WSL2-Linux-Kernel/Documentation/rfkill.txt

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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>
2009-06-02 15:01:37 +04:00
rfkill - RF kill switch support
===============================
.. contents::
:depth: 2
Introduction
============
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>
2009-06-02 15:01:37 +04:00
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.
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>
2009-06-02 15:01:37 +04:00
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
aircraft.
The rfkill subsystem has a concept of "hard" and "soft" block, which
differ little in their meaning (block == transmitters off) but rather in
whether they can be changed or not:
- hard block
read-only radio block that cannot be overridden by software
- soft block
writable radio block (need not be readable) that is set by
the system software.
The rfkill subsystem has two parameters, rfkill.default_state and
rfkill.master_switch_mode, which are documented in
admin-guide/kernel-parameters.rst.
Implementation details
======================
The rfkill subsystem is composed of three main components:
* the rfkill core,
* the deprecated rfkill-input module (an input layer handler, being
replaced by userspace policy code) and
* the rfkill drivers.
rfkill: remove transmitter blocking on suspend Currently, rfkill would stand in the way of properly supporting wireless devices that are capable of waking the system up from sleep or hibernation when they receive a special wireless message. It would also get in the way of mesh devices that need to remain operational even during platform suspend. To avoid that, stop trying to block the transmitters on the rfkill class suspend handler. Drivers that need rfkill's older behaviour will have to implement it by themselves in their own suspend handling. Do note that rfkill *will* attempt to restore the transmitter state on resume in any situation. This happens after the driver's resume method is called by the suspend core (class devices resume after the devices they are attached to have been resumed). The following drivers need to check if they need to explicitly block their transmitters in their own suspend handlers (maintainers Cc'd): arch/arm/mach-pxa/tosa-bt.c drivers/net/usb/hso.c drivers/net/wireless/rt2x00/* (USB might need it?) drivers/net/wireless/b43/ (SSB over USB might need it?) drivers/misc/hp-wmi.c eeepc-laptop w/rfkill support (not in mainline yet) Compal laptop w/rfkill support (not in mainline yet) toshiba-acpi w/rfkill support (not in mainline yet) Signed-off-by: Henrique de Moraes Holschuh <hmh@hmh.eng.br> Cc: Ivo van Doorn <IvDoorn@gmail.com> Cc: Matthew Garrett <mjg@redhat.com> Cc: Andrew Bird <ajb@spheresystems.co.uk> Cc: Greg Kroah-Hartman <gregkh@suse.de> Cc: Cezary Jackiewicz <cezary.jackiewicz@gmail.com> Cc: Philip Langdale <philipl@overt.org> Signed-off-by: John W. Linville <linville@tuxdriver.com>
2008-08-26 18:58:01 +04:00
The rfkill core provides API for kernel drivers to register their radio
transmitter with the kernel, methods for turning it on and off and, letting
the system know about hardware-disabled states that may be implemented on
the device.
rfkill: remove transmitter blocking on suspend Currently, rfkill would stand in the way of properly supporting wireless devices that are capable of waking the system up from sleep or hibernation when they receive a special wireless message. It would also get in the way of mesh devices that need to remain operational even during platform suspend. To avoid that, stop trying to block the transmitters on the rfkill class suspend handler. Drivers that need rfkill's older behaviour will have to implement it by themselves in their own suspend handling. Do note that rfkill *will* attempt to restore the transmitter state on resume in any situation. This happens after the driver's resume method is called by the suspend core (class devices resume after the devices they are attached to have been resumed). The following drivers need to check if they need to explicitly block their transmitters in their own suspend handlers (maintainers Cc'd): arch/arm/mach-pxa/tosa-bt.c drivers/net/usb/hso.c drivers/net/wireless/rt2x00/* (USB might need it?) drivers/net/wireless/b43/ (SSB over USB might need it?) drivers/misc/hp-wmi.c eeepc-laptop w/rfkill support (not in mainline yet) Compal laptop w/rfkill support (not in mainline yet) toshiba-acpi w/rfkill support (not in mainline yet) Signed-off-by: Henrique de Moraes Holschuh <hmh@hmh.eng.br> Cc: Ivo van Doorn <IvDoorn@gmail.com> Cc: Matthew Garrett <mjg@redhat.com> Cc: Andrew Bird <ajb@spheresystems.co.uk> Cc: Greg Kroah-Hartman <gregkh@suse.de> Cc: Cezary Jackiewicz <cezary.jackiewicz@gmail.com> Cc: Philip Langdale <philipl@overt.org> Signed-off-by: John W. Linville <linville@tuxdriver.com>
2008-08-26 18:58:01 +04:00
The rfkill core code also notifies userspace of state changes, and provides
ways for userspace to query the current states. See the "Userspace support"
section below.
