blob: 28b6ec87c64209b10a83dfe1a7bfcebf6f231991 [file] [log] [blame]
Ivo van Doorndac24ab2007-09-13 09:22:55 +02001rfkill - RF switch subsystem support
2====================================
3
Henrique de Moraes Holschuhdc288522008-06-23 17:23:08 -030041 Introduction
52 Implementation details
63 Kernel driver guidelines
Henrique de Moraes Holschuhf7983f72008-06-23 17:46:43 -030073.1 wireless device drivers
83.2 platform/switch drivers
93.3 input device drivers
Henrique de Moraes Holschuhdc288522008-06-23 17:23:08 -0300104 Kernel API
115 Userspace support
Ivo van Doorndac24ab2007-09-13 09:22:55 +020012
Henrique de Moraes Holschuhdc288522008-06-23 17:23:08 -030013
141. Introduction:
Ivo van Doorndac24ab2007-09-13 09:22:55 +020015
Henrique de Moraes Holschuhf3146af2008-06-23 17:22:56 -030016The rfkill switch subsystem exists to add a generic interface to circuitry that
Henrique de Moraes Holschuhdc288522008-06-23 17:23:08 -030017can enable or disable the signal output of a wireless *transmitter* of any
18type. By far, the most common use is to disable radio-frequency transmitters.
Henrique de Moraes Holschuhf3146af2008-06-23 17:22:56 -030019
Henrique de Moraes Holschuhf7983f72008-06-23 17:46:43 -030020Note that disabling the signal output means that the the transmitter is to be
21made to not emit any energy when "blocked". rfkill is not about blocking data
22transmissions, it is about blocking energy emission.
23
24The rfkill subsystem offers support for keys and switches often found on
25laptops to enable wireless devices like WiFi and Bluetooth, so that these keys
26and switches actually perform an action in all wireless devices of a given type
27attached to the system.
Henrique de Moraes Holschuhf3146af2008-06-23 17:22:56 -030028
Henrique de Moraes Holschuhdc288522008-06-23 17:23:08 -030029The buttons to enable and disable the wireless transmitters are important in
Ivo van Doorndac24ab2007-09-13 09:22:55 +020030situations where the user is for example using his laptop on a location where
Henrique de Moraes Holschuhdc288522008-06-23 17:23:08 -030031radio-frequency transmitters _must_ be disabled (e.g. airplanes).
32
33Because of this requirement, userspace support for the keys should not be made
34mandatory. Because userspace might want to perform some additional smarter
35tasks when the key is pressed, rfkill provides userspace the possibility to
36take over the task to handle the key events.
37
38===============================================================================
392: Implementation details
40
Henrique de Moraes Holschuhf7983f72008-06-23 17:46:43 -030041The rfkill subsystem is composed of various components: the rfkill class, the
42rfkill-input module (an input layer handler), and some specific input layer
43events.
44
Henrique de Moraes Holschuhdc288522008-06-23 17:23:08 -030045The rfkill class provides kernel drivers with an interface that allows them to
46know when they should enable or disable a wireless network device transmitter.
Henrique de Moraes Holschuhf7983f72008-06-23 17:46:43 -030047This is enabled by the CONFIG_RFKILL Kconfig option.
48
49The rfkill class support makes sure userspace will be notified of all state
50changes on rfkill devices through uevents. It provides a notification chain
51for interested parties in the kernel to also get notified of rfkill state
52changes in other drivers. It creates several sysfs entries which can be used
53by userspace. See section "Userspace support".
Henrique de Moraes Holschuhdc288522008-06-23 17:23:08 -030054
55The rfkill-input module provides the kernel with the ability to implement a
56basic response when the user presses a key or button (or toggles a switch)
57related to rfkill functionality. It is an in-kernel implementation of default
58policy of reacting to rfkill-related input events and neither mandatory nor
Henrique de Moraes Holschuhf7983f72008-06-23 17:46:43 -030059required for wireless drivers to operate. It is enabled by the
60CONFIG_RFKILL_INPUT Kconfig option.
