Q:

Find driver used for backlight control

I can control backlight using /sys/class/backlight/.. but is there a way to identify which driver (module) is used internally to actually control the backlight intensity? 

A:

$ ls -ld /sys/class/backlight/intel_backlight
lrwxrwxrwx. 1 root root 0 Jun  3 10:08 /sys/class/backlight/intel_backlight
 -> ../../devices/pci0000:00/0000:00:02.0/drm/card0/card0-eDP-1/intel_backlight

$ ls -l /sys/devices/pci0000:00/0000:00:02.0/driver
lrwxrwxrwx. 1 root root 0 Jun  3 09:08 /sys/devices/pci0000:00/0000:00:02.0/driver
 -> ../../../bus/pci/drivers/i915

$ ls -l /sys/bus/pci/drivers/i915/module
lrwxrwxrwx. 1 root root 0 Jun  4 17:04 /sys/bus/pci/drivers/i915/module 
 -> ../../../../module/i915

don't ask me exactly how I guess the level that holds driver :). I think you might be supposed to check each level, starting with the longest path and working down, but that's a bit tedious.

