Enabling LED timer trigger support in Android requires:

1. LED class driver implementing the blinking.

2. Patch the kernel to send uevents on sysfs changes:

   1. [1/3] sysfs: introduce a sysfs_create_file_uevent new API

   2. [2/3] drivers: add a new device_create_file_uevent API

   3. [3/3] ledtrig-timer: convert to use device_create_file_uevent API

3. Vold patch for changing the ownership of the delay_on/delay_off files upon receiving that uevent.

4. 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.