rfkill: remove transmitter blocking on suspend Currently, rfkill would stand in the way of properly supporting wireless devices that are capable of waking the system up from sleep or hibernation when they receive a special wireless message. It would also get in the way of mesh devices that need to remain operational even during platform suspend. To avoid that, stop trying to block the transmitters on the rfkill class suspend handler. Drivers that need rfkill's older behaviour will have to implement it by themselves in their own suspend handling. Do note that rfkill *will* attempt to restore the transmitter state on resume in any situation. This happens after the driver's resume method is called by the suspend core (class devices resume after the devices they are attached to have been resumed). The following drivers need to check if they need to explicitly block their transmitters in their own suspend handlers (maintainers Cc'd): arch/arm/mach-pxa/tosa-bt.c drivers/net/usb/hso.c drivers/net/wireless/rt2x00/* (USB might need it?) drivers/net/wireless/b43/ (SSB over USB might need it?) drivers/misc/hp-wmi.c eeepc-laptop w/rfkill support (not in mainline yet) Compal laptop w/rfkill support (not in mainline yet) toshiba-acpi w/rfkill support (not in mainline yet) Signed-off-by: Henrique de Moraes Holschuh <hmh@hmh.eng.br> Cc: Ivo van Doorn <IvDoorn@gmail.com> Cc: Matthew Garrett <mjg@redhat.com> Cc: Andrew Bird <ajb@spheresystems.co.uk> Cc: Greg Kroah-Hartman <gregkh@suse.de> Cc: Cezary Jackiewicz <cezary.jackiewicz@gmail.com> Cc: Philip Langdale <philipl@overt.org> Signed-off-by: John W. Linville <linville@tuxdriver.com>
2008-08-26 18:58:01 +04:00
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>
2009-06-02 15:01:37 +04:00
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 for additional software
block, but drivers can 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 fact, drivers should
use the return value of rfkill_set_hw_state() unless the hardware actually
keeps track of soft and hard block separately.
Kernel API
==========
Drivers for radio transmitters normally implement an rfkill driver.
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>
2009-06-02 15:01:37 +04:00
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 driver instead. This also applies if the platform provides
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>
2009-06-02 15:01:37 +04:00
a way to turn on/off the transmitter(s).
For some platforms, it is possible that the hardware state changes during
suspend/hibernation, in which case it will be necessary to update the rfkill
core with the current state is at resume time.
To create an rfkill driver, driver's Kconfig needs to have::
depends on RFKILL || !RFKILL
to ensure the driver cannot be built-in when rfkill is modular. The !RFKILL
case allows the driver to be built when rfkill is not configured, which
case all rfkill API can still be used but will be provided by static inlines
which compile to almost nothing.
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>
2009-06-02 15:01:37 +04:00
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.
RFKill provides per-switch LED triggers, which can be used to drive LEDs
according to the switch state (LED_FULL when blocked, LED_OFF otherwise).
Userspace support
=================
The recommended userspace interface to use is /dev/rfkill, which is a misc
character device that allows userspace to obtain and set the state of rfkill
devices and sets of devices. It also notifies userspace about device addition
and removal. The API is a simple read/write API that is defined in
linux/rfkill.h, with one ioctl that allows turning off the deprecated input
handler in the kernel for the transition period.
Except for the one ioctl, communication with the kernel is done via read()
and write() of instances of 'struct rfkill_event'. In this structure, the
soft and hard block are properly separated (unlike sysfs, see below) and
userspace is able to get a consistent snapshot of all rfkill devices in the
system. Also, it is possible to switch all rfkill drivers (or all drivers of
a specified type) into a state which also updates the default state for
hotplugged devices.
After an application opens /dev/rfkill, it can read the current state of all
devices. Changes can be either obtained by either polling the descriptor for
hotplug or state change events or by listening for uevents emitted by the
rfkill core framework.
Additionally, each rfkill device is registered in sysfs and emits uevents.
rfkill devices issue uevents (with an action of "change"), with the following
environment variables set::
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>
2009-06-02 15:01:37 +04:00
RFKILL_NAME
RFKILL_STATE
RFKILL_TYPE
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>
2009-06-02 15:01:37 +04:00
The contents of these variables corresponds to the "name", "state" and
"type" sysfs files explained above.
For further details consult Documentation/ABI/stable/sysfs-class-rfkill.