Bug 511288

Summary:	External monitor brightness reset to 100% after restart, plasma still thinks it's 70%
Product:	[Plasma] plasmashell	Reporter:	Cavalier0491 <flaviannxmbo>
Component:	Power management & brightness	Assignee:	Plasma Bugs List <plasma-bugs-null>
Status:	RESOLVED FIXED
Severity:	minor	CC:	kdedev, nate
Priority:	NOR
Version First Reported In:	6.4.5
Target Milestone:	1.0
Platform:	Fedora RPMs
OS:	Linux
Latest Commit:		Version Fixed/Implemented In:
Sentry Crash Report:

Description Cavalier0491 2025-10-28 20:06:55 UTC

SUMMARY
When i set the brightness to say, 70%, on my external monitor connected over mini-displayport, it works fine over dcc/ci as expected.
however, when i restart my pc, plasma/kscreen/kwin still thinks it's 70%, but my monitor has reverted to 100% as that's what it's set to by default in the firmware.
I know this is technically a bug in the monitor, that it doesen't store the DCC/CI brightness in it's flash, but i feel like this is something that could be fixed in plasmashell/kscreen/kwin as well. 

STEPS TO REPRODUCE
1. Set brightness to 70% on external monitor
2. Restart PC

OBSERVED RESULT
Monitor at 100% Brightness even though plasmashell/kscreen/kwin thinks it's 70%

EXPECTED RESULT
plasmashell/kscreen/kwin would reset back to 100% so it's in sync, 
OR
plasmashell/kscreen/kwin sends the DCC/CI command to the monitor on login to set to 70% until i manually change it again.

SOFTWARE/OS VERSIONS
Operating System: Fedora Linux 42
KDE Plasma Version: 6.4.5
KDE Frameworks Version: 6.19.0
Qt Version: 6.9.2
Kernel Version: 6.17.4-200.fc42.x86_64 (64-bit)
Graphics Platform: Wayland
Processors: 4 × Intel® Core™ i5-7300HQ CPU @ 2.50GHz
Memory: 24 GiB of RAM (23.3 GiB usable)
Graphics Processor 1: Intel® HD Graphics 630
Graphics Processor 2: NVIDIA GeForce GTX 1050 Ti
Manufacturer: ASUSTeK COMPUTER INC.
Product Name: FX502VE
System Version: 1.0

ADDITIONAL INFORMATION
I'm fine with either solution i wrote in expected result.
I usually only set the brightness to 70% when it's dark outside. I don't mind setting it manually every day, until https://bugs.kde.org/show_bug.cgi?id=413165 get's implemented, but it's annoying that i gotta first set it to 100% so the brightness syncs, and then back to 70%.
I don't mind the brightness resetting to 100% when restart, that part's fine.
But either behaviour is fine, i guess.

Comment 1 TraceyC 2025-10-29 20:24:29 UTC

Thanks for the bug report.  Can you please copy and paste the output of this into the report? Thanks.

kscreen-doctor -o

Also, what version of ddcutil is on your system?

Thanks.

Comment 2 Cavalier0491 2025-10-29 21:04:11 UTC

$ kscreen-doctor -o
Output: 1 eDP-1 dce38afa-9269-4853-a652-b9ba8356d228
        disabled
        connected
        priority 0
        Panel
        replication source:0
        Modes:  1:1920x1080@60*!  2:1280x1024@60  3:1280x1024@60  4:1024x768@60  5:1024x768@60  6:1280x800@60  7:1280x800@60  8:1600x900@60  9:1600x900@60  10:1368x768@60  11:1368x768@60  12:1280x720@60  13:1280x720@60 
        Geometry: 2560,1113 1920x1080
        Scale: 1
        Rotation: 1
        Overscan: 0
        Vrr: incapable
        RgbRange: Automatic
        HDR: incapable
        Wide Color Gamut: incapable
        ICC profile: none
        Color profile source: EDID
        Color power preference: prefer efficiency and performance
        Brightness control: supported, set to 100% and dimming to 100%
        Color resolution: automatic (10), range: [6; 12] bits per color
        Allow EDR: always
Output: 2 DP-1 6c54e07c-1306-4e8e-adc0-f96bdeead30a
        enabled
        connected
        priority 1
        DisplayPort
        replication source:0
        Modes:  14:2560x1440@60!  15:3840x2160@60  16:3840x2160@60  17:3840x2160@30  18:3840x2160@30  19:2560x1440@165*  20:2560x1440@120  21:1920x1080@165  22:1920x1080@120  23:1920x1080@120  24:1920x1080@100  25:1920x1080@60  26:1920x1080@60  27:1920x1080@60  28:1920x1080@50  29:1680x1050@60  30:1280x1024@75  31:1280x1024@60  32:1440x900@60  33:1280x720@120  34:1280x720@120  35:1280x720@100  36:1280x720@60  37:1280x720@60  38:1280x720@50  39:1024x768@75  40:1024x768@70  41:1024x768@60  42:800x600@75  43:800x600@72  44:800x600@60  45:800x600@56  46:720x576@50  47:720x576@50  48:720x480@60  49:720x480@60  50:720x480@60  51:720x480@60  52:640x480@75  53:640x480@73  54:640x480@67  55:640x480@60  56:640x480@60 
        Geometry: 0,0 2560x1440
        Scale: 1
        Rotation: 1
        Overscan: 0
        Vrr: incapable
        RgbRange: Automatic
        HDR: incapable
        Wide Color Gamut: disabled
        ICC profile: /home/nex/linuxstuff/msi-optix-rtings-icc-profile.icm
        Color profile source: sRGB
        Color power preference: prefer efficiency and performance
        Brightness control: supported, set to 80% and dimming to 100%
        DDC/CI: allowed
        Color resolution: automatic (10), range: [6; 12] bits per color
        Allow EDR: unsupported

nex@asus-nex ~
$ dnf list | rg "ddcutil"
Updating and loading repositories:
 Fedora 42 - x86_64 - Updates           100% |  24.9 KiB/s |  16.4 KiB |  00m01s
Repositories loaded.
ddcutil.x86_64                                                                           2.2.1-1.fc42                                                                    updates
libddcutil.x86_64                                                                        2.2.1-1.fc42                                                                    updates
libddcutil.i686                                                                          2.2.1-1.fc42                                                                    updates
libddcutil-devel.i686                                                                    2.2.1-1.fc42                                                                    updates
libddcutil-devel.x86_64                                                                  2.2.1-1.fc42                                                                    updates

Comment 3 TraceyC 2025-10-30 00:06:49 UTC

Thanks! I'll let the folks more knowledgeable about the brightness code take it from here.

Comment 4 Cavalier0491 2025-10-30 18:40:00 UTC

I should also mention that while i've loaded the ICC profile in the past to try it, and system settings/kscreen remembers its path, I do not use it; I select "None" in the color profile dropdown.

Comment 5 Cavalier0491 2025-12-26 16:31:26 UTC

I haven't been able to reproduce this anymore, so I'm closing it. Seems it has been fixed in the last few months. If it starts happening again, i'll re-open