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authorHenrique de Moraes Holschuh <hmh@hmh.eng.br>2008-07-21 21:18:17 -0300
committerJohn W. Linville <linville@tuxdriver.com>2008-07-29 16:36:32 -0400
commit2fd9b2212e25e6411b6f309707f4e2683d164250 (patch)
treeb886e6d11d3478f86ac7e270ef1dfc7fe02e7128 /Documentation/rfkill.txt
parent734b5aa911dc65f4563048f069dfc631c9aa7de7 (diff)
downloadlinux-linaro-stable-2fd9b2212e25e6411b6f309707f4e2683d164250.tar.gz
rfkill: document rfkill_force_state as required (v2)
While the rfkill class does work with just get_state(), it doesn't work well on devices that are subject to external events that cause rfkill state changes. Document that rfkill_force_state() is required in those cases. Signed-off-by: Henrique de Moraes Holschuh <hmh@hmh.eng.br> Acked-by: Ivo van Doorn <IvDoorn@gmail.com> Signed-off-by: John W. Linville <linville@tuxdriver.com>
Diffstat (limited to 'Documentation/rfkill.txt')
-rw-r--r--Documentation/rfkill.txt20
1 files changed, 16 insertions, 4 deletions
diff --git a/Documentation/rfkill.txt b/Documentation/rfkill.txt
index 0843ed0163a5..28b6ec87c642 100644
--- a/Documentation/rfkill.txt
+++ b/Documentation/rfkill.txt
@@ -390,9 +390,10 @@ 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.
-If it doesn't implement the get_state() hook, it must make sure that its calls
-to rfkill_force_state() are enough to keep the status always up-to-date, and it
-must do a rfkill_force_state() on resume from sleep.
+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.
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
@@ -422,13 +423,24 @@ 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.
+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.