61
62rfkill-input is a rfkill-related events input layer handler. This handler will
63listen to all rfkill key events and will change the rfkill state of the
64wireless devices accordingly. With this option enabled userspace could either
65do nothing or simply perform monitoring tasks.
Henrique de Moraes Holschuhdc288522008-06-23 17:23:08 -030066
67The rfkill-input module also provides EPO (emergency power-off) functionality
Henrique de Moraes Holschuhf7983f72008-06-23 17:46:43 -030068for all wireless transmitters. This function cannot be overridden, and it is
69always active. rfkill EPO is related to *_RFKILL_ALL input layer events.
Henrique de Moraes Holschuhdc288522008-06-23 17:23:08 -030070
Ivo van Doorndac24ab2007-09-13 09:22:55 +020071
Henrique de Moraes Holschuhf7983f72008-06-23 17:46:43 -030072Important terms for the rfkill subsystem:
Ivo van Doorndac24ab2007-09-13 09:22:55 +020073
Henrique de Moraes Holschuhf7983f72008-06-23 17:46:43 -030074In order to avoid confusion, we avoid the term "switch" in rfkill when it is
75referring to an electronic control circuit that enables or disables a
76transmitter. We reserve it for the physical device a human manipulates
77(which is an input device, by the way):
Ivo van Doorndac24ab2007-09-13 09:22:55 +020078
Henrique de Moraes Holschuhf7983f72008-06-23 17:46:43 -030079rfkill switch:
Ivo van Doorndac24ab2007-09-13 09:22:55 +020080
Henrique de Moraes Holschuhf7983f72008-06-23 17:46:43 -030081 A physical device a human manipulates. Its state can be perceived by
82 the kernel either directly (through a GPIO pin, ACPI GPE) or by its
83 effect on a rfkill line of a wireless device.
84
85rfkill controller:
86
87 A hardware circuit that controls the state of a rfkill line, which a
88 kernel driver can interact with *to modify* that state (i.e. it has
89 either write-only or read/write access).
90
91rfkill line:
92
93 An input channel (hardware or software) of a wireless device, which
94 causes a wireless transmitter to stop emitting energy (BLOCK) when it
95 is active. Point of view is extremely important here: rfkill lines are
96 always seen from the PoV of a wireless device (and its driver).
97
98soft rfkill line/software rfkill line:
99
100 A rfkill line the wireless device driver can directly change the state
101 of. Related to rfkill_state RFKILL_STATE_SOFT_BLOCKED.
102
103hard rfkill line/hardware rfkill line:
104
105 A rfkill line that works fully in hardware or firmware, and that cannot
106 be overridden by the kernel driver. The hardware device or the
107 firmware just exports its status to the driver, but it is read-only.
108 Related to rfkill_state RFKILL_STATE_HARD_BLOCKED.
109
110The enum rfkill_state describes the rfkill state of a transmitter:
111
112When a rfkill line or rfkill controller is in the RFKILL_STATE_UNBLOCKED state,
113the wireless transmitter (radio TX circuit for example) is *enabled*. When the
114it is in the RFKILL_STATE_SOFT_BLOCKED or RFKILL_STATE_HARD_BLOCKED, the
115wireless transmitter is to be *blocked* from operating.
Henrique de Moraes Holschuh50056572008-06-23 17:46:42 -0300116
117RFKILL_STATE_SOFT_BLOCKED indicates that a call to toggle_radio() can change
118that state. RFKILL_STATE_HARD_BLOCKED indicates that a call to toggle_radio()
119will not be able to change the state and will return with a suitable error if
120attempts are made to set the state to RFKILL_STATE_UNBLOCKED.
121
122RFKILL_STATE_HARD_BLOCKED is used by drivers to signal that the device is
123locked in the BLOCKED state by a hardwire rfkill line (typically an input pin
124that, when active, forces the transmitter to be disabled) which the driver
125CANNOT override.
