path: root/Documentation/rfkill.txt
diff options
authorJohannes Berg <johannes@sipsolutions.net>2009-06-02 13:01:37 +0200
committerJohn W. Linville <linville@tuxdriver.com>2009-06-03 14:06:13 -0400
commit19d337dff95cbf76edd3ad95c0cee2732c3e1ec5 (patch)
tree33326eeb09cb9664cc8427a5dc7cd2b08b5a57c3 /Documentation/rfkill.txt
parent0f6399c4c525b518644a9b09f8d6fb125a418c4d (diff)
rfkill: rewrite
This patch completely rewrites the rfkill core to address the following deficiencies: * all rfkill drivers need to implement polling where necessary rather than having one central implementation * updating the rfkill state cannot be done from arbitrary contexts, forcing drivers to use schedule_work and requiring lots of code * rfkill drivers need to keep track of soft/hard blocked internally -- the core should do this * the rfkill API has many unexpected quirks, for example being asymmetric wrt. alloc/free and register/unregister * rfkill can call back into a driver from within a function the driver called -- this is prone to deadlocks and generally should be avoided * rfkill-input pointlessly is a separate module * drivers need to #ifdef rfkill functions (unless they want to depend on or select RFKILL) -- rfkill should provide inlines that do nothing if it isn't compiled in * the rfkill structure is not opaque -- drivers need to initialise it correctly (lots of sanity checking code required) -- instead force drivers to pass the right variables to rfkill_alloc() * the documentation is hard to read because it always assumes the reader is completely clueless and contains way TOO MANY CAPS * the rfkill code needlessly uses a lot of locks and atomic operations in locked sections * fix LED trigger to actually change the LED when the radio state changes -- this wasn't done before Tested-by: Alan Jenkins <alan-jenkins@tuffmail.co.uk> Signed-off-by: Henrique de Moraes Holschuh <hmh@hmh.eng.br> [thinkpad] Signed-off-by: Johannes Berg <johannes@sipsolutions.net> Signed-off-by: John W. Linville <linville@tuxdriver.com>
Diffstat (limited to 'Documentation/rfkill.txt')
1 files changed, 78 insertions, 519 deletions
diff --git a/Documentation/rfkill.txt b/Documentation/rfkill.txt
index 40c3a3f10816..de941e309d47 100644
--- a/Documentation/rfkill.txt
+++ b/Documentation/rfkill.txt
@@ -1,571 +1,130 @@
-rfkill - RF switch subsystem support
+rfkill - RF kill switch support
-1 Introduction
-2 Implementation details
-3 Kernel driver guidelines
-3.1 wireless device drivers
-3.2 platform/switch drivers
-3.3 input device drivers
-4 Kernel API
-5 Userspace support
+1. Introduction
+2. Implementation details
+3. Kernel driver guidelines
+4. Kernel API
+5. Userspace support
-1. Introduction:
+1. Introduction
-The rfkill switch subsystem exists to add a generic interface to circuitry that
-can enable or disable the signal output of a wireless *transmitter* of any
-type. By far, the most common use is to disable radio-frequency transmitters.
+The rfkill subsystem provides a generic interface to disabling any radio
+transmitter in the system. When a transmitter is blocked, it shall not
+radiate any power.
-Note that disabling the signal output means that the the transmitter is to be
-made to not emit any energy when "blocked". rfkill is not about blocking data
-transmissions, it is about blocking energy emission.
+The subsystem also provides the ability to react on button presses and
+disable all transmitters of a certain type (or all). This is intended for
+situations where transmitters need to be turned off, for example on
-The rfkill subsystem offers support for keys and switches often found on
-laptops to enable wireless devices like WiFi and Bluetooth, so that these keys
-and switches actually perform an action in all wireless devices of a given type
-attached to the system.
-The buttons to enable and disable the wireless transmitters are important in
-situations where the user is for example using his laptop on a location where
-radio-frequency transmitters _must_ be disabled (e.g. airplanes).
