brightness control changes wrong backlight on hybrid GPU laptop
Submitted by Dan Robinson
Assigned to Ali Abdallah @ali
Description
I'm on a Thinkpad T530 which is an Optimus setup.
There are two backlight providers:
/sys/class/backlight/intel_backlight /sys/class/backlight/nv_backlight
Both are type raw.
Only intel_backlight controls the actual brightness of the screen.
gnome-settings-daemon works correctly on my hardware. They seem to be checking if *_backlight/device/enabled is actually reading "enabled" and using that one. As best I can tell, in xfpm-backlight-helper.c it's just looping through all of the available interfaces and picking the last one that shows up (in this case, nv_backlight which is alphabetically last and also wrong).
Unfortunately I don't know enough about gobject and udev to write an actual good patch that's submitted, but if we can check for device/enabled == "enabled" and use that instead of just looping through them that should fix the issue.
Version: 1.6.5