Henrique de Moraes Holschuhdc288522008-06-23 17:23:08 -0300126
127Full rfkill functionality requires two different subsystems to cooperate: the
128input layer and the rfkill class. The input layer issues *commands* to the
129entire system requesting that devices registered to the rfkill class change
130state. The way this interaction happens is not complex, but it is not obvious
131either:
132
133Kernel Input layer:
134
135 * Generates KEY_WWAN, KEY_WLAN, KEY_BLUETOOTH, SW_RFKILL_ALL, and
136 other such events when the user presses certain keys, buttons, or
137 toggles certain physical switches.
138
139 THE INPUT LAYER IS NEVER USED TO PROPAGATE STATUS, NOTIFICATIONS OR THE
140 KIND OF STUFF AN ON-SCREEN-DISPLAY APPLICATION WOULD REPORT. It is
141 used to issue *commands* for the system to change behaviour, and these
142 commands may or may not be carried out by some kernel driver or
143 userspace application. It follows that doing user feedback based only
Henrique de Moraes Holschuhf7983f72008-06-23 17:46:43 -0300144 on input events is broken, as there is no guarantee that an input event
Henrique de Moraes Holschuhdc288522008-06-23 17:23:08 -0300145 will be acted upon.
146
147 Most wireless communication device drivers implementing rfkill
148 functionality MUST NOT generate these events, and have no reason to
Henrique de Moraes Holschuhf7983f72008-06-23 17:46:43 -0300149 register themselves with the input layer. Doing otherwise is a common
Henrique de Moraes Holschuhdc288522008-06-23 17:23:08 -0300150 misconception. There is an API to propagate rfkill status change
151 information, and it is NOT the input layer.
152
153rfkill class:
154
155 * Calls a hook in a driver to effectively change the wireless
156 transmitter state;
157 * Keeps track of the wireless transmitter state (with help from
158 the driver);
159 * Generates userspace notifications (uevents) and a call to a
160 notification chain (kernel) when there is a wireless transmitter
161 state change;
162 * Connects a wireless communications driver with the common rfkill
163 control system, which, for example, allows actions such as
164 "switch all bluetooth devices offline" to be carried out by
165 userspace or by rfkill-input.
166
167 THE RFKILL CLASS NEVER ISSUES INPUT EVENTS. THE RFKILL CLASS DOES
168 NOT LISTEN TO INPUT EVENTS. NO DRIVER USING THE RFKILL CLASS SHALL
Henrique de Moraes Holschuhf7983f72008-06-23 17:46:43 -0300169 EVER LISTEN TO, OR ACT ON RFKILL INPUT EVENTS. Doing otherwise is
170 a layering violation.
Henrique de Moraes Holschuhdc288522008-06-23 17:23:08 -0300171
172 Most wireless data communication drivers in the kernel have just to
173 implement the rfkill class API to work properly. Interfacing to the
Henrique de Moraes Holschuhf7983f72008-06-23 17:46:43 -0300174 input layer is not often required (and is very often a *bug*) on
175 wireless drivers.
176
177 Platform drivers often have to attach to the input layer to *issue*
178 (but never to listen to) rfkill events for rfkill switches, and also to
179 the rfkill class to export a control interface for the platform rfkill
180 controllers to the rfkill subsystem. This does NOT mean the rfkill
181 switch is attached to a rfkill class (doing so is almost always wrong).
182 It just means the same kernel module is the driver for different
183 devices (rfkill switches and rfkill controllers).
184
Henrique de Moraes Holschuhdc288522008-06-23 17:23:08 -0300185
186Userspace input handlers (uevents) or kernel input handlers (rfkill-input):
187
188 * Implements the policy of what should happen when one of the input
189 layer events related to rfkill operation is received.
190 * Uses the sysfs interface (userspace) or private rfkill API calls
191 to tell the devices registered with the rfkill class to change
192 their state (i.e. translates the input layer event into real
193 action).
194 * rfkill-input implements EPO by handling EV_SW SW_RFKILL_ALL 0
195 (power off all transmitters) in a special way: it ignores any
Henrique de Moraes Holschuh50056572008-06-23 17:46:42 -0300196 overrides and local state cache and forces all transmitters to the
197 RFKILL_STATE_SOFT_BLOCKED state (including those which are already
198 supposed to be BLOCKED). Note that the opposite event (power on all
199 transmitters) is handled normally.