-Because of this requirement, userspace support for the keys should not be made
-mandatory. Because userspace might want to perform some additional smarter
-tasks when the key is pressed, rfkill provides userspace the possibility to
-take over the task to handle the key events.
-2: Implementation details
+2. Implementation details
The rfkill subsystem is composed of various components: the rfkill class, the
rfkill-input module (an input layer handler), and some specific input layer
-The rfkill class provides kernel drivers with an interface that allows them to
-know when they should enable or disable a wireless network device transmitter.
-This is enabled by the CONFIG_RFKILL Kconfig option.
-The rfkill class support makes sure userspace will be notified of all state
-changes on rfkill devices through uevents. It provides a notification chain
-for interested parties in the kernel to also get notified of rfkill state
-changes in other drivers. It creates several sysfs entries which can be used
-by userspace. See section "Userspace support".
-The rfkill-input module provides the kernel with the ability to implement a
-basic response when the user presses a key or button (or toggles a switch)
-related to rfkill functionality. It is an in-kernel implementation of default
-policy of reacting to rfkill-related input events and neither mandatory nor
-required for wireless drivers to operate. It is enabled by the
-CONFIG_RFKILL_INPUT Kconfig option.
-rfkill-input is a rfkill-related events input layer handler. This handler will
-listen to all rfkill key events and will change the rfkill state of the
-wireless devices accordingly. With this option enabled userspace could either
-do nothing or simply perform monitoring tasks.
-The rfkill-input module also provides EPO (emergency power-off) functionality
-for all wireless transmitters. This function cannot be overridden, and it is
-always active. rfkill EPO is related to *_RFKILL_ALL input layer events.
-Important terms for the rfkill subsystem:
-In order to avoid confusion, we avoid the term "switch" in rfkill when it is
-referring to an electronic control circuit that enables or disables a
-transmitter. We reserve it for the physical device a human manipulates
-(which is an input device, by the way):
-rfkill switch:
- A physical device a human manipulates. Its state can be perceived by
- the kernel either directly (through a GPIO pin, ACPI GPE) or by its
- effect on a rfkill line of a wireless device.
-rfkill controller:
- A hardware circuit that controls the state of a rfkill line, which a
- kernel driver can interact with *to modify* that state (i.e. it has
- either write-only or read/write access).
-rfkill line:
- An input channel (hardware or software) of a wireless device, which
- causes a wireless transmitter to stop emitting energy (BLOCK) when it
- is active. Point of view is extremely important here: rfkill lines are
- always seen from the PoV of a wireless device (and its driver).
-soft rfkill line/software rfkill line:
- A rfkill line the wireless device driver can directly change the state
- of. Related to rfkill_state RFKILL_STATE_SOFT_BLOCKED.
-hard rfkill line/hardware rfkill line:
- A rfkill line that works fully in hardware or firmware, and that cannot
- be overridden by the kernel driver. The hardware device or the
- firmware just exports its status to the driver, but it is read-only.
- Related to rfkill_state RFKILL_STATE_HARD_BLOCKED.
-The enum rfkill_state describes the rfkill state of a transmitter:
-When a rfkill line or rfkill controller is in the RFKILL_STATE_UNBLOCKED state,
-the wireless transmitter (radio TX circuit for example) is *enabled*. When the
-wireless transmitter is to be *blocked* from operating.
-RFKILL_STATE_SOFT_BLOCKED indicates that a call to toggle_radio() can change
-that state. RFKILL_STATE_HARD_BLOCKED indicates that a call to toggle_radio()
-will not be able to change the state and will return with a suitable error if
-attempts are made to set the state to RFKILL_STATE_UNBLOCKED.
-RFKILL_STATE_HARD_BLOCKED is used by drivers to signal that the device is
-locked in the BLOCKED state by a hardwire rfkill line (typically an input pin
-that, when active, forces the transmitter to be disabled) which the driver
-CANNOT override.
-Full rfkill functionality requires two different subsystems to cooperate: the
-input layer and the rfkill class. The input layer issues *commands* to the
-entire system requesting that devices registered to the rfkill class change
-state. The way this interaction happens is not complex, but it is not obvious
-Kernel Input layer:
- other such events when the user presses certain keys, buttons, or
- toggles certain physical switches.
