Backlight part should work with Linux 5.8.6 and newer. This part can be dropped I think.
Fix came in with 5.8.6
Author: Alexander Monakov <email@example.com> Date: Tue Aug 4 23:13:13 2020 +0300 drm/amd/display: use correct scale for actual_brightness commit 69d9f4278d0f9d24607645f10e5ac5c59c77a4ac upstream. Documentation for sysfs backlight level interface requires that values in both 'brightness' and 'actual_brightness' files are interpreted to be in range from 0 to the value given in the 'max_brightness' file. With amdgpu, max_brightness gives 255, and values written by the user into 'brightness' are internally rescaled to a wider range. However, reading from 'actual_brightness' gives the raw register value without inverse rescaling. This causes issues for various userspace tools such as PowerTop and systemd that expect the value to be in the correct range. Introduce a helper to retrieve internal backlight range. Use it to reimplement 'convert_brightness' as 'convert_brightness_from_user' and introduce 'convert_brightness_to_user'. Bug: https://bugzilla.kernel.org/show_bug.cgi?id=203905 Bug: https://gitlab.freedesktop.org/drm/amd/-/issues/1242 Cc: Alex Deucher <firstname.lastname@example.org> Cc: Nicholas Kazlauskas <email@example.com> Reviewed-by: Alex Deucher <firstname.lastname@example.org> Signed-off-by: Alexander Monakov <email@example.com> Signed-off-by: Alex Deucher <firstname.lastname@example.org> Cc: email@example.com Signed-off-by: Greg Kroah-Hartman <firstname.lastname@example.org>
I also tried it and for me it works just fine.