Henrique de Moraes Holschuhdc288522008-06-23 17:23:08 -0300200
201Userspace uevent handler or kernel platform-specific drivers hooked to the
202rfkill notifier chain:
203
204 * Taps into the rfkill notifier chain or to KOBJ_CHANGE uevents,
205 in order to know when a device that is registered with the rfkill
206 class changes state;
207 * Issues feedback notifications to the user;
208 * In the rare platforms where this is required, synthesizes an input
209 event to command all *OTHER* rfkill devices to also change their
210 statues when a specific rfkill device changes state.
211
212
213===============================================================================
2143: Kernel driver guidelines
215
Henrique de Moraes Holschuhf7983f72008-06-23 17:46:43 -0300216Remember: point-of-view is everything for a driver that connects to the rfkill
217subsystem. All the details below must be measured/perceived from the point of
218view of the specific driver being modified.
Henrique de Moraes Holschuhdc288522008-06-23 17:23:08 -0300219
Henrique de Moraes Holschuhf7983f72008-06-23 17:46:43 -0300220The first thing one needs to know is whether his driver should be talking to
221the rfkill class or to the input layer. In rare cases (platform drivers), it
222could happen that you need to do both, as platform drivers often handle a
223variety of devices in the same driver.
224
225Do not mistake input devices for rfkill controllers. The only type of "rfkill
Henrique de Moraes Holschuhdc288522008-06-23 17:23:08 -0300226switch" device that is to be registered with the rfkill class are those
227directly controlling the circuits that cause a wireless transmitter to stop
Henrique de Moraes Holschuhf7983f72008-06-23 17:46:43 -0300228working (or the software equivalent of them), i.e. what we call a rfkill
229controller. Every other kind of "rfkill switch" is just an input device and
230MUST NOT be registered with the rfkill class.
Henrique de Moraes Holschuhdc288522008-06-23 17:23:08 -0300231
232A driver should register a device with the rfkill class when ALL of the
Henrique de Moraes Holschuhf7983f72008-06-23 17:46:43 -0300233following conditions are met (they define a rfkill controller):
Henrique de Moraes Holschuhdc288522008-06-23 17:23:08 -0300234
2351. The device is/controls a data communications wireless transmitter;
236
2372. The kernel can interact with the hardware/firmware to CHANGE the wireless
238 transmitter state (block/unblock TX operation);
239
Henrique de Moraes Holschuhf7983f72008-06-23 17:46:43 -03002403. The transmitter can be made to not emit any energy when "blocked":
241 rfkill is not about blocking data transmissions, it is about blocking
242 energy emission;
243
Henrique de Moraes Holschuhdc288522008-06-23 17:23:08 -0300244A driver should register a device with the input subsystem to issue
245rfkill-related events (KEY_WLAN, KEY_BLUETOOTH, KEY_WWAN, KEY_WIMAX,
246SW_RFKILL_ALL, etc) when ALL of the folowing conditions are met:
247
2481. It is directly related to some physical device the user interacts with, to
249 command the O.S./firmware/hardware to enable/disable a data communications
250 wireless transmitter.
251
252 Examples of the physical device are: buttons, keys and switches the user
253 will press/touch/slide/switch to enable or disable the wireless
254 communication device.
255
2562. It is NOT slaved to another device, i.e. there is no other device that
257 issues rfkill-related input events in preference to this one.
258
Henrique de Moraes Holschuhf7983f72008-06-23 17:46:43 -0300259 Please refer to the corner cases and examples section for more details.
Henrique de Moraes Holschuhdc288522008-06-23 17:23:08 -0300260
261When in doubt, do not issue input events. For drivers that should generate
262input events in some platforms, but not in others (e.g. b43), the best solution
263is to NEVER generate input events in the first place. That work should be
264deferred to a platform-specific kernel module (which will know when to generate
265events through the rfkill notifier chain) or to userspace. This avoids the
266usual maintenance problems with DMI whitelisting.