- used to issue *commands* for the system to change behaviour, and these
- commands may or may not be carried out by some kernel driver or
- userspace application. It follows that doing user feedback based only
- on input events is broken, as there is no guarantee that an input event
- will be acted upon.
- Most wireless communication device drivers implementing rfkill
- functionality MUST NOT generate these events, and have no reason to
- register themselves with the input layer. Doing otherwise is a common
- misconception. There is an API to propagate rfkill status change
- information, and it is NOT the input layer.
-rfkill class:
- * Calls a hook in a driver to effectively change the wireless
- transmitter state;
- * Keeps track of the wireless transmitter state (with help from
- the driver);
- * Generates userspace notifications (uevents) and a call to a
- notification chain (kernel) when there is a wireless transmitter
- state change;
- * Connects a wireless communications driver with the common rfkill
- control system, which, for example, allows actions such as
- "switch all bluetooth devices offline" to be carried out by
- userspace or by rfkill-input.
- a layering violation.
- Most wireless data communication drivers in the kernel have just to
- implement the rfkill class API to work properly. Interfacing to the
- input layer is not often required (and is very often a *bug*) on
- wireless drivers.
- Platform drivers often have to attach to the input layer to *issue*
- (but never to listen to) rfkill events for rfkill switches, and also to
- the rfkill class to export a control interface for the platform rfkill
- controllers to the rfkill subsystem. This does NOT mean the rfkill
- switch is attached to a rfkill class (doing so is almost always wrong).
- It just means the same kernel module is the driver for different
- devices (rfkill switches and rfkill controllers).
-Userspace input handlers (uevents) or kernel input handlers (rfkill-input):
- * Implements the policy of what should happen when one of the input
- layer events related to rfkill operation is received.
- * Uses the sysfs interface (userspace) or private rfkill API calls
- to tell the devices registered with the rfkill class to change
- their state (i.e. translates the input layer event into real
- action).
- * rfkill-input implements EPO by handling EV_SW SW_RFKILL_ALL 0
- (power off all transmitters) in a special way: it ignores any
- overrides and local state cache and forces all transmitters to the
- RFKILL_STATE_SOFT_BLOCKED state (including those which are already
- supposed to be BLOCKED).
- * rfkill EPO will remain active until rfkill-input receives an
- EV_SW SW_RFKILL_ALL 1 event. While the EPO is active, transmitters
- are locked in the blocked state (rfkill will refuse to unblock them).
- * rfkill-input implements different policies that the user can
- select for handling EV_SW SW_RFKILL_ALL 1. It will unlock rfkill,
- and either do nothing (leave transmitters blocked, but now unlocked),
- restore the transmitters to their state before the EPO, or unblock
- them all.
-Userspace uevent handler or kernel platform-specific drivers hooked to the
-rfkill notifier chain:
- * Taps into the rfkill notifier chain or to KOBJ_CHANGE uevents,
- in order to know when a device that is registered with the rfkill
- class changes state;
- * Issues feedback notifications to the user;
- * In the rare platforms where this is required, synthesizes an input
- event to command all *OTHER* rfkill devices to also change their
- statues when a specific rfkill device changes state.
-3: Kernel driver guidelines
-Remember: point-of-view is everything for a driver that connects to the rfkill
-subsystem. All the details below must be measured/perceived from the point of
-view of the specific driver being modified.
-The first thing one needs to know is whether his driver should be talking to
-the rfkill class or to the input layer. In rare cases (platform drivers), it
-could happen that you need to do both, as platform drivers often handle a
-variety of devices in the same driver.
-Do not mistake input devices for rfkill controllers. The only type of "rfkill
-switch" device that is to be registered with the rfkill class are those
-directly controlling the circuits that cause a wireless transmitter to stop
-working (or the software equivalent of them), i.e. what we call a rfkill
-controller. Every other kind of "rfkill switch" is just an input device and
-MUST NOT be registered with the rfkill class.
