudelft.nl/</ulink>) - projects. - </para> - - <para> Erik </para> </preface> diff --git a/Documentation/DocBook/procfs_example.c b/Documentation/DocBook/procfs_example.c index 2f3de0fb8365..8c6396e4bf31 100644 --- a/Documentation/DocBook/procfs_example.c +++ b/Documentation/DocBook/procfs_example.c @@ -1,28 +1,16 @@ /* * procfs_example.c: an example proc interface * - * Copyright (C) 2001, Erik Mouw (J.A.K.Mouw@its.tudelft.nl) + * Copyright (C) 2001, Erik Mouw (mouw@nl.linux.org) * * This file accompanies the procfs-guide in the Linux kernel * source. Its main use is to demonstrate the concepts and * functions described in the guide. * * This software has been developed while working on the LART - * computing board (http://www.lart.tudelft.nl/), which is - * sponsored by the Mobile Multi-media Communications - * (http://www.mmc.tudelft.nl/) and Ubiquitous Communications - * (http://www.ubicom.tudelft.nl/) projects. - * - * The author can be reached at: - * - * Erik Mouw - * Information and Communication Theory Group - * Faculty of Information Technology and Systems - * Delft University of Technology - * P.O. Box 5031 - * 2600 GA Delft - * The Netherlands - * + * computing board (http://www.lartmaker.nl), which was sponsored + * by the Delt University of Technology projects Mobile Multi-media + * Communications and Ubiquitous Communications. * * This program is free software; you can redistribute * it and/or modify it under the terms of the GNU General diff --git a/Documentation/DocBook/videobook.tmpl b/Documentation/DocBook/videobook.tmpl deleted file mode 100644 index 0bc25949b668..000000000000 --- a/Documentation/DocBook/videobook.tmpl +++ /dev/null @@ -1,1654 +0,0 @@ -<?xml version="1.0" encoding="UTF-8"?> -<!DOCTYPE book PUBLIC "-//OASIS//DTD DocBook XML V4.1.2//EN" - "http://www.oasis-open.org/docbook/xml/4.1.2/docbookx.dtd" []> - -<book id="V4LGuide"> - <bookinfo> - <title>Video4Linux Programming</title> - - <authorgroup> - <author> - <firstname>Alan</firstname> - <surname>Cox</surname> - <affiliation> - <address> - <email>alan@redhat.com</email> - </address> - </affiliation> - </author> - </authorgroup> - - <copyright> - <year>2000</year> - <holder>Alan Cox</holder> - </copyright> - - <legalnotice> - <para> - This documentation is free software; you can redistribute - it and/or modify it under the terms of the GNU General Public - License as published by the Free Software Foundation; either - version 2 of the License, or (at your option) any later - version. - </para> - - <para> - This program is distributed in the hope that it will be - useful, but WITHOUT ANY WARRANTY; without even the implied - warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. - See the GNU General Public License for more details. - </para> - - <para> - You should have received a copy of the GNU General Public - License along with this program; if not, write to the Free - Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, - MA 02111-1307 USA - </para> - - <para> - For more details see the file COPYING in the source - distribution of Linux. - </para> - </legalnotice> - </bookinfo> - -<toc></toc> - - <chapter id="intro"> - <title>Introduction</title> - <para> - Parts of this document first appeared in Linux Magazine under a - ninety day exclusivity. - </para> - <para> - Video4Linux is intended to provide a common programming interface - for the many TV and capture cards now on the market, as well as - parallel port and USB video cameras. Radio, teletext decoders and - vertical blanking data interfaces are also provided. - </para> - </chapter> - <chapter id="radio"> - <title>Radio Devices</title> - <para> - There are a wide variety of radio interfaces available for PC's, and these - are generally very simple to program. The biggest problem with supporting - such devices is normally extracting documentation from the vendor. - </para> - <para> - The radio interface supports a simple set of control ioctls standardised - across all radio and tv interfaces. It does not support read or write, which - are used for video streams. The reason radio cards do not allow you to read - the audio stream into an application is that without exception they provide - a connection on to a soundcard. Soundcards can be used to read the radio - data just fine. - </para> - <sect1 id="registerradio"> - <title>Registering Radio Devices</title> - <para> - The Video4linux core provides an interface for registering devices. The - first step in writing our radio card driver is to register it. - </para> - <programlisting> - - -static struct video_device my_radio -{ - "My radio", - VID_TYPE_TUNER, - radio_open. - radio_close, - NULL, /* no read */ - NULL, /* no write */ - NULL, /* no poll */ - radio_ioctl, - NULL, /* no special init function */ - NULL /* no private data */ -}; - - - </programlisting> - <para> - This declares our video4linux device driver interface. The VID_TYPE_ value - defines what kind of an interface we are, and defines basic capabilities. - </para> - <para> - The only defined value relevant for a radio card is VID_TYPE_TUNER which - indicates that the device can be tuned. Clearly our radio is going to have some - way to change channel so it is tuneable. - </para> - <para> - We declare an open and close routine, but we do not need read or write, - which are used to read and write video data to or from the card itself. As - we have no read or write there is no poll function. - </para> - <para> - The private initialise function is run when the device is registered. In - this driver we've already done all the work needed. The final pointer is a - private data pointer that can be used by the device driver to attach and - retrieve private data structures. We set this field "priv" to NULL for - the moment. - </para> - <para> - Having the structure defined is all very well but we now need to register it - with the kernel. - </para> - <programlisting> - - -static int io = 0x320; - -int __init myradio_init(struct video_init *v) -{ - if(!request_region(io, MY_IO_SIZE, "myradio")) - { - printk(KERN_ERR - "myradio: port 0x%03X is in use.\n", io); - return -EBUSY; - } - - if(video_device_register(&my_radio, VFL_TYPE_RADIO)==-1) { - release_region(io, MY_IO_SIZE); - return -EINVAL; - } - return 0; -} - - </programlisting> - <para> - The first stage of the initialisation, as is normally the case, is to check - that the I/O space we are about to fiddle with doesn't belong to some other - driver. If it is we leave well alone. If the user gives the address of the - wrong device then we will spot this. These policies will generally avoid - crashing the machine. - </para> - <para> - Now we ask the Video4Linux layer to register the device for us. We hand it - our carefully designed video_device structure and also tell it which group - of devices we want it registered with. In this case VFL_TYPE_RADIO. - </para> - <para> - The types available are - </para> - <table frame="all" id="Device_Types"><title>Device Types</title> - <tgroup cols="3" align="left"> - <tbody> - <row> - <entry>VFL_TYPE_RADIO</entry><entry>/dev/radio{n}</entry><entry> - - Radio devices are assigned in this block. As with all of these - selections the actual number assignment is done by the video layer - accordijng to what is free.</entry> - </row><row> - <entry>VFL_TYPE_GRABBER</entry><entry>/dev/video{n}</entry><entry> - Video capture devices and also -- counter-intuitively for the name -- - hardware video playback devices such as MPEG2 cards.</entry> - </row><row> - <entry>VFL_TYPE_VBI</entry><entry>/dev/vbi{n}</entry><entry> - The VBI devices capture the hidden lines on a television picture - that carry further information like closed caption data, teletext - (primarily in Europe) and now Intercast and the ATVEC internet - television encodings.</entry> - </row><row> - <entry>VFL_TYPE_VTX</entry><entry>/dev/vtx[n}</entry><entry> - VTX is 'Videotext' also known as 'Teletext'. This is a system for - sending numbered, 40x25, mostly textual page images over the hidden - lines. Unlike the /dev/vbi interfaces, this is for 'smart' decoder - chips. (The use of the word smart here has to be taken in context, - the smartest teletext chips are fairly dumb pieces of technology). - </entry> - </row> - </tbody> - </tgroup> - </table> - <para> - We are most definitely a radio. - </para> - <para> - Finally we allocate our I/O space so that nobody treads on us and return 0 - to signify general happiness with the state of the universe. - </para> - </sect1> - <sect1 id="openradio"> - <title>Opening And Closing The Radio</title> - - <para> - The functions we declared in our video_device are mostly very simple. - Firstly we can drop in what is basically standard code for open and close. - </para> - <programlisting> - - -static int users = 0; - -static int radio_open(struct video_device *dev, int flags) -{ - if(users) - return -EBUSY; - users++; - return 0; -} - - </programlisting> - <para> - At open time we need to do nothing but check if someone else is also using - the radio card. If nobody is using it we make a note that we are using it, - then we ensure that nobody unloads our driver on us. - </para> - <programlisting> - - -static int radio_close(struct video_device *dev) -{ - users--; -} - - </programlisting> - <para> - At close time we simply need to reduce the user count and allow the module - to become unloadable. - </para> - <para> - If you are sharp you will have noticed neither the open nor the close - routines attempt to reset or change the radio settings. This is intentional. - It allows an application to set up the radio and exit. It avoids a user - having to leave an application running all the time just to listen to the - radio. - </para> - </sect1> - <sect1 id="ioctlradio"> - <title>The Ioctl Interface</title> - <para> - This leaves the ioctl routine, without which the driver will not be - terribly useful to anyone. - </para> - <programlisting> - - -static int radio_ioctl(struct video_device *dev, unsigned int cmd, void *arg) -{ - switch(cmd) - { - case VIDIOCGCAP: - { - struct video_capability v; - v.type = VID_TYPE_TUNER; - v.channels = 1; - v.audios = 1; - v.maxwidth = 0; - v.minwidth = 0; - v.maxheight = 0; - v.minheight = 0; - strcpy(v.name, "My Radio"); - if(copy_to_user(arg, &v, sizeof(v))) - return -EFAULT; - return 0; - } - - </programlisting> - <para> - VIDIOCGCAP is the first ioctl all video4linux devices must support. It - allows the applications to find out what sort of a card they have found and - to figure out what they want to do about it. The fields in the structure are - </para> - <table frame="all" id="video_capability_fields"><title>struct video_capability fields</title> - <tgroup cols="2" align="left"> - <tbody> - <row> - <entry>name</entry><entry>The device text name. This is intended for the user.</entry> - </row><row> - <entry>channels</entry><entry>The number of different channels you can tune on - this card. It could even by zero for a card that has - no tuning capability. For our simple FM radio it is 1. - An AM/FM radio would report 2.</entry> - </row><row> - <entry>audios</entry><entry>The number of audio inputs on this device. For our - radio there is only one audio input.</entry> - </row><row> - <entry>minwidth,minheight</entry><entry>The smallest size the card is capable of capturing - images in. We set these to zero. Radios do not - capture pictures</entry> - </row><row> - <entry>maxwidth,maxheight</entry><entry>The largest image size the card is capable of - capturing. For our radio we report 0. - </entry> - </row><row> - <entry>type</entry><entry>This reports the capabilities of the device, and - matches the field we filled in in the struct - video_device when registering.</entry> - </row> - </tbody> - </tgroup> - </table> - <para> - Having filled in the fields, we use copy_to_user to copy the structure into - the users buffer. If the copy fails we return an EFAULT to the application - so that it knows it tried to feed us garbage. - </para> - <para> - The next pair of ioctl operations select which tuner is to be used and let - the application find the tuner properties. We have only a single FM band - tuner in our example device. - </para> - <programlisting> - - - case VIDIOCGTUNER: - { - struct video_tuner v; - if(copy_from_user(&v, arg, sizeof(v))!=0) - return -EFAULT; - if(v.tuner) - return -EINVAL; - v.rangelow=(87*16000); - v.rangehigh=(108*16000); - v.flags = VIDEO_TUNER_LOW; - v.mode = VIDEO_MODE_AUTO; - v.signal = 0xFFFF; - strcpy(v.name, "FM"); - if(copy_to_user(&v, arg, sizeof(v))!=0) - return -EFAULT; - return 0; - } - - </programlisting> - <para> - The VIDIOCGTUNER ioctl allows applications to query a tuner. The application - sets the tuner field to the tuner number it wishes to query. The query does - not change the tuner that is being used, it merely enquires about the tuner - in question. - </para> - <para> - We have exactly one tuner so after copying the user buffer to our temporary - structure we complain if they asked for a tuner other than tuner 0. - </para> - <para> - The video_tuner structure has the following fields - </para> - <table frame="all" id="video_tuner_fields"><title>struct video_tuner fields</title> - <tgroup cols="2" align="left"> - <tbody> - <row> - <entry>int tuner</entry><entry>The number of the tuner in question</entry> - </row><row> - <entry>char name[32]</entry><entry>A text description of this tuner. "FM" will do fine. - This is intended for the application.</entry> - </row><row> - <entry>u32 flags</entry> - <entry>Tuner capability flags</entry> - </row> - <row> - <entry>u16 mode</entry><entry>The current reception mode</entry> - - </row><row> - <entry>u16 signal</entry><entry>The signal strength scaled between 0 and 65535. If - a device cannot tell the signal strength it should - report 65535. Many simple cards contain only a - signal/no signal bit. Such cards will report either - 0 or 65535.</entry> - - </row><row> - <entry>u32 rangelow, rangehigh</entry><entry> - The range of frequencies supported by the radio - or TV. It is scaled according to the VIDEO_TUNER_LOW - flag.</entry> - - </row> - </tbody> - </tgroup> - </table> - - <table frame="all" id="video_tuner_flags"><title>struct video_tuner flags</title> - <tgroup cols="2" align="left"> - <tbody> - <row> - <entry>VIDEO_TUNER_PAL</entry><entry>A PAL TV tuner</entry> - </row><row> - <entry>VIDEO_TUNER_NTSC</entry><entry>An NTSC (US) TV tuner</entry> - </row><row> - <entry>VIDEO_TUNER_SECAM</entry><entry>A SECAM (French) TV tuner</entry> - </row><row> - <entry>VIDEO_TUNER_LOW</entry><entry> - The tuner frequency is scaled in 1/16th of a KHz - steps. If not it is in 1/16th of a MHz steps - </entry> - </row><row> - <entry>VIDEO_TUNER_NORM</entry><entry>The tuner can set its format</entry> - </row><row> - <entry>VIDEO_TUNER_STEREO_ON</entry><entry>The tuner is currently receiving a stereo signal</entry> - </row> - </tbody> - </tgroup> - </table> - - <table frame="all" id="video_tuner_modes"><title>struct video_tuner modes</title> - <tgroup cols="2" align="left"> - <tbody> - <row> - <entry>VIDEO_MODE_PAL</entry><entry>PAL Format</entry> - </row><row> - <entry>VIDEO_MODE_NTSC</entry><entry>NTSC Format (USA)</entry> - </row><row> - <entry>VIDEO_MODE_SECAM</entry><entry>French Format</entry> - </row><row> - <entry>VIDEO_MODE_AUTO</entry><entry>A device that does not need to do - TV format switching</entry> - </row> - </tbody> - </tgroup> - </table> - <para> - The settings for the radio card are thus fairly simple. We report that we - are a tuner called "FM" for FM radio. In order to get the best tuning - resolution we report VIDEO_TUNER_LOW and select tuning to 1/16th of KHz. Its - unlikely our card can do that resolution but it is a fair bet the card can - do better than 1/16th of a MHz. VIDEO_TUNER_LOW is appropriate to almost all - radio usage. - </para> - <para> - We report that the tuner automatically handles deciding what format it is - receiving - true enough as it only handles FM radio. Our example card is - also incapable of detecting stereo or signal strengths so it reports a - strength of 0xFFFF (maximum) and no stereo detected. - </para> - <para> - To finish off we set the range that can be tuned to be 87-108Mhz, the normal - FM broadcast radio range. It is important to find out what the card is - actually capable of tuning. It is easy enough to simply use the FM broadcast - range. Unfortunately if you do this you will discover the FM broadcast - ranges in the USA, Europe and Japan are all subtly different and some users - cannot receive all the stations they wish. - </para> - <para> - The application also needs to be able to set the tuner it wishes to use. In - our case, with a single tuner this is rather simple to arrange. - </para> - <programlisting> - - case VIDIOCSTUNER: - { - struct video_tuner v; - if(copy_from_user(&v, arg, sizeof(v))) - return -EFAULT; - if(v.tuner != 0) - return -EINVAL; - return 0; - } - - </programlisting> - <para> - We copy the user supplied structure into kernel memory so we can examine it. - If the user has selected a tuner other than zero we reject the request. If - they wanted tuner 0 then, surprisingly enough, that is the current tuner already. - </para> - <para> - The next two ioctls we need to provide are to get and set the frequency of - the radio. These both use an unsigned long argument which is the frequency. - The scale of the frequency depends on the VIDEO_TUNER_LOW flag as I - mentioned earlier on. Since we have VIDEO_TUNER_LOW set this will be in - 1/16ths of a KHz. - </para> - <programlisting> - -static unsigned long current_freq; - - - - case VIDIOCGFREQ: - if(copy_to_user(arg, &current_freq, - sizeof(unsigned long)) - return -EFAULT; - return 0; - - </programlisting> - <para> - Querying the frequency in our case is relatively simple. Our radio card is - too dumb to let us query the signal strength so we remember our setting if - we know it. All we have to do is copy it to the user. - </para> - <programlisting> - - - case VIDIOCSFREQ: - { - u32 freq; - if(copy_from_user(arg, &freq, - sizeof(unsigned long))!=0) - return -EFAULT; - if(hardware_set_freq(freq)<0) - return -EINVAL; - current_freq = freq; - return 0; - } - - </programlisting> - <para> - Setting the frequency is a little more complex. We begin by copying the - desired frequency into kernel space. Next we call a hardware specific routine - to set the radio up. This might be as simple as some scaling and a few - writes to an I/O port. For most radio cards it turns out a good deal more - complicated and may involve programming things like a phase locked loop on - the card. This is what documentation is for. - </para> - <para> - The final set of operations we need to provide for our radio are the - volume controls. Not all radio cards can even do volume control. After all - there is a perfectly good volume control on the sound card. We will assume - our radio card has a simple 4 step volume control. - </para> - <para> - There are two ioctls with audio we need to support - </para> - <programlisting> - -static int current_volume=0; - - case VIDIOCGAUDIO: - { - struct video_audio v; - if(copy_from_user(&v, arg, sizeof(v))) - return -EFAULT; - if(v.audio != 0) - return -EINVAL; - v.volume = 16384*current_volume; - v.step = 16384; - strcpy(v.name, "Radio"); - v.mode = VIDEO_SOUND_MONO; - v.balance = 0; - v.base = 0; - v.treble = 0; - - if(copy_to_user(arg. &v, sizeof(v))) - return -EFAULT; - return 0; - } - - </programlisting> - <para> - Much like the tuner we start by copying the user structure into kernel - space. Again we check if the user has asked for a valid audio input. We have - only input 0 and we punt if they ask for another input. - </para> - <para> - Then we fill in the video_audio structure. This has the following format - </para> - <table frame="all" id="video_audio_fields"><title>struct video_audio fields</title> - <tgroup cols="2" align="left"> - <tbody> - <row> - <entry>audio</entry><entry>The input the user wishes to query</entry> - </row><row> - <entry>volume</entry><entry>The volume setting on a scale of 0-65535</entry> - </row><row> - <entry>base</entry><entry>The base level on a scale of 0-65535</entry> - </row><row> - <entry>treble</entry><entry>The treble level on a scale of 0-65535</entry> - </row><row> - <entry>flags</entry><entry>The features this audio device supports - </entry> - </row><row> - <entry>name</entry><entry>A text name to display to the user. We picked - "Radio" as it explains things quite nicely.</entry> - </row><row> - <entry>mode</entry><entry>The current reception mode for the audio - - We report MONO because our card is too stupid to know if it is in - mono or stereo. - </entry> - </row><row> - <entry>balance</entry><entry>The stereo balance on a scale of 0-65535, 32768 is - middle.</entry> - </row><row> - <entry>step</entry><entry>The step by which the volume control jumps. This is - used to help make it easy for applications to set - slider behaviour.</entry> - </row> - </tbody> - </tgroup> - </table> - - <table frame="all" id="video_audio_flags"><title>struct video_audio flags</title> - <tgroup cols="2" align="left"> - <tbody> - <row> - <entry>VIDEO_AUDIO_MUTE</entry><entry>The audio is currently muted. We - could fake this in our driver but we - choose not to bother.</entry> - </row><row> - <entry>VIDEO_AUDIO_MUTABLE</entry><entry>The input has a mute option</entry> - </row><row> - <entry>VIDEO_AUDIO_TREBLE</entry><entry>The input has a treble control</entry> - </row><row> - <entry>VIDEO_AUDIO_BASS</entry><entry>The input has a base control</entry> - </row> - </tbody> - </tgroup> - </table> - - <table frame="all" id="video_audio_modes"><title>struct video_audio modes</title> - <tgroup cols="2" align="left"> - <tbody> - <row> - <entry>VIDEO_SOUND_MONO</entry><entry>Mono sound</entry> - </row><row> - <entry>VIDEO_SOUND_STEREO</entry><entry>Stereo sound</entry> - </row><row> - <entry>VIDEO_SOUND_LANG1</entry><entry>Alternative language 1 (TV specific)</entry> - </row><row> - <entry>VIDEO_SOUND_LANG2</entry><entry>Alternative language 2 (TV specific)</entry> - </row> - </tbody> - </tgroup> - </table> - <para> - Having filled in the structure we copy it back to user space. - </para> - <para> - The VIDIOCSAUDIO ioctl allows the user to set the audio parameters in the - video_audio structure. The driver does its best to honour the request. - </para> - <programlisting> - - case VIDIOCSAUDIO: - { - struct video_audio v; - if(copy_from_user(&v, arg, sizeof(v))) - return -EFAULT; - if(v.audio) - return -EINVAL; - current_volume = v/16384; - hardware_set_volume(current_volume); - return 0; - } - - </programlisting> - <para> - In our case there is very little that the user can set. The volume is - basically the limit. Note that we could pretend to have a mute feature - by rewriting this to - </para> - <programlisting> - - case VIDIOCSAUDIO: - { - struct video_audio v; - if(copy_from_user(&v, arg, sizeof(v))) - return -EFAULT; - if(v.audio) - return -EINVAL; - current_volume = v/16384; - if(v.flags&VIDEO_AUDIO_MUTE) - hardware_set_volume(0); - else - hardware_set_volume(current_volume); - current_muted = v.flags & - VIDEO_AUDIO_MUTE; - return 0; - } - - </programlisting> - <para> - This with the corresponding changes to the VIDIOCGAUDIO code to report the - state of the mute flag we save and to report the card has a mute function, - will allow applications to use a mute facility with this card. It is - questionable whether this is a good idea however. User applications can already - fake this themselves and kernel space is precious. - </para> - <para> - We now have a working radio ioctl handler. So we just wrap up the function - </para> - <programlisting> - - - } - return -ENOIOCTLCMD; -} - - </programlisting> - <para> - and pass the Video4Linux layer back an error so that it knows we did not - understand the request we got passed. - </para> - </sect1> - <sect1 id="modradio"> - <title>Module Wrapper</title> - <para> - Finally we add in the usual module wrapping and the driver is done. - </para> - <programlisting> - -#ifndef MODULE - -static int io = 0x300; - -#else - -static int io = -1; - -#endif - -MODULE_AUTHOR("Alan Cox"); -MODULE_DESCRIPTION("A driver for an imaginary radio card."); -module_param(io, int, 0444); -MODULE_PARM_DESC(io, "I/O address of the card."); - -static int __init init(void) -{ - if(io==-1) - { - printk(KERN_ERR - "You must set an I/O address with io=0x???\n"); - return -EINVAL; - } - return myradio_init(NULL); -} - -static void __exit cleanup(void) -{ - video_unregister_device(&my_radio); - release_region(io, MY_IO_SIZE); -} - -module_init(init); -module_exit(cleanup); - - </programlisting> - <para> - In this example we set the IO base by default if the driver is compiled into - the kernel: you can still set it using "my_radio.irq" if this file is called <filename>my_radio.c</filename>. For the module we require the - user sets the parameter. We set io to a nonsense port (-1) so that we can - tell if the user supplied an io parameter or not. - </para> - <para> - We use MODULE_ defines to give an author for the card driver and a - description. We also use them to declare that io is an integer and it is the - address of the card, and can be read by anyone from sysfs. - </para> - <para> - The clean-up routine unregisters the video_device we registered, and frees - up the I/O space. Note that the unregister takes the actual video_device - structure as its argument. Unlike the file operations structure which can be - shared by all instances of a device a video_device structure as an actual - instance of the device. If you are registering multiple radio devices you - need to fill in one structure per device (most likely by setting up a - template and copying it to each of the actual device structures). - </para> - </sect1> - </chapter> - <chapter id="Video_Capture_Devices"> - <title>Video Capture Devices</title> - <sect1 id="introvid"> - <title>Video Capture Device Types</title> - <para> - The video capture devices share the same interfaces as radio devices. In - order to explain the video capture interface I will use the example of a - camera that has no tuners or audio input. This keeps the example relatively - clean. To get both combine the two driver examples. - </para> - <para> - Video capture devices divide into four categories. A little technology - backgrounder. Full motion video even at television resolution (which is - actually fairly low) is pretty resource-intensive. You are continually - passing megabytes of data every second from the capture card to the display. - several alternative approaches have emerged because copying this through the - processor and the user program is a particularly bad idea . - </para> - <para> - The first is to add the television image onto the video output directly. - This is also how some 3D cards work. These basic cards can generally drop the - video into any chosen rectangle of the display. Cards like this, which - include most mpeg1 cards that used the feature connector, aren't very - friendly in a windowing environment. They don't understand windows or - clipping. The video window is always on the top of the display. - </para> - <para> - Chroma keying is a technique used by cards to get around this. It is an old - television mixing trick where you mark all the areas you wish to replace - with a single clear colour that isn't used in the image - TV people use an - incredibly bright blue while computing people often use a particularly - virulent purple. Bright blue occurs on the desktop. Anyone with virulent - purple windows has another problem besides their TV overlay. - </para> - <para> - The third approach is to copy the data from the capture card to the video - card, but to do it directly across the PCI bus. This relieves the processor - from doing the work but does require some smartness on the part of the video - capture chip, as well as a suitable video card. Programming this kind of - card and more so debugging it can be extremely tricky. There are some quite - complicated interactions with the display and you may also have to cope with - various chipset bugs that show up when PCI cards start talking to each - other. - </para> - <para> - To keep our example fairly simple we will assume a card that supports - overlaying a flat rectangular image onto the frame buffer output, and which - can also capture stuff into processor memory. - </para> - </sect1> - <sect1 id="regvid"> - <title>Registering Video Capture Devices</title> - <para> - This time we need to add more functions for our camera device. - </para> - <programlisting> -static struct video_device my_camera -{ - "My Camera", - VID_TYPE_OVERLAY|VID_TYPE_SCALES|\ - VID_TYPE_CAPTURE|VID_TYPE_CHROMAKEY, - camera_open. - camera_close, - camera_read, /* no read */ - NULL, /* no write */ - camera_poll, /* no poll */ - camera_ioctl, - NULL, /* no special init function */ - NULL /* no private data */ -}; - </programlisting> - <para> - We need a read() function which is used for capturing data from - the card, and we need a poll function so that a driver can wait for the next - frame to be captured. - </para> - <para> - We use the extra video capability flags that did not apply to the - radio interface. The video related flags are - </para> - <table frame="all" id="Capture_Capabilities"><title>Capture Capabilities</title> - <tgroup cols="2" align="left"> - <tbody> - <row> -<entry>VID_TYPE_CAPTURE</entry><entry>We support image capture</entry> -</row><row> -<entry>VID_TYPE_TELETEXT</entry><entry>A teletext capture device (vbi{n])</entry> -</row><row> -<entry>VID_TYPE_OVERLAY</entry><entry>The image can be directly overlaid onto the - frame buffer</entry> -</row><row> -<entry>VID_TYPE_CHROMAKEY</entry><entry>Chromakey can be used to select which parts - of the image to display</entry> -</row><row> -<entry>VID_TYPE_CLIPPING</entry><entry>It is possible to give the board a list of - rectangles to draw around. </entry> -</row><row> -<entry>VID_TYPE_FRAMERAM</entry><entry>The video capture goes into the video memory - and actually changes it. Applications need - to know this so they can clean up after the - card</entry> -</row><row> -<entry>VID_TYPE_SCALES</entry><entry>The image can be scaled to various sizes, - rather than being a single fixed size.