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Diffstat (limited to 'Documentation/rfkill.txt')
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diff --git a/Documentation/rfkill.txt b/Documentation/rfkill.txt new file mode 100644 index 00000000000..a83ff23cd68 --- /dev/null +++ b/Documentation/rfkill.txt @@ -0,0 +1,89 @@ +rfkill - RF switch subsystem support +==================================== + +1 Implementation details +2 Driver support +3 Userspace support + +=============================================================================== +1: Implementation details + +The rfkill switch subsystem offers support for keys often found on laptops +to enable wireless devices like WiFi and Bluetooth. + +This is done by providing the user 3 possibilities: + 1 - The rfkill system handles all events; userspace is not aware of events. + 2 - The rfkill system handles all events; userspace is informed about the events. + 3 - The rfkill system does not handle events; userspace handles all events. + +The buttons to enable and disable the wireless radios are important in +situations where the user is for example using his laptop on a location where +wireless radios _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 still provides userspace the possibility +to take over the task to handle the key events. + +The system inside the kernel has been split into 2 separate sections: + 1 - RFKILL + 2 - RFKILL_INPUT + +The first option enables rfkill support and will make sure userspace will +be notified of any events through the input device. It also creates several +sysfs entries which can be used by userspace. See section "Userspace support". + +The second option provides an rfkill input handler. This handler will +listen to all rfkill key events and will toggle the radio accordingly. +With this option enabled userspace could either do nothing or simply +perform monitoring tasks. + +==================================== +2: Driver support + +To build a driver with rfkill subsystem support, the driver should +depend on the Kconfig symbol RFKILL; it should _not_ depend on +RKFILL_INPUT. + +Unless key events trigger an interrupt to which the driver listens, polling +will be required to determine the key state changes. For this the input +layer providers the input-polldev handler. + +A driver should implement a few steps to correctly make use of the +rfkill subsystem. First for non-polling drivers: + + - rfkill_allocate() + - input_allocate_device() + - rfkill_register() + - input_register_device() + +For polling drivers: + + - rfkill_allocate() + - input_allocate_polled_device() + - rfkill_register() + - input_register_polled_device() + +When a key event has been detected, the correct event should be +sent over the input device which has been registered by the driver. + +==================================== +3: Userspace support + +For each key an input device will be created which will send out the correct +key event when the rfkill key has been pressed. + +The following sysfs entries will be created: + + 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 key. 1: On, 0: Off. + 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 all radios, 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. |