267
268
269Corner cases and examples:
Ivo van Doorndac24ab2007-09-13 09:22:55 +0200270====================================
Ivo van Doorndac24ab2007-09-13 09:22:55 +0200271
Henrique de Moraes Holschuhdc288522008-06-23 17:23:08 -03002721. If the device is an input device that, because of hardware or firmware,
273causes wireless transmitters to be blocked regardless of the kernel's will, it
274is still just an input device, and NOT to be registered with the rfkill class.
Ivo van Doorndac24ab2007-09-13 09:22:55 +0200275
Henrique de Moraes Holschuhdc288522008-06-23 17:23:08 -03002762. If the wireless transmitter switch control is read-only, it is an input
277device and not to be registered with the rfkill class (and maybe not to be made
278an input layer event source either, see below).
Ivo van Doorndac24ab2007-09-13 09:22:55 +0200279
Henrique de Moraes Holschuhdc288522008-06-23 17:23:08 -03002803. If there is some other device driver *closer* to the actual hardware the
281user interacted with (the button/switch/key) to issue an input event, THAT is
282the device driver that should be issuing input events.
Ivo van Doorndac24ab2007-09-13 09:22:55 +0200283
Henrique de Moraes Holschuhdc288522008-06-23 17:23:08 -0300284E.g:
285 [RFKILL slider switch] -- [GPIO hardware] -- [WLAN card rf-kill input]
286 (platform driver) (wireless card driver)
Ivo van Doorndac24ab2007-09-13 09:22:55 +0200287
Henrique de Moraes Holschuhdc288522008-06-23 17:23:08 -0300288The user is closer to the RFKILL slide switch plaform driver, so the driver
289which must issue input events is the platform driver looking at the GPIO
290hardware, and NEVER the wireless card driver (which is just a slave). It is
291very likely that there are other leaves than just the WLAN card rf-kill input
292(e.g. a bluetooth card, etc)...
Ivo van Doorndac24ab2007-09-13 09:22:55 +0200293
Henrique de Moraes Holschuhdc288522008-06-23 17:23:08 -0300294On the other hand, some embedded devices do this:
Ivo van Doorndac24ab2007-09-13 09:22:55 +0200295
Henrique de Moraes Holschuhdc288522008-06-23 17:23:08 -0300296 [RFKILL slider switch] -- [WLAN card rf-kill input]
297 (wireless card driver)
Ivo van Doorndac24ab2007-09-13 09:22:55 +0200298
Henrique de Moraes Holschuhdc288522008-06-23 17:23:08 -0300299In this situation, the wireless card driver *could* register itself as an input
300device and issue rf-kill related input events... but in order to AVOID the need
301for DMI whitelisting, the wireless card driver does NOT do it. Userspace (HAL)
302or a platform driver (that exists only on these embedded devices) will do the
303dirty job of issuing the input events.
304
305
306COMMON MISTAKES in kernel drivers, related to rfkill:
Ivo van Doorndac24ab2007-09-13 09:22:55 +0200307====================================
Ivo van Doorndac24ab2007-09-13 09:22:55 +0200308
Henrique de Moraes Holschuhdc288522008-06-23 17:23:08 -03003091. NEVER confuse input device keys and buttons with input device switches.
310
311 1a. Switches are always set or reset. They report the current state
312 (on position or off position).
313
314 1b. Keys and buttons are either in the pressed or not-pressed state, and
315 that's it. A "button" that latches down when you press it, and
316 unlatches when you press it again is in fact a switch as far as input
317 devices go.
318
319Add the SW_* events you need for switches, do NOT try to emulate a button using
320KEY_* events just because there is no such SW_* event yet. Do NOT try to use,
321for example, KEY_BLUETOOTH when you should be using SW_BLUETOOTH instead.