</entry> -</row><row> -<entry>VID_TYPE_MONOCHROME</entry><entry>The capture will be monochrome. This isn't a - complete answer to the question since a mono - camera on a colour capture card will still - produce mono output.</entry> -</row><row> -<entry>VID_TYPE_SUBCAPTURE</entry><entry>The card allows only part of its field of - view to be captured. This enables - applications to avoid copying all of a large - image into memory when only some section is - relevant.</entry> - </row> - </tbody> - </tgroup> - </table> - <para> - We set VID_TYPE_CAPTURE so that we are seen as a capture card, - VID_TYPE_CHROMAKEY so the application knows it is time to draw in virulent - purple, and VID_TYPE_SCALES because we can be resized. - </para> - <para> - Our setup is fairly similar. This time we also want an interrupt line - for the 'frame captured' signal. Not all cards have this so some of them - cannot handle poll(). - </para> - <programlisting> - - -static int io = 0x320; -static int irq = 11; - -int __init mycamera_init(struct video_init *v) -{ - if(!request_region(io, MY_IO_SIZE, "mycamera")) - { - printk(KERN_ERR - "mycamera: port 0x%03X is in use.\n", io); - return -EBUSY; - } - - if(video_device_register(&my_camera, - VFL_TYPE_GRABBER)==-1) { - release_region(io, MY_IO_SIZE); - return -EINVAL; - } - return 0; -} - - </programlisting> - <para> - This is little changed from the needs of the radio card. We specify - VFL_TYPE_GRABBER this time as we want to be allocated a /dev/video name. - </para> - </sect1> - <sect1 id="opvid"> - <title>Opening And Closing The Capture Device</title> - <programlisting> - - -static int users = 0; - -static int camera_open(struct video_device *dev, int flags) -{ - if(users) - return -EBUSY; - if(request_irq(irq, camera_irq, 0, "camera", dev)<0) - return -EBUSY; - users++; - return 0; -} - - -static int camera_close(struct video_device *dev) -{ - users--; - free_irq(irq, dev); -} - </programlisting> - <para> - The open and close routines are also quite similar. The only real change is - that we now request an interrupt for the camera device interrupt line. If we - cannot get the interrupt we report EBUSY to the application and give up. - </para> - </sect1> - <sect1 id="irqvid"> - <title>Interrupt Handling</title> - <para> - Our example handler is for an ISA bus device. If it was PCI you would be - able to share the interrupt and would have set IRQF_SHARED to indicate a - shared IRQ. We pass the device pointer as the interrupt routine argument. We - don't need to since we only support one card but doing this will make it - easier to upgrade the driver for multiple devices in the future. - </para> - <para> - Our interrupt routine needs to do little if we assume the card can simply - queue one frame to be read after it captures it. - </para> - <programlisting> - - -static struct wait_queue *capture_wait; -static int capture_ready = 0; - -static void camera_irq(int irq, void *dev_id, - struct pt_regs *regs) -{ - capture_ready=1; - wake_up_interruptible(&capture_wait); -} - </programlisting> - <para> - The interrupt handler is nice and simple for this card as we are assuming - the card is buffering the frame for us. This means we have little to do but - wake up anybody interested. We also set a capture_ready flag, as we may - capture a frame before an application needs it. In this case we need to know - that a frame is ready. If we had to collect the frame on the interrupt life - would be more complex. - </para> - <para> - The two new routines we need to supply are camera_read which returns a - frame, and camera_poll which waits for a frame to become ready. - </para> - <programlisting> - - -static int camera_poll(struct video_device *dev, - struct file *file, struct poll_table *wait) -{ - poll_wait(file, &capture_wait, wait); - if(capture_read) - return POLLIN|POLLRDNORM; - return 0; -} - - </programlisting> - <para> - Our wait queue for polling is the capture_wait queue. This will cause the - task to be woken up by our camera_irq routine. We check capture_read to see - if there is an image present and if so report that it is readable. - </para> - </sect1> - <sect1 id="rdvid"> - <title>Reading The Video Image</title> - <programlisting> - - -static long camera_read(struct video_device *dev, char *buf, - unsigned long count) -{ - struct wait_queue wait = { current, NULL }; - u8 *ptr; - int len; - int i; - - add_wait_queue(&capture_wait, &wait); - - while(!capture_ready) - { - if(file->flags&O_NDELAY) - { - remove_wait_queue(&capture_wait, &wait); - current->state = TASK_RUNNING; - return -EWOULDBLOCK; - } - if(signal_pending(current)) - { - remove_wait_queue(&capture_wait, &wait); - current->state = TASK_RUNNING; - return -ERESTARTSYS; - } - schedule(); - current->state = TASK_INTERRUPTIBLE; - } - remove_wait_queue(&capture_wait, &wait); - current->state = TASK_RUNNING; - - </programlisting> - <para> - The first thing we have to do is to ensure that the application waits until - the next frame is ready. The code here is almost identical to the mouse code - we used earlier in this chapter. It is one of the common building blocks of - Linux device driver code and probably one which you will find occurs in any - drivers you write. - </para> - <para> - We wait for a frame to be ready, or for a signal to interrupt our waiting. If a - signal occurs we need to return from the system call so that the signal can - be sent to the application itself. We also check to see if the user actually - wanted to avoid waiting - ie if they are using non-blocking I/O and have other things - to get on with. - </para> - <para> - Next we copy the data from the card to the user application. This is rarely - as easy as our example makes out. We will add capture_w, and capture_h here - to hold the width and height of the captured image. We assume the card only - supports 24bit RGB for now. - </para> - <programlisting> - - - - capture_ready = 0; - - ptr=(u8 *)buf; - len = capture_w * 3 * capture_h; /* 24bit RGB */ - - if(len>count) - len=count; /* Doesn't all fit */ - - for(i=0; i<len; i++) - { - put_user(inb(io+IMAGE_DATA), ptr); - ptr++; - } - - hardware_restart_capture(); - - return i; -} - - </programlisting> - <para> - For a real hardware device you would try to avoid the loop with put_user(). - Each call to put_user() has a time overhead checking whether the accesses to user - space are allowed. It would be better to read a line into a temporary buffer - then copy this to user space in one go. - </para> - <para> - Having captured the image and put it into user space we can kick the card to - get the next frame acquired. - </para> - </sect1> - <sect1 id="iocvid"> - <title>Video Ioctl Handling</title> - <para> - As with the radio driver the major control interface is via the ioctl() - function. Video capture devices support the same tuner calls as a radio - device and also support additional calls to control how the video functions - are handled. In this simple example the card has no tuners to avoid making - the code complex. - </para> - <programlisting> - - - -static int camera_ioctl(struct video_device *dev, unsigned int cmd, void *arg) -{ - switch(cmd) - { - case VIDIOCGCAP: - { - struct video_capability v; - v.type = VID_TYPE_CAPTURE|\ - VID_TYPE_CHROMAKEY|\ - VID_TYPE_SCALES|\ - VID_TYPE_OVERLAY; - v.channels = 1; - v.audios = 0; - v.maxwidth = 640; - v.minwidth = 16; - v.maxheight = 480; - v.minheight = 16; - strcpy(v.name, "My Camera"); - if(copy_to_user(arg, &v, sizeof(v))) - return -EFAULT; - return 0; - } - - - </programlisting> - <para> - The first ioctl we must support and which all video capture and radio - devices are required to support is VIDIOCGCAP. This behaves exactly the same - as with a radio device. This time, however, we report the extra capabilities - we outlined earlier on when defining our video_dev structure. - </para> - <para> - We now set the video flags saying that we support overlay, capture, - scaling and chromakey. We also report size limits - our smallest image is - 16x16 pixels, our largest is 640x480. - </para> - <para> - To keep things simple we report no audio and no tuning capabilities at all. - </para> - <programlisting> - - case VIDIOCGCHAN: - { - struct video_channel v; - if(copy_from_user(&v, arg, sizeof(v))) - return -EFAULT; - if(v.channel != 0) - return -EINVAL; - v.flags = 0; - v.tuners = 0; - v.type = VIDEO_TYPE_CAMERA; - v.norm = VIDEO_MODE_AUTO; - strcpy(v.name, "Camera Input");break; - if(copy_to_user(&v, arg, sizeof(v))) - return -EFAULT; - return 0; - } - - - </programlisting> - <para> - This follows what is very much the standard way an ioctl handler looks - in Linux. We copy the data into a kernel space variable and we check that the - request is valid (in this case that the input is 0). Finally we copy the - camera info back to the user. - </para> - <para> - The VIDIOCGCHAN ioctl allows a user to ask about video channels (that is - inputs to the video card). Our example card has a single camera input. The - fields in the structure are - </para> - <table frame="all" id="video_channel_fields"><title>struct video_channel fields</title> - <tgroup cols="2" align="left"> - <tbody> - <row> - - <entry>channel</entry><entry>The channel number we are selecting</entry> - </row><row> - <entry>name</entry><entry>The name for this channel. This is intended - to describe the port to the user. - Appropriate names are therefore things like - "Camera" "SCART input"</entry> - </row><row> - <entry>flags</entry><entry>Channel properties</entry> - </row><row> - <entry>type</entry><entry>Input type</entry> - </row><row> - <entry>norm</entry><entry>The current television encoding being used - if relevant for this channel. - </entry> - </row> - </tbody> - </tgroup> - </table> - <table frame="all" id="video_channel_flags"><title>struct video_channel flags</title> - <tgroup cols="2" align="left"> - <tbody> - <row> - <entry>VIDEO_VC_TUNER</entry><entry>Channel has a tuner.</entry> - </row><row> - <entry>VIDEO_VC_AUDIO</entry><entry>Channel has audio.</entry> - </row> - </tbody> - </tgroup> - </table> - <table frame="all" id="video_channel_types"><title>struct video_channel types</title> - <tgroup cols="2" align="left"> - <tbody> - <row> - <entry>VIDEO_TYPE_TV</entry><entry>Television input.</entry> - </row><row> - <entry>VIDEO_TYPE_CAMERA</entry><entry>Fixed camera input.</entry> - </row><row> - <entry>0</entry><entry>Type is unknown.</entry> - </row> - </tbody> - </tgroup> - </table> - <table frame="all" id="video_channel_norms"><title>struct video_channel norms</title> - <tgroup cols="2" align="left"> - <tbody> - <row> - <entry>VIDEO_MODE_PAL</entry><entry>PAL encoded Television</entry> - </row><row> - <entry>VIDEO_MODE_NTSC</entry><entry>NTSC (US) encoded Television</entry> - </row><row> - <entry>VIDEO_MODE_SECAM</entry><entry>SECAM (French) Television </entry> - </row><row> - <entry>VIDEO_MODE_AUTO</entry><entry>Automatic switching, or format does not - matter</entry> - </row> - </tbody> - </tgroup> - </table> - <para> - The corresponding VIDIOCSCHAN ioctl allows a user to change channel and to - request the norm is changed - for example to switch between a PAL or an NTSC - format camera. - </para> - <programlisting> - - - case VIDIOCSCHAN: - { - struct video_channel v; - if(copy_from_user(&v, arg, sizeof(v))) - return -EFAULT; - if(v.channel != 0) - return -EINVAL; - if(v.norm != VIDEO_MODE_AUTO) - return -EINVAL; - return 0; - } - - - </programlisting> - <para> - The implementation of this call in our driver is remarkably easy. Because we - are assuming fixed format hardware we need only check that the user has not - tried to change anything. - </para> - <para> - The user also needs to be able to configure and adjust the picture they are - seeing. This is much like adjusting a television set. A user application - also needs to know the palette being used so that it knows how to display - the image that has been captured. The VIDIOCGPICT and VIDIOCSPICT ioctl - calls provide this information. - </para> - <programlisting> - - - case VIDIOCGPICT - { - struct video_picture v; - v.brightness = hardware_brightness(); - v.hue = hardware_hue(); - v.colour = hardware_saturation(); - v.contrast = hardware_brightness(); - /* Not settable */ - v.whiteness = 32768; - v.depth = 24; /* 24bit */ - v.palette = VIDEO_PALETTE_RGB24; - if(copy_to_user(&v, arg, - sizeof(v))) - return -EFAULT; - return 0; - } - - - </programlisting> - <para> - The brightness, hue, color, and contrast provide the picture controls that - are akin to a conventional television. Whiteness provides additional - control for greyscale images. All of these values are scaled between 0-65535 - and have 32768 as the mid point setting. The scaling means that applications - do not have to worry about the capability range of the hardware but can let - it make a best effort attempt. - </para> - <para> - Our depth is 24, as this is in bits. We will be returning RGB24 format. This - has one byte of red, then one of green, then one of blue. This then repeats - for every other pixel in the image. The other common formats the interface - defines are - </para> - <table frame="all" id="Framebuffer_Encodings"><title>Framebuffer Encodings</title> - <tgroup cols="2" align="left"> - <tbody> - <row> - <entry>GREY</entry><entry>Linear greyscale. This is for simple cameras and the - like</entry> - </row><row> - <entry>RGB565</entry><entry>The top 5 bits hold 32 red levels, the next six bits - hold green and the low 5 bits hold blue. </entry> - </row><row> - <entry>RGB555</entry><entry>The top bit is clear. The red green and blue levels - each occupy five bits.</entry> - </row> - </tbody> - </tgroup> - </table> - <para> - Additional modes are support for YUV capture formats. These are common for - TV and video conferencing applications. - </para> - <para> - The VIDIOCSPICT ioctl allows a user to set some of the picture parameters. - Exactly which ones are supported depends heavily on the card itself. It is - possible to support many modes and effects in software. In general doing - this in the kernel is a bad idea. Video capture is a performance-sensitive - application and the programs can often do better if they aren't being - 'helped' by an overkeen driver writer. Thus for our device we will report - RGB24 only and refuse to allow a change. - </para> - <programlisting> - - - case VIDIOCSPICT: - { - struct video_picture v; - if(copy_from_user(&v, arg, sizeof(v))) - return -EFAULT; - if(v.depth!=24 || - v.palette != VIDEO_PALETTE_RGB24) - return -EINVAL; - set_hardware_brightness(v.brightness); - set_hardware_hue(v.hue); - set_hardware_saturation(v.colour); - set_hardware_brightness(v.contrast); - return 0; - } - - - </programlisting> - <para> - We check the user has not tried to change the palette or the depth. We do - not want to carry out some of the changes and then return an error. This may - confuse the application which will be assuming no change occurred. - </para> - <para> - In much the same way as you need to be able to set the picture controls to - get the right capture images, many cards need to know what they are - displaying onto when generating overlay output. In some cases getting this - wrong even makes a nasty mess or may crash the computer. For that reason - the VIDIOCSBUF ioctl used to set up the frame buffer information may well - only be usable by root. - </para> - <para> - We will assume our card is one of the old ISA devices with feature connector - and only supports a couple of standard video modes. Very common for older - cards although the PCI devices are way smarter than this. - </para> - <programlisting> - - -static struct video_buffer capture_fb; - - case VIDIOCGFBUF: - { - if(copy_to_user(arg, &capture_fb, - sizeof(capture_fb))) - return -EFAULT; - return 0; - - } - - - </programlisting> - <para> - We keep the frame buffer information in the format the ioctl uses. This - makes it nice and easy to work with in the ioctl calls. - </para> - <programlisting> - - case VIDIOCSFBUF: - { - struct video_buffer v; - - if(!capable(CAP_SYS_ADMIN)) - return -EPERM; - - if(copy_from_user(&v, arg, sizeof(v))) - return -EFAULT; - if(v.width!=320 && v.width!=640) - return -EINVAL; - if(v.height!=200 && v.height!=240 - && v.height!=400 - && v.height !=480) - return -EINVAL; - memcpy(&capture_fb, &v, sizeof(v)); - hardware_set_fb(&v); - return 0; - } - - - - </programlisting> - <para> - The capable() function checks a user has the required capability. The Linux - operating system has a set of about 30 capabilities indicating privileged - access to services. The default set up gives the superuser (uid 0) all of - them and nobody else has any. - </para> - <para> - We check that the user has the SYS_ADMIN capability, that is they are - allowed to operate as the machine administrator. We don't want anyone but - the administrator making a mess of the display. - </para> - <para> - Next we check for standard PC video modes (320 or 640 wide with either - EGA or VGA depths). If the mode is not a standard video mode we reject it as - not supported by our card. If the mode is acceptable we save it so that - VIDIOCFBUF will give the right answer next time it is called. The - hardware_set_fb() function is some undescribed card specific function to - program the card for the desired mode. - </para> - <para> - Before the driver can display an overlay window it needs to know where the - window should be placed, and also how large it should be. If the card - supports clipping it needs to know which rectangles to omit from the - display. The video_window structure is used to describe the way the image - should be displayed. - </para> - <table frame="all" id="video_window_fields"><title>struct video_window fields</title> - <tgroup cols="2" align="left"> - <tbody> - <row> - <entry>width</entry><entry>The width in pixels of the desired image. The card - may use a smaller size if this size is not available</entry> - </row><row> - <entry>height</entry><entry>The height of the image. The card may use a smaller - size if this size is not available.</entry> - </row><row> - <entry>x</entry><entry> The X position of the top left of the window. This - is in pixels relative to the left hand edge of the - picture. Not all cards can display images aligned on - any pixel boundary. If the position is unsuitable - the card adjusts the image right and reduces the - width.</entry> - </row><row> - <entry>y</entry><entry> The Y position of the top left of the window. This - is counted in pixels relative to the top edge of the - picture. As with the width if the card cannot - display starting on this line it will adjust the - values.</entry> - </row><row> - <entry>chromakey</entry><entry>The colour (expressed in RGB32 format) for the - chromakey colour if chroma keying is being used. </entry> - </row><row> - <entry>clips</entry><entry>An array of rectangles that must not be drawn - over.</entry> - </row><row> - <entry>clipcount</entry><entry>The number of clips in this array.</entry> - </row> - </tbody> - </tgroup> - </table> - <para> - Each clip is a struct video_clip which has the following fields - </para> - <table frame="all" id="video_clip_fields"><title>video_clip fields</title> - <tgroup cols="2" align="left"> - <tbody> - <row> - <entry>x, y</entry><entry>Co-ordinates relative to the display</entry> - </row><row> - <entry>width, height</entry><entry>Width and height in pixels</entry> - </row><row> - <entry>next</entry><entry>A spare field for the application to use</entry> - </row> - </tbody> - </tgroup> - </table> - <para> - The driver is required to ensure it always draws in the area requested or a smaller area, and that it never draws in any of the areas that are clipped. - This may well mean it has to leave alone. small areas the application wished to be - drawn. - </para> - <para> - Our example card uses chromakey so does not have to address most of the - clipping. We will add a video_window structure to our global variables to - remember our parameters, as we did with the frame buffer. - </para> - <programlisting> - - - case VIDIOCGWIN: - { - if(copy_to_user(arg, &capture_win, - sizeof(capture_win))) - return -EFAULT; - return 0; - } - - - case VIDIOCSWIN: - { - struct video_window v; - if(copy_from_user(&v, arg, sizeof(v))) - return -EFAULT; - if(v.width > 640 || v.height > 480) - return -EINVAL; - if(v.width < 16 || v.height < 16) - return -EINVAL; - hardware_set_key(v.chromakey); - hardware_set_window(v); - memcpy(&capture_win, &v, sizeof(v)); - capture_w = v.width; - capture_h = v.height; - return 0; - } - - - </programlisting> - <para> - Because we are using Chromakey our setup is fairly simple. Mostly we have to - check the values are sane and load them into the capture card. - </para> - <para> - With all the setup done we can now turn on the actual capture/overlay. This - is done with the VIDIOCCAPTURE ioctl. This takes a single integer argument - where 0 is on and 1 is off. - </para> - <programlisting> - - - case VIDIOCCAPTURE: - { - int v; - if(get_user(v, (int *)arg)) - return -EFAULT; - if(v==0) - hardware_capture_off(); - else - { - if(capture_fb.width == 0 - || capture_w == 0) - return -EINVAL; - hardware_capture_on(); - } - return 0; - } - - - </programlisting> - <para> - We grab the flag from user space and either enable or disable according to - its value. There is one small corner case we have to consider here. Suppose - that the capture was requested before the video window or the frame buffer - had been set up. In those cases there will be unconfigured fields in our - card data, as well as unconfigured hardware settings. We check for this case and - return an error if the frame buffer or the capture window width is zero. - </para> - <programlisting> - - - default: - return -ENOIOCTLCMD; - } -} - </programlisting> - <para> - - We don't need to support any other ioctls, so if we get this far, it is time - to tell the video layer that we don't now what the user is talking about. - </para> - </sect1> - <sect1 id="endvid"> - <title>Other Functionality</title> - <para> - The Video4Linux layer supports additional features, including a high - performance mmap() based capture mode and capturing part of the image. - These features are out of the scope of the book. You should however have enough - example code to implement most simple video4linux devices for radio and TV - cards. - </para> - </sect1> - </chapter> - <chapter id="bugs"> - <title>Known Bugs And Assumptions</title> - <para> - <variablelist> - <varlistentry><term>Multiple Opens</term> - <listitem> - <para> - The driver assumes multiple opens should not be allowed. A driver - can work around this but not cleanly. - </para> - </listitem></varlistentry> - - <varlistentry><term>API Deficiencies</term> - <listitem> - <para> - The existing API poorly reflects compression capable devices. There - are plans afoot to merge V4L, V4L2 and some other ideas into a - better interface. - </para> - </listitem></varlistentry> - </variablelist> - - </para> - </chapter> - - <chapter id="pubfunctions"> - <title>Public Functions Provided</title> -!Edrivers/media/video/v4l2-dev.c - </chapter> - -</book> diff --git a/Documentation/HOWTO b/Documentation/HOWTO index 48a3955f05fc..8495fc970391 100644 --- a/Documentation/HOWTO +++ b/Documentation/HOWTO @@ -112,7 +112,7 @@ required reading: Other excellent descriptions of how to create patches properly are: "The Perfect Patch" - http://www.zip.com.au/~akpm/linux/patches/stuff/tpp.txt + http://userweb.kernel.org/~akpm/stuff/tpp.txt "Linux kernel patch submission format" http://linux.yyz.us/patch-format.html @@ -620,7 +620,7 @@ all time. It should describe the patch completely, containing: For more details on what this should all look like, please see the ChangeLog section of the document: "The Perfect Patch" - http://www.zip.com.au/~akpm/linux/patches/stuff/tpp.txt + http://userweb.kernel.org/~akpm/stuff/tpp.txt diff --git a/Documentation/SAK.txt b/Documentation/SAK.txt index b9019ca872ea..74be14679ed8 100644 --- a/Documentation/SAK.txt +++ b/Documentation/SAK.txt @@ -1,5 +1,5 @@ Linux 2.4.2 Secure Attention Key (SAK) handling -18 March 2001, Andrew Morton <akpm@osdl.org> +18 March 2001, Andrew Morton An operating system's Secure Attention Key is a security tool which is provided as protection against trojan password capturing programs. It diff --git a/Documentation/SubmitChecklist b/Documentation/SubmitChecklist index 21f0795af20f..ac5e0b2f1097 100644 --- a/Documentation/SubmitChecklist +++ b/Documentation/SubmitChecklist @@ -85,3 +85,6 @@ kernel patches. 23: Tested after it has been merged into the -mm patchset to make sure that it still works with all of the other queued patches and various changes in the VM, VFS, and other subsystems. + +24: All memory barriers {e.g., barrier(), rmb(), wmb()} need a comment in the + source code that explains the logic of what they are doing and why. diff --git a/Documentation/SubmittingDrivers b/Documentation/SubmittingDrivers index 24f2eb40cae5..99e72a81fa2f 100644 --- a/Documentation/SubmittingDrivers +++ b/Documentation/SubmittingDrivers @@ -41,7 +41,7 @@ Linux 2.4: Linux 2.6: The same rules apply as 2.4 except that you should follow linux-kernel to track changes in API's. The final contact point for Linux 2.6 - submissions is Andrew Morton <akpm@osdl.org>. + submissions is Andrew Morton. What Criteria Determine Acceptance ---------------------------------- diff --git a/Documentation/SubmittingPatches b/Documentation/SubmittingPatches index f79ad9ff6031..f309d3c6221c 100644 --- a/Documentation/SubmittingPatches +++ b/Documentation/SubmittingPatches @@ -77,7 +77,7 @@ Quilt: http://savannah.nongnu.org/projects/quilt Andrew Morton's patch scripts: -http://www.zip.com.au/~akpm/linux/patches/ +http://userweb.kernel.org/~akpm/stuff/patch-scripts.tar.gz Instead of these scripts, quilt is the recommended patch management tool (see above). @@ -405,7 +405,7 @@ person it names. This tag documents that potentially interested parties have been included in the discussion -14) Using Test-by: and Reviewed-by: +14) Using Tested-by: and Reviewed-by: A Tested-by: tag indicates that the patch has been successfully tested (in some environment) by the person named. This tag informs maintainers that @@ -653,7 +653,7 @@ SECTION 3 - REFERENCES ---------------------- Andrew Morton, "The perfect patch" (tpp). - <http://www.zip.com.au/~akpm/linux/patches/stuff/tpp.txt> + <http://userweb.kernel.org/~akpm/stuff/tpp.txt> Jeff Garzik, "Linux kernel patch submission format". <http://linux.yyz.us/patch-format.html> @@ -672,4 +672,9 @@ Kernel Documentation/CodingStyle: Linus Torvalds's mail on the canonical patch format: <http://lkml.org/lkml/2005/4/7/183> + +Andi Kleen, "On submitting kernel patches" + Some strategies to get difficult or controversal changes in. + http://halobates.de/on-submitting-patches.pdf + -- diff --git a/Documentation/block/data-integrity.txt b/Documentation/block/data-integrity.txt index e9dc8d86adc7..e8ca040ba2cf 100644 --- a/Documentation/block/data-integrity.txt +++ b/Documentation/block/data-integrity.txt @@ -246,7 +246,7 @@ will require extra work due to the application tag. retrieve the tag buffer using bio_integrity_get_tag(). -6.3 PASSING EXISTING INTEGRITY METADATA +5.3 PASSING EXISTING INTEGRITY METADATA Filesystems that either generate their own integrity metadata or are capable of transferring IMD from user space can use the @@ -283,7 +283,7 @@ will require extra work due to the application tag. integrity upon completion. -6.4 REGISTERING A BLOCK DEVICE AS CAPABLE OF EXCHANGING INTEGRITY +5.4 REGISTERING A BLOCK DEVICE AS CAPABLE OF EXCHANGING INTEGRITY METADATA To enable integrity exchange on a block device the gendisk must be diff --git a/Documentation/cris/README b/Documentation/cris/README index 795a1dabe6c7..d9b086869a60 100644 --- a/Documentation/cris/README +++ b/Documentation/cris/README @@ -27,7 +27,7 @@ operating system. The ETRAX 100LX chip -------------------- -For reference, plase see the press-release: +For reference, please see the press-release: http://www.axis.com/news/us/001101_etrax.htm diff --git a/Documentation/development-process/1.Intro b/Documentation/development-process/1.Intro new file mode 100644 index 000000000000..8cc2cba2b10d --- /dev/null +++ b/Documentation/development-process/1.Intro @@ -0,0 +1,274 @@ +1: A GUIDE TO THE KERNEL DEVELOPMENT PROCESS + +The purpose of this document is to help developers (and their managers) +work with the development community with a minimum of frustration. It is +an attempt to document how this community works in a way which is +accessible to those who are not intimately familiar with Linux kernel +development (or, indeed, free software development in general). While +there is some technical material here, this is very much a process-oriented +discussion which does not require a deep knowledge of kernel programming to +understand. + + +1.1: EXECUTIVE SUMMARY + +The rest of this section covers the scope of the kernel development process +and the kinds of frustrations that developers and their employers can +encounter there. There are a great many reasons why kernel code should be +merged into the official ("mainline") kernel, including automatic +availability to users, community support in many forms, and the ability to +influence the direction of kernel development. Code contributed to the +Linux kernel must be made available under a GPL-compatible license. + +Section 2 introduces the development process, the kernel release cycle, and +the mechanics of the merge window. The various phases in the patch +development, review, and merging cycle are covered. There is some +discussion of tools and mailing lists. Developers wanting to get started +with kernel development are encouraged to track down and fix bugs as an +initial exercise. + +Section 3 covers early-stage project planning, with an emphasis on +involving the development community as soon as possible. + +Section 4 is about the coding process; several pitfalls which have been +encountered by other developers are discussed. Some requirements for +patches are covered, and there is an introduction to some of the tools +which can help to ensure that kernel patches are correct. + +Section 5 talks about the process of posting patches for review. To be +taken seriously by the development community, patches must be properly +formatted and described, and they must be sent to the right place. +Following the advice in this section