-A driver should register a device with the rfkill class when ALL of the
-following conditions are met (they define a rfkill controller):
-1. The device is/controls a data communications wireless transmitter;
-2. The kernel can interact with the hardware/firmware to CHANGE the wireless
- transmitter state (block/unblock TX operation);
-3. The transmitter can be made to not emit any energy when "blocked":
- rfkill is not about blocking data transmissions, it is about blocking
- energy emission;
-A driver should register a device with the input subsystem to issue
-rfkill-related events (KEY_WLAN, KEY_BLUETOOTH, KEY_WWAN, KEY_WIMAX,
-SW_RFKILL_ALL, etc) when ALL of the folowing conditions are met:
-1. It is directly related to some physical device the user interacts with, to
- command the O.S./firmware/hardware to enable/disable a data communications
- wireless transmitter.
- Examples of the physical device are: buttons, keys and switches the user
- will press/touch/slide/switch to enable or disable the wireless
- communication device.
-2. It is NOT slaved to another device, i.e. there is no other device that
- issues rfkill-related input events in preference to this one.
- Please refer to the corner cases and examples section for more details.
-When in doubt, do not issue input events. For drivers that should generate
-input events in some platforms, but not in others (e.g. b43), the best solution
-is to NEVER generate input events in the first place. That work should be
-deferred to a platform-specific kernel module (which will know when to generate
-events through the rfkill notifier chain) or to userspace. This avoids the
-usual maintenance problems with DMI whitelisting.
-Corner cases and examples:
-1. If the device is an input device that, because of hardware or firmware,
-causes wireless transmitters to be blocked regardless of the kernel's will, it
-is still just an input device, and NOT to be registered with the rfkill class.
-2. If the wireless transmitter switch control is read-only, it is an input
-device and not to be registered with the rfkill class (and maybe not to be made
-an input layer event source either, see below).
-3. If there is some other device driver *closer* to the actual hardware the
-user interacted with (the button/switch/key) to issue an input event, THAT is
-the device driver that should be issuing input events.
- [RFKILL slider switch] -- [GPIO hardware] -- [WLAN card rf-kill input]
- (platform driver) (wireless card driver)
-The user is closer to the RFKILL slide switch plaform driver, so the driver
-which must issue input events is the platform driver looking at the GPIO
-hardware, and NEVER the wireless card driver (which is just a slave). It is
-very likely that there are other leaves than just the WLAN card rf-kill input
-(e.g. a bluetooth card, etc)...
-On the other hand, some embedded devices do this:
- [RFKILL slider switch] -- [WLAN card rf-kill input]
- (wireless card driver)
-In this situation, the wireless card driver *could* register itself as an input
-device and issue rf-kill related input events... but in order to AVOID the need
-for DMI whitelisting, the wireless card driver does NOT do it. Userspace (HAL)
-or a platform driver (that exists only on these embedded devices) will do the
-dirty job of issuing the input events.
-COMMON MISTAKES in kernel drivers, related to rfkill:
-1. NEVER confuse input device keys and buttons with input device switches.
- 1a. Switches are always set or reset. They report the current state
- (on position or off position).
- 1b. Keys and buttons are either in the pressed or not-pressed state, and
- that's it. A "button" that latches down when you press it, and
- unlatches when you press it again is in fact a switch as far as input
- devices go.
-Add the SW_* events you need for switches, do NOT try to emulate a button using
-KEY_* events just because there is no such SW_* event yet. Do NOT try to use,
-for example, KEY_BLUETOOTH when you should be using SW_BLUETOOTH instead.
-2. Input device switches (sources of EV_SW events) DO store their current state
-(so you *must* initialize it by issuing a gratuitous input layer event on
-driver start-up and also when resuming from sleep), and that state CAN be
-queried from userspace through IOCTLs. There is no sysfs interface for this,
-but that doesn't mean you should break things trying to hook it to the rfkill
-class to get a sysfs interface :-)
-3. Do not issue *_RFKILL_ALL events by default, unless you are sure it is the
-correct event for your switch/button. These events are emergency power-off
-events when they are trying to turn the transmitters off. An example of an
-input device which SHOULD generate *_RFKILL_ALL events is the wireless-kill
-switch in a laptop which is NOT a hotkey, but a real sliding/rocker switch.
