Bug 503030

Summary:	Plasma brightness setting overrides monitor OSD value after sleep or reboot
Product:	[Plasma] plasmashell	Reporter:	Oleksii Zolotarevskyi <rockingcat>
Component:	Power management & brightness	Assignee:	Plasma Bugs List <plasma-bugs-null>
Status:	RESOLVED FIXED
Severity:	normal	CC:	jpetso, kdedev, nate
Priority:	NOR
Version First Reported In:	6.3.4
Target Milestone:	1.0
Platform:	Manjaro
OS:	Linux
Latest Commit:		Version Fixed/Implemented In:
Sentry Crash Report:

Description Oleksii Zolotarevskyi 2025-04-19 20:57:11 UTC

SUMMARY
Adjusting the brightness via the System Tray in Plasma works well with my external monitor (MSI MAG274QRF-QD) — the new value is correctly reflected in the monitor's OSD. However, if I manually change the brightness via the monitor’s OSD, Plasma does not register the new value. After a reboot or when the monitor wakes from sleep, the brightness reverts to the value previously set in Plasma.

Ideally, Plasma should detect the brightness change made via the monitor OSD and update its internal setting accordingly to prevent this override.

STEPS TO REPRODUCE
1. Adjust brightness via the System Tray (Brightness and Color).
2. Manually change brightness using the monitor’s OSD.
3. Let the monitor enter sleep mode.
4. Wake the monitor.

OBSERVED RESULT
Brightness resets to the value last set in Plasma.

EXPECTED RESULT
Brightness remains at the value set via the monitor OSD.

SOFTWARE/OS VERSIONS
KDE Plasma Version: 6.3.4
KDE Frameworks Version: 6.12.0
Qt Version: 6.9.0
Graphics platform: X11

ADDITIONAL INFORMATION
System uses hybrid Intel+Nvidia graphics, with Nvidia configured as the primary GPU.

Comment 1 Oleksii Zolotarevskyi 2025-04-19 22:18:45 UTC

I came across a detailed discussion on this topic in the KDE forum: https://discuss.kde.org/t/powerdevil-is-re-setting-my-display-brightness-after-the-display-wakes-up/23079

As a workaround, I’ve resolved the issue on my system by disabling `ddcutil` — simply by defining POWERDEVIL_NO_DDCUTIL=1 as environment variable to PowerDevil service configuration. It also looks like there are ongoing discussions about adding this option directly to the Display Configuration settings page. 

Additionally, a recent merge request that might address this behavior when automatic dimming is disabled has already been merged: https://invent.kde.org/plasma/powerdevil/-/merge_requests/480

So feel free to decide whether this should remain open as a bug.

Comment 2 TraceyC 2025-08-12 22:04:48 UTC

Thanks for the bug report. I'm sorry we weren't able to get to it yet. Are you still seeing this happen with ddcutil 2.2.1 or greater and Plasma 6.4.4 or later?

Comment 3 Oleksii Zolotarevskyi 2025-08-17 16:07:56 UTC

(In reply to TraceyC from comment #2)
> Thanks for the bug report. I'm sorry we weren't able to get to it yet. Are
> you still seeing this happen with ddcutil 2.2.1 or greater and Plasma 6.4.4
> or later?

Thanks for following up.
With powerdevil version 6.3.6-1 and Automatic Dimming disabled in Power Management, adjusting the brightness via the monitor’s OSD doesn’t immediately update the value in the Brightness and Color widget, but it does reflect correctly after a reboot. The brightness also no longer resets. That’s good enough for me, so I’ll go ahead and close this issue.
Thank you again!

Comment 4 TraceyC 2025-08-18 17:36:33 UTC

That's great to hear. Thanks for letting us know.