should help to ensure the best +possible reception for your work. + +Section 6 covers what happens after posting patches; the job is far from +done at that point. Working with reviewers is a crucial part of the +development process; this section offers a number of tips on how to avoid +problems at this important stage. Developers are cautioned against +assuming that the job is done when a patch is merged into the mainline. + +Section 7 introduces a couple of "advanced" topics: managing patches with +git and reviewing patches posted by others. + +Section 8 concludes the document with pointers to sources for more +information on kernel development. + + +1.2: WHAT THIS DOCUMENT IS ABOUT + +The Linux kernel, at over 6 million lines of code and well over 1000 active +contributors, is one of the largest and most active free software projects +in existence. Since its humble beginning in 1991, this kernel has evolved +into a best-of-breed operating system component which runs on pocket-sized +digital music players, desktop PCs, the largest supercomputers in +existence, and all types of systems in between. It is a robust, efficient, +and scalable solution for almost any situation. + +With the growth of Linux has come an increase in the number of developers +(and companies) wishing to participate in its development. Hardware +vendors want to ensure that Linux supports their products well, making +those products attractive to Linux users. Embedded systems vendors, who +use Linux as a component in an integrated product, want Linux to be as +capable and well-suited to the task at hand as possible. Distributors and +other software vendors who base their products on Linux have a clear +interest in the capabilities, performance, and reliability of the Linux +kernel. And end users, too, will often wish to change Linux to make it +better suit their needs. + +One of the most compelling features of Linux is that it is accessible to +these developers; anybody with the requisite skills can improve Linux and +influence the direction of its development. Proprietary products cannot +offer this kind of openness, which is a characteristic of the free software +process. But, if anything, the kernel is even more open than most other +free software projects. A typical three-month kernel development cycle can +involve over 1000 developers working for more than 100 different companies +(or for no company at all). + +Working with the kernel development community is not especially hard. But, +that notwithstanding, many potential contributors have experienced +difficulties when trying to do kernel work. The kernel community has +evolved its own distinct ways of operating which allow it to function +smoothly (and produce a high-quality product) in an environment where +thousands of lines of code are being changed every day. So it is not +surprising that Linux kernel development process differs greatly from +proprietary development methods. + +The kernel's development process may come across as strange and +intimidating to new developers, but there are good reasons and solid +experience behind it. A developer who does not understand the kernel +community's ways (or, worse, who tries to flout or circumvent them) will +have a frustrating experience in store. The development community, while +being helpful to those who are trying to learn, has little time for those +who will not listen or who do not care about the development process. + +It is hoped that those who read this document will be able to avoid that +frustrating experience. There is a lot of material here, but the effort +involved in reading it will be repaid in short order. The development +community is always in need of developers who will help to make the kernel +better; the following text should help you - or those who work for you - +join our community. + + +1.3: CREDITS + +This document was written by Jonathan Corbet, corbet@lwn.net. It has been +improved by comments from Johannes Berg, James Berry, Alex Chiang, Roland +Dreier, Randy Dunlap, Jake Edge, Jiri Kosina, Matt Mackall, Arthur Marsh, +Amanda McPherson, Andrew Morton, Andrew Price, Tsugikazu Shibata, and +Jochen Voß. + +This work was supported by the Linux Foundation; thanks especially to +Amanda McPherson, who saw the value of this effort and made it all happen. + + +1.4: THE IMPORTANCE OF GETTING CODE INTO THE MAINLINE + +Some companies and developers occasionally wonder why they should bother +learning how to work with the kernel community and get their code into the +mainline kernel (the "mainline" being the kernel maintained by Linus +Torvalds and used as a base by Linux distributors). In the short term, +contributing code can look like an avoidable expense; it seems easier to +just keep the code separate and support users directly. The truth of the +matter is that keeping code separate ("out of tree") is a false economy. + +As a way of illustrating the costs of out-of-tree code, here are a few +relevant aspects of the kernel development process; most of these will be +discussed in greater detail later in this document. Consider: + +- Code which has been merged into the mainline kernel is available to all + Linux users. It will automatically be present on all distributions which + enable it. There is no need for driver disks, downloads, or the hassles + of supporting multiple versions of multiple distributions; it all just + works, for the developer and for the user. Incorporation into the + mainline solves a large number of distribution and support problems. + +- While kernel developers strive to maintain a stable interface to user + space, the internal kernel API is in constant flux. The lack of a stable + internal interface is a deliberate design decision; it allows fundamental + improvements to be made at any time and results in higher-quality code. + But one result of that policy is that any out-of-tree code requires + constant upkeep if it is to work with new kernels. Maintaining + out-of-tree code requires significant amounts of work just to keep that + code working. + + Code which is in the mainline, instead, does not require this work as the + result of a simple rule requiring any developer who makes an API change + to also fix any code that breaks as the result of that change. So code + which has been merged into the mainline has significantly lower + maintenance costs. + +- Beyond that, code which is in the kernel will often be improved by other + developers. Surprising results can come from empowering your user + community and customers to improve your product. + +- Kernel code is subjected to review, both before and after merging into + the mainline. No matter how strong the original developer's skills are, + this review process invariably finds ways in which the code can be + improved. Often review finds severe bugs and security problems. This is + especially true for code which has been developed in a closed + environment; such code benefits strongly from review by outside + developers. Out-of-tree code is lower-quality code. + +- Participation in the development process is your way to influence the + direction of kernel development. Users who complain from the sidelines + are heard, but active developers have a stronger voice - and the ability + to implement changes which make the kernel work better for their needs. + +- When code is maintained separately, the possibility that a third party + will contribute a different implementation of a similar feature always + exists. Should that happen, getting your code merged will become much + harder - to the point of impossibility. Then you will be faced with the + unpleasant alternatives of either (1) maintaining a nonstandard feature + out of tree indefinitely, or (2) abandoning your code and migrating your + users over to the in-tree version. + +- Contribution of code is the fundamental action which makes the whole + process work. By contributing your code you can add new functionality to + the kernel and provide capabilities and examples which are of use to + other kernel developers. If you have developed code for Linux (or are + thinking about doing so), you clearly have an interest in the continued + success of this platform; contributing code is one of the best ways to + help ensure that success. + +All of the reasoning above applies to any out-of-tree kernel code, +including code which is distributed in proprietary, binary-only form. +There are, however, additional factors which should be taken into account +before considering any sort of binary-only kernel code distribution. These +include: + +- The legal issues around the distribution of proprietary kernel modules + are cloudy at best; quite a few kernel copyright holders believe that + most binary-only modules are derived products of the kernel and that, as + a result, their distribution is a violation of the GNU General Public + license (about which more will be said below). Your author is not a + lawyer, and nothing in this document can possibly be considered to be + legal advice. The true legal status of closed-source modules can only be + determined by the courts. But the uncertainty which haunts those modules + is there regardless. + +- Binary modules greatly increase the difficulty of debugging kernel + problems, to the point that most kernel developers will not even try. So + the distribution of binary-only modules will make it harder for your + users to get support from the community. + +- Support is also harder for distributors of binary-only modules, who must + provide a version of the module for every distribution and every kernel + version they wish to support. Dozens of builds of a single module can + be required to provide reasonably comprehensive coverage, and your users + will have to upgrade your module separately every time they upgrade their + kernel. + +- Everything that was said above about code review applies doubly to + closed-source code. Since this code is not available at all, it cannot + have been reviewed by the community and will, beyond doubt, have serious + problems. + +Makers of embedded systems, in particular, may be tempted to disregard much +of what has been said in this section in the belief that they are shipping +a self-contained product which uses a frozen kernel version and requires no +more development after its release. This argument misses the value of +widespread code review and the value of allowing your users to add +capabilities to your product. But these products, too, have a limited +commercial life, after which a new version must be released. At that +point, vendors whose code is in the mainline and well maintained will be +much better positioned to get the new product ready for market quickly. + + +1.5: LICENSING + +Code is contributed to the Linux kernel under a number of licenses, but all +code must be compatible with version 2 of the GNU General Public License +(GPLv2), which is the license covering the kernel distribution as a whole. +In practice, that means that all code contributions are covered either by +GPLv2 (with, optionally, language allowing distribution under later +versions of the GPL) or the three-clause BSD license. Any contributions +which are not covered by a compatible license will not be accepted into the +kernel. + +Copyright assignments are not required (or requested) for code contributed +to the kernel. All code merged into the mainline kernel retains its +original ownership; as a result, the kernel now has thousands of owners. + +One implication of this ownership structure is that any attempt to change +the licensing of the kernel is doomed to almost certain failure. There are +few practical scenarios where the agreement of all copyright holders could +be obtained (or their code removed from the kernel). So, in particular, +there is no prospect of a migration to version 3 of the GPL in the +foreseeable future. + +It is imperative that all code contributed to the kernel be legitimately +free software. For that reason, code from anonymous (or pseudonymous) +contributors will not be accepted. All contributors are required to "sign +off" on their code, stating that the code can be distributed with the +kernel under the GPL. Code which has not been licensed as free software by +its owner, or which risks creating copyright-related problems for the +kernel (such as code which derives from reverse-engineering efforts lacking +proper safeguards) cannot be contributed. + +Questions about copyright-related issues are common on Linux development +mailing lists. Such questions will normally receive no shortage of +answers, but one should bear in mind that the people answering those +questions are not lawyers and cannot provide legal advice. If you have +legal questions relating to Linux source code, there is no substitute for +talking with a lawyer who understands this field. Relying on answers +obtained on technical mailing lists is a risky affair. diff --git a/Documentation/development-process/2.Process b/Documentation/development-process/2.Process new file mode 100644 index 000000000000..d750321acd5a --- /dev/null +++ b/Documentation/development-process/2.Process @@ -0,0 +1,459 @@ +2: HOW THE DEVELOPMENT PROCESS WORKS + +Linux kernel development in the early 1990's was a pretty loose affair, +with relatively small numbers of users and developers involved. With a +user base in the millions and with some 2,000 developers involved over the +course of one year, the kernel has since had to evolve a number of +processes to keep development happening smoothly. A solid understanding of +how the process works is required in order to be an effective part of it. + + +2.1: THE BIG PICTURE + +The kernel developers use a loosely time-based release process, with a new +major kernel release happening every two or three months. The recent +release history looks like this: + + 2.6.26 July 13, 2008 + 2.6.25 April 16, 2008 + 2.6.24 January 24, 2008 + 2.6.23 October 9, 2007 + 2.6.22 July 8, 2007 + 2.6.21 April 25, 2007 + 2.6.20 February 4, 2007 + +Every 2.6.x release is a major kernel release with new features, internal +API changes, and more. A typical 2.6 release can contain over 10,000 +changesets with changes to several hundred thousand lines of code. 2.6 is +thus the leading edge of Linux kernel development; the kernel uses a +rolling development model which is continually integrating major changes. + +A relatively straightforward discipline is followed with regard to the +merging of patches for each release. At the beginning of each development +cycle, the "merge window" is said to be open. At that time, code which is +deemed to be sufficiently stable (and which is accepted by the development +community) is merged into the mainline kernel. The bulk of changes for a +new development cycle (and all of the major changes) will be merged during +this time, at a rate approaching 1,000 changes ("patches," or "changesets") +per day. + +(As an aside, it is worth noting that the changes integrated during the +merge window do not come out of thin air; they have been collected, tested, +and staged ahead of time. How that process works will be described in +detail later on). + +The merge window lasts for two weeks. At the end of this time, Linus +Torvalds will declare that the window is closed and release the first of +the "rc" kernels. For the kernel which is destined to be 2.6.26, for +example, the release which happens at the end of the merge window will be +called 2.6.26-rc1. The -rc1 release is the signal that the time to merge +new features has passed, and that the time to stabilize the next kernel has +begun. + +Over the next six to ten weeks, only patches which fix problems should be +submitted to the mainline. On occasion a more significant change will be +allowed, but such occasions are rare; developers who try to merge new +features outside of the merge window tend to get an unfriendly reception. +As a general rule, if you miss the merge window for a given feature, the +best thing to do is to wait for the next development cycle. (An occasional +exception is made for drivers for previously-unsupported hardware; if they +touch no in-tree code, they cannot cause regressions and should be safe to +add at any time). + +As fixes make their way into the mainline, the patch rate will slow over +time. Linus releases new -rc kernels about once a week; a normal series +will get up to somewhere between -rc6 and -rc9 before the kernel is +considered to be sufficiently stable and the final 2.6.x release is made. +At that point the whole process starts over again. + +As an example, here is how the 2.6.25 development cycle went (all dates in +2008): + + January 24 2.6.24 stable release + February 10 2.6.25-rc1, merge window closes + February 15 2.6.25-rc2 + February 24 2.6.25-rc3 + March 4 2.6.25-rc4 + March 9 2.6.25-rc5 + March 16 2.6.25-rc6 + March 25 2.6.25-rc7 + April 1 2.6.25-rc8 + April 11 2.6.25-rc9 + April 16 2.6.25 stable release + +How do the developers decide when to close the development cycle and create +the stable release? The most significant metric used is the list of +regressions from previous releases. No bugs are welcome, but those which +break systems which worked in the past are considered to be especially +serious. For this reason, patches which cause regressions are looked upon +unfavorably and are quite likely to be reverted during the stabilization +period. + +The developers' goal is to fix all known regressions before the stable +release is made. In the real world, this kind of perfection is hard to +achieve; there are just too many variables in a project of this size. +There comes a point where delaying the final release just makes the problem +worse; the pile of changes waiting for the next merge window will grow +larger, creating even more regressions the next time around. So most 2.6.x +kernels go out with a handful of known regressions though, hopefully, none +of them are serious. + +Once a stable release is made, its ongoing maintenance is passed off to the +"stable team," currently comprised of Greg Kroah-Hartman and Chris Wright. +The stable team will release occasional updates to the stable release using +the 2.6.x.y numbering scheme. To be considered for an update release, a +patch must (1) fix a significant bug, and (2) already be merged into the +mainline for the next development kernel. Continuing our 2.6.25 example, +the history (as of this writing) is: + + May 1 2.6.25.1 + May 6 2.6.25.2 + May 9 2.6.25.3 + May 15 2.6.25.4 + June 7 2.6.25.5 + June 9 2.6.25.6 + June 16 2.6.25.7 + June 21 2.6.25.8 + June 24 2.6.25.9 + +Stable updates for a given kernel are made for approximately six months; +after that, the maintenance of stable releases is solely the responsibility +of the distributors which have shipped that particular kernel. + + +2.2: THE LIFECYCLE OF A PATCH + +Patches do not go directly from the developer's keyboard into the mainline +kernel. There is, instead, a somewhat involved (if somewhat informal) +process designed to ensure that each patch is reviewed for quality and that +each patch implements a change which is desirable to have in the mainline. +This process can happen quickly for minor fixes, or, in the case of large +and controversial changes, go on for years. Much developer frustration +comes from a lack of understanding of this process or from attempts to +circumvent it. + +In the hopes of reducing that frustration, this document will describe how +a patch gets into the kernel. What follows below is an introduction which +describes the process in a somewhat idealized way. A much more detailed +treatment will come in later sections. + +The stages that a patch goes through are, generally: + + - Design. This is where the real requirements for the patch - and the way + those requirements will be met - are laid out. Design work is often + done without involving the community, but it is better to do this work + in the open if at all possible; it can save a lot of time redesigning + things later. + + - Early review. Patches are posted to the relevant mailing list, and + developers on that list reply with any comments they may have. This + process should turn up any major problems with a patch if all goes + well. + + - Wider review. When the patch is getting close to ready for mainline + inclusion, it will be accepted by a relevant subsystem maintainer - + though this acceptance is not a guarantee that the patch will make it + all the way to the mainline. The patch will show up in the maintainer's + subsystem tree and into the staging trees (described below). When the + process works, this step leads to more extensive review of the patch and + the discovery of any problems resulting from the integration of this + patch with work being done by others. + + - Merging into the mainline. Eventually, a successful patch will be + merged into the mainline repository managed by Linus Torvalds. More + comments and/or problems may surface at this time; it is important that + the developer be responsive to these and fix any issues which arise. + + - Stable release. The number of users potentially affected by the patch + is now large, so, once again, new problems may arise. + + - Long-term maintenance. While it is certainly possible for a developer + to forget about code after merging it, that sort of behavior tends to + leave a poor impression in the development community. Merging code + eliminates some of the maintenance burden, in that others will fix + problems caused by API changes. But the original developer should + continue to take responsibility for the code if it is to remain useful + in the longer term. + +One of the largest mistakes made by kernel developers (or their employers) +is to try to cut the process down to a single "merging into the mainline" +step. This approach invariably leads to frustration for everybody +involved. + + +2.3: HOW PATCHES GET INTO THE KERNEL + +There is exactly one person who can merge patches into the mainline kernel +repository: Linus Torvalds. But, of the over 12,000 patches which went +into the 2.6.25 kernel, only 250 (around 2%) were directly chosen by Linus +himself. The kernel project has long since grown to a size where no single +developer could possibly inspect and select every patch unassisted. The +way the kernel developers have addressed this growth is through the use of +a lieutenant system built around a chain of trust. + +The kernel code base is logically broken down into a set of subsystems: +networking, specific architecture support, memory management, video +devices, etc. Most subsystems have a designated maintainer, a developer +who has overall responsibility for the code within that subsystem. These +subsystem maintainers are the gatekeepers (in a loose way) for the portion +of the kernel they manage; they are the ones who will (usually) accept a +patch for inclusion into the mainline kernel. + +Subsystem maintainers each manage their own version of the kernel source +tree, usually (but certainly not always) using the git source management +tool. Tools like git (and related tools like quilt or mercurial) allow +maintainers to track a list of patches, including authorship information +and other metadata. At any given time, the maintainer can identify which +patches in his or her repository are not found in the mainline. + +When the merge window opens, top-level maintainers will ask Linus to "pull" +the patches they have selected for merging from their repositories. If +Linus agrees, the stream of patches will flow up into his repository, +becoming part of the mainline kernel. The amount of attention that Linus +pays to specific patches received in a pull operation varies. It is clear +that, sometimes, he looks quite closely. But, as a general rule, Linus +trusts the subsystem maintainers to not send bad patches upstream. + +Subsystem maintainers, in turn, can pull patches from other maintainers. +For example, the networking tree is built from patches which accumulated +first in trees dedicated to network device drivers, wireless networking, +etc. This chain of repositories can be arbitrarily long, though it rarely +exceeds two or three links. Since each maintainer in the chain trusts +those managing lower-level trees, this process is known as the "chain of +trust." + +Clearly, in a system like this, getting patches into the kernel depends on +finding the right maintainer. Sending patches directly to Linus is not +normally the right way to go. + + +2.4: STAGING TREES + +The chain of subsystem trees guides the flow of patches into the kernel, +but it also raises an interesting question: what if somebody wants to look +at all of the patches which are being prepared for the next merge window? +Developers will be interested in what other changes are pending to see +whether there are any conflicts to worry about; a patch which changes a +core kernel function prototype, for example, will conflict with any other +patches which use the older form of that function. Reviewers and testers +want access to the changes in their integrated form before all of those +changes land in the mainline kernel. One could pull changes from all of +the interesting subsystem trees, but that would be a big and error-prone +job. + +The answer comes in the form of staging trees, where subsystem trees are +collected for testing and review. The older of these trees, maintained by +Andrew Morton, is called "-mm" (for memory management, which is how it got +started). The -mm tree integrates patches from a long list of subsystem +trees; it also has some patches aimed at helping with debugging. + +Beyond that, -mm contains a significant collection of patches which have +been selected by Andrew directly. These patches may have been posted on a +mailing list, or they may apply to a part of the kernel for which there is +no designated subsystem tree. As a result, -mm operates as a sort of +subsystem tree of last resort; if there is no other obvious path for a +patch into the mainline, it is likely to end up in -mm. Miscellaneous +patches which accumulate in -mm will eventually either be forwarded on to +an appropriate subsystem tree or be sent directly to Linus. In a typical +development cycle, approximately 10% of the patches going into the mainline +get there via -mm. + +The current -mm patch can always be found from the front page of + + http://kernel.org/ + +Those who want to see the current state of -mm can get the "-mm of the +moment" tree, found at: + + http://userweb.kernel.org/~akpm/mmotm/ + +Use of the MMOTM tree is likely to be a frustrating experience, though; +there is a definite chance that it will not even compile. + +The other staging tree, started more recently, is linux-next, maintained by +Stephen Rothwell. The linux-next tree is, by design, a snapshot of what +the mainline is expected to look like after the next merge window closes. +Linux-next trees are announced on the linux-kernel and linux-next mailing +lists when they are assembled; they can be downloaded from: + + http://www.kernel.org/pub/linux/kernel/people/sfr/linux-next/ + +Some information about linux-next has been gathered at: + + http://linux.f-seidel.de/linux-next/pmwiki/ + +How the linux-next tree will fit into the development process is still +changing. As of this writing, the first full development cycle involving +linux-next (2.6.26) is coming to an end; thus far, it has proved to be a +valuable resource for finding and fixing integration problems before the +beginning of the merge window. See http://lwn.net/Articles/287155/ for +more information on how linux-next has worked to set up the 2.6.27 merge +window. + +Some developers have begun to suggest that linux-next should be used as the +target for future development as well. The linux-next tree does tend to be +far ahead of the mainline and is more representative of the tree into which +any new work will be merged. The downside to this idea is that the +volatility of linux-next tends to make it a difficult development target. +See http://lwn.net/Articles/289013/ for more information on this topic, and +stay tuned; much is still in flux where linux-next is involved. + + +2.5: TOOLS + +As can be seen from the above text, the kernel development process depends +heavily on the ability to herd collections of patches in various +directions. The whole thing would not work anywhere near as well as it +does without suitably powerful tools. Tutorials on how to use these tools +are well beyond the scope of this document, but there is space for a few +pointers. + +By far the dominant source code management system used by the kernel +community is git. Git is one of a number of distributed version control +systems being developed in the free software community. It is well tuned +for kernel development, in that it performs quite well when dealing with +large repositories and large numbers of patches. It also has a reputation +for being difficult to learn and use, though it has gotten better over +time. Some sort of familiarity with git is almost a requirement for kernel +developers; even if they do not use it for their own work, they'll need git +to keep up with what other developers (and the mainline) are doing. + +Git is now packaged by almost all Linux distributions. There is a home +page at + + http://git.or.cz/ + +That page has pointers to documentation and tutorials. One should be +aware, in particular, of the Kernel Hacker's Guide to git, which has +information specific to kernel development: + + http://linux.yyz.us/git-howto.html + +Among the kernel developers who do not use git, the most popular choice is +almost certainly Mercurial: + + http://www.selenic.com/mercurial/ + +Mercurial shares many features with git, but it provides an interface which +many find easier to use. + +The other tool worth knowing about is Quilt: + + http://savannah.nongnu.org/projects/quilt/ + +Quilt is a patch management system, rather than a source code management +system. It does not track history over time; it is, instead, oriented +toward tracking a specific set of changes against an evolving code base. +Some major subsystem maintainers use quilt to manage patches intended to go +upstream. For the management of certain kinds of trees (-mm, for example), +quilt is the best tool for the job. + + +2.6: MAILING LISTS + +A great deal of Linux kernel development work is done by way of mailing +lists. It is hard to be a