-An example of an input device which SHOULD NOT generate *_RFKILL_ALL events by
-default, is any sort of hot key that is type-specific (e.g. the one for WLAN).
-3.1 Guidelines for wireless device drivers
-(in this text, rfkill->foo means the foo field of struct rfkill).
-1. Each independent transmitter in a wireless device (usually there is only one
-transmitter per device) should have a SINGLE rfkill class attached to it.
-2. If the device does not have any sort of hardware assistance to allow the
-driver to rfkill the device, the driver should emulate it by taking all actions
-required to silence the transmitter.
-3. If it is impossible to silence the transmitter (i.e. it still emits energy,
-even if it is just in brief pulses, when there is no data to transmit and there
-is no hardware support to turn it off) do NOT lie to the users. Do not attach
-it to a rfkill class. The rfkill subsystem does not deal with data
-transmission, it deals with energy emission. If the transmitter is emitting
-energy, it is not blocked in rfkill terms.
-4. It doesn't matter if the device has multiple rfkill input lines affecting
-the same transmitter, their combined state is to be exported as a single state
-per transmitter (see rule 1).
-This rule exists because users of the rfkill subsystem expect to get (and set,
-when possible) the overall transmitter rfkill state, not of a particular rfkill
+The rfkill class is provided for kernel drivers to register their radio
+transmitter with the kernel, provide methods for turning it on and off and,
+optionally, letting the system know about hardware-disabled states that may
+be implemented on the device. This code is enabled with the CONFIG_RFKILL
+Kconfig option, which drivers can "select".
-5. The wireless device driver MUST NOT leave the transmitter enabled during
-suspend and hibernation unless:
+The rfkill class code also notifies userspace of state changes, this is
+achieved via uevents. It also provides some sysfs files for userspace to
+check the status of radio transmitters. See the "Userspace support" section
- 5.1. The transmitter has to be enabled for some sort of functionality
- like wake-on-wireless-packet or autonomous packed forwarding in a mesh
- network, and that functionality is enabled for this suspend/hibernation
- cycle.
+The rfkill-input code implements a basic response to rfkill buttons -- it
+implements turning on/off all devices of a certain class (or all).
- 5.2. The device was not on a user-requested BLOCKED state before
- the suspend (i.e. the driver must NOT unblock a device, not even
- to support wake-on-wireless-packet or remain in the mesh).
+When the device is hard-blocked (either by a call to rfkill_set_hw_state()
+or from query_hw_block) set_block() will be invoked but drivers can well
+ignore the method call since they can use the return value of the function
+rfkill_set_hw_state() to sync the software state instead of keeping track
+of calls to set_block().
-In other words, there is absolutely no allowed scenario where a driver can
-automatically take action to unblock a rfkill controller (obviously, this deals
-with scenarios where soft-blocking or both soft and hard blocking is happening.
-Scenarios where hardware rfkill lines are the only ones blocking the
-transmitter are outside of this rule, since the wireless device driver does not
-control its input hardware rfkill lines in the first place).
-6. During resume, rfkill will try to restore its previous state.
+The entire functionality is spread over more than one subsystem:
-7. After a rfkill class is suspended, it will *not* call rfkill->toggle_radio
-until it is resumed.
+ * The kernel input layer generates KEY_WWAN, KEY_WLAN etc. and
+ SW_RFKILL_ALL -- when the user presses a button. Drivers for radio
+ transmitters generally do not register to the input layer, unless the
+ device really provides an input device (i.e. a button that has no
+ effect other than generating a button press event)
+ * The rfkill-input code hooks up to these events and switches the soft-block
+ of the various radio transmitters, depending on the button type.
-Example of a WLAN wireless driver connected to the rfkill subsystem:
+ * The rfkill drivers turn off/on their transmitters as requested.
-A certain WLAN card has one input pin that causes it to block the transmitter
-and makes the status of that input pin available (only for reading!) to the
-kernel driver. This is a hard rfkill input line (it cannot be overridden by
-the kernel driver).
