https://bugs.kde.org/show_bug.cgi?id=495819
Bug ID: 495819
Summary: Plasma 6.2 regression: DDC-based brightness setting
not working with EDID overrides
Classification: Plasma
Product: Powerdevil
Version: 6.2.2
Platform: Arch Linux
OS: Linux
Status: REPORTED
Severity: normal
Priority: NOR
Component: general
Assignee: plasma-b...@kde.org
Reporter: honza.k...@gmail.com
CC: natalie_clar...@yahoo.de
Target Milestone: ---
SUMMARY
When using drm.edid_firmware kernel parameter to override monitor EDID(s), DDC
brightness setting stops working on monitor(s) whose EDID was overriden (but
KEEPS working on other displays) and software / color management dimming is
used instead (which of course looks horrible on LCD screens). This is a
regression from 6.1 and is almost certainly linked to recent changes in
brightness handling (e.g. per-monitor brightness setting and similar changes).
STEPS TO REPRODUCE
1. Make sure no EDIDs are overriden (check that the kernel did not boot with
drm.edid_firmware parameter)
2. Check that DDC-based brightness setting works correctly.
3. Reboot with e.g. "drm.edid_firmware=DP-1:FILENAME.edid.bin" parameter (in my
case the EDID just adds some custom resolutions, everything else is identical
to the original)
OBSERVED RESULT
On DP-1 display, software dimming is now used. Assuming there is another
monitor connected to DP-2, DDC-based brightness setting still works on DP-2.
If DP-2 EDID is also overriden, then it stops working on DP-2 as well.
EXPECTED RESULT
DDC-based brightness still works regardless of EDID overrides, as it used to in
6.1.
SOFTWARE/OS VERSIONS
Linux/KDE Plasma: Arch Linux
KDE Plasma Version: 6.2.2
KDE Frameworks Version: 6.7
Qt Version: 6.8
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