Monitors magically go to 100 % brightness during Plasma login & config updates

English Hardware
,
1

The problem:
Right after login, during the process of loading the profile and preparing the desktop, my three screens automagically go to 100 % brightness.
This also happens when I open System Settings → Display & Monitor, select one and change any setting that will cause an update, like overscan, color profile, etc. After clicking apply, the selected monitor will go to 100 % brightness.
A third occasion is when I disconnect / reconnect a single monitor; this will set all screens to 100 %. I don’t know when this began, being new to OpenSUSE / Tumbleweed (but not Linux and KDE as such), and I recently noticed it. Using TW for around two month now, I could swear that I’d have noticed it earlier if it was that way right from the start.

I’m currently on openSUSE Tumbleweed, Release 20241016, Linux […] 6.11.3-1-default #1 SMP PREEMPT_DYNAMIC Fri Oct 11 06:48:36 UTC 2024 (7881e90) x86_64.
Using three good old HP LP2475W monitors via DP on an AMD Vega 64, I’m not on a notebook or another mobile device.

Funny is the fact, that
“xrandr --output DP-1 --brightness [some value]”
doesn’t alter my monitor settings. I always assumed that my monitors weren’t able to be controlled remotely, because I remember having tried tools that provided brightness controls out of curiosity, back when I used Windows XP and also later up to today. None of those ever worked. So I wonder what exactly makes my monitors do that.

When searching for “brightness” and synonyms, I can only find that screen dimming setting in energy settings. This, by the way, also doesn’t work; it won’t alter the brightness.

Normally, I’d say that it doesn’t matter, because I only need to set it right back manually by using the bezel controls after each login. But that will cause two NVRAM write cycles per boot, and I’m not fine with trashing my screens just because their flash failed. Or due to heat death because I forgot setting them back; they’re not LED.

If anyone has an idea which calls are made at the aforementioned points and which to comment out or intercept by some means, I’d appreciate any good hints or concrete instructions.

Thank you for your time, everyone.

2

There is another thread with a link to the upstream KDE discussion.

2 Likes
3

Solution for those who seek a short answer:

In console:
systemctl --user edit plasma-powerdevil.service

Then insert the following service section between the comments:

...
### Anything between here and the comment below will become the contents of the drop-in file

[Service]
Environment="POWERDEVIL_NO_DDCUTIL=1"

### Edits below this comment will be discarded
...

To optionally apply immediately, you can do:
systemctl --user restart plasma-powerdevil.service

1 Like
4

This topic was automatically closed 7 days after the last reply. New replies are no longer allowed.