322
Henrique de Moraes Holschuhf7983f72008-06-23 17:46:43 -03003232. Input device switches (sources of EV_SW events) DO store their current state
324(so you *must* initialize it by issuing a gratuitous input layer event on
325driver start-up and also when resuming from sleep), and that state CAN be
326queried from userspace through IOCTLs. There is no sysfs interface for this,
327but that doesn't mean you should break things trying to hook it to the rfkill
328class to get a sysfs interface :-)
Henrique de Moraes Holschuhdc288522008-06-23 17:23:08 -0300329
Henrique de Moraes Holschuhf7983f72008-06-23 17:46:43 -03003303. Do not issue *_RFKILL_ALL events by default, unless you are sure it is the
331correct event for your switch/button. These events are emergency power-off
332events when they are trying to turn the transmitters off. An example of an
333input device which SHOULD generate *_RFKILL_ALL events is the wireless-kill
334switch in a laptop which is NOT a hotkey, but a real switch that kills radios
335in hardware, even if the O.S. has gone to lunch. An example of an input device
336which SHOULD NOT generate *_RFKILL_ALL events by default, is any sort of hot
337key that does nothing by itself, as well as any hot key that is type-specific
338(e.g. the one for WLAN).
Henrique de Moraes Holschuhdc288522008-06-23 17:23:08 -0300339
340
Henrique de Moraes Holschuhf7983f72008-06-23 17:46:43 -03003413.1 Guidelines for wireless device drivers
342------------------------------------------
343
3441. Each independent transmitter in a wireless device (usually there is only one
345transmitter per device) should have a SINGLE rfkill class attached to it.
346
3472. If the device does not have any sort of hardware assistance to allow the
348driver to rfkill the device, the driver should emulate it by taking all actions
349required to silence the transmitter.
350
3513. If it is impossible to silence the transmitter (i.e. it still emits energy,
352even if it is just in brief pulses, when there is no data to transmit and there
353is no hardware support to turn it off) do NOT lie to the users. Do not attach
354it to a rfkill class. The rfkill subsystem does not deal with data
355transmission, it deals with energy emission. If the transmitter is emitting
356energy, it is not blocked in rfkill terms.
357
3584. It doesn't matter if the device has multiple rfkill input lines affecting
359the same transmitter, their combined state is to be exported as a single state
360per transmitter (see rule 1).
361
362This rule exists because users of the rfkill subsystem expect to get (and set,
363when possible) the overall transmitter rfkill state, not of a particular rfkill
364line.
365
366Example of a WLAN wireless driver connected to the rfkill subsystem:
367--------------------------------------------------------------------
368
369A certain WLAN card has one input pin that causes it to block the transmitter
370and makes the status of that input pin available (only for reading!) to the
371kernel driver. This is a hard rfkill input line (it cannot be overridden by
372the kernel driver).
373
374The card also has one PCI register that, if manipulated by the driver, causes
375it to block the transmitter. This is a soft rfkill input line.
376
377It has also a thermal protection circuitry that shuts down its transmitter if
378the card overheats, and makes the status of that protection available (only for
379reading!) to the kernel driver. This is also a hard rfkill input line.
380
381If either one of these rfkill lines are active, the transmitter is blocked by
382the hardware and forced offline.
383
384The driver should allocate and attach to its struct device *ONE* instance of
385the rfkill class (there is only one transmitter).
386
387It can implement the get_state() hook, and return RFKILL_STATE_HARD_BLOCKED if
388either one of its two hard rfkill input lines are active. If the two hard
389rfkill lines are inactive, it must return RFKILL_STATE_SOFT_BLOCKED if its soft
390rfkill input line is active. Only if none of the rfkill input lines are
391active, will it return RFKILL_STATE_UNBLOCKED.
392
Henrique de Moraes Holschuh2fd9b222008-07-21 21:18:17 -0300393Since the device has a hardware rfkill line, it IS subject to state changes
394external to rfkill. Therefore, the driver must make sure that it calls
395rfkill_force_state() to keep the status always up-to-date, and it must do a
396rfkill_force_state() on resume from sleep.
Henrique de Moraes Holschuhf7983f72008-06-23 17:46:43 -0300397
398Every time the driver gets a notification from the card that one of its rfkill
399lines changed state (polling might be needed on badly designed cards that don't
400generate interrupts for such events), it recomputes the rfkill state as per
401above, and calls rfkill_force_state() to update it.
