GitLab

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
...