fully-functioning member of the community +without joining at least one list somewhere. But Linux mailing lists also +represent a potential hazard to developers, who risk getting buried under a +load of electronic mail, running afoul of the conventions used on the Linux +lists, or both. + +Most kernel mailing lists are run on vger.kernel.org; the master list can +be found at: + + http://vger.kernel.org/vger-lists.html + +There are lists hosted elsewhere, though; a number of them are at +lists.redhat.com. + +The core mailing list for kernel development is, of course, linux-kernel. +This list is an intimidating place to be; volume can reach 500 messages per +day, the amount of noise is high, the conversation can be severely +technical, and participants are not always concerned with showing a high +degree of politeness. But there is no other place where the kernel +development community comes together as a whole; developers who avoid this +list will miss important information. + +There are a few hints which can help with linux-kernel survival: + +- Have the list delivered to a separate folder, rather than your main + mailbox. One must be able to ignore the stream for sustained periods of + time. + +- Do not try to follow every conversation - nobody else does. It is + important to filter on both the topic of interest (though note that + long-running conversations can drift away from the original subject + without changing the email subject line) and the people who are + participating. + +- Do not feed the trolls. If somebody is trying to stir up an angry + response, ignore them. + +- When responding to linux-kernel email (or that on other lists) preserve + the Cc: header for all involved. In the absence of a strong reason (such + as an explicit request), you should never remove recipients. Always make + sure that the person you are responding to is in the Cc: list. This + convention also makes it unnecessary to explicitly ask to be copied on + replies to your postings. + +- Search the list archives (and the net as a whole) before asking + questions. Some developers can get impatient with people who clearly + have not done their homework. + +- Avoid top-posting (the practice of putting your answer above the quoted + text you are responding to). It makes your response harder to read and + makes a poor impression. + +- Ask on the correct mailing list. Linux-kernel may be the general meeting + point, but it is not the best place to find developers from all + subsystems. + +The last point - finding the correct mailing list - is a common place for +beginning developers to go wrong. Somebody who asks a networking-related +question on linux-kernel will almost certainly receive a polite suggestion +to ask on the netdev list instead, as that is the list frequented by most +networking developers. Other lists exist for the SCSI, video4linux, IDE, +filesystem, etc. subsystems. The best place to look for mailing lists is +in the MAINTAINERS file packaged with the kernel source. + + +2.7: GETTING STARTED WITH KERNEL DEVELOPMENT + +Questions about how to get started with the kernel development process are +common - from both individuals and companies. Equally common are missteps +which make the beginning of the relationship harder than it has to be. + +Companies often look to hire well-known developers to get a development +group started. This can, in fact, be an effective technique. But it also +tends to be expensive and does not do much to grow the pool of experienced +kernel developers. It is possible to bring in-house developers up to speed +on Linux kernel development, given the investment of a bit of time. Taking +this time can endow an employer with a group of developers who understand +the kernel and the company both, and who can help to train others as well. +Over the medium term, this is often the more profitable approach. + +Individual developers are often, understandably, at a loss for a place to +start. Beginning with a large project can be intimidating; one often wants +to test the waters with something smaller first. This is the point where +some developers jump into the creation of patches fixing spelling errors or +minor coding style issues. Unfortunately, such patches create a level of +noise which is distracting for the development community as a whole, so, +increasingly, they are looked down upon. New developers wishing to +introduce themselves to the community will not get the sort of reception +they wish for by these means. + +Andrew Morton gives this advice for aspiring kernel developers + + The #1 project for all kernel beginners should surely be "make sure + that the kernel runs perfectly at all times on all machines which + you can lay your hands on". Usually the way to do this is to work + with others on getting things fixed up (this can require + persistence!) but that's fine - it's a part of kernel development. + +(http://lwn.net/Articles/283982/). + +In the absence of obvious problems to fix, developers are advised to look +at the current lists of regressions and open bugs in general. There is +never any shortage of issues in need of fixing; by addressing these issues, +developers will gain experience with the process while, at the same time, +building respect with the rest of the development community. diff --git a/Documentation/development-process/3.Early-stage b/Documentation/development-process/3.Early-stage new file mode 100644 index 000000000000..307a159a70ca --- /dev/null +++ b/Documentation/development-process/3.Early-stage @@ -0,0 +1,195 @@ +3: EARLY-STAGE PLANNING + +When contemplating a Linux kernel development project, it can be tempting +to jump right in and start coding. As with any significant project, +though, much of the groundwork for success is best laid before the first +line of code is written. Some time spent in early planning and +communication can save far more time later on. + + +3.1: SPECIFYING THE PROBLEM + +Like any engineering project, a successful kernel enhancement starts with a +clear description of the problem to be solved. In some cases, this step is +easy: when a driver is needed for a specific piece of hardware, for +example. In others, though, it is tempting to confuse the real problem +with the proposed solution, and that can lead to difficulties. + +Consider an example: some years ago, developers working with Linux audio +sought a way to run applications without dropouts or other artifacts caused +by excessive latency in the system. The solution they arrived at was a +kernel module intended to hook into the Linux Security Module (LSM) +framework; this module could be configured to give specific applications +access to the realtime scheduler. This module was implemented and sent to +the linux-kernel mailing list, where it immediately ran into problems. + +To the audio developers, this security module was sufficient to solve their +immediate problem. To the wider kernel community, though, it was seen as a +misuse of the LSM framework (which is not intended to confer privileges +onto processes which they would not otherwise have) and a risk to system +stability. Their preferred solutions involved realtime scheduling access +via the rlimit mechanism for the short term, and ongoing latency reduction +work in the long term. + +The audio community, however, could not see past the particular solution +they had implemented; they were unwilling to accept alternatives. The +resulting disagreement left those developers feeling disillusioned with the +entire kernel development process; one of them went back to an audio list +and posted this: + + There are a number of very good Linux kernel developers, but they + tend to get outshouted by a large crowd of arrogant fools. Trying + to communicate user requirements to these people is a waste of + time. They are much too "intelligent" to listen to lesser mortals. + +(http://lwn.net/Articles/131776/). + +The reality of the situation was different; the kernel developers were far +more concerned about system stability, long-term maintenance, and finding +the right solution to the problem than they were with a specific module. +The moral of the story is to focus on the problem - not a specific solution +- and to discuss it with the development community before investing in the +creation of a body of code. + +So, when contemplating a kernel development project, one should obtain +answers to a short set of questions: + + - What, exactly, is the problem which needs to be solved? + + - Who are the users affected by this problem? Which use cases should the + solution address? + + - How does the kernel fall short in addressing that problem now? + +Only then does it make sense to start considering possible solutions. + + +3.2: EARLY DISCUSSION + +When planning a kernel development project, it makes great sense to hold +discussions with the community before launching into implementation. Early +communication can save time and trouble in a number of ways: + + - It may well be that the problem is addressed by the kernel in ways which + you have not understood. The Linux kernel is large and has a number of + features and capabilities which are not immediately obvious. Not all + kernel capabilities are documented as well as one might like, and it is + easy to miss things. Your author has seen the posting of a complete + driver which duplicated an existing driver that the new author had been + unaware of. Code which reinvents existing wheels is not only wasteful; + it will also not be accepted into the mainline kernel. + + - There may be elements of the proposed solution which will not be + acceptable for mainline merging. It is better to find out about + problems like this before writing the code. + + - It's entirely possible that other developers have thought about the + problem; they may have ideas for a better solution, and may be willing + to help in the creation of that solution. + +Years of experience with the kernel development community have taught a +clear lesson: kernel code which is designed and developed behind closed +doors invariably has problems which are only revealed when the code is +released into the community. Sometimes these problems are severe, +requiring months or years of effort before the code can be brought up to +the kernel community's standards. Some examples include: + + - The Devicescape network stack was designed and implemented for + single-processor systems. It could not be merged into the mainline + until it was made suitable for multiprocessor systems. Retrofitting + locking and such into code is a difficult task; as a result, the merging + of this code (now called mac80211) was delayed for over a year. + + - The Reiser4 filesystem included a number of capabilities which, in the + core kernel developers' opinion, should have been implemented in the + virtual filesystem layer instead. It also included features which could + not easily be implemented without exposing the system to user-caused + deadlocks. The late revelation of these problems - and refusal to + address some of them - has caused Reiser4 to stay out of the mainline + kernel. + + - The AppArmor security module made use of internal virtual filesystem + data structures in ways which were considered to be unsafe and + unreliable. This code has since been significantly reworked, but + remains outside of the mainline. + +In each of these cases, a great deal of pain and extra work could have been +avoided with some early discussion with the kernel developers. + + +3.3: WHO DO YOU TALK TO? + +When developers decide to take their plans public, the next question will +be: where do we start? The answer is to find the right mailing list(s) and +the right maintainer. For mailing lists, the best approach is to look in +the MAINTAINERS file for a relevant place to post. If there is a suitable +subsystem list, posting there is often preferable to posting on +linux-kernel; you are more likely to reach developers with expertise in the +relevant subsystem and the environment may be more supportive. + +Finding maintainers can be a bit harder. Again, the MAINTAINERS file is +the place to start. That file tends to not always be up to date, though, +and not all subsystems are represented there. The person listed in the +MAINTAINERS file may, in fact, not be the person who is actually acting in +that role currently. So, when there is doubt about who to contact, a +useful trick is to use git (and "git log" in particular) to see who is +currently active within the subsystem of interest. Look at who is writing +patches, and who, if anybody, is attaching Signed-off-by lines to those +patches. Those are the people who will be best placed to help with a new +development project. + +If all else fails, talking to Andrew Morton can be an effective way to +track down a maintainer for a specific piece of code. + + +3.4: WHEN TO POST? + +If possible, posting your plans during the early stages can only be +helpful. Describe the problem being solved and any plans that have been +made on how the implementation will be done. Any information you can +provide can help the development community provide useful input on the +project. + +One discouraging thing which can happen at this stage is not a hostile +reaction, but, instead, little or no reaction at all. The sad truth of the +matter is (1) kernel developers tend to be busy, (2) there is no shortage +of people with grand plans and little code (or even prospect of code) to +back them up, and (3) nobody is obligated to review or comment on ideas +posted by others. If a request-for-comments posting yields little in the +way of comments, do not assume that it means there is no interest in the +project. Unfortunately, you also cannot assume that there are no problems +with your idea. The best thing to do in this situation is to proceed, +keeping the community informed as you go. + + +3.5: GETTING OFFICIAL BUY-IN + +If your work is being done in a corporate environment - as most Linux +kernel work is - you must, obviously, have permission from suitably +empowered managers before you can post your company's plans or code to a +public mailing list. The posting of code which has not been cleared for +release under a GPL-compatible license can be especially problematic; the +sooner that a company's management and legal staff can agree on the posting +of a kernel development project, the better off everybody involved will be. + +Some readers may be thinking at this point that their kernel work is +intended to support a product which does not yet have an officially +acknowledged existence. Revealing their employer's plans on a public +mailing list may not be a viable option. In cases like this, it is worth +considering whether the secrecy is really necessary; there is often no real +need to keep development plans behind closed doors. + +That said, there are also cases where a company legitimately cannot +disclose its plans early in the development process. Companies with +experienced kernel developers may choose to proceed in an open-loop manner +on the assumption that they will be able to avoid serious integration +problems later. For companies without that sort of in-house expertise, the +best option is often to hire an outside developer to review the plans under +a non-disclosure agreement. The Linux Foundation operates an NDA program +designed to help with this sort of situation; more information can be found +at: + + http://www.linuxfoundation.org/en/NDA_program + +This kind of review is often enough to avoid serious problems later on +without requiring public disclosure of the project. diff --git a/Documentation/development-process/4.Coding b/Documentation/development-process/4.Coding new file mode 100644 index 000000000000..014aca8f14e2 --- /dev/null +++ b/Documentation/development-process/4.Coding @@ -0,0 +1,384 @@ +4: GETTING THE CODE RIGHT + +While there is much to be said for a solid and community-oriented design +process, the proof of any kernel development project is in the resulting +code. It is the code which will be examined by other developers and merged +(or not) into the mainline tree. So it is the quality of this code which +will determine the ultimate success of the project. + +This section will examine the coding process. We'll start with a look at a +number of ways in which kernel developers can go wrong. Then the focus +will shift toward doing things right and the tools which can help in that +quest. + + +4.1: PITFALLS + +* Coding style + +The kernel has long had a standard coding style, described in +Documentation/CodingStyle. For much of that time, the policies described +in that file were taken as being, at most, advisory. As a result, there is +a substantial amount of code in the kernel which does not meet the coding +style guidelines. The presence of that code leads to two independent +hazards for kernel developers. + +The first of these is to believe that the kernel coding standards do not +matter and are not enforced. The truth of the matter is that adding new +code to the kernel is very difficult if that code is not coded according to +the standard; many developers will request that the code be reformatted +before they will even review it. A code base as large as the kernel +requires some uniformity of code to make it possible for developers to +quickly understand any part of it. So there is no longer room for +strangely-formatted code. + +Occasionally, the kernel's coding style will run into conflict with an +employer's mandated style. In such cases, the kernel's style will have to +win before the code can be merged. Putting code into the kernel means +giving up a degree of control in a number of ways - including control over +how the code is formatted. + +The other trap is to assume that code which is already in the kernel is +urgently in need of coding style fixes. Developers may start to generate +reformatting patches as a way of gaining familiarity with the process, or +as a way of getting their name into the kernel changelogs - or both. But +pure coding style fixes are seen as noise by the development community; +they tend to get a chilly reception. So this type of patch is best +avoided. It is natural to fix the style of a piece of code while working +on it for other reasons, but coding style changes should not be made for +their own sake. + +The coding style document also should not be read as an absolute law which +can never be transgressed. If there is a good reason to go against the +style (a line which becomes far less readable if split to fit within the +80-column limit, for example), just do it. + + +* Abstraction layers + +Computer Science professors teach students to make extensive use of +abstraction layers in the name of flexibility and information hiding. +Certainly the kernel makes extensive use of abstraction; no project +involving several million lines of code could do otherwise and survive. +But experience has shown that excessive or premature abstraction can be +just as harmful as premature optimization. Abstraction should be used to +the level required and no further. + +At a simple level, consider a function which has an argument which is +always passed as zero by all callers. One could retain that argument just +in case somebody eventually needs to use the extra flexibility that it +provides. By that time, though, chances are good that the code which +implements this extra argument has been broken in some subtle way which was +never noticed - because it has never been used. Or, when the need for +extra flexibility arises, it does not do so in a way which matches the +programmer's early expectation. Kernel developers will routinely submit +patches to remove unused arguments; they should, in general, not be added +in the first place. + +Abstraction layers which hide access to hardware - often to allow the bulk +of a driver to be used with multiple operating systems - are especially +frowned upon. Such layers obscure the code and may impose a performance +penalty; they do not belong in the Linux kernel. + +On the other hand, if you find yourself copying significant amounts of code +from another kernel subsystem, it is time to ask whether it would, in fact, +make sense to pull out some of that code into a separate library or to +implement that functionality at a higher level. There is no value in +replicating the same code throughout the kernel. + + +* #ifdef and preprocessor use in general + +The C preprocessor seems to present a powerful temptation to some C +programmers, who see it as a way to efficiently encode a great deal of +flexibility into a source file. But the preprocessor is not C, and heavy +use of it results in code which is much harder for others to read and +harder for the compiler to check for correctness. Heavy preprocessor use +is almost always a sign of code which needs some cleanup work. + +Conditional compilation with #ifdef is, indeed, a powerful feature, and it +is used within the kernel. But there is little desire to see code which is +sprinkled liberally with #ifdef blocks. As a general rule, #ifdef use +should be confined to header files whenever possible. +Conditionally-compiled code can be confined to functions which, if the code +is not to be present, simply become empty. The compiler will then quietly +optimize out the call to the empty function. The result is far cleaner +code which is easier to follow. + +C preprocessor macros present a number of hazards, including possible +multiple evaluation of expressions with side effects and no type safety. +If you are tempted to define a macro, consider creating an inline function +instead. The code which results will be the same, but inline functions are +easier to read, do not evaluate their arguments multiple times, and allow +the compiler to perform type checking on the arguments and return value. + + +* Inline functions + +Inline functions present a hazard of their own, though. Programmers can +become enamored of the perceived efficiency inherent in avoiding a function +call and fill a source file with inline functions. Those functions, +however, can actually reduce performance. Since their code is replicated +at each call site, they end up bloating the size of the compiled kernel. +That, in turn, creates pressure on the processor's memory caches, which can +slow execution dramatically. Inline functions, as a rule, should be quite +small and relatively rare. The cost of a function call, after all, is not +that high; the creation of large numbers of inline functions is a classic +example of premature optimization. + +In general, kernel programmers ignore cache effects at their peril. The +classic time/space tradeoff taught in beginning data structures classes +often does not apply to contemporary hardware. Space *is* time, in that a +larger program will run slower than one which is more compact. + + +* Locking + +In May, 2006, the "Devicescape" networking stack was, with great +fanfare, released under the GPL and made available for inclusion in the +mainline kernel. This donation was welcome news; support for wireless +networking in Linux was considered substandard at best, and the Devicescape +stack offered the promise of fixing that situation. Yet, this code did not +actually make it into the mainline until June, 2007 (2.6.22). What +happened? + +This code showed a number of signs of having been developed behind +corporate doors. But one large problem in particular was that it was not +designed to work on multiprocessor systems. Before this networking stack +(now called mac80211) could be merged, a locking scheme needed to be +retrofitted onto it. + +Once upon a time, Linux kernel code could be developed without thinking +about the concurrency issues presented by multiprocessor systems. Now, +however, this document is being written on a dual-core laptop. Even on +single-processor systems, work being done to improve responsiveness will +raise the level of concurrency within the kernel. The days when kernel +code could be written without thinking about locking are long past. + +Any resource (data structures, hardware registers, etc.) which could be +accessed concurrently by more than one thread must be protected by a lock. +New code should be written with this requirement in mind; retrofitting +locking after the fact is a rather more difficult task. Kernel developers +should take the time to understand the available locking primitives well +enough to pick the right tool for the job. Code which shows a lack of +attention to concurrency will have a difficult path into the mainline. + + +* Regressions + +One final hazard worth mentioning is this: it can be tempting to make a +change (which may bring big improvements) which causes something to break +for existing users. This kind of change is called a "regression," and +regressions have become most unwelcome in the mainline kernel. With few +exceptions, changes which cause regressions will be backed out if the +regression cannot be fixed in a timely manner. Far better to avoid the +regression in the first place. + +It is often argued that a regression can be justified if it causes things +to work for more people than it creates problems for. Why not make a +change if it brings new functionality to ten systems for each one it +breaks? The best answer to this question was expressed by Linus in July, +2007: + + So we don't fix bugs by introducing new problems. That way lies + madness, and nobody ever knows if you actually make any real + progress at all. Is it two steps forwards, one step back, or one + step forward and two steps back? + +(http://lwn.net/Articles/243460/). + +An especially unwelcome type of regression is any sort of change to the +user-space ABI. Once an interface has been exported to user space, it must +be supported indefinitely. This fact makes the creation of user-space +interfaces particularly challenging: since they cannot be changed in +incompatible ways, they must be done right the first time. For this +reason, a great deal of thought, clear documentation, and wide review for +user-space interfaces is always required. + + + +4.2: CODE CHECKING TOOLS + +For now, at least, the writing of error-free code remains an ideal that few +of us can reach. What we can hope to do, though, is to catch and fix as +many of those errors as possible before our code goes into the mainline +kernel. To that end, the kernel developers have put together an impressive +array of tools which can catch a wide variety of obscure problems in an +automated way. Any problem caught by the computer is a problem which will +not afflict a user later on, so it stands to reason that the automated +tools should be used whenever possible. + +The first step is simply to heed the warnings produced by the compiler. +Contemporary versions of gcc can detect (and warn about) a large number of +potential errors. Quite often, these warnings point to real problems. +Code submitted for review should, as a rule, not produce any compiler +warnings. When silencing warnings, take care to understand the real cause +and try to avoid "fixes" which make the warning go away without addressing +its cause. + +Note that not all compiler warnings are enabled by default. Build the +kernel with "make EXTRA_CFLAGS=-W" to get the full set. + +The kernel provides several configuration options which turn on debugging +features; most of these are found in the "kernel hacking" submenu. Several +of these options should be turned on for any kernel used for development or +testing purposes. In particular, you should turn on: + + - ENABLE_WARN_DEPRECATED, ENABLE_MUST_CHECK, and FRAME_WARN to get an + extra set of warnings for problems like the use of deprecated interfaces + or ignoring an important return value from a function. The output + generated by these warnings can be verbose, but one need not worry about + warnings from other parts of the kernel. + + - DEBUG_OBJECTS will add code to track the lifetime of various objects + created by the kernel and warn when things are done out of order. If + you are adding a subsystem which creates (and exports) complex objects + of its own, consider adding support for the object debugging + infrastructure. + + - DEBUG_SLAB can find a variety of memory allocation and use errors; it + should be used on most development kernels. + + - DEBUG_SPINLOCK, DEBUG_SPINLOCK_SLEEP, and DEBUG_MUTEXES will find a + number of common locking errors. + +There are quite a few other debugging options, some of which will be +discussed below. Some of them have a significant performance impact and +should not be used all of the time. But some time spent learning the +available options will likely be paid back many times over in short order. + +One of the heavier debugging tools is the locking checker, or "lockdep." +This tool will track the acquisition and release of every lock (spinlock or +mutex) in the system, the order in which locks are acquired relative to +each other, the current interrupt environment, and more. It can then +ensure that locks are always acquired in the same order, that the same +interrupt assumptions apply in all situations, and so on. In other words, +lockdep can find a number of scenarios in which the system could, on rare +occasion, deadlock. This kind of problem can be painful (for both +developers and users) in a deployed system; lockdep allows them to be found +in an automated manner ahead of time. Code with any sort of non-trivial +locking should be run with lockdep enabled before being submitted for +inclusion. + +As a diligent kernel programmer, you will, beyond doubt, check the return +status of any operation (such as a memory allocation) which can fail. The +fact of the matter, though, is that the resulting failure recovery paths +are, probably, completely untested. Untested code tends to be broken code; +you could be much more confident of your code if all those error-handling +paths had been exercised a few times. + +The kernel provides a fault injection framework which can do exactly that, +especially where memory allocations are involved. With fault injection +enabled, a configurable percentage of memory allocations will be made to +fail; these failures can be restricted to a specific range of code. +Running with fault injection enabled allows the programmer to see how the +code responds when things go badly. See +Documentation/fault-injection/fault-injection.text for more information