402
403The driver should implement the toggle_radio() hook, that:
404
4051. Returns an error if one of the hardware rfkill lines are active, and the
406caller asked for RFKILL_STATE_UNBLOCKED.
407
4082. Activates the soft rfkill line if the caller asked for state
409RFKILL_STATE_SOFT_BLOCKED. It should do this even if one of the hard rfkill
410lines are active, effectively double-blocking the transmitter.
411
4123. Deactivates the soft rfkill line if none of the hardware rfkill lines are
413active and the caller asked for RFKILL_STATE_UNBLOCKED.
414
Henrique de Moraes Holschuhdc288522008-06-23 17:23:08 -0300415===============================================================================
4164: Kernel API
417
418To build a driver with rfkill subsystem support, the driver should depend on
Henrique de Moraes Holschuhf7983f72008-06-23 17:46:43 -0300419(or select) the Kconfig symbol RFKILL; it should _not_ depend on RKFILL_INPUT.
Henrique de Moraes Holschuhdc288522008-06-23 17:23:08 -0300420
421The hardware the driver talks to may be write-only (where the current state
422of the hardware is unknown), or read-write (where the hardware can be queried
423about its current state).
424
425The rfkill class will call the get_state hook of a device every time it needs
Henrique de Moraes Holschuh2fd9b222008-07-21 21:18:17 -0300426to know the *real* current state of the hardware. This can happen often, but
427it does not do any polling, so it is not enough on hardware that is subject
428to state changes outside of the rfkill subsystem.
429
430Therefore, calling rfkill_force_state() when a state change happens is
431mandatory when the device has a hardware rfkill line, or when something else
432like the firmware could cause its state to be changed without going through the
433rfkill class.
Henrique de Moraes Holschuhdc288522008-06-23 17:23:08 -0300434
435Some hardware provides events when its status changes. In these cases, it is
436best for the driver to not provide a get_state hook, and instead register the
437rfkill class *already* with the correct status, and keep it updated using
438rfkill_force_state() when it gets an event from the hardware.
439
Henrique de Moraes Holschuh2fd9b222008-07-21 21:18:17 -0300440rfkill_force_state() must be used on the device resume handlers to update the
441rfkill status, should there be any chance of the device status changing during
442the sleep.
443
Henrique de Moraes Holschuhdc288522008-06-23 17:23:08 -0300444There is no provision for a statically-allocated rfkill struct. You must
445use rfkill_allocate() to allocate one.
446
447You should:
448 - rfkill_allocate()
449 - modify rfkill fields (flags, name)
450 - modify state to the current hardware state (THIS IS THE ONLY TIME
451 YOU CAN ACCESS state DIRECTLY)
452 - rfkill_register()
453
Henrique de Moraes Holschuh50056572008-06-23 17:46:42 -0300454The only way to set a device to the RFKILL_STATE_HARD_BLOCKED state is through
455a suitable return of get_state() or through rfkill_force_state().
456
457When a device is in the RFKILL_STATE_HARD_BLOCKED state, the only way to switch
458it to a different state is through a suitable return of get_state() or through
459rfkill_force_state().
460
461If toggle_radio() is called to set a device to state RFKILL_STATE_SOFT_BLOCKED
462when that device is already at the RFKILL_STATE_HARD_BLOCKED state, it should
463not return an error. Instead, it should try to double-block the transmitter,
464so that its state will change from RFKILL_STATE_HARD_BLOCKED to
465RFKILL_STATE_SOFT_BLOCKED should the hardware blocking cease.
466
Henrique de Moraes Holschuhdc288522008-06-23 17:23:08 -0300467Please refer to the source for more documentation.
468
469===============================================================================
4705: Userspace support
471
472rfkill devices issue uevents (with an action of "change"), with the following
473environment variables set:
474
475RFKILL_NAME
476RFKILL_STATE
477RFKILL_TYPE
478
479The ABI for these variables is defined by the sysfs attributes. It is best
480to take a quick look at the source to make sure of the possible values.