+ * The rfkill class will generate userspace notifications (uevents) to tell
+ userspace what the current state is.
-The card also has one PCI register that, if manipulated by the driver, causes
-it to block the transmitter. This is a soft rfkill input line.
-It has also a thermal protection circuitry that shuts down its transmitter if
-the card overheats, and makes the status of that protection available (only for
-reading!) to the kernel driver. This is also a hard rfkill input line.
-If either one of these rfkill lines are active, the transmitter is blocked by
-the hardware and forced offline.
+3. Kernel driver guidelines
-The driver should allocate and attach to its struct device *ONE* instance of
-the rfkill class (there is only one transmitter).
-It can implement the get_state() hook, and return RFKILL_STATE_HARD_BLOCKED if
-either one of its two hard rfkill input lines are active. If the two hard
-rfkill lines are inactive, it must return RFKILL_STATE_SOFT_BLOCKED if its soft
-rfkill input line is active. Only if none of the rfkill input lines are
-active, will it return RFKILL_STATE_UNBLOCKED.
+Drivers for radio transmitters normally implement only the rfkill class.
+These drivers may not unblock the transmitter based on own decisions, they
+should act on information provided by the rfkill class only.
-Since the device has a hardware rfkill line, it IS subject to state changes
-external to rfkill. Therefore, the driver must make sure that it calls
-rfkill_force_state() to keep the status always up-to-date, and it must do a
-rfkill_force_state() on resume from sleep.
+Platform drivers might implement input devices if the rfkill button is just
+that, a button. If that button influences the hardware then you need to
+implement an rfkill class instead. This also applies if the platform provides
+a way to turn on/off the transmitter(s).
-Every time the driver gets a notification from the card that one of its rfkill
-lines changed state (polling might be needed on badly designed cards that don't
-generate interrupts for such events), it recomputes the rfkill state as per
-above, and calls rfkill_force_state() to update it.
+During suspend/hibernation, transmitters should only be left enabled when
+wake-on wlan or similar functionality requires it and the device wasn't
+blocked before suspend/hibernate. Note that it may be necessary to update
+the rfkill subsystem's idea of what the current state is at resume time if
+the state may have changed over suspend.
-The driver should implement the toggle_radio() hook, that:
-1. Returns an error if one of the hardware rfkill lines are active, and the
-caller asked for RFKILL_STATE_UNBLOCKED.
-2. Activates the soft rfkill line if the caller asked for state
-RFKILL_STATE_SOFT_BLOCKED. It should do this even if one of the hard rfkill
-lines are active, effectively double-blocking the transmitter.
-3. Deactivates the soft rfkill line if none of the hardware rfkill lines are
-active and the caller asked for RFKILL_STATE_UNBLOCKED.
-4: Kernel API
+4. Kernel API
To build a driver with rfkill subsystem support, the driver should depend on
-(or select) the Kconfig symbol RFKILL; it should _not_ depend on RKFILL_INPUT.
+(or select) the Kconfig symbol RFKILL.
The hardware the driver talks to may be write-only (where the current state
of the hardware is unknown), or read-write (where the hardware can be queried
about its current state).
-The rfkill class will call the get_state hook of a device every time it needs
-to know the *real* current state of the hardware. This can happen often, but
-it does not do any polling, so it is not enough on hardware that is subject
-to state changes outside of the rfkill subsystem.
-Therefore, calling rfkill_force_state() when a state change happens is
-mandatory when the device has a hardware rfkill line, or when something else
-like the firmware could cause its state to be changed without going through the
-rfkill class.
-Some hardware provides events when its status changes. In these cases, it is
-best for the driver to not provide a get_state hook, and instead register the
-rfkill class *already* with the correct status, and keep it updated using
-rfkill_force_state() when it gets an event from the hardware.
-rfkill_force_state() must be used on the device resume handlers to update the
-rfkill status, should there be any chance of the device status changing during
-the sleep.
-There is no provision for a statically-allocated rfkill struct. You must
-use rfkill_allocate() to allocate one.
