Enabling LED timer trigger support in Android requires:
- LED class driver implementing the blinking.
- Patch the kernel to send uevents on sysfs changes:
- Vold patch for changing the ownership of the delay_on/delay_off files upon receiving that uevent.
- liblights setting up the “timer” trigger every time blinking is required (setting the brightness to 0 would disable the trigger).
This was discussed here – http://comments.gmane.org/gmane.linux.kernel/1331117, but the patches have not entered the mainline kernel.
It turns that’s not as straightforward as I thought.