On Thu, May 03, 2012 at 12:19:21PM -0600, Shuah Khan wrote: > Sorry, forgot to Cc stable when the patch was sent to lkml. Please note > this patch depends on > [PATCH 1/2] leds: add new field to led_classdev struct to save activation > state > > ------------------------------------------------------------------------------ > > The leds timer trigger does not currently have an interface to activate > a one shot timer. The current support allows for setting two timers, one for > specifying how long a state to be on, and the second for how long the state > to be off. The delay_on value specifies the time period an LED should stay > in on state, followed by a delay_off value that specifies how long the LED > should stay in off state. The on and off cycle repeats until the trigger > gets deactivated. There is no provision for one time activation to implement > features that require an on or off state to be held just once and then stay in > the original state forever. > > Without one shot timer interface, user space can still use timer trigger to > set a timer to hold a state, however when user space application crashes or > goes away without deactivating the timer, the hardware will be left in that > state permanently. > > As a specific example of this use-case, let's look at vibrate feature on > phones. Vibrate function on phones is implemented using PWM pins on SoC or > PMIC. There is a need to activate one shot timer to control the vibrate > feature, to prevent user space crashes leaving the phone in vibrate mode > permanently causing the battery to drain. > > This trigger exports three properties, activate, state, and duration When > transient trigger is activated these properties are set to default values. > > - duration allows setting timer value in msecs. The initial value is 0. > - activate allows activating and deactivating the timer specified by > duration as needed. The initial and default value is 0. This will allow > duration to be set after trigger activation. > - state allows user to specify a transient state to be held for the specified > duration. > > >From a8249a6738020823277ef02d7787e8078c17844b Mon Sep 17 00:00:00 2001 > From: Shuah Khan <shuahk...@gmail.com> > Date: Mon, 30 Apr 2012 14:18:16 -0600 > Subject: [PATCH v3] leds: add new transient trigger for one shot timer > activation > > > Signed-off-by: Shuah Khan <shuahk...@gmail.com> > Cc: <stable@vger.kernel.org> v3.3 > Cc: <stable@vger.kernel.org> v3.2 > Cc: <stable@vger.kernel.org> v3.0 > --- > Documentation/leds/ledtrig-transient.txt | 152 +++++++++++++++++++ > drivers/leds/Kconfig | 8 + > drivers/leds/Makefile | 1 + > drivers/leds/ledtrig-transient.c | 237 > ++++++++++++++++++++++++++++++ > 4 files changed, 398 insertions(+), 0 deletions(-) > create mode 100644 Documentation/leds/ledtrig-transient.txt > create mode 100644 drivers/leds/ledtrig-transient.c
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