on +how to use this facility. + +Other kinds of errors can be found with the "sparse" static analysis tool. +With sparse, the programmer can be warned about confusion between +user-space and kernel-space addresses, mixture of big-endian and +small-endian quantities, the passing of integer values where a set of bit +flags is expected, and so on. Sparse must be installed separately (it can +be found at http://www.kernel.org/pub/software/devel/sparse/ if your +distributor does not package it); it can then be run on the code by adding +"C=1" to your make command. + +Other kinds of portability errors are best found by compiling your code for +other architectures. If you do not happen to have an S/390 system or a +Blackfin development board handy, you can still perform the compilation +step. A large set of cross compilers for x86 systems can be found at + + http://www.kernel.org/pub/tools/crosstool/ + +Some time spent installing and using these compilers will help avoid +embarrassment later. + + +4.3: DOCUMENTATION + +Documentation has often been more the exception than the rule with kernel +development. Even so, adequate documentation will help to ease the merging +of new code into the kernel, make life easier for other developers, and +will be helpful for your users. In many cases, the addition of +documentation has become essentially mandatory. + +The first piece of documentation for any patch is its associated +changelog. Log entries should describe the problem being solved, the form +of the solution, the people who worked on the patch, any relevant +effects on performance, and anything else that might be needed to +understand the patch. + +Any code which adds a new user-space interface - including new sysfs or +/proc files - should include documentation of that interface which enables +user-space developers to know what they are working with. See +Documentation/ABI/README for a description of how this documentation should +be formatted and what information needs to be provided. + +The file Documentation/kernel-parameters.txt describes all of the kernel's +boot-time parameters. Any patch which adds new parameters should add the +appropriate entries to this file. + +Any new configuration options must be accompanied by help text which +clearly explains the options and when the user might want to select them. + +Internal API information for many subsystems is documented by way of +specially-formatted comments; these comments can be extracted and formatted +in a number of ways by the "kernel-doc" script. If you are working within +a subsystem which has kerneldoc comments, you should maintain them and add +them, as appropriate, for externally-available functions. Even in areas +which have not been so documented, there is no harm in adding kerneldoc +comments for the future; indeed, this can be a useful activity for +beginning kernel developers. The format of these comments, along with some +information on how to create kerneldoc templates can be found in the file +Documentation/kernel-doc-nano-HOWTO.txt. + +Anybody who reads through a significant amount of existing kernel code will +note that, often, comments are most notable by their absence. Once again, +the expectations for new code are higher than they were in the past; +merging uncommented code will be harder. That said, there is little desire +for verbosely-commented code. The code should, itself, be readable, with +comments explaining the more subtle aspects. + +Certain things should always be commented. Uses of memory barriers should +be accompanied by a line explaining why the barrier is necessary. The +locking rules for data structures generally need to be explained somewhere. +Major data structures need comprehensive documentation in general. +Non-obvious dependencies between separate bits of code should be pointed +out. Anything which might tempt a code janitor to make an incorrect +"cleanup" needs a comment saying why it is done the way it is. And so on. + + +4.4: INTERNAL API CHANGES + +The binary interface provided by the kernel to user space cannot be broken +except under the most severe circumstances. The kernel's internal +programming interfaces, instead, are highly fluid and can be changed when +the need arises. If you find yourself having to work around a kernel API, +or simply not using a specific functionality because it does not meet your +needs, that may be a sign that the API needs to change. As a kernel +developer, you are empowered to make such changes. + +There are, of course, some catches. API changes can be made, but they need +to be well justified. So any patch making an internal API change should be +accompanied by a description of what the change is and why it is +necessary. This kind of change should also be broken out into a separate +patch, rather than buried within a larger patch. + +The other catch is that a developer who changes an internal API is +generally charged with the task of fixing any code within the kernel tree +which is broken by the change. For a widely-used function, this duty can +lead to literally hundreds or thousands of changes - many of which are +likely to conflict with work being done by other developers. Needless to +say, this can be a large job, so it is best to be sure that the +justification is solid. + +When making an incompatible API change, one should, whenever possible, +ensure that code which has not been updated is caught by the compiler. +This will help you to be sure that you have found all in-tree uses of that +interface. It will also alert developers of out-of-tree code that there is +a change that they need to respond to. Supporting out-of-tree code is not +something that kernel developers need to be worried about, but we also do +not have to make life harder for out-of-tree developers than it it needs to +be. diff --git a/Documentation/development-process/5.Posting b/Documentation/development-process/5.Posting new file mode 100644 index 000000000000..dd48132a74dd --- /dev/null +++ b/Documentation/development-process/5.Posting @@ -0,0 +1,278 @@ +5: POSTING PATCHES + +Sooner or later, the time comes when your work is ready to be presented to +the community for review and, eventually, inclusion into the mainline +kernel. Unsurprisingly, the kernel development community has evolved a set +of conventions and procedures which are used in the posting of patches; +following them will make life much easier for everybody involved. This +document will attempt to cover these expectations in reasonable detail; +more information can also be found in the files SubmittingPatches, +SubmittingDrivers, and SubmitChecklist in the kernel documentation +directory. + + +5.1: WHEN TO POST + +There is a constant temptation to avoid posting patches before they are +completely "ready." For simple patches, that is not a problem. If the +work being done is complex, though, there is a lot to be gained by getting +feedback from the community before the work is complete. So you should +consider posting in-progress work, or even making a git tree available so +that interested developers can catch up with your work at any time. + +When posting code which is not yet considered ready for inclusion, it is a +good idea to say so in the posting itself. Also mention any major work +which remains to be done and any known problems. Fewer people will look at +patches which are known to be half-baked, but those who do will come in +with the idea that they can help you drive the work in the right direction. + + +5.2: BEFORE CREATING PATCHES + +There are a number of things which should be done before you consider +sending patches to the development community. These include: + + - Test the code to the extent that you can. Make use of the kernel's + debugging tools, ensure that the kernel will build with all reasonable + combinations of configuration options, use cross-compilers to build for + different architectures, etc. + + - Make sure your code is compliant with the kernel coding style + guidelines. + + - Does your change have performance implications? If so, you should run + benchmarks showing what the impact (or benefit) of your change is; a + summary of the results should be included with the patch. + + - Be sure that you have the right to post the code. If this work was done + for an employer, the employer likely has a right to the work and must be + agreeable with its release under the GPL. + +As a general rule, putting in some extra thought before posting code almost +always pays back the effort in short order. + + +5.3: PATCH PREPARATION + +The preparation of patches for posting can be a surprising amount of work, +but, once again, attempting to save time here is not generally advisable +even in the short term. + +Patches must be prepared against a specific version of the kernel. As a +general rule, a patch should be based on the current mainline as found in +Linus's git tree. It may become necessary to make versions against -mm, +linux-next, or a subsystem tree, though, to facilitate wider testing and +review. Depending on the area of your patch and what is going on +elsewhere, basing a patch against these other trees can require a +significant amount of work resolving conflicts and dealing with API +changes. + +Only the most simple changes should be formatted as a single patch; +everything else should be made as a logical series of changes. Splitting +up patches is a bit of an art; some developers spend a long time figuring +out how to do it in the way that the community expects. There are a few +rules of thumb, however, which can help considerably: + + - The patch series you post will almost certainly not be the series of + changes found in your working revision control system. Instead, the + changes you have made need to be considered in their final form, then + split apart in ways which make sense. The developers are interested in + discrete, self-contained changes, not the path you took to get to those + changes. + + - Each logically independent change should be formatted as a separate + patch. These changes can be small ("add a field to this structure") or + large (adding a significant new driver, for example), but they should be + conceptually small and amenable to a one-line description. Each patch + should make a specific change which can be reviewed on its own and + verified to do what it says it does. + + - As a way of restating the guideline above: do not mix different types of + changes in the same patch. If a single patch fixes a critical security + bug, rearranges a few structures, and reformats the code, there is a + good chance that it will be passed over and the important fix will be + lost. + + - Each patch should yield a kernel which builds and runs properly; if your + patch series is interrupted in the middle, the result should still be a + working kernel. Partial application of a patch series is a common + scenario when the "git bisect" tool is used to find regressions; if the + result is a broken kernel, you will make life harder for developers and + users who are engaging in the noble work of tracking down problems. + + - Do not overdo it, though. One developer recently posted a set of edits + to a single file as 500 separate patches - an act which did not make him + the most popular person on the kernel mailing list. A single patch can + be reasonably large as long as it still contains a single *logical* + change. + + - It can be tempting to add a whole new infrastructure with a series of + patches, but to leave that infrastructure unused until the final patch + in the series enables the whole thing. This temptation should be + avoided if possible; if that series adds regressions, bisection will + finger the last patch as the one which caused the problem, even though + the real bug is elsewhere. Whenever possible, a patch which adds new + code should make that code active immediately. + +Working to create the perfect patch series can be a frustrating process +which takes quite a bit of time and thought after the "real work" has been +done. When done properly, though, it is time well spent. + + +5.4: PATCH FORMATTING + +So now you have a perfect series of patches for posting, but the work is +not done quite yet. Each patch needs to be formatted into a message which +quickly and clearly communicates its purpose to the rest of the world. To +that end, each patch will be composed of the following: + + - An optional "From" line naming the author of the patch. This line is + only necessary if you are passing on somebody else's patch via email, + but it never hurts to add it when in doubt. + + - A one-line description of what the patch does. This message should be + enough for a reader who sees it with no other context to figure out the + scope of the patch; it is the line that will show up in the "short form" + changelogs. This message is usually formatted with the relevant + subsystem name first, followed by the purpose of the patch. For + example: + + gpio: fix build on CONFIG_GPIO_SYSFS=n + + - A blank line followed by a detailed description of the contents of the + patch. This description can be as long as is required; it should say + what the patch does and why it should be applied to the kernel. + + - One or more tag lines, with, at a minimum, one Signed-off-by: line from + the author of the patch. Tags will be described in more detail below. + +The above three items should, normally, be the text used when committing +the change to a revision control system. They are followed by: + + - The patch itself, in the unified ("-u") patch format. Using the "-p" + option to diff will associate function names with changes, making the + resulting patch easier for others to read. + +You should avoid including changes to irrelevant files (those generated by +the build process, for example, or editor backup files) in the patch. The +file "dontdiff" in the Documentation directory can help in this regard; +pass it to diff with the "-X" option. + +The tags mentioned above are used to describe how various developers have +been associated with the development of this patch. They are described in +detail in the SubmittingPatches document; what follows here is a brief +summary. Each of these lines has the format: + + tag: Full Name <email address> optional-other-stuff + +The tags in common use are: + + - Signed-off-by: this is a developer's certification that he or she has + the right to submit the patch for inclusion into the kernel. It is an + agreement to the Developer's Certificate of Origin, the full text of + which can be found in Documentation/SubmittingPatches. Code without a + proper signoff cannot be merged into the mainline. + + - Acked-by: indicates an agreement by another developer (often a + maintainer of the relevant code) that the patch is appropriate for + inclusion into the kernel. + + - Tested-by: states that the named person has tested the patch and found + it to work. + + - Reviewed-by: the named developer has reviewed the patch for correctness; + see the reviewer's statement in Documentation/SubmittingPatches for more + detail. + + - Reported-by: names a user who reported a problem which is fixed by this + patch; this tag is used to give credit to the (often underappreciated) + people who test our code and let us know when things do not work + correctly. + + - Cc: the named person received a copy of the patch and had the + opportunity to comment on it. + +Be careful in the addition of tags to your patches: only Cc: is appropriate +for addition without the explicit permission of the person named. + + +5.5: SENDING THE PATCH + +Before you mail your patches, there are a couple of other things you should +take care of: + + - Are you sure that your mailer will not corrupt the patches? Patches + which have had gratuitous white-space changes or line wrapping performed + by the mail client will not apply at the other end, and often will not + be examined in any detail. If there is any doubt at all, mail the patch + to yourself and convince yourself that it shows up intact. + + Documentation/email-clients.txt has some helpful hints on making + specific mail clients work for sending patches. + + - Are you sure your patch is free of silly mistakes? You should always + run patches through scripts/checkpatch.pl and address the complaints it + comes up with. Please bear in mind that checkpatch.pl, while being the + embodiment of a fair amount of thought about what kernel patches should + look like, is not smarter than you. If fixing a checkpatch.pl complaint + would make the code worse, don't do it. + +Patches should always be sent as plain text. Please do not send them as +attachments; that makes it much harder for reviewers to quote sections of +the patch in their replies. Instead, just put the patch directly into your +message. + +When mailing patches, it is important to send copies to anybody who might +be interested in it. Unlike some other projects, the kernel encourages +people to err on the side of sending too many copies; don't assume that the +relevant people will see your posting on the mailing lists. In particular, +copies should go to: + + - The maintainer(s) of the affected subsystem(s). As described earlier, + the MAINTAINERS file is the first place to look for these people. + + - Other developers who have been working in the same area - especially + those who might be working there now. Using git to see who else has + modified the files you are working on can be helpful. + + - If you are responding to a bug report or a feature request, copy the + original poster as well. + + - Send a copy to the relevant mailing list, or, if nothing else applies, + the linux-kernel list. + + - If you are fixing a bug, think about whether the fix should go into the + next stable update. If so, stable@kernel.org should get a copy of the + patch. Also add a "Cc: stable@kernel.org" to the tags within the patch + itself; that will cause the stable team to get a notification when your + fix goes into the mainline. + +When selecting recipients for a patch, it is good to have an idea of who +you think will eventually accept the patch and get it merged. While it +is possible to send patches directly to Linus Torvalds and have him merge +them, things are not normally done that way. Linus is busy, and there are +subsystem maintainers who watch over specific parts of the kernel. Usually +you will be wanting that maintainer to merge your patches. If there is no +obvious maintainer, Andrew Morton is often the patch target of last resort. + +Patches need good subject lines. The canonical format for a patch line is +something like: + + [PATCH nn/mm] subsys: one-line description of the patch + +where "nn" is the ordinal number of the patch, "mm" is the total number of +patches in the series, and "subsys" is the name of the affected subsystem. +Clearly, nn/mm can be omitted for a single, standalone patch. + +If you have a significant series of patches, it is customary to send an +introductory description as part zero. This convention is not universally +followed though; if you use it, remember that information in the +introduction does not make it into the kernel changelogs. So please ensure +that the patches, themselves, have complete changelog information. + +In general, the second and following parts of a multi-part patch should be +sent as a reply to the first part so that they all thread together at the +receiving end. Tools like git and quilt have commands to mail out a set of +patches with the proper threading. If you have a long series, though, and +are using git, please provide the --no-chain-reply-to option to avoid +creating exceptionally deep nesting. diff --git a/Documentation/development-process/6.Followthrough b/Documentation/development-process/6.Followthrough new file mode 100644 index 000000000000..a8fba3d83a85 --- /dev/null +++ b/Documentation/development-process/6.Followthrough @@ -0,0 +1,202 @@ +6: FOLLOWTHROUGH + +At this point, you have followed the guidelines given so far and, with the +addition of your own engineering skills, have posted a perfect series of +patches. One of the biggest mistakes that even experienced kernel +developers can make is to conclude that their work is now done. In truth, +posting patches indicates a transition into the next stage of the process, +with, possibly, quite a bit of work yet to be done. + +It is a rare patch which is so good at its first posting that there is no +room for improvement. The kernel development process recognizes this fact, +and, as a result, is heavily oriented toward the improvement of posted +code. You, as the author of that code, will be expected to work with the +kernel community to ensure that your code is up to the kernel's quality +standards. A failure to participate in this process is quite likely to +prevent the inclusion of your patches into the mainline. + + +6.1: WORKING WITH REVIEWERS + +A patch of any significance will result in a number of comments from other +developers as they review the code. Working with reviewers can be, for +many developers, the most intimidating part of the kernel development +process. Life can be made much easier, though, if you keep a few things in +mind: + + - If you have explained your patch well, reviewers will understand its + value and why you went to the trouble of writing it. But that value + will not keep them from asking a fundamental question: what will it be + like to maintain a kernel with this code in it five or ten years later? + Many of the changes you may be asked to make - from coding style tweaks + to substantial rewrites - come from the understanding that Linux will + still be around and under development a decade from now. + + - Code review is hard work, and it is a relatively thankless occupation; + people remember who wrote kernel code, but there is little lasting fame + for those who reviewed it. So reviewers can get grumpy, especially when + they see the same mistakes being made over and over again. If you get a + review which seems angry, insulting, or outright offensive, resist the + impulse to respond in kind. Code review is about the code, not about + the people, and code reviewers are not attacking you personally. + + - Similarly, code reviewers are not trying to promote their employers' + agendas at the expense of your own. Kernel developers often expect to + be working on the kernel years from now, but they understand that their + employer could change. They truly are, almost without exception, + working toward the creation of the best kernel they can; they are not + trying to create discomfort for their employers' competitors. + +What all of this comes down to is that, when reviewers send you comments, +you need to pay attention to the technical observations that they are +making. Do not let their form of expression or your own pride keep that +from happening. When you get review comments on a patch, take the time to +understand what the reviewer is trying to say. If possible, fix the things +that the reviewer is asking you to fix. And respond back to the reviewer: +thank them, and describe how you will answer their questions. + +Note that you do not have to agree with every change suggested by +reviewers. If you believe that the reviewer has misunderstood your code, +explain what is really going on. If you have a technical objection to a +suggested change, describe it and justify your solution to the problem. If +your explanations make sense, the reviewer will accept them. Should your +explanation not prove persuasive, though, especially if others start to +agree with the reviewer, take some time to think things over again. It can +be easy to become blinded by your own solution to a problem to the point +that you don't realize that something is fundamentally wrong or, perhaps, +you're not even solving the right problem. + +One fatal mistake is to ignore review comments in the hope that they will +go away. They will not go away. If you repost code without having +responded to the comments you got the time before, you're likely to find +that your patches go nowhere. + +Speaking of reposting code: please bear in mind that reviewers are not +going to remember all the details of the code you posted the last time +around. So it is always a good idea to remind reviewers of previously +raised issues and how you dealt with them; the patch changelog is a good +place for this kind of information. Reviewers should not have to search +through list archives to familiarize themselves with what was said last +time; if you help them get a running start, they will be in a better mood +when they revisit your code. + +What if you've tried to do everything right and things still aren't going +anywhere? Most technical disagreements can be resolved through discussion, +but there are times when somebody simply has to make a decision. If you +honestly believe that this decision is going against you wrongly, you can +always try appealing to a higher power. As of this writing, that higher +power tends to be Andrew Morton. Andrew has a great deal of respect in the +kernel development community; he can often unjam a situation which seems to +be hopelessly blocked. Appealing to Andrew should not be done lightly, +though, and not before all other alternatives have been explored. And bear +in mind, of course, that he may not agree with you either. + + +6.2: WHAT HAPPENS NEXT + +If a patch is considered to be a good thing to add to the kernel, and once +most of the review issues have been resolved, the next step is usually +entry into a subsystem maintainer's tree. How that works varies from one +subsystem to the next; each maintainer has his or her own way of doing +things. In particular, there may be more than one tree - one, perhaps, +dedicated to patches planned for the next merge window, and another for +longer-term work. + +For patches applying to areas for which there is no obvious subsystem tree +(memory management patches, for example), the default tree often ends up +being -mm. Patches which affect multiple subsystems can also end up going +through the -mm tree. + +Inclusion into a subsystem tree can bring a higher level of visibility to a +patch. Now other developers working with that tree will get the patch by +default. Subsystem trees typically feed into -mm and linux-next as well, +making their contents visible to the development community as a whole. At +this point, there's a good chance that you will get more comments from a +new set of reviewers; these comments need to be answered as in the previous +round. + +What may also happen at this point, depending on the nature of your patch, +is that conflicts with work being done by others turn up. In the worst +case, heavy patch conflicts can result in some work being put on the back +burner so that the remaining patches can be worked into shape and merged. +Other times, conflict resolution will involve working with the other +developers and, possibly, moving some patches between trees to ensure that +everything applies cleanly. This work can be a pain, but count your +blessings: before the advent of the linux-next tree, these conflicts often +only turned up during the merge window and had to be addressed in a hurry. +Now they can be resolved at leisure, before the merge window opens. + +Some day, if all goes well, you'll log on and see that your patch has been +merged into the mainline kernel. Congratulations! Once the celebration is +complete (and you have added yourself to the MAINTAINERS file), though, it +is worth remembering an important little fact: the job still is not done. +Merging into the mainline brings its own challenges. + +To begin with, the visibility of your patch has increased yet again. There +may be a new round of comments from developers who had not been aware of +the patch before. It may be tempting to ignore them, since there is no +longer any question of your code being merged. Resist that temptation, +though; you still need to be responsive to developers who have questions or +suggestions. + +More importantly, though: inclusion into the mainline puts your code into +the hands of a much larger group of testers. Even if you have contributed +a driver for hardware which is not yet available, you will be surprised by +how many people will build your code into their kernels. And, of course, +where there are testers, there will be bug reports. + +The worst sort of bug reports are regressions. If your patch causes a +regression, you'll find an uncomfortable number of eyes upon you; +regressions need to be fixed as soon as possible. If you are unwilling or +unable to fix the regression (and nobody else does it for you), your patch +will almost certainly be removed during the stabilization period. Beyond +negating all of the work you have done to get your patch into the mainline, +having a patch pulled as the result of a failure to fix a regression could +well make it harder for you to get work merged in the future. + +After any regressions have been dealt with, there may be other, ordinary +bugs to deal with. The stabilization period is your best opportunity to +fix these bugs and ensure that your code's debut in a mainline kernel +release is as solid as possible. So, please, answer bug reports, and fix +the problems if at all possible. That's what the stabilization period is +for; you can start creating cool new patches once any problems with the old +ones have been taken care of. + +And don't forget that there are other milestones which may also create bug +reports: the next mainline stable release, when prominent distributors pick +up a version of the kernel containing your patch, etc. Continuing to +respond to these reports is a matter of basic pride in your work. If that +is insufficient motivation, though, it's also worth considering that the +development community remembers developers who lose interest in their code +after it's merged. The next time you post a patch, they will be evaluating +it with the assumption that you will not be around to maintain it +afterward. + + +6.3: OTHER THINGS THAT CAN HAPPEN + +One day, you may open your mail client and see that somebody has mailed you +a patch to your code. That is one of the advantages of having your code +out there in the open, after all. If you agree with the patch, you can +either forward it on to the subsystem maintainer (be sure to include a +proper From: line so that the attribution is correct, and