Commit:     dac24ab396fc92985060d5cb3c467d2d0ffc0c20
Parent:     e0665486b78b8efb9c25019ad29b4a4c9c1e9dfc
Author:     Ivo van Doorn <[EMAIL PROTECTED]>
AuthorDate: Thu Sep 13 09:22:55 2007 +0200
Committer:  David S. Miller <[EMAIL PROTECTED]>
CommitDate: Wed Oct 10 16:49:24 2007 -0700

    [RFKILL]: Add rfkill documentation
    Add a documentation file which contains
    a short description about rfkill with some
    notes about drivers and the userspace interface.
    Changes since v1 and v2:
     - Spellchecking
    Signed-off-by: Ivo van Doorn <[EMAIL PROTECTED]>
    Acked-by: Dmitry Torokhov <[EMAIL PROTECTED]>
    Acked-by: Randy Dunlap <[EMAIL PROTECTED]>
 Documentation/rfkill.txt |   89 ++++++++++++++++++++++++++++++++++++++++++++++
 1 files changed, 89 insertions(+), 0 deletions(-)

diff --git a/Documentation/rfkill.txt b/Documentation/rfkill.txt
new file mode 100644
index 0000000..a83ff23
--- /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 
+ 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
+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.
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