-You should:
- - rfkill_allocate()
- - modify rfkill fields (flags, name)
- - modify state to the current hardware state (THIS IS THE ONLY TIME
- - rfkill_register()
+Calling rfkill_set_hw_state() when a state change happens is required from
+rfkill drivers that control devices that can be hard-blocked unless they also
+assign the poll_hw_block() callback (then the rfkill core will poll the
+device). Don't do this unless you cannot get the event in any other way.
-The only way to set a device to the RFKILL_STATE_HARD_BLOCKED state is through
-a suitable return of get_state() or through rfkill_force_state().
-When a device is in the RFKILL_STATE_HARD_BLOCKED state, the only way to switch
-it to a different state is through a suitable return of get_state() or through
-If toggle_radio() is called to set a device to state RFKILL_STATE_SOFT_BLOCKED
-when that device is already at the RFKILL_STATE_HARD_BLOCKED state, it should
-not return an error. Instead, it should try to double-block the transmitter,
-so that its state will change from RFKILL_STATE_HARD_BLOCKED to
-RFKILL_STATE_SOFT_BLOCKED should the hardware blocking cease.
-Please refer to the source for more documentation.
-5: Userspace support
-rfkill devices issue uevents (with an action of "change"), with the following
-environment variables set:
+5. Userspace support
-The ABI for these variables is defined by the sysfs attributes. It is best
-to take a quick look at the source to make sure of the possible values.
-It is expected that HAL will trap those, and bridge them to DBUS, etc. These
-events CAN and SHOULD be used to give feedback to the user about the rfkill
-status of the system.
-Input devices may issue events that are related to rfkill. These are the
-various KEY_* events and SW_* events supported by rfkill-input.c.
-Userspace may not change the state of an rfkill switch in response to an
-input event, it should refrain from changing states entirely.
-Userspace cannot assume it is the only source of control for rfkill switches.
-Their state can change due to firmware actions, direct user actions, and the
-rfkill-input EPO override for *_RFKILL_ALL.
-When rfkill-input is not active, userspace must initiate a rfkill status
-change by writing to the "state" attribute in order for anything to happen.
-Take particular care to implement EV_SW SW_RFKILL_ALL properly. When that
-switch is set to OFF, *every* rfkill device *MUST* be immediately put into the
-RFKILL_STATE_SOFT_BLOCKED state, no questions asked.
-The following sysfs entries will be created:
+The following sysfs entries exist for every rfkill device:
name: Name assigned by driver to this key (interface or driver name).
type: Name of the key type ("wlan", "bluetooth", etc).
state: Current state of the transmitter
- transmitter is forced off, but one can override it
- by a write to the state attribute;
+ transmitter is turned off by software
- transmiter is NOT forced off, and may operate if
- all other conditions for such operation are met
- (such as interface is up and configured, etc);
+ transmiter is (potentially) active
transmitter is forced off by something outside of
- the driver's control. One cannot set a device to
- this state through writes to the state attribute;
- claim: 1: Userspace handles events, 0: Kernel handles events
-Both the "state" and "claim" entries are also writable. For the "state" entry
-this means that when 1 or 0 is written, the device rfkill state (if not yet in
-the requested state), will be will be toggled accordingly.
-For the "claim" entry writing 1 to it means that the kernel no longer handles
-key events even though RFKILL_INPUT input was enabled. When "claim" has been
-set to 0, userspace should make sure that it listens for the input events or
-check the sysfs "state" entry regularly to correctly perform the required tasks
-when the rkfill key is pressed.
-A note about input devices and EV_SW events:
-In order to know the current state of an input device switch (like
-SW_RFKILL_ALL), you will need to use an IOCTL. That information is not
-available through sysfs in a generic way at this time, and it is not available
-through the rfkill class AT ALL.
+ the driver's control.
+ claim: 0: Kernel handles events (currently always reads that value)
+rfkill devices also issue uevents (with an action of "change"), with the
+following environment variables set:
+The contents of these variables corresponds to the "name", "state" and
+"type" sysfs files explained above.