add a signoff of +your own), or send an Acked-by: response back and let the original poster +send it upward. + +If you disagree with the patch, send a polite response explaining why. If +possible, tell the author what changes need to be made to make the patch +acceptable to you. There is a certain resistance to merging patches which +are opposed by the author and maintainer of the code, but it only goes so +far. If you are seen as needlessly blocking good work, those patches will +eventually flow around you and get into the mainline anyway. In the Linux +kernel, nobody has absolute veto power over any code. Except maybe Linus. + +On very rare occasion, you may see something completely different: another +developer posts a different solution to your problem. At that point, +chances are that one of the two patches will not be merged, and "mine was +here first" is not considered to be a compelling technical argument. If +somebody else's patch displaces yours and gets into the mainline, there is +really only one way to respond: be pleased that your problem got solved and +get on with your work. Having one's work shoved aside in this manner can +be hurtful and discouraging, but the community will remember your reaction +long after they have forgotten whose patch actually got merged. diff --git a/Documentation/development-process/7.AdvancedTopics b/Documentation/development-process/7.AdvancedTopics new file mode 100644 index 000000000000..a2cf74093aa1 --- /dev/null +++ b/Documentation/development-process/7.AdvancedTopics @@ -0,0 +1,173 @@ +7: ADVANCED TOPICS + +At this point, hopefully, you have a handle on how the development process +works. There is still more to learn, however! This section will cover a +number of topics which can be helpful for developers wanting to become a +regular part of the Linux kernel development process. + +7.1: MANAGING PATCHES WITH GIT + +The use of distributed version control for the kernel began in early 2002, +when Linus first started playing with the proprietary BitKeeper +application. While BitKeeper was controversial, the approach to software +version management it embodied most certainly was not. Distributed version +control enabled an immediate acceleration of the kernel development +project. In current times, there are several free alternatives to +BitKeeper. For better or for worse, the kernel project has settled on git +as its tool of choice. + +Managing patches with git can make life much easier for the developer, +especially as the volume of those patches grows. Git also has its rough +edges and poses certain hazards; it is a young and powerful tool which is +still being civilized by its developers. This document will not attempt to +teach the reader how to use git; that would be sufficient material for a +long document in its own right. Instead, the focus here will be on how git +fits into the kernel development process in particular. Developers who +wish to come up to speed with git will find more information at: + + http://git.or.cz/ + + http://www.kernel.org/pub/software/scm/git/docs/user-manual.html + +and on various tutorials found on the web. + +The first order of business is to read the above sites and get a solid +understanding of how git works before trying to use it to make patches +available to others. A git-using developer should be able to obtain a copy +of the mainline repository, explore the revision history, commit changes to +the tree, use branches, etc. An understanding of git's tools for the +rewriting of history (such as rebase) is also useful. Git comes with its +own terminology and concepts; a new user of git should know about refs, +remote branches, the index, fast-forward merges, pushes and pulls, detached +heads, etc. It can all be a little intimidating at the outset, but the +concepts are not that hard to grasp with a bit of study. + +Using git to generate patches for submission by email can be a good +exercise while coming up to speed. + +When you are ready to start putting up git trees for others to look at, you +will, of course, need a server that can be pulled from. Setting up such a +server with git-daemon is relatively straightforward if you have a system +which is accessible to the Internet. Otherwise, free, public hosting sites +(Github, for example) are starting to appear on the net. Established +developers can get an account on kernel.org, but those are not easy to come +by; see http://kernel.org/faq/ for more information. + +The normal git workflow involves the use of a lot of branches. Each line +of development can be separated into a separate "topic branch" and +maintained independently. Branches in git are cheap, there is no reason to +not make free use of them. And, in any case, you should not do your +development in any branch which you intend to ask others to pull from. +Publicly-available branches should be created with care; merge in patches +from development branches when they are in complete form and ready to go - +not before. + +Git provides some powerful tools which can allow you to rewrite your +development history. An inconvenient patch (one which breaks bisection, +say, or which has some other sort of obvious bug) can be fixed in place or +made to disappear from the history entirely. A patch series can be +rewritten as if it had been written on top of today's mainline, even though +you have been working on it for months. Changes can be transparently +shifted from one branch to another. And so on. Judicious use of git's +ability to revise history can help in the creation of clean patch sets with +fewer problems. + +Excessive use of this capability can lead to other problems, though, beyond +a simple obsession for the creation of the perfect project history. +Rewriting history will rewrite the changes contained in that history, +turning a tested (hopefully) kernel tree into an untested one. But, beyond +that, developers cannot easily collaborate if they do not have a shared +view of the project history; if you rewrite history which other developers +have pulled into their repositories, you will make life much more difficult +for those developers. So a simple rule of thumb applies here: history +which has been exported to others should generally be seen as immutable +thereafter. + +So, once you push a set of changes to your publicly-available server, those +changes should not be rewritten. Git will attempt to enforce this rule if +you try to push changes which do not result in a fast-forward merge +(i.e. changes which do not share the same history). It is possible to +override this check, and there may be times when it is necessary to rewrite +an exported tree. Moving changesets between trees to avoid conflicts in +linux-next is one example. But such actions should be rare. This is one +of the reasons why development should be done in private branches (which +can be rewritten if necessary) and only moved into public branches when +it's in a reasonably advanced state. + +As the mainline (or other tree upon which a set of changes is based) +advances, it is tempting to merge with that tree to stay on the leading +edge. For a private branch, rebasing can be an easy way to keep up with +another tree, but rebasing is not an option once a tree is exported to the +world. Once that happens, a full merge must be done. Merging occasionally +makes good sense, but overly frequent merges can clutter the history +needlessly. Suggested technique in this case is to merge infrequently, and +generally only at specific release points (such as a mainline -rc +release). If you are nervous about specific changes, you can always +perform test merges in a private branch. The git "rerere" tool can be +useful in such situations; it remembers how merge conflicts were resolved +so that you don't have to do the same work twice. + +One of the biggest recurring complaints about tools like git is this: the +mass movement of patches from one repository to another makes it easy to +slip in ill-advised changes which go into the mainline below the review +radar. Kernel developers tend to get unhappy when they see that kind of +thing happening; putting up a git tree with unreviewed or off-topic patches +can affect your ability to get trees pulled in the future. Quoting Linus: + + You can send me patches, but for me to pull a git patch from you, I + need to know that you know what you're doing, and I need to be able + to trust things *without* then having to go and check every + individual change by hand. + +(http://lwn.net/Articles/224135/). + +To avoid this kind of situation, ensure that all patches within a given +branch stick closely to the associated topic; a "driver fixes" branch +should not be making changes to the core memory management code. And, most +importantly, do not use a git tree to bypass the review process. Post an +occasional summary of the tree to the relevant list, and, when the time is +right, request that the tree be included in linux-next. + +If and when others start to send patches for inclusion into your tree, +don't forget to review them. Also ensure that you maintain the correct +authorship information; the git "am" tool does its best in this regard, but +you may have to add a "From:" line to the patch if it has been relayed to +you via a third party. + +When requesting a pull, be sure to give all the relevant information: where +your tree is, what branch to pull, and what changes will result from the +pull. The git request-pull command can be helpful in this regard; it will +format the request as other developers expect, and will also check to be +sure that you have remembered to push those changes to the public server. + + +7.2: REVIEWING PATCHES + +Some readers will certainly object to putting this section with "advanced +topics" on the grounds that even beginning kernel developers should be +reviewing patches. It is certainly true that there is no better way to +learn how to program in the kernel environment than by looking at code +posted by others. In addition, reviewers are forever in short supply; by +looking at code you can make a significant contribution to the process as a +whole. + +Reviewing code can be an intimidating prospect, especially for a new kernel +developer who may well feel nervous about questioning code - in public - +which has been posted by those with more experience. Even code written by +the most experienced developers can be improved, though. Perhaps the best +piece of advice for reviewers (all reviewers) is this: phrase review +comments as questions rather than criticisms. Asking "how does the lock +get released in this path?" will always work better than stating "the +locking here is wrong." + +Different developers will review code from different points of view. Some +are mostly concerned with coding style and whether code lines have trailing +white space. Others will focus primarily on whether the change implemented +by the patch as a whole is a good thing for the kernel or not. Yet others +will check for problematic locking, excessive stack usage, possible +security issues, duplication of code found elsewhere, adequate +documentation, adverse effects on performance, user-space ABI changes, etc. +All types of review, if they lead to better code going into the kernel, are +welcome and worthwhile. + + diff --git a/Documentation/development-process/8.Conclusion b/Documentation/development-process/8.Conclusion new file mode 100644 index 000000000000..1990ab4b4949 --- /dev/null +++ b/Documentation/development-process/8.Conclusion @@ -0,0 +1,74 @@ +8: FOR MORE INFORMATION + +There are numerous sources of information on Linux kernel development and +related topics. First among those will always be the Documentation +directory found in the kernel source distribution. The top-level HOWTO +file is an important starting point; SubmittingPatches and +SubmittingDrivers are also something which all kernel developers should +read. Many internal kernel APIs are documented using the kerneldoc +mechanism; "make htmldocs" or "make pdfdocs" can be used to generate those +documents in HTML or PDF format (though the version of TeX shipped by some +distributions runs into internal limits and fails to process the documents +properly). + +Various web sites discuss kernel development at all levels of detail. Your +author would like to humbly suggest http://lwn.net/ as a source; +information on many specific kernel topics can be found via the LWN kernel +index at: + + http://lwn.net/Kernel/Index/ + +Beyond that, a valuable resource for kernel developers is: + + http://kernelnewbies.org/ + +Information about the linux-next tree gathers at: + + http://linux.f-seidel.de/linux-next/pmwiki/ + +And, of course, one should not forget http://kernel.org/, the definitive +location for kernel release information. + +There are a number of books on kernel development: + + Linux Device Drivers, 3rd Edition (Jonathan Corbet, Alessandro + Rubini, and Greg Kroah-Hartman). Online at + http://lwn.net/Kernel/LDD3/. + + Linux Kernel Development (Robert Love). + + Understanding the Linux Kernel (Daniel Bovet and Marco Cesati). + +All of these books suffer from a common fault, though: they tend to be +somewhat obsolete by the time they hit the shelves, and they have been on +the shelves for a while now. Still, there is quite a bit of good +information to be found there. + +Documentation for git can be found at: + + http://www.kernel.org/pub/software/scm/git/docs/ + + http://www.kernel.org/pub/software/scm/git/docs/user-manual.html + + +9: CONCLUSION + +Congratulations to anybody who has made it through this long-winded +document. Hopefully it has provided a helpful understanding of how the +Linux kernel is developed and how you can participate in that process. + +In the end, it's the participation that matters. Any open source software +project is no more than the sum of what its contributors put into it. The +Linux kernel has progressed as quickly and as well as it has because it has +been helped by an impressively large group of developers, all of whom are +working to make it better. The kernel is a premier example of what can be +done when thousands of people work together toward a common goal. + +The kernel can always benefit from a larger developer base, though. There +is always more work to do. But, just as importantly, most other +participants in the Linux ecosystem can benefit through contributing to the +kernel. Getting code into the mainline is the key to higher code quality, +lower maintenance and distribution costs, a higher level of influence over +the direction of kernel development, and more. It is a situation where +everybody involved wins. Fire up your editor and come join us; you will be +more than welcome. diff --git a/Documentation/dontdiff b/Documentation/dontdiff index 27809357da58..1e89a51ea49b 100644 --- a/Documentation/dontdiff +++ b/Documentation/dontdiff @@ -2,11 +2,13 @@ *.aux *.bin *.cpio -*.css +*.csp +*.dsp *.dvi +*.elf *.eps -*.fw.gen.S *.fw +*.gen.S *.gif *.grep *.grp @@ -30,6 +32,7 @@ *.s *.sgml *.so +*.so.dbg *.symtypes *.tab.c *.tab.h @@ -38,24 +41,17 @@ *.xml *_MODULES *_vga16.c -*cscope* *~ *.9 *.9.gz .* -.cscope -.gitignore -.mailmap .mm 53c700_d.h -53c8xx_d.h* -COPYING -CREDITS CVS ChangeSet Image Kerntypes -MODS.txt +Module.markers Module.symvers PENDING SCCS @@ -73,7 +69,9 @@ autoconf.h* bbootsect bin2c binkernel.spec +binoffset bootsect +bounds.h bsetup btfixupprep build @@ -89,39 +87,36 @@ config_data.h* config_data.gz* conmakehash consolemap_deftbl.c* +cpustr.h crc32table.h* cscope.* -defkeymap.c* +defkeymap.c devlist.h* docproc -dummy_sym.c* elf2ecoff elfconfig.h* -filelist fixdep fore200e_mkfirm fore200e_pca_fw.c* gconf gen-devlist -gen-kdb_cmds.c* gen_crc32table gen_init_cpio genksyms -gentbl *_gray256.c +ihex2fw ikconfig.h* initramfs_data.cpio initramfs_data.cpio.gz initramfs_list kallsyms kconfig -kconfig.tk -keywords.c* +keywords.c ksym.c* ksym.h* kxgettext lkc_defs.h -lex.c* +lex.c lex.*.c logo_*.c logo_*_clut224.c @@ -130,7 +125,6 @@ lxdialog mach-types mach-types.h machtypes.h -make_times_h map maui_boot.h mconf @@ -138,6 +132,7 @@ miboot* mk_elfconfig mkboot mkbugboot +mkcpustr mkdep mkprep mktables @@ -145,11 +140,12 @@ mktree modpost modules.order modversions.h* +ncscope.* offset.h offsets.h oui.c* -parse.c* -parse.h* +parse.c +parse.h patches* pca200e.bin pca200e_ecd.bin2 @@ -157,7 +153,7 @@ piggy.gz piggyback pnmtologo ppc_defs.h* -promcon_tbl.c* +promcon_tbl.c pss_boot.h qconf raid6altivec*.c @@ -168,27 +164,38 @@ series setup setup.bin setup.elf -sim710_d.h* sImage sm_tbl* split-include +syscalltab.h tags tftpboot.img timeconst.h times.h* -tkparse trix_boot.h utsrelease.h* +vdso-syms.lds vdso.lds +vdso32-int80-syms.lds +vdso32-syms.lds +vdso32-syscall-syms.lds +vdso32-sysenter-syms.lds +vdso32.lds +vdso32.so.dbg +vdso64.lds +vdso64.so.dbg version.h* vmlinux vmlinux-* vmlinux.aout -vmlinux*.lds* -vmlinux*.scr +vmlinux.lds vsyscall.lds +vsyscall_32.lds wanxlfw.inc uImage unifdef +wakeup.bin +wakeup.elf +wakeup.lds zImage* zconf.hash.c diff --git a/Documentation/fb/intelfb.txt b/Documentation/fb/intelfb.txt index 27a3160650a4..dd9e944ea628 100644 --- a/Documentation/fb/intelfb.txt +++ b/Documentation/fb/intelfb.txt @@ -14,6 +14,7 @@ graphics devices. These would include: Intel 915GM Intel 945G Intel 945GM + Intel 945GME Intel 965G Intel 965GM diff --git a/Documentation/fb/uvesafb.txt b/Documentation/fb/uvesafb.txt index bcfc233a0080..7ac3c4078ff9 100644 --- a/Documentation/fb/uvesafb.txt +++ b/Documentation/fb/uvesafb.txt @@ -52,7 +52,7 @@ are either given on the kernel command line or as module parameters, e.g.: video=uvesafb:1024x768-32,mtrr:3,ywrap (compiled into the kernel) - # modprobe uvesafb mode=1024x768-32 mtrr=3 scroll=ywrap (module) + # modprobe uvesafb mode_option=1024x768-32 mtrr=3 scroll=ywrap (module) Accepted options: @@ -105,7 +105,7 @@ vtotal:n <mode> The mode you want to set, in the standard modedb format. Refer to modedb.txt for a detailed description. When uvesafb is compiled as a module, the mode string should be provided as a value of the - 'mode' option. + 'mode_option' option. vbemode:x Force the use of VBE mode x. The mode will only be set if it's diff --git a/Documentation/fb/viafb.modes b/Documentation/fb/viafb.modes new file mode 100644 index 000000000000..02e5b487f00e --- /dev/null +++ b/Documentation/fb/viafb.modes @@ -0,0 +1,870 @@ +# +# +# These data are based on the CRTC parameters in +# +# VIA Integration Graphics Chip +# (C) 2004 VIA Technologies Inc. +# + +# +# 640x480, 60 Hz, Non-Interlaced (25.175 MHz dotclock) +# +# Horizontal Vertical +# Resolution 640 480 +# Scan Frequency 31.469 kHz 59.94 Hz +# Sync Width 3.813 us 0.064 ms +# 12 chars 2 lines +# Front Porch 0.636 us 0.318 ms +# 2 chars 10 lines +# Back Porch 1.907 us 1.048 ms +# 6 chars 33 lines +# Active Time 25.422 us 15.253 ms +# 80 chars 480 lines +# Blank Time 6.356 us 1.430 ms +# 20 chars 45 lines +# Polarity negative negative +# + +mode "640x480-60" +# D: 25.175 MHz, H: 31.469 kHz, V: 59.94 Hz + geometry 640 480 640 480 32 + timings 39722 48 16 33 10 96 2 endmode mode "480x640-60" +# D: 24.823 MHz, H: 39.780 kHz, V: 60.00 Hz + geometry 480 640 480 640 32 timings 39722 72 24 19 1 48 3 endmode +# +# 640x480, 75 Hz, Non-Interlaced (31.50 MHz dotclock) +# +# Horizontal Vertical +# Resolution 640 480 +# Scan Frequency 37.500 kHz 75.00 Hz +# Sync Width 2.032 us 0.080 ms +# 8 chars 3 lines +# Front Porch 0.508 us 0.027 ms +# 2 chars 1 lines +# Back Porch 3.810 us 0.427 ms +# 15 chars 16 lines +# Active Time 20.317 us 12.800 ms +# 80 chars 480 lines +# Blank Time 6.349 us 0.533 ms +# 25 chars 20 lines +# Polarity negative negative +# + mode "640x480-75" +# D: 31.50 MHz, H: 37.500 kHz, V: 75.00 Hz + geometry 640 480 640 480 32 timings 31747 120 16 16 1 64 3 endmode +# +# 640x480, 85 Hz, Non-Interlaced (36.000 MHz dotclock) +# +# Horizontal Vertical +# Resolution 640 480 +# Scan Frequency 43.269 kHz 85.00 Hz +# Sync Width 1.556 us 0.069 ms +# 7 chars 3 lines +# Front Porch 1.556 us 0.023 ms +# 7 chars 1 lines +# Back Porch 2.222 us 0.578 ms +# 10 chars 25 lines +# Active Time 17.778 us 11.093 ms +# 80 chars 480 lines +# Blank Time 5.333 us 0.670 ms +# 24 chars 29 lines +# Polarity negative negative +# + mode "640x480-85" +# D: 36.000 MHz, H: 43.269 kHz, V: 85.00 Hz + geometry 640 480 640 480 32 timings 27777 80 56 25 1 56 3 endmode +# +# 640x480, 100 Hz, Non-Interlaced (43.163 MHz dotclock) +# +# Horizontal Vertical +# Resolution 640 480 +# Scan Frequency 50.900 kHz 100.00 Hz +# Sync Width 1.483 us 0.058 ms +# 8 chars 3 lines +# Front Porch 0.927 us 0.019 ms +# 5 chars 1 lines +# Back Porch 2.409 us 0.475 ms +# 13 chars 25 lines +# Active Time 14.827 us 9.430 ms +# 80 chars 480 lines +# Blank Time 4.819 us 0.570 ms +# 26 chars 29 lines +# Polarity positive positive +# + mode "640x480-100" +# D: 43.163 MHz, H: 50.900 kHz, V: 100.00 Hz + geometry 640 480 640 480 32 timings 23168 104 40 25 1 64 3 endmode +# +# 640x480, 120 Hz, Non-Interlaced (52.406 MHz dotclock) +# +# Horizontal Vertical +# Resolution 640 480 +# Scan Frequency 61.800 kHz 120.00 Hz +# Sync Width 1.221 us 0.048 ms +# 8 chars 3 lines +# Front Porch 0.763 us 0.016 ms +# 5 chars 1 lines +# Back Porch 1.984 us 0.496 ms +# 13 chars 31 lines +# Active Time 12.212 us 7.767 ms +# 80 chars 480 lines +# Blank Time 3.969 us 0.566 ms +# 26 chars 35 lines +# Polarity positive positive +# + mode "640x480-120" +# D: 52.406 MHz, H: 61.800 kHz, V: 120.00 Hz + geometry 640 480 640 480 32 timings 19081 104 40 31 1 64 3 endmode +# +# 720x480, 60 Hz, Non-Interlaced (26.880 MHz dotclock) +# +# Horizontal Vertical +# Resolution 720 480 +# Scan Frequency 30.000 kHz 60.241 Hz +# Sync Width 2.679 us 0.099 ms +# 9 chars 3 lines +# Front Porch 0.595 us 0.033 ms +# 2 chars 1 lines +# Back Porch 3.274 us 0.462 ms +# 11 chars 14 lines +# Active Time 26.786 us 16.000 ms +# 90 chars 480 lines +# Blank Time 6.548 us 0.600 ms +# 22 chars 18 lines +# Polarity positive positive +# + mode "720x480-60" +# D: 26.880 MHz, H: 30.000 kHz, V: 60.24 Hz + geometry 720 480 720 480 32 timings 37202 88 16 14 1 72 3 endmode +# +# 800x480, 60 Hz, Non-Interlaced (29.581 MHz dotclock) +# +# Horizontal Vertical +# Resolution 800 480 +# Scan Frequency 29.892 kHz 60.00 Hz +# Sync Width 2.704 us 100.604 us +# 10 chars 3 lines +# Front Porch 0.541 us 33.535 us +# 2 chars 1 lines +# Back Porch 3.245 us 435.949 us +# 12 chars 13 lines +# Active Time 27.044 us 16.097 ms +# 100 chars 480 lines +# Blank Time 6.491 us 0.570 ms +# 24 chars 17 lines +# Polarity positive positive +# + mode "800x480-60" +# D: 29.500 MHz, H: 29.738 kHz, V: 60.00 Hz + geometry 800 480 800 480 32 timings 33805 96 24 10 3 72 7 endmode +# +# 720x576, 60 Hz, Non-Interlaced (32.668 MHz dotclock) +# +# Horizontal Vertical +# Resolution 720 576 +# Scan Frequency 35.820 kHz 60.00 Hz +# Sync Width 2.204 us 0.083 ms +# 9 chars 3 lines +# Front Porch 0.735 us 0.027 ms +# 3 chars 1 lines +# Back Porch 2.939 us 0.459 ms +# 12 chars 17 lines +# Active Time 22.040 us 16.080 ms +# 90 chars 476 lines +# Blank Time 5.877 us 0.586 ms +# 24 chars 21 lines +# Polarity positive positive +# + mode "720x576-60" +# D: 32.668 MHz, H: 35.820 kHz, V: 60.00 Hz + geometry 720 576 720 576 32 timings 30611 96 24 17 1 72 3 endmode +# +# 800x600, 60 Hz, Non-Interlaced (40.00 MHz dotclock) +# +# Horizontal Vertical +# Resolution 800 600 +# Scan Frequency 37.879 kHz 60.32 Hz +# Sync Width 3.200 us 0.106 ms +# 16 chars 4 lines +# Front Porch 1.000 us 0.026 ms +# 5 chars 1 lines +# Back Porch 2.200 us 0.607 ms +# 11 chars 23 lines +# Active Time 20.000 us 15.840 ms +# 100 chars 600 lines +# Blank Time 6.400 us 0.739 ms +# 32 chars 28 lines +# Polarity positive positive +# + mode "800x600-60" +# D: 40.00 MHz, H: 37.879 kHz, V: 60.32 Hz + geometry 800 600 800 600 32 + timings 25000 88 40 23 1 128 4 hsync high vsync high endmode +# +# 800x600, 75 Hz, Non-Interlaced (49.50 MHz dotclock) +# +# Horizontal Vertical +# Resolution 800 600 +# Scan Frequency 46.875 kHz 75.00 Hz +# Sync Width 1.616 us 0.064 ms +# 10 chars 3 lines +# Front Porch 0.323 us 0.021 ms +# 2 chars 1 lines +# Back Porch 3.232 us 0.448 ms +# 20 chars 21 lines +# Active Time 16.162 us 12.800 ms +# 100 chars 600 lines +# Blank Time 5.172 us 0.533 ms +# 32 chars 25 lines +# Polarity positive positive +# + mode "800x600-75" +# D: 49.50 MHz, H: 46.875 kHz, V: 75.00 Hz + geometry 800 600 800 600 32 + timings 20203 160 16 21 1 80 3 hsync high vsync high endmode +# +# 800x600, 85 Hz, Non-Interlaced (56.25 MHz dotclock) +# +# Horizontal Vertical +# Resolution 800 600 +# Scan Frequency 53.674 kHz 85.061 Hz +# Sync Width 1.138 us 0.056 ms +# 8 chars 3 lines +# Front Porch 0.569 us 0.019 ms +# 4 chars 1 lines +# Back Porch 2.702 us 0.503 ms +# 19 chars 27 lines +# Active Time 14.222 us 11.179 ms +# 100 chars 600 lines +# Blank Time 4.409 us 0.578 ms +# 31 chars 31 lines +# Polarity positive positive +# + mode "800x600-85" +# D: 56.25 MHz, H: 53.674 kHz, V: 85.061 Hz + geometry 800 600 800 600 32 + timings 17777 152 32 27 1 64 3 hsync high vsync high endmode +# +# 800x600, 100 Hz, Non-Interlaced (67.50 MHz dotclock) +# +# Horizontal Vertical +# Resolution 800 600 +# Scan Frequency 62.500 kHz 100.00 Hz +# Sync Width 0.948 us 0.064 ms +# 8 chars 4 lines +# Front Porch 0.000 us 0.112 ms +# 0 chars 7 lines +# Back Porch 3.200 us 0.224 ms +# 27 chars 14 lines +# Active Time 11.852 us 9.600 ms +# 100 chars 600 lines +# Blank Time 4.148 us 0.400 ms +# 35 chars 25 lines +# Polarity positive positive +# + mode "800x600-100" +# D: 67.50 MHz, H: 62.500 kHz, V: 100.00 Hz + geometry 800 600 800 600 32 + timings 14667 216 0 14 7 64 4 hsync high vsync high endmode +# +# 800x600, 120 Hz, Non-Interlaced (83.950 MHz dotclock) +# +# Horizontal Vertical +# Resolution 800 600 +# Scan Frequency 77.160 kHz 120.00 Hz +# Sync Width 1.048 us 0.039 ms +# 11 chars 3 lines +# Front Porch 0.667 us 0.013 ms +# 7 chars 1 lines +# Back Porch 1.715 us 0.507 ms +# 18 chars 39 lines +# Active Time 9.529 us 7.776 ms +# 100 chars 600 lines +# Blank Time 3.431 us 0.557 ms +# 36 chars 43 lines +# Polarity positive positive +# + mode "800x600-120" +# D: 83.950 MHz, H: 77.160 kHz, V: 120.00 Hz + geometry 800 600 800 600 32 + timings 11912 144 56 39 1 88 3 hsync high vsync high endmode +# +# 848x480, 60 Hz, Non-Interlaced (31.490 MHz dotclock) +# +# Horizontal Vertical +# Resolution 848 480 +# Scan Frequency 29.820 kHz 60.00 Hz +# Sync Width 2.795 us 0.099 ms +# 11 chars 3 lines +# Front Porch 0.508 us 0.033 ms +# 2 chars 1 lines +# Back Porch 3.303 us 0.429 ms +# 13 chars 13 lines +# Active Time 26.929 us 16.097 ms +# 106 chars 480 lines +# Blank Time 6.605 us 0.570 ms +# 26 chars 17 lines +# Polarity positive positive +# + mode "848x480-60" +# D: 31.500 MHz, H: 29.830 kHz, V: 60.00 Hz + geometry 848 480 848 480 32 + timings 31746 104 24 12 3 80 5 hsync high vsync high endmode +# +# 856x480, 60 Hz, Non-Interlaced (31.728 MHz dotclock) +# +# Horizontal Vertical +# Resolution 856 480 +# Scan Frequency 29.820 kHz 60.00 Hz +# Sync Width 2.774 us 0.099 ms +# 11 chars 3 lines +# Front Porch 0.504 us 0.033 ms +# 2 chars 1 lines +# Back Porch 3.728 us 0.429 ms +# 13 chars 13 lines +# Active Time 26.979 us 16.097 ms +# 107 chars 480 lines +# Blank Time 6.556 us 0.570 ms +# 26 chars 17 lines +# Polarity positive positive +# + mode "856x480-60" +# D: 31.728 MHz, H: 29.820 kHz, V: 60.00 Hz + geometry 856 480 856 480 32 + timings 31518 104 16 13 1 88 3 + hsync high vsync high endmode mode "960x600-60" +# D: 45.250 MHz, H: 37.212 kHz, V: 60.00 Hz + geometry 960 600 960 600 32 timings 22099 128 32 15 3 96 6 endmode +# +# 1000x600, 60 Hz, Non-Interlaced (48.068 MHz dotclock) +# +# Horizontal Vertical +# Resolution 1000 600 +# Scan Frequency 37.320 kHz 60.00 Hz +# Sync Width 2.164 us 0.080 ms +# 13 chars 3 lines +# Front Porch 0.832 us 0.027 ms +# 5 chars 1 lines +# Back Porch 2.996 us 0.483 ms +# 18 chars 18 lines +# Active Time 20.804 us 16.077 ms +# 125 chars 600 lines +# Blank Time 5.991 us 0.589 ms +# 36 chars 22 lines +# Polarity negative positive +# + mode "1000x600-60" +# D: 48.068 MHz, H: 37.320 kHz, V: 60.00 Hz + geometry 1000 600 1000 600 32 + timings 20834 144 40 18 1 104 3 endmode mode "1024x576-60" +# D: 46.996 MHz, H: 35.820 kHz, V: 60.00 Hz + geometry 1024 576 1024 576 32 + timings 21278 144 40 17 1 104 3 endmode mode "1024x600-60" +# D: 48.964 MHz, H: 37.320 kHz, V: 60.00 Hz + geometry 1024 600 1024 600 32 + timings 20461 144 40 18 1 104 3 endmode mode "1088x612-60" +# D: 52.952 MHz, H: 38.040 kHz, V: 60.00 Hz + geometry 1088 612 1088 612 32 timings 18877 152 48 16 3 104 5 endmode +# +# 1024x512, 60 Hz, Non-Interlaced (41.291 MHz dotclock) +# +# Horizontal Vertical +# Resolution 1024 512 +# Scan Frequency 31.860 kHz 60.00 Hz +# Sync Width 2.519 us 0.094 ms +# 13 chars 3 lines +# Front Porch 0.775 us 0.031 ms +# 4 chars 1 lines +# Back Porch 3.294 us 0.465 ms +# 17 chars 15 lines +# Active Time 24.800 us 16.070 ms +# 128 chars 512 lines +# Blank Time 6.587 us 0.596 ms +# 34 chars 19 lines +# Polarity positive positive +# + mode "1024x512-60" +# D: 41.291 MHz, H: 31.860 kHz, V: 60.00 Hz + geometry 1024 512 1024 512 32 + timings 24218 126 32 15 1 104 3 hsync high vsync high endmode +# +# 1024x600, 60 Hz, Non-Interlaced (48.875 MHz dotclock) +# +# Horizontal Vertical +# Resolution 1024 768 +# Scan Frequency 37.252 kHz 60.00 Hz +# Sync Width 2.128 us 80.532us +# 13 chars 3 lines +# Front Porch 0.818 us 26.844 us +# 5 chars 1 lines +# Back Porch 2.946 us 483.192 us +# 18 chars 18 lines +# Active Time 20.951 us 16.697 ms +# 128 chars 622 lines +# Blank Time 5.893 us 0.591 ms +# 36 chars 22 lines +# Polarity negative positive +# +#mode "1024x600-60" +# # D: 48.875 MHz, H: 37.252 kHz, V: 60.00 Hz +# geometry 1024 600 1024 600 32 +# timings 20460 144 40 18 1 104 3 +# endmode +# +# 1024x768, 60 Hz, Non-Interlaced (65.00 MHz dotclock) +# +# Horizontal Vertical +# Resolution 1024 768 +# Scan Frequency 48.363 kHz 60.00 Hz +# Sync Width 2.092 us 0.124 ms +# 17 chars 6 lines +# Front Porch 0.369 us 0.062 ms +# 3 chars 3 lines +# Back Porch 2.462 us 0.601 ms +# 20 chars 29 lines +# Active Time 15.754 us 15.880 ms +# 128 chars 768 lines +# Blank Time 4.923 us 0.786 ms +# 40 chars 38 lines +# Polarity negative negative +# + mode "1024x768-60" +# D: 65.00 MHz, H: 48.363 kHz, V: 60.00 Hz + geometry 1024 768 1024 768 32 timings 15385 160 24 29 3 136 6 endmode +# +# 1024x768, 75 Hz, Non-Interlaced (78.75 MHz dotclock) +# +# Horizontal Vertical +# Resolution 1024 768 +# Scan Frequency 60.023 kHz 75.03 Hz +# Sync Width 1.219 us 0.050 ms +# 12 chars 3 lines +# Front Porch 0.203 us 0.017 ms +# 2 chars 1 lines +# Back Porch 2.235 us 0.466 ms +# 22 chars 28 lines +# Active Time 13.003 us 12.795 ms +# 128 chars 768 lines +# Blank Time 3.657 us 0.533 ms +# 36 chars 32 lines +# Polarity positive positive +# + mode "1024x768-75" +# D: 78.75 MHz, H: 60.023 kHz, V: 75.03 Hz + geometry 1024 768 1024 768 32 + timings 12699 176 16 28 1 96 3 hsync high vsync high endmode +# +# 1024x768, 85 Hz, Non-Interlaced (94.50 MHz dotclock) +# +# Horizontal Vertical +# Resolution 1024 768 +# Scan Frequency 68.677 kHz 85.00 Hz +# Sync Width 1.016 us 0.044 ms +# 12 chars 3 lines +# Front Porch 0.508 us 0.015 ms +# 6 chars 1 lines +# Back Porch 2.201 us 0.524 ms +# 26 chars 36 lines +# Active Time 10.836 us 11.183 ms +# 128 chars 768 lines +# Blank Time 3.725 us 0.582 ms +# 44 chars 40 lines +# Polarity positive positive +# + mode "1024x768-85" +# D: 94.50 MHz, H: 68.677 kHz, V: 85.00 Hz + geometry 1024 768 1024 768 32 + timings 10582 208 48 36 1 96 3 hsync high vsync high endmode +# +# 1024x768, 100 Hz, Non-Interlaced (110.0 MHz dotclock) +# +# Horizontal Vertical +# Resolution 1024 768 +# Scan Frequency 79.023 kHz 99.78 Hz +# Sync Width 0.800 us 0.101 ms +# 11 chars 8 lines +# Front Porch 0.000 us 0.000 ms +# 0 chars 0 lines +# Back Porch 2.545 us 0.202 ms +# 35 chars 16 lines +# Active Time 9.309 us 9.719 ms +# 128 chars 768 lines +# Blank Time 3.345 us 0.304 ms +# 46 chars 24 lines +# Polarity negative negative +# + mode "1024x768-100" +# D: 113.3 MHz, H: 79.023 kHz, V: 99.78 Hz + geometry 1024 768 1024 768 32 + timings 8825 280 0 16 0 88 8 endmode mode "1152x720-60" +# D: 66.750 MHz, H: 44.859 kHz, V: 60.00 Hz + geometry 1152 720 1152 720 32 timings 14981 168 56 19 3 112 6 endmode +# +# 1152x864, 75 Hz, Non-Interlaced (110.0 MHz dotclock) +# +# Horizontal Vertical +# Resolution 1152 864 +# Scan Frequency 75.137 kHz 74.99 Hz +# Sync Width 1.309 us 0.106 ms +# 18 chars 8 lines +# Front Porch 0.245 us 0.599 ms +# 3 chars 45 lines +# Back Porch 1.282 us 1.132 ms +# 18 chars 85 lines +# Active Time 10.473 us 11.499 ms +# 144 chars 864 lines +# Blank Time 2.836 us 1.837 ms +# 39 chars 138 lines +# Polarity positive positive +# + mode "1152x864-75" +# D: 110.0 MHz, H: 75.137 kHz, V: 74.99 Hz + geometry 1152 864 1152 864 32 + timings 9259 144 24 85 45 144 8 + hsync high vsync high endmode mode "1200x720-60" +# D: 70.184 MHz, H: 44.760 kHz, V: 60.00 Hz + geometry 1200 720 1200 720 32 + timings 14253 184 28 22 1 128 3 endmode mode "1280x600-60" +# D: 61.503 MHz, H: 37.320 kHz, V: 60.00 Hz + geometry 1280 600 1280 600 32 + timings 16260 184 28 18 1 128 3 endmode mode "1280x720-50" +# D: 60.466 MHz, H: 37.050 kHz, V: 50.00 Hz + geometry 1280 720 1280 720 32 + timings 16538 176 48 17 1 128 3 endmode mode "1280x768-50" +# D: 65.178 MHz, H: 39.550 kHz, V: 50.00 Hz + geometry 1280 768 1280 768 32 timings 15342 184 28 19 1 128 3 endmode +# +# 1280x768, 60 Hz, Non-Interlaced (80.136 MHz dotclock) +# +# Horizontal Vertical +# Resolution 1280 768 +# Scan Frequency 47.700 kHz 60.00 Hz +# Sync Width 1.697 us 0.063 ms +# 17 chars 3 lines +# Front Porch 0.799 us 0.021 ms +# 8 chars 1 lines +# Back Porch 2.496 us 0.483 ms +# 25 chars 23 lines +# Active Time 15.973 us 16.101 ms +# 160 chars 768 lines +# Blank Time 4.992 us 0.566 ms +# 50 chars 27 lines +# Polarity positive positive +# + mode "1280x768-60" +# D: 80.13 MHz, H: 47.700 kHz, V: 60.00 Hz + geometry 1280 768 1280 768 32 + timings 12480 200 48 23 1 126 3 hsync high vsync high endmode +# +# 1280x800, 60 Hz, Non-Interlaced (83.375 MHz dotclock) +# +# Horizontal Vertical +# Resolution 1280 800 +# Scan Frequency 49.628 kHz 60.00 Hz +# Sync Width 1.631 us 60.450 us +# 17 chars 3 lines +# Front Porch 0.768 us 20.15 us +# 8 chars 1 lines +# Back Porch 2.399 us 0.483 ms +# 25 chars 24 lines +# Active Time 15.352 us 16.120 ms +# 160 chars 800 lines +# Blank Time 4.798 us 0.564 ms +# 50 chars 28 lines +# Polarity negtive positive +# + mode "1280x800-60" +# D: 83.500 MHz, H: 49.702 kHz, V: 60.00 Hz + geometry 1280 800 1280 800 32 timings 11994 200 72 22 3 128 6 endmode +# +# 1280x960, 60 Hz, Non-Interlaced (108.00 MHz dotclock) +# +# Horizontal Vertical +# Resolution 1280 960 +# Scan Frequency 60.000 kHz 60.00 Hz +# Sync Width 1.037 us 0.050 ms +# 14 chars 3 lines +# Front Porch 0.889 us 0.017 ms +# 12 chars 1 lines +# Back Porch 2.889 us 0.600 ms +# 39 chars 36 lines +# Active Time 11.852 us 16.000 ms +# 160 chars 960 lines +# Blank Time 4.815 us 0.667 ms +# 65 chars 40 lines +# Polarity positive positive +# + mode "1280x960-60" +# D: 108.00 MHz, H: 60.000 kHz, V: 60.00 Hz + geometry 1280 960 1280 960 32 + timings 9259 312 96 36 1 112 3 hsync high vsync high endmode +# +# 1280x1024, 60 Hz, Non-Interlaced (108.00 MHz dotclock) +# +# Horizontal Vertical +# Resolution 1280 1024 +# Scan Frequency 63.981 kHz 60.02 Hz +# Sync Width 1.037 us 0.047 ms +# 14 chars 3 lines +# Front Porch 0.444 us 0.015 ms +# 6 chars 1 lines +# Back Porch 2.297 us 0.594 ms +# 31 chars 38 lines +# Active Time 11.852 us 16.005 ms +# 160 chars 1024 lines +# Blank Time 3.778 us 0.656 ms +# 51 chars 42 lines +# Polarity positive positive +# + mode "1280x1024-60" +# D: 108.00 MHz, H: 63.981 kHz, V: 60.02 Hz + geometry 1280 1024 1280 1024 32 + timings 9260 248 48 38 1 112 3 hsync high vsync high endmode +# +# 1280x1024, 75 Hz, Non-Interlaced (135.00 MHz dotclock) +# +# Horizontal Vertical +# Resolution 1280 1024 +# Scan Frequency 79.976 kHz 75.02 Hz +# Sync Width 1.067 us 0.038 ms +# 18 chars 3 lines +# Front Porch 0.119 us 0.012 ms +# 2 chars 1 lines +# Back Porch 1.837 us 0.475 ms +# 31 chars 38 lines +# Active Time 9.481 us 12.804 ms +# 160 chars 1024 lines +# Blank Time 3.022 us 0.525 ms +# 51 chars 42 lines +# Polarity positive positive +# + mode "1280x1024-75" +# D: 135.00 MHz, H: 79.976 kHz, V: 75.02 Hz + geometry 1280 1024 1280 1024 32 + timings 7408 248 16 38 1 144 3 hsync high vsync high endmode +# +# 1280x1024, 85 Hz, Non-Interlaced (157.50 MHz dotclock) +# +# Horizontal Vertical +# Resolution 1280 1024 +# Scan Frequency 91.146 kHz 85.02 Hz +# Sync Width 1.016 us 0.033 ms +# 20 chars 3 lines +# Front Porch 0.406 us 0.011 ms +# 8 chars 1 lines +# Back Porch 1.422 us 0.483 ms +# 28 chars 44 lines +# Active Time 8.127 us 11.235 ms +# 160 chars 1024 lines +# Blank Time 2.844 us 0.527 ms +# 56 chars 48 lines +# Polarity positive positive +# + mode "1280x1024-85" +# D: 157.50 MHz, H: 91.146 kHz, V: 85.02 Hz + geometry 1280 1024 1280 1024 32 + timings 6349 224 64 44 1 160 3 + hsync high vsync high endmode mode "1440x900-60" +# D: 106.500 MHz, H: 55.935 kHz, V: 60.00 Hz + geometry 1440 900 1440 900 32 + timings 9390 232 80 25 3 152 6 + hsync high vsync high endmode mode "1440x900-75" +# D: 136.750 MHz, H: 70.635 kHz, V: 75.00 Hz + geometry 1440 900 1440 900 32 + timings 7315 248 96 33 3 152 6 hsync high vsync high endmode +# +# 1440x1050, 60 Hz, Non-Interlaced (125.10 MHz dotclock) +# +# Horizontal Vertical +# Resolution 1440 1050 +# Scan Frequency 65.220 kHz 60.00 Hz +# Sync Width 1.204 us 0.046 ms +# 19 chars 3 lines +# Front Porch 0.760 us 0.015 ms +# 12 chars 1 lines +# Back Porch 1.964 us 0.495 ms +# 31 chars 33 lines +# Active Time 11.405 us 16.099 ms +# 180 chars 1050 lines +# Blank Time 3.928 us 0.567 ms +# 62 chars 37 lines +# Polarity positive positive +# + mode "1440x1050-60" +# D: 125.10 MHz, H: 65.220 kHz, V: 60.00 Hz + geometry 1440 1050 1440 1050 32 + timings 7993 248 96 33 1 152 3 + hsync high vsync high endmode mode "1600x900-60" +# D: 118.250 MHz, H: 55.990 kHz, V: 60.00 Hz + geometry 1600 900 1600 900 32 + timings 8415 256 88 26 3 168 5 endmode mode "1600x1024-60" +# D: 136.358 MHz, H: 63.600 kHz, V: 60.00 Hz + geometry 1600 1024 1600 1024 32 timings 7315 272 104 32 1 168 3 endmode +# +# 1600x1200, 60 Hz, Non-Interlaced (156.00 MHz dotclock) +# +# Horizontal Vertical +# Resolution 1600 1200 +# Scan Frequency 76.200 kHz 60.00 Hz +# Sync Width 1.026 us 0.105 ms +# 20 chars 8 lines +# Front Porch 0.205 us 0.131 ms +# 4 chars 10 lines +# Back Porch 1.636 us 0.682 ms +# 32 chars 52 lines +# Active Time 10.256 us 15.748 ms +# 200 chars 1200 lines +# Blank Time 2.872 us 0.866 ms +# 56 chars 66 lines +# Polarity negative negative +# + mode "1600x1200-60" +# D: 156.00 MHz, H: 76.200 kHz, V: 60.00 Hz + geometry 1600 1200 1600 1200 32 timings 6172 256 32 52 10 160 8 endmode +# +# 1600x1200, 75 Hz, Non-Interlaced (202.50 MHz dotclock) +# +# Horizontal Vertical +# Resolution 1600 1200 +# Scan Frequency 93.750 kHz 75.00 Hz +# Sync Width 0.948 us 0.032 ms +# 24 chars 3 lines +# Front Porch 0.316 us 0.011 ms +# 8 chars 1 lines +# Back Porch 1.501 us 0.491 ms +# 38 chars 46 lines +# Active Time 7.901 us 12.800 ms +# 200 chars 1200 lines +# Blank Time 2.765 us 0.533 ms +# 70 chars 50 lines +# Polarity positive positive +# + mode "1600x1200-75" +# D: 202.50 MHz, H: 93.750 kHz, V: 75.00 Hz + geometry 1600 1200 1600 1200 32 + timings 4938 304 64 46 1 192 3 + hsync high vsync high endmode mode "1680x1050-60" +# D: 146.250 MHz, H: 65.290 kHz, V: 59.954 Hz + geometry 1680 1050 1680 1050 32 + timings 6814 280 104 30 3 176 6 + hsync high vsync high endmode mode "1680x1050-75" +# D: 187.000 MHz, H: 82.306 kHz, V: 74.892 Hz + geometry 1680 1050 1680 1050 32 + timings 5348 296 120 40 3 176 6 + hsync high vsync high endmode mode "1792x1344-60" +# D: 202.975 MHz, H: 83.460 kHz, V: 60.00 Hz + geometry 1792 1344 1792 1344 32 + timings 4902 320 128 43 1 192 3 + hsync high vsync high endmode mode "1856x1392-60" +# D: 218.571 MHz, H: 86.460 kHz, V: 60.00 Hz + geometry 1856 1392 1856 1392 32 + timings 4577 336 136 45 1 200 3 + hsync high vsync high endmode mode "1920x1200-60" +# D: 193.250 MHz, H: 74.556 kHz, V: 60.00 Hz + geometry 1920 1200 1920 1200 32 + timings 5173 336 136 36 3 200 6 + hsync high vsync high endmode mode "1920x1440-60" +# D: 234.000 MHz, H:90.000 kHz, V: 60.00 Hz + geometry 1920 1440 1920 1440 32 + timings 4274 344 128 56 1 208 3 + hsync high vsync high endmode mode "1920x1440-75" +# D: 297.000 MHz, H:112.500 kHz, V: 75.00 Hz + geometry 1920 1440 1920 1440 32 + timings 3367 352 144 56 1 224 3 + hsync high vsync high endmode mode "2048x1536-60" +# D: 267.250 MHz, H: 95.446 kHz, V: 60.00 Hz + geometry 2048 1536 2048 1536 32 + timings 3742 376 152 49 3 224 4 hsync high vsync high endmode +# +# 1280x720, 60 Hz, Non-Interlaced (74.481 MHz dotclock) +# +# Horizontal Vertical +# Resolution 1280 720 +# Scan Frequency 44.760 kHz 60.00 Hz +# Sync Width 1.826 us 67.024 ms +# 17 chars 3 lines +# Front Porch 0.752 us 22.341 ms +# 7 chars 1 lines +# Back Porch 2.578 us 491.510 ms +# 24 chars 22 lines +# Active Time 17.186 us 16.086 ms +# 160 chars 720 lines +# Blank Time 5.156 us 0.581 ms +# 48 chars 26 lines +# Polarity negative negative +# + mode "1280x720-60" +# D: 74.481 MHz, H: 44.760 kHz, V: 60.00 Hz + geometry 1280 720 1280 720 32 timings 13426 192 64 22 1 136 3 endmode +# +# 1920x1080, 60 Hz, Non-Interlaced (172.798 MHz dotclock) +# +# Horizontal Vertical +# Resolution 1920 1080 +# Scan Frequency 67.080 kHz 60.00 Hz +# Sync Width 1.204 us 44.723 ms +# 26 chars 3 lines +# Front Porch 0.694 us 14.908 ms +# 15 chars 1 lines +# Back Porch 1.898 us 506.857 ms +# 41 chars 34 lines +# Active Time 11.111 us 16.100 ms +# 240 chars 1080 lines +# Blank Time 3.796 us 0.566 ms +# 82 chars 38 lines +# Polarity negative negative +# + mode "1920x1080-60" +# D: 74.481 MHz, H: 67.080 kHz, V: 60.00 Hz + geometry 1920 1080 1920 1080 32 timings 5787 328 120 34 1 208 3 endmode +# +# 1400x1050, 60 Hz, Non-Interlaced (122.61 MHz dotclock) +# +# Horizontal Vertical +# Resolution 1400 1050 +# Scan Frequency 65.218 kHz 59.99 Hz +# Sync Width 1.037 us 0.047 ms +# 19 chars 3 lines +# Front Porch 0.444 us 0.015 ms +# 11 chars 1 lines +# Back Porch 1.185 us 0.188 ms +# 30 chars 33 lines +# Active Time 12.963 us 16.411 ms +# 175 chars 1050 lines +# Blank Time 2.667 us 0.250 ms +# 60 chars 37 lines +# Polarity negative positive +# + mode "1400x1050-60" +# D: 122.750 MHz, H: 65.317 kHz, V: 59.99 Hz + geometry 1400 1050 1408 1050 32 + timings 8214 232 88 32 3 144 4 endmode mode "1400x1050-75" +# D: 156.000 MHz, H: 82.278 kHz, V: 74.867 Hz + geometry 1400 1050 1408 1050 32 timings 6410 248 104 42 3 144 4 endmode +# +# 1366x768, 60 Hz, Non-Interlaced (85.86 MHz dotclock) +# +# Horizontal Vertical +# Resolution 1366 768 +# Scan Frequency 47.700 kHz 60.00 Hz +# Sync Width 1.677 us 0.063 ms +# 18 chars 3 lines +# Front Porch 0.839 us 0.021 ms +# 9 chars 1 lines +# Back Porch 2.516 us 0.482 ms +# 27 chars 23 lines +# Active Time 15.933 us 16.101 ms +# 171 chars 768 lines +# Blank Time 5.031 us 0.566 ms +# 54 chars 27 lines +# Polarity negative positive +# + mode "1360x768-60" +# D: 84.750 MHz, H: 47.720 kHz, V: 60.00 Hz + geometry 1360 768 1360 768 32 + timings 11799 208 72 22 3 136 5 endmode mode "1366x768-60" +# D: 85.86 MHz, H: 47.700 kHz, V: 60.00 Hz + geometry 1366 768 1366 768 32 + timings 11647 216 72 23 1 144 3 endmode mode "1366x768-50" +# D: 69,924 MHz, H: 39.550 kHz, V: 50.00 Hz + geometry 1366 768 1366 768 32 timings 14301 200 56 19 1 144 3 endmode diff --git a/Documentation/fb/viafb.txt b/Documentation/fb/viafb.txt new file mode 100644 index 000000000000..67dbf442b0b6 --- /dev/null +++ b/Documentation/fb/viafb.txt @@ -0,0 +1,214 @@ + + VIA Integration Graphic Chip Console Framebuffer Driver + +[Platform] +----------------------- + The console framebuffer driver is for graphics chips of + VIA UniChrome Family(CLE266, PM800 / CN400 / CN300, + P4M800CE / P4M800Pro / CN700 / VN800, + CX700 / VX700, K8M890, P4M890, + CN896 / P4M900, VX800) + +[Driver features] +------------------------ + Device: CRT, LCD, DVI + + Support viafb_mode: + CRT: + 640x480(60, 75, 85, 100, 120 Hz), 720x480(60 Hz), + 720x576(60 Hz), 800x600(60, 75, 85, 100, 120 Hz), + 848x480(60 Hz), 856x480(60 Hz), 1024x512(60 Hz), + 1024x768(60, 75, 85, 100 Hz), 1152x864(75 Hz), + 1280x768(60 Hz), 1280x960(60 Hz), 1280x1024(60, 75, 85 Hz), + 1440x1050(60 Hz), 1600x1200(60, 75 Hz), 1280x720(60 Hz), + 1920x1080(60 Hz), 1400x1050(60 Hz), 800x480(60 Hz) + + color depth: 8 bpp, 16 bpp, 32 bpp supports. + + Support 2D hardware accelerator. + +[Using the viafb module] +-- -- -------------------- + Start viafb with default settings: + #modprobe viafb + + Start viafb with with user options: + #modprobe viafb viafb_mode=800x600 viafb_bpp=16 viafb_refresh=60 + viafb_active_dev=CRT+DVI viafb_dvi_port=DVP1 + viafb_mode1=1024x768 viafb_bpp=16 viafb_refresh1=60 + viafb_SAMM_ON=1 + + viafb_mode: + 640x480 (default) + 720x480 + 800x600 + 1024x768 + ...... + + viafb_bpp: + 8, 16, 32 (default:32) + + viafb_refresh: + 60, 75, 85, 100, 120 (default:60) + + viafb_lcd_dsp_method: + 0 : expansion (default) + 1 : centering + + viafb_lcd_mode: + 0 : LCD panel with LSB data format input (default) + 1 : LCD panel with MSB data format input + + viafb_lcd_panel_id: + 0 : Resolution: 640x480, Channel: single, Dithering: Enable + 1 : Resolution: 800x600, Channel: single, Dithering: Enable + 2 : Resolution: 1024x768, Channel: single, Dithering: Enable (default) + 3 : Resolution: 1280x768, Channel: single, Dithering: Enable + 4 : Resolution: 1280x1024, Channel: dual, Dithering: Enable + 5 : Resolution: 1400x1050, Channel: dual, Dithering: Enable + 6 : Resolution: 1600x1200, Channel: dual, Dithering: Enable + + 8 : Resolution: 800x480, Channel: single, Dithering: Enable + 9 : Resolution: 1024x768, Channel: dual, Dithering: Enable + 10: Resolution: 1024x768, Channel: single, Dithering: Disable + 11: Resolution: 1024x768, Channel: dual, Dithering: Disable + 12: Resolution: 1280x768, Channel: single, Dithering: Disable + 13: Resolution: 1280x1024, Channel: dual, Dithering: Disable + 14: Resolution: 1400x1050, Channel: dual, Dithering: Disable + 15: Resolution: 1600x1200, Channel: dual, Dithering: Disable + 16: Resolution: 1366x768, Channel: single, Dithering: Disable + 17: Resolution: 1024x600, Channel: single, Dithering: Enable + 18: Resolution: 1280x768, Channel: dual, Dithering: Enable + 19: Resolution: 1280x800, Channel: single, Dithering: Enable + + viafb_accel: + 0 : No 2D Hardware Acceleration + 1 : 2D Hardware Acceleration (default) + + viafb_SAMM_ON: + 0 : viafb_SAMM_ON disable (default) + 1 : viafb_SAMM_ON enable + + viafb_mode1: (secondary display device) + 640x480 (default) + 720x480 + 800x600 + 1024x768 + ... ... + + viafb_bpp1: (secondary display device) + 8, 16, 32 (default:32) + + viafb_refresh1: (secondary display device) + 60, 75, 85, 100, 120 (default:60) + + viafb_active_dev: + This option is used to specify active devices.(CRT, DVI, CRT+LCD...) + DVI stands for DVI or HDMI, E.g., If you want to enable HDMI, + set viafb_active_dev=DVI. In SAMM case, the previous of + viafb_active_dev is primary device, and the following is + secondary device. + + For example: + To enable one device, such as DVI only, we can use: + modprobe viafb viafb_active_dev=DVI + To enable two devices, such as CRT+DVI: + modprobe viafb viafb_active_dev=CRT+DVI; + + For DuoView case, we can use: + modprobe viafb viafb_active_dev=CRT+DVI + OR + modprobe viafb viafb_active_dev=DVI+CRT... + + For SAMM case: + If CRT is primary and DVI is secondary, we should use: + modprobe viafb viafb_active_dev=CRT+DVI viafb_SAMM_ON=1... + If DVI is primary and CRT is secondary, we should use: + modprobe viafb viafb_active_dev=DVI+CRT viafb_SAMM_ON=1... + + viafb_display_hardware_layout: + This option is used to specify display hardware layout for CX700 chip. + 1 : LCD only + 2 : DVI only + 3 : LCD+DVI (default) + 4 : LCD1+LCD2 (internal + internal) + 16: LCD1+ExternalLCD2 (internal + external) + + viafb_second_size: + This option is used to set second device memory size(MB) in SAMM case. + The minimal size is 16. + + viafb_platform_epia_dvi: + This option is used to enable DVI on EPIA - M + 0 : No DVI on EPIA - M (default) + 1 : DVI on EPIA - M + + viafb_bus_width: + When using 24 - Bit Bus Width Digital Interface, + this option should be set. + 12: 12-Bit LVDS or 12-Bit TMDS (default) + 24: 24-Bit LVDS or 24-Bit TMDS + + viafb_device_lcd_dualedge: + When using Dual Edge Panel, this option should be set. + 0 : No Dual Edge Panel (default) + 1 : Dual Edge Panel + + viafb_video_dev: + This option is used to specify video output devices(CRT, DVI, LCD) for + duoview case. + For example: + To output video on DVI, we should use: + modprobe viafb viafb_video_dev=DVI... + + viafb_lcd_port: + This option is used to specify LCD output port, + available values are "DVP0" "DVP1" "DFP_HIGHLOW" "DFP_HIGH" "DFP_LOW". + for external LCD + external DVI on CX700(External LCD is on DVP0), + we should use: + modprobe viafb viafb_lcd_port=DVP0... + +Notes: + 1. CRT may not display properly for DuoView CRT & DVI display at + the "640x480" PAL mode with DVI overscan enabled. + 2. SAMM stands for single adapter multi monitors. It is different from + multi-head since SAMM support multi monitor at driver layers, thus fbcon + layer doesn't even know about it; SAMM's second screen doesn't have a + device node file, thus a user mode application can't access it directly. + When SAMM is enabled, viafb_mode and viafb_mode1, viafb_bpp and + viafb_bpp1, viafb_refresh and viafb_refresh1 can be different. + 3. When console is depending on viafbinfo1, dynamically change resolution + and bpp, need to call VIAFB specified ioctl interface VIAFB_SET_DEVICE + instead of calling common ioctl function FBIOPUT_VSCREENINFO since + viafb doesn't support multi-head well, or it will cause screen crush. + 4. VX800 2D accelerator hasn't been supported in this driver yet. When + using driver on VX800, the driver will disable the acceleration + function as default. + + +[Configure viafb with "fbset" tool] +----------------------------------- + "fbset" is an inbox utility of Linux. + 1. Inquire current viafb information, type, + # fbset -i + + 2. Set various resolutions and viafb_refresh rates, + # fbset <resolution-vertical_sync> + + example, + # fbset "1024x768-75" + or + # fbset -g 1024 768 1024 768 32 + Check the file "/etc/fb.modes" to find display modes available. + + 3. Set the color depth, + # fbset -depth <value> + + example, + # fbset -depth 16 + +[Bootup with viafb]: +-------------------- + Add the following line to your grub.conf: + append = "video=viafb:viafb_mode=1024x768,viafb_bpp=32,viafb_refresh=85" + diff --git a/Documentation/feature-removal-schedule.txt b/Documentation/feature-removal-schedule.txt index 4d2566a7d168..f5f812daf9f4 100644 --- a/Documentation/feature-removal-schedule.txt +++ b/Documentation/feature-removal-schedule.txt @@ -294,6 +294,15 @@ Who: Jiri Slaby <jirislaby@gmail.com> --------------------------- +What: print_fn_descriptor_symbol() +When: October 2009 +Why: The %pF vsprintf format provides the same functionality in a + simpler way. print_fn_descriptor_symbol() is deprecated but + still present to give out-of-tree modules time to change. +Who: Bjorn Helgaas <bjorn.helgaas@hp.com> + +--------------------------- + What: /sys/o2cb symlink When: January 2010 Why: /sys/fs/o2cb is the proper location for this information - /sys/o2cb diff --git a/Documentation/filesystems/autofs4-mount-control.txt b/Documentation/filesystems/autofs4-mount-control.txt new file mode 100644 index 000000000000..c6341745df37 --- /dev/null +++ b/Documentation/filesystems/autofs4-mount-control.txt @@ -0,0 +1,393 @@ + +Miscellaneous Device control operations for the autofs4 kernel module +==================================================================== + +The problem +=========== + +There is a problem with active restarts in autofs (that is to say +restarting autofs when there are busy mounts). + +During normal operation autofs uses a file descriptor opened on the +directory that is being managed in order to be able to issue control +operations. Using a file descriptor gives ioctl operations access to +autofs specific information stored in the super block. The operations +are things such as setting an autofs mount catatonic, setting the +expire timeout and requesting expire checks. As is explained below, +certain types of autofs triggered mounts can end up covering an autofs +mount itself which prevents us being able to use open(2) to obtain a +file descriptor for these operations if we don't already have one open. + +Currently autofs uses "umount -l" (lazy umount) to clear active mounts +at restart. While using lazy umount works for most cases, anything that +needs to walk back up the mount tree to construct a path, such as +getcwd(2) and the proc file system /proc/<pid>/cwd, no longer works +because the point from which the path is constructed has been detached +from the mount tree. + +The actual problem with autofs is that it can't reconnect to existing +mounts. Immediately one thinks of just adding the ability to remount +autofs file systems would solve it, but alas, that can't work. This is +because autofs direct mounts and the implementation of "on demand mount +and expire" of nested mount trees have the file system mounted directly +on top of the mount trigger directory dentry. + +For example, there are two types of automount maps, direct (in the kernel +module source you will see a third type called an offset, which is just +a direct mount in disguise) and indirect. + +Here is a master map with direct and indirect map entries: + +/- /etc/auto.direct +/test /etc/auto.indirect + +and the corresponding map files: + +/etc/auto.direct: + +/automount/dparse/g6 budgie:/autofs/export1 +/automount/dparse/g1 shark:/autofs/export1 +and so on. + +/etc/auto.indirect: + +g1 shark:/autofs/export1 +g6 budgie:/autofs/export1 +and so on. + +For the above indirect map an autofs file system is mounted on /test and +mounts are triggered for each sub-directory key by the inode lookup +operation. So we see a mount of shark:/autofs/export1 on /test/g1, for +example. + +The way that direct mounts are handled is by making an autofs mount on +each full path, such as /automount/dparse/g1, and using it as a mount +trigger. So when we walk on the path we mount shark:/autofs/export1 "on +top of this mount point". Since these are always directories we can +use the follow_link inode operation to trigger the mount. + +But, each entry in direct and indirect maps can have offsets (making +them multi-mount map entries). + +For example, an indirect mount map entry could also be: + +g1 \ + / shark:/autofs/export5/testing/test \ + /s1 shark:/autofs/export/testing/test/s1 \ + /s2 shark:/autofs/export5/testing/test/s2 \ + /s1/ss1 shark:/autofs/export1 \ + /s2/ss2 shark:/autofs/export2 + +and a similarly a direct mount map entry could also be: + +/automount/dparse/g1 \ + / shark:/autofs/export5/testing/test \ + /s1 shark:/autofs/export/testing/test/s1 \ + /s2 shark:/autofs/export5/testing/test/s2 \ + /s1/ss1 shark:/autofs/export2 \ + /s2/ss2 shark:/autofs/export2 + +One of the issues with version 4 of autofs was that, when mounting an +entry with a large number of offsets, possibly with nesting, we needed +to mount and umount all of the offsets as a single unit. Not really a +problem, except for people with a large number of offsets in map entries. +This mechanism is used for the well known "hosts" map and we have seen +cases (in 2.4) where the available number of mounts are exhausted or +where the number of privileged ports available is exhausted. + +In version 5 we mount only as we go down the tree of offsets and +similarly for expiring them which resolves the above problem. There is +somewhat more detail to the implementation but it isn't needed for the +sake of the problem explanation. The one important detail is that these +offsets are implemented using the same mechanism as the direct mounts +above and so the mount points can be covered by a mount. + +The current autofs implementation uses an ioctl file descriptor opened +on the mount point for control operations. The references held by the +descriptor are accounted for in checks made to determine if a mount is +in use and is also used to access autofs file system information held +in the mount super block. So the use of a file handle needs to be +retained. + + +The Solution +============ + +To be able to restart autofs leaving existing direct, indirect and +offset mounts in place we need to be able to obtain a file handle +for these potentially covered autofs mount points. Rather than just +implement an isolated operation it was decided to re-implement the +existing ioctl interface and add new operations to provide this +functionality. + +In addition, to be able to reconstruct a mount tree that has busy mounts, +the uid and gid of the last user that triggered the mount needs to be +available because these can be used as macro substitution variables in +autofs maps. They are recorded at mount request time and an operation +has been added to retrieve them. + +Since we're re-implementing the control interface, a couple of other +problems with the existing interface have been addressed. First, when +a mount or expire operation completes a status is returned to the +kernel by either a "send ready" or a "send fail" operation. The +"send fail" operation of the ioctl interface could only ever send +ENOENT so the re-implementation allows user space to send an actual +status. Another expensive operation in user space, for those using +very large maps, is discovering if a mount is present. Usually this +involves scanning /proc/mounts and since it needs to be done quite +often it can introduce significant overhead when there are many entries +in the mount table. An operation to lookup the mount status of a mount +point dentry (covered or not) has also been added. + +Current kernel development policy recommends avoiding the use of the +ioctl mechanism in favor of systems such as Netlink. An implementation +using this system was attempted to evaluate its suitability and it was +found to be inadequate, in this case. The Generic Netlink system was +used for this as raw Netlink would lead to a significant increase in +complexity. There's no question that the Generic Netlink system is an +elegant solution for common case ioctl functions but it's not a complete +replacement probably because it's primary purpose in life is to be a +message bus implementation rather than specifically an ioctl replacement. +While it would be possible to work around this there is one concern +that lead to the decision to not use it. This is that the autofs +expire in the daemon has become far to complex because umount +candidates are enumerated, almost for no other reason than to "count" +the number of times to call the expire ioctl. This involves scanning +the mount table which has proved to be a big overhead for users with +large maps. The best way to improve this is try and get back to the +way the expire was done long ago. That is, when an expire request is +issued for a mount (file handle) we should continually call back to +the daemon until we can't umount any more mounts, then return the +appropriate status to the daemon. At the moment we just expire one +mount at a time. A Generic Netlink implementation would exclude this +possibility for future development due to the requirements of the +message bus architecture. + + +autofs4 Miscellaneous Device mount control interface +==================================================== + +The control interface is opening a device node, typically /dev/autofs. + +All the ioctls use a common structure to pass the needed parameter +information and return operation results: + +struct autofs_dev_ioctl { + __u32 ver_major; + __u32 ver_minor; + __u32 size; /* total size of data passed in + * including this struct */ + __s32 ioctlfd; /* automount command fd */ + + __u32 arg1; /* Command parameters */ + __u32 arg2; + + char path[0]; +}; + +The ioctlfd field is a mount point file descriptor of an autofs mount +point. It is returned by the open call and is used by all calls except +the check for whether a given path is a mount point, where it may +optionally be used to check a specific mount corresponding to a given +mount point file descriptor, and when requesting the uid and gid of the +last successful mount on a directory within the autofs file system. + +The fields arg1 and arg2 are used to communicate parameters and results of +calls made as described below. + +The path field is used to pass a path where