Talk:ASUS X421IA

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

https://cdn.kernel.org/pub/linux/kernel/v5.x/ChangeLog-5.8.6

   Author: Alexander Monakov <amonakov@ispras.ru>
   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 <alexander.deucher@amd.com>
   Cc: Nicholas Kazlauskas <nicholas.kazlauskas@amd.com>
   Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
   Signed-off-by: Alexander Monakov <amonakov@ispras.ru>
   Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
   Cc: stable@vger.kernel.org
   Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

I also tried it and for me it works just fine.

Fabis.cafe (talk) 12:19, 22 September 2020 (UTC)

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