diff options
Diffstat (limited to 'Documentation/fb/modedb.txt')
| -rw-r--r-- | Documentation/fb/modedb.txt | 151 |
1 files changed, 0 insertions, 151 deletions
diff --git a/Documentation/fb/modedb.txt b/Documentation/fb/modedb.txt deleted file mode 100644 index 16aa08453911..000000000000 --- a/Documentation/fb/modedb.txt +++ /dev/null @@ -1,151 +0,0 @@ - - - modedb default video mode support - - -Currently all frame buffer device drivers have their own video mode databases, -which is a mess and a waste of resources. The main idea of modedb is to have - - - one routine to probe for video modes, which can be used by all frame buffer - devices - - one generic video mode database with a fair amount of standard videomodes - (taken from XFree86) - - the possibility to supply your own mode database for graphics hardware that - needs non-standard modes, like amifb and Mac frame buffer drivers (which - use macmodes.c) - -When a frame buffer device receives a video= option it doesn't know, it should -consider that to be a video mode option. If no frame buffer device is specified -in a video= option, fbmem considers that to be a global video mode option. - -Valid mode specifiers (mode_option argument): - - <xres>x<yres>[M][R][-<bpp>][@<refresh>][i][m][eDd] - <name>[-<bpp>][@<refresh>] - -with <xres>, <yres>, <bpp> and <refresh> decimal numbers and <name> a string. -Things between square brackets are optional. - -If 'M' is specified in the mode_option argument (after <yres> and before -<bpp> and <refresh>, if specified) the timings will be calculated using -VESA(TM) Coordinated Video Timings instead of looking up the mode from a table. -If 'R' is specified, do a 'reduced blanking' calculation for digital displays. -If 'i' is specified, calculate for an interlaced mode. And if 'm' is -specified, add margins to the calculation (1.8% of xres rounded down to 8 -pixels and 1.8% of yres). - - Sample usage: 1024x768M@60m - CVT timing with margins - -DRM drivers also add options to enable or disable outputs: - -'e' will force the display to be enabled, i.e. it will override the detection -if a display is connected. 'D' will force the display to be enabled and use -digital output. This is useful for outputs that have both analog and digital -signals (e.g. HDMI and DVI-I). For other outputs it behaves like 'e'. If 'd' -is specified the output is disabled. - -You can additionally specify which output the options matches to. -To force the VGA output to be enabled and drive a specific mode say: - video=VGA-1:1280x1024@60me - -Specifying the option multiple times for different ports is possible, e.g.: - video=LVDS-1:d video=HDMI-1:D - -***** oOo ***** oOo ***** oOo ***** oOo ***** oOo ***** oOo ***** oOo ***** - -What is the VESA(TM) Coordinated Video Timings (CVT)? - -From the VESA(TM) Website: - - "The purpose of CVT is to provide a method for generating a consistent - and coordinated set of standard formats, display refresh rates, and - timing specifications for computer display products, both those - employing CRTs, and those using other display technologies. The - intention of CVT is to give both source and display manufacturers a - common set of tools to enable new timings to be developed in a - consistent manner that ensures greater compatibility." - -This is the third standard approved by VESA(TM) concerning video timings. The -first was the Discrete Video Timings (DVT) which is a collection of -pre-defined modes approved by VESA(TM). The second is the Generalized Timing -Formula (GTF) which is an algorithm to calculate the timings, given the -pixelclock, the horizontal sync frequency, or the vertical refresh rate. - -The GTF is limited by the fact that it is designed mainly for CRT displays. -It artificially increases the pixelclock because of its high blanking -requirement. This is inappropriate for digital display interface with its high -data rate which requires that it conserves the pixelclock as much as possible. -Also, GTF does not take into account the aspect ratio of the display. - -The CVT addresses these limitations. If used with CRT's, the formula used -is a derivation of GTF with a few modifications. If used with digital -displays, the "reduced blanking" calculation can be used. - -From the framebuffer subsystem perspective, new formats need not be added -to the global mode database whenever a new mode is released by display -manufacturers. Specifying for CVT will work for most, if not all, relatively -new CRT displays and probably with most flatpanels, if 'reduced blanking' -calculation is specified. (The CVT compatibility of the display can be -determined from its EDID. The version 1.3 of the EDID has extra 128-byte -blocks where additional timing information is placed. As of this time, there -is no support yet in the layer to parse this additional blocks.) - -CVT also introduced a new naming convention (should be seen from dmesg output): - - <pix>M<a>[-R] - - where: pix = total amount of pixels in MB (xres x yres) - M = always present - a = aspect ratio (3 - 4:3; 4 - 5:4; 9 - 15:9, 16:9; A - 16:10) - -R = reduced blanking - - example: .48M3-R - 800x600 with reduced blanking - -Note: VESA(TM) has restrictions on what is a standard CVT timing: - - - aspect ratio can only be one of the above values - - acceptable refresh rates are 50, 60, 70 or 85 Hz only - - if reduced blanking, the refresh rate must be at 60Hz - -If one of the above are not satisfied, the kernel will print a warning but the -timings will still be calculated. - -***** oOo ***** oOo ***** oOo ***** oOo ***** oOo ***** oOo ***** oOo ***** - -To find a suitable video mode, you just call - -int __init fb_find_mode(struct fb_var_screeninfo *var, - struct fb_info *info, const char *mode_option, - const struct fb_videomode *db, unsigned int dbsize, - const struct fb_videomode *default_mode, - unsigned int default_bpp) - -with db/dbsize your non-standard video mode database, or NULL to use the -standard video mode database. - -fb_find_mode() first tries the specified video mode (or any mode that matches, -e.g. there can be multiple 640x480 modes, each of them is tried). If that -fails, the default mode is tried. If that fails, it walks over all modes. - -To specify a video mode at bootup, use the following boot options: - video=<driver>:<xres>x<yres>[-<bpp>][@refresh] - -where <driver> is a name from the table below. Valid default modes can be -found in linux/drivers/video/modedb.c. Check your driver's documentation. -There may be more modes. - - Drivers that support modedb boot options - Boot Name Cards Supported - - amifb - Amiga chipset frame buffer - aty128fb - ATI Rage128 / Pro frame buffer - atyfb - ATI Mach64 frame buffer - pm2fb - Permedia 2/2V frame buffer - pm3fb - Permedia 3 frame buffer - sstfb - Voodoo 1/2 (SST1) chipset frame buffer - tdfxfb - 3D Fx frame buffer - tridentfb - Trident (Cyber)blade chipset frame buffer - vt8623fb - VIA 8623 frame buffer - -BTW, only a few fb drivers use this at the moment. Others are to follow -(feel free to send patches). The DRM drivers also support this. |