it is needed and the size field +is used account for the increased structure length when translating the +structure sent from user space. + +This structure can be initialized before setting specific fields by using +the void function call init_autofs_dev_ioctl(struct autofs_dev_ioctl *). + +All of the ioctls perform a copy of this structure from user space to +kernel space and return -EINVAL if the size parameter is smaller than +the structure size itself, -ENOMEM if the kernel memory allocation fails +or -EFAULT if the copy itself fails. Other checks include a version check +of the compiled in user space version against the module version and a +mismatch results in a -EINVAL return. If the size field is greater than +the structure size then a path is assumed to be present and is checked to +ensure it begins with a "/" and is NULL terminated, otherwise -EINVAL is +returned. Following these checks, for all ioctl commands except +AUTOFS_DEV_IOCTL_VERSION_CMD, AUTOFS_DEV_IOCTL_OPENMOUNT_CMD and +AUTOFS_DEV_IOCTL_CLOSEMOUNT_CMD the ioctlfd is validated and if it is +not a valid descriptor or doesn't correspond to an autofs mount point +an error of -EBADF, -ENOTTY or -EINVAL (not an autofs descriptor) is +returned. + + +The ioctls +========== + +An example of an implementation which uses this interface can be seen +in autofs version 5.0.4 and later in file lib/dev-ioctl-lib.c of the +distribution tar available for download from kernel.org in directory +/pub/linux/daemons/autofs/v5. + +The device node ioctl operations implemented by this interface are: + + +AUTOFS_DEV_IOCTL_VERSION +------------------------ + +Get the major and minor version of the autofs4 device ioctl kernel module +implementation. It requires an initialized struct autofs_dev_ioctl as an +input parameter and sets the version information in the passed in structure. +It returns 0 on success or the error -EINVAL if a version mismatch is +detected. + + +AUTOFS_DEV_IOCTL_PROTOVER_CMD and AUTOFS_DEV_IOCTL_PROTOSUBVER_CMD +------------------------------------------------------------------ + +Get the major and minor version of the autofs4 protocol version understood +by loaded module. This call requires an initialized struct autofs_dev_ioctl +with the ioctlfd field set to a valid autofs mount point descriptor +and sets the requested version number in structure field arg1. These +commands return 0 on success or one of the negative error codes if +validation fails. + + +AUTOFS_DEV_IOCTL_OPENMOUNT and AUTOFS_DEV_IOCTL_CLOSEMOUNT +---------------------------------------------------------- + +Obtain and release a file descriptor for an autofs managed mount point +path. The open call requires an initialized struct autofs_dev_ioctl with +the the path field set and the size field adjusted appropriately as well +as the arg1 field set to the device number of the autofs mount. The +device number can be obtained from the mount options shown in +/proc/mounts. The close call requires an initialized struct +autofs_dev_ioct with the ioctlfd field set to the descriptor obtained +from the open call. The release of the file descriptor can also be done +with close(2) so any open descriptors will also be closed at process exit. +The close call is included in the implemented operations largely for +completeness and to provide for a consistent user space implementation. + + +AUTOFS_DEV_IOCTL_READY_CMD and AUTOFS_DEV_IOCTL_FAIL_CMD +-------------------------------------------------------- + +Return mount and expire result status from user space to the kernel. +Both of these calls require an initialized struct autofs_dev_ioctl +with the ioctlfd field set to the descriptor obtained from the open +call and the arg1 field set to the wait queue token number, received +by user space in the foregoing mount or expire request. The arg2 field +is set to the status to be returned. For the ready call this is always +0 and for the fail call it is set to the errno of the operation. + + +AUTOFS_DEV_IOCTL_SETPIPEFD_CMD +------------------------------ + +Set the pipe file descriptor used for kernel communication to the daemon. +Normally this is set at mount time using an option but when reconnecting +to a existing mount we need to use this to tell the autofs mount about +the new kernel pipe descriptor. In order to protect mounts against +incorrectly setting the pipe descriptor we also require that the autofs +mount be catatonic (see next call). + +The call requires an initialized struct autofs_dev_ioctl with the +ioctlfd field set to the descriptor obtained from the open call and +the arg1 field set to descriptor of the pipe. On success the call +also sets the process group id used to identify the controlling process +(eg. the owning automount(8) daemon) to the process group of the caller. + + +AUTOFS_DEV_IOCTL_CATATONIC_CMD +------------------------------ + +Make the autofs mount point catatonic. The autofs mount will no longer +issue mount requests, the kernel communication pipe descriptor is released +and any remaining waits in the queue released. + +The call requires an initialized struct autofs_dev_ioctl with the +ioctlfd field set to the descriptor obtained from the open call. + + +AUTOFS_DEV_IOCTL_TIMEOUT_CMD +---------------------------- + +Set the expire timeout for mounts withing an autofs mount point. + +The call requires an initialized struct autofs_dev_ioctl with the +ioctlfd field set to the descriptor obtained from the open call. + + +AUTOFS_DEV_IOCTL_REQUESTER_CMD +------------------------------ + +Return the uid and gid of the last process to successfully trigger a the +mount on the given path dentry. + +The call requires an initialized struct autofs_dev_ioctl with the path +field set to the mount point in question and the size field adjusted +appropriately as well as the arg1 field set to the device number of the +containing autofs mount. Upon return the struct field arg1 contains the +uid and arg2 the gid. + +When reconstructing an autofs mount tree with active mounts we need to +re-connect to mounts that may have used the original process uid and +gid (or string variations of them) for mount lookups within the map entry. +This call provides the ability to obtain this uid and gid so they may be +used by user space for the mount map lookups. + + +AUTOFS_DEV_IOCTL_EXPIRE_CMD +--------------------------- + +Issue an expire request to the kernel for an autofs mount. Typically +this ioctl is called until no further expire candidates are found. + +The call requires an initialized struct autofs_dev_ioctl with the +ioctlfd field set to the descriptor obtained from the open call. In +addition an immediate expire, independent of the mount timeout, can be +requested by setting the arg1 field to 1. If no expire candidates can +be found the ioctl returns -1 with errno set to EAGAIN. + +This call causes the kernel module to check the mount corresponding +to the given ioctlfd for mounts that can be expired, issues an expire +request back to the daemon and waits for completion. + +AUTOFS_DEV_IOCTL_ASKUMOUNT_CMD +------------------------------ + +Checks if an autofs mount point is in use. + +The call requires an initialized struct autofs_dev_ioctl with the +ioctlfd field set to the descriptor obtained from the open call and +it returns the result in the arg1 field, 1 for busy and 0 otherwise. + + +AUTOFS_DEV_IOCTL_ISMOUNTPOINT_CMD +--------------------------------- + +Check if the given path is a mountpoint. + +The call requires an initialized struct autofs_dev_ioctl. There are two +possible variations. Both use the path field set to the path of the mount +point to check and the size field adjusted appropriately. One uses the +ioctlfd field to identify a specific mount point to check while the other +variation uses the path and optionaly arg1 set to an autofs mount type. +The call returns 1 if this is a mount point and sets arg1 to the device +number of the mount and field arg2 to the relevant super block magic +number (described below) or 0 if it isn't a mountpoint. In both cases +the the device number (as returned by new_encode_dev()) is returned +in field arg1. + +If supplied with a file descriptor we're looking for a specific mount, +not necessarily at the top of the mounted stack. In this case the path +the descriptor corresponds to is considered a mountpoint if it is itself +a mountpoint or contains a mount, such as a multi-mount without a root +mount. In this case we return 1 if the descriptor corresponds to a mount +point and and also returns the super magic of the covering mount if there +is one or 0 if it isn't a mountpoint. + +If a path is supplied (and the ioctlfd field is set to -1) then the path +is looked up and is checked to see if it is the root of a mount. If a +type is also given we are looking for a particular autofs mount and if +a match isn't found a fail is returned. If the the located path is the +root of a mount 1 is returned along with the super magic of the mount +or 0 otherwise. + diff --git a/Documentation/filesystems/ext3.txt b/Documentation/filesystems/ext3.txt index b45f3c1b8b43..295f26cd895a 100644 --- a/Documentation/filesystems/ext3.txt +++ b/Documentation/filesystems/ext3.txt @@ -193,6 +193,5 @@ kernel source: <file:fs/ext3/> programs: http://e2fsprogs.sourceforge.net/ http://ext2resize.sourceforge.net -useful links: http://www.zip.com.au/~akpm/linux/ext3/ext3-usage.html - http://www-106.ibm.com/developerworks/linux/library/l-fs7/ +useful links: http://www-106.ibm.com/developerworks/linux/library/l-fs7/ http://www-106.ibm.com/developerworks/linux/library/l-fs8/ diff --git a/Documentation/filesystems/nfsroot.txt b/Documentation/filesystems/nfsroot.txt index 31b329172343..68baddf3c3e0 100644 --- a/Documentation/filesystems/nfsroot.txt +++ b/Documentation/filesystems/nfsroot.txt @@ -169,7 +169,7 @@ They depend on various facilities being available: 3.1) Booting from a floppy using syslinux When building kernels, an easy way to create a boot floppy that uses - syslinux is to use the zdisk or bzdisk make targets which use + syslinux is to use the zdisk or bzdisk make targets which use zimage and bzimage images respectively. Both targets accept the FDARGS parameter which can be used to set the kernel command line. diff --git a/Documentation/filesystems/proc.txt b/Documentation/filesystems/proc.txt index b488edad743c..c032bf39e8b9 100644 --- a/Documentation/filesystems/proc.txt +++ b/Documentation/filesystems/proc.txt @@ -1321,6 +1321,18 @@ debugging information is displayed on console. NMI switch that most IA32 servers have fires unknown NMI up, for example. If a system hangs up, try pressing the NMI switch. +panic_on_unrecovered_nmi +------------------------ + +The default Linux behaviour on an NMI of either memory or unknown is to continue +operation. For many environments such as scientific computing it is preferable +that the box is taken out and the error dealt with than an uncorrected +parity/ECC error get propogated. + +A small number of systems do generate NMI's for bizarre random reasons such as +power management so the default is off. That sysctl works like the existing +panic controls already in that directory. + nmi_watchdog ------------ diff --git a/Documentation/filesystems/ramfs-rootfs-initramfs.txt b/Documentation/filesystems/ramfs-rootfs-initramfs.txt index 7be232b44ee4..62fe9b1e0890 100644 --- a/Documentation/filesystems/ramfs-rootfs-initramfs.txt +++ b/Documentation/filesystems/ramfs-rootfs-initramfs.txt @@ -263,7 +263,7 @@ User Mode Linux, like so: sleep(999999999); } EOF - gcc -static hello2.c -o init + gcc -static hello.c -o init echo init | cpio -o -H newc | gzip > test.cpio.gz # Testing external initramfs using the initrd loading mechanism. qemu -kernel /boot/vmlinuz -initrd test.cpio.gz /dev/zero diff --git a/Documentation/gpio.txt b/Documentation/gpio.txt index 18022e249c53..b1b988701247 100644 --- a/Documentation/gpio.txt +++ b/Documentation/gpio.txt @@ -240,6 +240,10 @@ signal, or (b) something wrongly believes it's safe to remove drivers needed to manage a signal that's in active use. That is, requesting a GPIO can serve as a kind of lock. +Some platforms may also use knowledge about what GPIOs are active for +power management, such as by powering down unused chip sectors and, more +easily, gating off unused clocks. + These two calls are optional because not not all current Linux platforms offer such functionality in their GPIO support; a valid implementation could return success for all gpio_request() calls. Unlike the other calls, @@ -264,7 +268,7 @@ map between them using calls like: /* map GPIO numbers to IRQ numbers */ int gpio_to_irq(unsigned gpio); - /* map IRQ numbers to GPIO numbers */ + /* map IRQ numbers to GPIO numbers (avoid using this) */ int irq_to_gpio(unsigned irq); Those return either the corresponding number in the other namespace, or @@ -284,7 +288,8 @@ system wakeup capabilities. Non-error values returned from irq_to_gpio() would most commonly be used with gpio_get_value(), for example to initialize or update driver state -when the IRQ is edge-triggered. +when the IRQ is edge-triggered. Note that some platforms don't support +this reverse mapping, so you should avoid using it. Emulating Open Drain Signals diff --git a/Documentation/ia64/kvm.txt b/Documentation/ia64/kvm.txt index 914d07f49268..84f7cb3d5bec 100644 --- a/Documentation/ia64/kvm.txt +++ b/Documentation/ia64/kvm.txt @@ -1,7 +1,8 @@ -Currently, kvm module in EXPERIMENTAL stage on IA64. This means that -interfaces are not stable enough to use. So, plase had better don't run -critical applications in virtual machine. We will try our best to make it -strong in future versions! +Currently, kvm module is in EXPERIMENTAL stage on IA64. This means that +interfaces are not stable enough to use. So, please don't run critical +applications in virtual machine. +We will try our best to improve it in future versions! + Guide: How to boot up guests on kvm/ia64 This guide is to describe how to enable kvm support for IA-64 systems. diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt index b429c84ceef2..dd28a0d56981 100644 --- a/Documentation/kernel-parameters.txt +++ b/Documentation/kernel-parameters.txt @@ -796,6 +796,7 @@ and is between 256 and 4096 characters. It is defined in the file Defaults to the default architecture's huge page size if not specified. + i8042.debug [HW] Toggle i8042 debug mode i8042.direct [HW] Put keyboard port into non-translated mode i8042.dumbkbd [HW] Pretend that controller can only read data from keyboard and cannot control its state diff --git a/Documentation/networking/cs89x0.txt b/Documentation/networking/cs89x0.txt index 6387d3decf85..c725d33b316f 100644 --- a/Documentation/networking/cs89x0.txt +++ b/Documentation/networking/cs89x0.txt @@ -3,7 +3,7 @@ NOTE ---- This document was contributed by Cirrus Logic for kernel 2.2.5. This version -has been updated for 2.3.48 by Andrew Morton <andrewm@uow.edu.au> +has been updated for 2.3.48 by Andrew Morton. Cirrus make a copy of this driver available at their website, as described below. In general, you should use the driver version which @@ -690,7 +690,7 @@ latest drivers and technical publications. 6.4 Current maintainer In February 2000 the maintenance of this driver was assumed by Andrew -Morton <akpm@zip.com.au> +Morton. 6.5 Kernel module parameters diff --git a/Documentation/networking/phonet.txt b/Documentation/networking/phonet.txt index 0e6e592f4f55..6a07e45d4a93 100644 --- a/Documentation/networking/phonet.txt +++ b/Documentation/networking/phonet.txt @@ -146,8 +146,8 @@ WARNING: When polling a connected pipe socket for writability, there is an intrinsic race condition whereby writability might be lost between the polling and the writing system calls. In this case, the socket will -block until write because possible again, unless non-blocking mode -becomes enabled. +block until write becomes possible again, unless non-blocking mode +is enabled. The pipe protocol provides two socket options at the SOL_PNPIPE level: diff --git a/Documentation/networking/vortex.txt b/Documentation/networking/vortex.txt index 6356d3faed36..bd70976b8160 100644 --- a/Documentation/networking/vortex.txt +++ b/Documentation/networking/vortex.txt @@ -1,5 +1,5 @@ Documentation/networking/vortex.txt -Andrew Morton <andrewm@uow.edu.au> +Andrew Morton 30 April 2000 @@ -11,7 +11,7 @@ The driver was written by Donald Becker <becker@scyld.com> Don is no longer the prime maintainer of this version of the driver. Please report problems to one or more of: - Andrew Morton <akpm@osdl.org> + Andrew Morton Netdev mailing list <netdev@vger.kernel.org> Linux kernel mailing list <linux-kernel@vger.kernel.org> @@ -305,11 +305,6 @@ Donald's wake-on-LAN page: ftp://ftp.3com.com/pub/nic/3c90x/3c90xx2.exe -Driver updates and a detailed changelog for the modifications which -were made for the 2.3/2,4 series kernel is available at - - http://www.zip.com.au/~akpm/linux/#3c59x-bc - Autonegotiation notes --------------------- diff --git a/Documentation/power/s2ram.txt b/Documentation/power/s2ram.txt index b05f512130ea..2ebdc6091ce1 100644 --- a/Documentation/power/s2ram.txt +++ b/Documentation/power/s2ram.txt @@ -54,3 +54,21 @@ used to run with "radeonfb" (it's an ATI Radeon mobility). It turns out that "radeonfb" simply cannot resume that device - it tries to set the PLL's, and it just _hangs_. Using the regular VGA console and letting X resume it instead works fine. + +NOTE +==== +pm_trace uses the system's Real Time Clock (RTC) to save the magic number. +Reason for this is that the RTC is the only reliably available piece of +hardware during resume operations where a value can be set that will +survive a reboot. + +Consequence is that after a resume (even if it is successful) your system +clock will have a value corresponding to the magic mumber instead of the +correct date/time! It is therefore advisable to use a program like ntp-date +or rdate to reset the correct date/time from an external time source when +using this trace option. + +As the clock keeps ticking it is also essential that the reboot is done +quickly after the resume failure. The trace option does not use the seconds +or the low order bits of the minutes of the RTC, but a too long delay will +corrupt the magic value. diff --git a/Documentation/scsi/ChangeLog.megaraid b/Documentation/scsi/ChangeLog.megaraid index 37796fe45bd0..eaa4801f2ce6 100644 --- a/Documentation/scsi/ChangeLog.megaraid +++ b/Documentation/scsi/ChangeLog.megaraid @@ -409,7 +409,7 @@ i. Function reordering so that inline functions are defined before they megaraid_mbox_prepare_pthru, megaraid_mbox_prepare_epthru, megaraid_busywait_mbox - - Andrew Morton <akpm@osdl.org>, 08.19.2004 + - Andrew Morton, 08.19.2004 linux-scsi mailing list "Something else to clean up after inclusion: every instance of an @@ -471,13 +471,13 @@ vi. Add support for 64-bit applications. Current drivers assume only vii. Move the function declarations for the management module from megaraid_mm.h to megaraid_mm.c - - Andrew Morton <akpm@osdl.org>, 08.19.2004 + - Andrew Morton, 08.19.2004 linux-scsi mailing list viii. Change default values for MEGARAID_NEWGEN, MEGARAID_MM, and MEGARAID_MAILBOX to 'n' in Kconfig.megaraid - - Andrew Morton <akpm@osdl.org>, 08.19.2004 + - Andrew Morton, 08.19.2004 linux-scsi mailing list ix. replace udelay with msleep diff --git a/Documentation/spi/pxa2xx b/Documentation/spi/pxa2xx index bbe8dee681a5..6bb916d57c95 100644 --- a/Documentation/spi/pxa2xx +++ b/Documentation/spi/pxa2xx @@ -96,7 +96,7 @@ Each slave device attached to the PXA must provide slave specific configuration information via the structure "pxa2xx_spi_chip" found in "arch/arm/mach-pxa/include/mach/pxa2xx_spi.h". The pxa2xx_spi master controller driver will uses the configuration whenever the driver communicates with the slave -device. +device. All fields are optional. struct pxa2xx_spi_chip { u8 tx_threshold; @@ -112,14 +112,17 @@ used to configure the SSP hardware fifo. These fields are critical to the performance of pxa2xx_spi driver and misconfiguration will result in rx fifo overruns (especially in PIO mode transfers). Good default values are - .tx_threshold = 12, - .rx_threshold = 4, + .tx_threshold = 8, + .rx_threshold = 8, + +The range is 1 to 16 where zero indicates "use default". The "pxa2xx_spi_chip.dma_burst_size" field is used to configure PXA2xx DMA engine and is related the "spi_device.bits_per_word" field. Read and understand the PXA2xx "Developer Manual" sections on the DMA controller and SSP Controllers to determine the correct value. An SSP configured for byte-wide transfers would -use a value of 8. +use a value of 8. The driver will determine a reasonable default if +dma_burst_size == 0. The "pxa2xx_spi_chip.timeout" fields is used to efficiently handle trailing bytes in the SSP receiver fifo. The correct value for this field is @@ -137,7 +140,13 @@ function for asserting/deasserting a slave device chip select. If the field is NULL, the pxa2xx_spi master controller driver assumes that the SSP port is configured to use SSPFRM instead. -NSSP SALVE SAMPLE +NOTE: the SPI driver cannot control the chip select if SSPFRM is used, so the +chipselect is dropped after each spi_transfer. Most devices need chip select +asserted around the complete message. Use SSPFRM as a GPIO (through cs_control) +to accomodate these chips. + + +NSSP SLAVE SAMPLE ----------------- The pxa2xx_spi_chip structure is passed to the pxa2xx_spi driver in the "spi_board_info.controller_data" field. Below is a sample configuration using @@ -206,18 +215,21 @@ static void __init streetracer_init(void) DMA and PIO I/O Support ----------------------- -The pxa2xx_spi driver support both DMA and interrupt driven PIO message -transfers. The driver defaults to PIO mode and DMA transfers must enabled by -setting the "enable_dma" flag in the "pxa2xx_spi_master" structure and -ensuring that the "pxa2xx_spi_chip.dma_burst_size" field is non-zero. The DMA -mode support both coherent and stream based DMA mappings. +The pxa2xx_spi driver supports both DMA and interrupt driven PIO message +transfers. The driver defaults to PIO mode and DMA transfers must be enabled +by setting the "enable_dma" flag in the "pxa2xx_spi_master" structure. The DMA +mode supports both coherent and stream based DMA mappings. The following logic is used to determine the type of I/O to be used on a per "spi_transfer" basis: -if !enable_dma or dma_burst_size == 0 then +if !enable_dma then always use PIO transfers +if spi_message.len > 8191 then + print "rate limited" warning + use PIO transfers + if spi_message.is_dma_mapped and rx_dma_buf != 0 and tx_dma_buf != 0 then use coherent DMA mode diff --git a/Documentation/w1/00-INDEX b/Documentation/w1/00-INDEX index 5270cf4cb109..cb49802745dc 100644 --- a/Documentation/w1/00-INDEX +++ b/Documentation/w1/00-INDEX @@ -1,5 +1,7 @@ 00-INDEX - This file +slaves/ + - Drivers that provide support for specific family codes. masters/ - Individual chips providing 1-wire busses. w1.generic diff --git a/Documentation/w1/masters/ds2490 b/Documentation/w1/masters/ds2490 index 239f9ae01843..28176def3d6f 100644 --- a/Documentation/w1/masters/ds2490 +++ b/Documentation/w1/masters/ds2490 @@ -16,3 +16,55 @@ which allows to build USB <-> W1 bridges. DS9490(R) is a USB <-> W1 bus master device which has 0x81 family ID integrated chip and DS2490 low-level operational chip. + +Notes and limitations. +- The weak pullup current is a minimum of 0.9mA and maximum of 6.0mA. +- The 5V strong pullup is supported with a minimum of 5.9mA and a + maximum of 30.4 mA. (From DS2490.pdf) +- While the ds2490 supports a hardware search the code doesn't take + advantage of it (in tested case it only returned first device). +- The hardware will detect when devices are attached to the bus on the + next bus (reset?) operation, however only a message is printed as + the core w1 code doesn't make use of the information. Connecting + one device tends to give multiple new device notifications. +- The number of USB bus transactions could be reduced if w1_reset_send + was added to the API. The name is just a suggestion. It would take + a write buffer and a read buffer (along with sizes) as arguments. + The ds2490 block I/O command supports reset, write buffer, read + buffer, and strong pullup all in one command, instead of the current + 1 reset bus, 2 write the match rom command and slave rom id, 3 block + write and read data. The write buffer needs to have the match rom + command and slave rom id prepended to the front of the requested + write buffer, both of which are known to the driver. +- The hardware supports normal, flexible, and overdrive bus + communication speeds, but only the normal is supported. +- The registered w1_bus_master functions don't define error + conditions. If a bus search is in progress and the ds2490 is + removed it can produce a good amount of error output before the bus + search finishes. +- The hardware supports detecting some error conditions, such as + short, alarming presence on reset, and no presence on reset, but the + driver doesn't query those values. +- The ds2490 specification doesn't cover short bulk in reads in + detail, but my observation is if fewer bytes are requested than are + available, the bulk read will return an error and the hardware will + clear the entire bulk in buffer. It would be possible to read the + maximum buffer size to not run into this error condition, only extra + bytes in the buffer is a logic error in the driver. The code should + should match reads and writes as well as data sizes. Reads and + writes are serialized and the status verifies that the chip is idle + (and data is available) before the read is executed, so it should + not happen. +- Running x86_64 2.6.24 UHCI under qemu 0.9.0 under x86_64 2.6.22-rc6 + with a OHCI controller, ds2490 running in the guest would operate + normally the first time the module was loaded after qemu attached + the ds2490 hardware, but if the module was unloaded, then reloaded + most of the time one of the bulk out or in, and usually the bulk in + would fail. qemu sets a 50ms timeout and the bulk in would timeout + even when the status shows data available. A bulk out write would + show a successful completion, but the ds2490 status register would + show 0 bytes written. Detaching qemu from the ds2490 hardware and + reattaching would clear the problem. usbmon output in the guest and + host did not explain the problem. My guess is a bug in either qemu + or the host OS and more likely the host OS. +-- 03-06-2008 David Fries <David@Fries.net> diff --git a/Documentation/w1/slaves/00-INDEX b/Documentation/w1/slaves/00-INDEX new file mode 100644 index 000000000000..f8101d6b07b7 --- /dev/null +++ b/Documentation/w1/slaves/00-INDEX @@ -0,0 +1,4 @@ +00-INDEX + - This file +w1_therm + - The Maxim/Dallas Semiconductor ds18*20 temperature sensor. diff --git a/Documentation/w1/slaves/w1_therm b/Documentation/w1/slaves/w1_therm new file mode 100644 index 000000000000..0403aaaba878 --- /dev/null +++ b/Documentation/w1/slaves/w1_therm @@ -0,0 +1,41 @@ +Kernel driver w1_therm +==================== + +Supported chips: + * Maxim ds18*20 based temperature sensors. + +Author: Evgeniy Polyakov <johnpol@2ka.mipt.ru> + + +Description +----------- + +w1_therm provides basic temperature conversion for ds18*20 devices. +supported family codes: +W1_THERM_DS18S20 0x10 +W1_THERM_DS1822 0x22 +W1_THERM_DS18B20 0x28 + +Support is provided through the sysfs w1_slave file. Each open and +read sequence will initiate a temperature conversion then provide two +lines of ASCII output. The first line contains the nine hex bytes +read along with a calculated crc value and YES or NO if it matched. +If the crc matched the returned values are retained. The second line +displays the retained values along with a temperature in millidegrees +Centigrade after t=. + +Parasite powered devices are limited to one slave performing a +temperature conversion at a time. If none of the devices are parasite +powered it would be possible to convert all the devices at the same +time and then go back to read individual sensors. That isn't +currently supported. The driver also doesn't support reduced +precision (which would also reduce the conversion time). + +The module parameter strong_pullup can be set to 0 to disable the +strong pullup or 1 to enable. If enabled the 5V strong pullup will be +enabled when the conversion is taking place provided the master driver +must support the strong pullup (or it falls back to a pullup +resistor). The DS18b20 temperature sensor specification lists a +maximum current draw of 1.5mA and that a 5k pullup resistor is not +sufficient. The strong pullup is designed to provide the additional +current required. diff --git a/Documentation/w1/w1.generic b/Documentation/w1/w1.generic index 4c6509dd4789..e3333eec4320 100644 --- a/Documentation/w1/w1.generic +++ b/Documentation/w1/w1.generic @@ -79,10 +79,13 @@ w1 master sysfs interface <xx-xxxxxxxxxxxxx> - a directory for a found device. The format is family-serial bus - (standard) symlink to the w1 bus driver - (standard) symlink to the w1 driver +w1_master_add - Manually register a slave device w1_master_attempts - the number of times a search was attempted w1_master_max_slave_count - the maximum slaves that may be attached to a master w1_master_name - the name of the device (w1_bus_masterX) +w1_master_pullup - 5V strong pullup 0 enabled, 1 disabled +w1_master_remove - Manually remove a slave device w1_master_search - the number of searches left to do, -1=continual (default) w1_master_slave_count - the number of slaves found @@ -90,7 +93,13 @@ w1_master_slaves - the names of the slaves, one per line w1_master_timeout - the delay in seconds between searches If you have a w1 bus that never changes (you don't add or remove devices), -you can set w1_master_search to a positive value to disable searches. +you can set the module parameter search_count to a small positive number +for an initially small number of bus searches. Alternatively it could be +set to zero, then manually add the slave device serial numbers by +w1_master_add device file. The w1_master_add and w1_master_remove files +generally only make sense when searching is disabled, as a search will +redetect manually removed devices that are present and timeout manually +added devices that aren't on the bus. w1 slave sysfs interface |