481
482It is expected that HAL will trap those, and bridge them to DBUS, etc. These
483events CAN and SHOULD be used to give feedback to the user about the rfkill
484status of the system.
485
486Input devices may issue events that are related to rfkill. These are the
487various KEY_* events and SW_* events supported by rfkill-input.c.
488
489******IMPORTANT******
490When rfkill-input is ACTIVE, userspace is NOT TO CHANGE THE STATE OF AN RFKILL
491SWITCH IN RESPONSE TO AN INPUT EVENT also handled by rfkill-input, unless it
492has set to true the user_claim attribute for that particular switch. This rule
493is *absolute*; do NOT violate it.
494******IMPORTANT******
495
496Userspace must not assume it is the only source of control for rfkill switches.
Henrique de Moraes Holschuhf7983f72008-06-23 17:46:43 -0300497Their state CAN and WILL change due to firmware actions, direct user actions,
498and the rfkill-input EPO override for *_RFKILL_ALL.
Henrique de Moraes Holschuhdc288522008-06-23 17:23:08 -0300499
Henrique de Moraes Holschuhf7983f72008-06-23 17:46:43 -0300500When rfkill-input is not active, userspace must initiate a rfkill status
Henrique de Moraes Holschuhdc288522008-06-23 17:23:08 -0300501change by writing to the "state" attribute in order for anything to happen.
502
503Take particular care to implement EV_SW SW_RFKILL_ALL properly. When that
504switch is set to OFF, *every* rfkill device *MUST* be immediately put into the
Henrique de Moraes Holschuh50056572008-06-23 17:46:42 -0300505RFKILL_STATE_SOFT_BLOCKED state, no questions asked.
Ivo van Doorndac24ab2007-09-13 09:22:55 +0200506
507The following sysfs entries will be created:
508
509 name: Name assigned by driver to this key (interface or driver name).
510 type: Name of the key type ("wlan", "bluetooth", etc).
Henrique de Moraes Holschuh50056572008-06-23 17:46:42 -0300511 state: Current state of the transmitter
512 0: RFKILL_STATE_SOFT_BLOCKED
Henrique de Moraes Holschuhf7983f72008-06-23 17:46:43 -0300513 transmitter is forced off, but one can override it
514 by a write to the state attribute;
Henrique de Moraes Holschuh50056572008-06-23 17:46:42 -0300515 1: RFKILL_STATE_UNBLOCKED
516 transmiter is NOT forced off, and may operate if
517 all other conditions for such operation are met
Henrique de Moraes Holschuhf7983f72008-06-23 17:46:43 -0300518 (such as interface is up and configured, etc);
Henrique de Moraes Holschuh50056572008-06-23 17:46:42 -0300519 2: RFKILL_STATE_HARD_BLOCKED
520 transmitter is forced off by something outside of
Henrique de Moraes Holschuhf7983f72008-06-23 17:46:43 -0300521 the driver's control. One cannot set a device to
522 this state through writes to the state attribute;
Ivo van Doorndac24ab2007-09-13 09:22:55 +0200523 claim: 1: Userspace handles events, 0: Kernel handles events
524
525Both the "state" and "claim" entries are also writable. For the "state" entry
Henrique de Moraes Holschuhdc288522008-06-23 17:23:08 -0300526this means that when 1 or 0 is written, the device rfkill state (if not yet in
527the requested state), will be will be toggled accordingly.
528
Ivo van Doorndac24ab2007-09-13 09:22:55 +0200529For the "claim" entry writing 1 to it means that the kernel no longer handles
530key events even though RFKILL_INPUT input was enabled. When "claim" has been
531set to 0, userspace should make sure that it listens for the input events or
Henrique de Moraes Holschuhdc288522008-06-23 17:23:08 -0300532check the sysfs "state" entry regularly to correctly perform the required tasks
533when the rkfill key is pressed.
534
535A note about input devices and EV_SW events:
536
537In order to know the current state of an input device switch (like
538SW_RFKILL_ALL), you will need to use an IOCTL. That information is not
539available through sysfs in a generic way at this time, and it is not available
540through the rfkill class AT ALL.