Talk:ASUS X421IA

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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 <>
   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
   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'.
   Cc: Alex Deucher <>
   Cc: Nicholas Kazlauskas <>
   Reviewed-by: Alex Deucher <>
   Signed-off-by: Alexander Monakov <>
   Signed-off-by: Alex Deucher <>
   Signed-off-by: Greg Kroah-Hartman <>

I also tried it and for me it works just fine. (talk) 12:19, 22 September 2020 (UTC)

Checked and working for me, tqvm! YNShung (talk) 12:45, 1 October 2020 (UTC)