Xbacklight is used to adjust the backlight brightness where supported.
It uses the RandR extension to find all outputs on the X server
supporting backlight brightness control and changes them all in the
same way.

All questions regarding this software should be directed at the
Xorg mailing list:

  https://lists.x.org/mailman/listinfo/xorg

The master development code repository can be found at:

  https://gitlab.freedesktop.org/xorg/app/xbacklight

Please submit bug reports and requests to merge patches there.

For patch submission instructions, see:

  https://www.x.org/wiki/Development/Documentation/SubmittingPatches