Bug 512820

Summary: Powerdevil not reporting/not letting me change DDC/CI Brightness
Product: [Plasma] plasmashell Reporter: syzzori
Component: Brightness and Color widgetAssignee: Plasma Bugs List <plasma-bugs-null>
Status: RESOLVED UPSTREAM    
Severity: normal CC: kdedev, natalie_clarius, nate
Priority: NOR    
Version First Reported In: 6.5.3   
Target Milestone: 1.0   
Platform: Arch Linux   
OS: Linux   
Latest Commit: Version Fixed/Implemented In:
Sentry Crash Report:

Description syzzori 2025-12-01 01:31:32 UTC
SUMMARY
The tray icon where you'd normally change the brightness of a monitor disappeared. 

STEPS TO REPRODUCE
1. Open up the tray icon
2. The monitor brightness briefly appears, you can change it
3. The slider disappears and the systemd service throws warnings

OBSERVED RESULT
The brightness slider disappears

EXPECTED RESULT
Change the brightness.

SOFTWARE/OS VERSIONS
Linux/KDE Plasma: Arch Linux
KDE Plasma Version: 6.5.3
KDE Frameworks Version: 6.20.0
Qt Version: 6.10.1

ADDITIONAL INFORMATION
[DDCutilDisplay]: ddca_set_non_table_vcp_value -3023
DDCutilDisplay]: "Odyssey G40B" retrying to set DDC/CI brightness in 2000 milliseconds - attempt no. 2
[DDCutilDisplay]: ddca_set_non_table_vcp_value -3023
[DDCutilDisplay]: "Odyssey G40B" retrying to set DDC/CI brightness in 3000 milliseconds - attempt no. 3
[DDCutilDisplay]: ddca_set_non_table_vcp_value -3023
[DDCutilDisplay]: "Odyssey G40B" failed to set DDC/CI brightness

Here's the SystemD service log

running "ddcutil detect" outputs
Display 1
   I2C bus:  /dev/i2c-2
   DRM_connector:           card0-DP-1
   EDID synopsis:
      Mfg id:               SAM - Samsung Electric Company
      Model:                Odyssey G40B
      Product code:         ----------------
      Serial number:        -----------------
      Binary serial number: -----------------
      Manufacture year:     2024,  Week: 10
   VCP version:         2.0

and trying to change the brightness with "ddcutil setvcp 10 {brightness%}" works perfectly fine
tried clearing kde config and reinstalling the whole plasma group
Comment 1 syzzori 2025-12-01 01:33:07 UTC
Forgot to add: I'm using nvidia-open-dkms as my driver version 580.105.08-4
Comment 2 TraceyC 2025-12-01 20:41:21 UTC
Possibly related
https://github.com/rockowitz/ddcutil/issues/562
Comment 3 Nate Graham 2025-12-11 17:27:30 UTC
I'd recommend reporting this upstream to the DDCutil folks at https://github.com/rockowitz/ddcutil/issues, as there's no indication there's a Plasma issue at play here.