Dev1 Galaxy Forum / Thinkpad T14s gen 3 and display backlight (adjustment not working)

Re: Thinkpad T14s gen 3 and display backlight (adjustment not working)

dummy@example.com (bigcat) — Mon, 05 Jun 2023 22:56:14 +0000

Standardpoodle wrote:

Seems like it suddenly started working. Will write again if there is still a problem.

I vaguely recall configuration in xorg.conf might be needed. See this for example: https://unix.stackexchange.com/question … xbacklight

Apologies if this is not relevant.

Re: Thinkpad T14s gen 3 and display backlight (adjustment not working)

dummy@example.com (Standardpoodle) — Sun, 28 May 2023 00:14:16 +0000

Seems like it suddenly started working. Will write again if there is still a problem.

Thinkpad T14s gen 3 and display backlight (adjustment not working)

dummy@example.com (Standardpoodle) — Tue, 16 May 2023 01:27:41 +0000

I installed Daedalus 20230508 into a fresh Thinkpad T14s gen 3, but no method that I've tried lets me adjust the display brightness.

Directory /sys/class/backlight is empty.

I think xrandr doesn't adjust the backlight at all.

With or without sudo, xbacklight has no effect.

Adjusting the brightness works in Ubuntu 22.04 liveCD. There is /sys/class/backlight/amdgpu_bl0 that is populated.

Installing firmware-amd-graphics 20230210-5 caused the login screen to remain black (with backlight on). The directory under /sys is populated though, and echo 128 > /sys/class/backlight/amdgpu_bl0/brightness works (also without sudo). Removing the firmware package restored the previous situation (I was able to use X again but not adjust the backlight).