Bug 501354

Summary: 100% brightness in the Brightness and Colour plasmoid correlates to 30% brightness in the VCP firmware, and this cannot be overridden
Product: [Plasma] plasmashell Reporter: Roke Julian Lockhart Beedell <4wy78uwh>
Component: Brightness and Color widgetAssignee: Plasma Bugs List <plasma-bugs-null>
Status: RESOLVED DUPLICATE    
Severity: normal CC: natalie_clarius, nate
Priority: NOR    
Version First Reported In: 6.3.2   
Target Milestone: 1.0   
Platform: Fedora RPMs   
OS: Linux   
URL: https://discuss.kde.org/t/disable-kde-monitor-brightness-control/25134/17?u=rokejulianlockhart
Latest Commit: Version Fixed In:
Sentry Crash Report:
Attachments: A Screenshot of the Plasmoid

Description Roke Julian Lockhart Beedell 2025-03-11 12:56:24 UTC 
Created attachment 179299 [details]
A Screenshot of the Plasmoid

SUMMARY
-------

Ater invoking `ddcutil getvcp 10`, I see, verbatim:

> ~~~YAML
> VCP code 0x10 (Brightness                    ): current value =    30, max value =   100
> ~~~

However, as the attached screenshot depicts, the Brightness and Colour plasmoid returns 100% for this value. Consequently, I am restricted to 30% brightness, but *can* reduce it to 0%.

STEPS TO REPRODUCE
------------------

I don't know, because I don't know when this commenced. However, this OS installation is barely 2 days old, and I've done little more to it than add RPMFusion, and Mesa Freeworld from it. This did not reproduce on my previous installation.

OBSERVED RESULT
---------------

100% in the plasmoid correlates to 30% brightness in the VCP firmware, and how to rectify this isn't evident. Attempting to modify the brightness to > 30% via `ddcutil setvcp 10 $int` momentarily applies that value before it is reverted. The same occurs if set via the monitor's integrated VCP GUI (accessible via physical buttons).

EXPECTED RESULT
---------------

100% in the plasmoid shouldn't correlate to 30% brightness in the VCP firmware. It should correlate to 100%.

SOFTWARE/OS VERSIONS
--------------------

1.	~~~YAML
	#!/usr/bin/env sh
	kinfo
	~~~

2.	> ~~~YAML
	> Operating System: Fedora Linux 41
	> KDE Plasma Version: 6.3.2
	> KDE Frameworks Version: 6.11.0
	> Qt Version: 6.8.2
	> Kernel Version: 6.13.5-200.fc41.x86_64 (64-bit)
	> Graphics Platform: Wayland
	> Processors: 12 × AMD Ryzen 5 7600X 6-Core Processor
	> Memory: 30.4 GiB of RAM
	> Graphics Processor 1: AMD Radeon RX 5700
	> Graphics Processor 2: AMD Radeon Graphics
	> ~~~

ADDITIONAL INFORMATION
----------------------

1.	~~~YAML
	#!/usr/bin/env sh
	ddcutil detect
	~~~

2.	> ~~~YAML
	> Display 1
	>    I2C bus:  /dev/i2c-8
	>    DRM connector:           card1-DP-1
	>    EDID synopsis:
	>       Mfg id:               AOC - UNK
	>       Model:                Q3279WG5B
	>       Product code:         12921  (0x3279)
	>       Serial number:        
	>       Binary serial number: 40899 (0x00009fc3)
	>       Manufacture year:     2019,  Week: 51
	>    VCP version:         2.2
	> ~~~
Comment 1 Bug Janitor Service 2025-03-11 13:33:37 UTC 
Thank you for the bug report!

However Plasma 6.2.5 is no longer eligible for support or maintenance from KDE; supported versions are 5.27. (LTS), and 6.3 (non-LTS) or newer. Please upgrade to a supported version as soon as your distribution makes it available to you. Plasma is a fast-moving project, and bugs in one version are often fixed in the next one.

If you need support for Plasma 6.2.5, please contact your distribution, who bears the responsibility of providing support for older releases that are no longer supported by KDE.

If you can reproduce the issue after upgrading to a supported version, feel free to re-open this bug report.
Comment 2 Roke Julian Lockhart Beedell 2025-03-11 13:44:56 UTC 
(In reply to Bug Janitor Service from comment #1)  
The version was incorrectly prefilled, despite me invoking the report URI via the plasmoid's GUI.
Comment 3 Roke Julian Lockhart Beedell 2025-03-11 14:40:41 UTC 
(In reply to Roke Julian Lockhart Beedell from comment #0)  
> Attempting to modify the brightness to > 30% via `ddcutil setvcp 10 $int` momentarily applies that value before it is reverted. The same occurs if set via the monitor's integrated VCP GUI (accessible via physical buttons).

I've verified at [`discuss.kde.org/t/25134/17`][1] that `Environment=POWERDEVIL_NO_DDCUTIL=1` remediates this.

[1]: https://discuss.kde.org/t/disable-kde-monitor-brightness-control/25134/17?u=rokejulianlockhart#:~:text=I%20can%20now%20set%20my%20brightness%20(via%20ddcutil%20setvcp%2010%20$int)
Comment 4 Nate Graham 2025-03-11 22:44:30 UTC 
This bug report is practically unreadable due to the unnecessary formatting that isn't rendered by Bugzilla; please open a new one that's human-readable. Thanks.
Comment 5 Roke Julian Lockhart Beedell 2025-03-12 10:04:18 UTC 
(In reply to Nate Graham from comment #4)  
I suppose this would be another example of when having an edit function in BZ would be useful. I'll *try* when I've ascertained in the other issue how this is meant to be formatted instead.
Comment 6 Roke Julian Lockhart Beedell 2025-03-14 22:33:41 UTC 

*** This bug has been marked as a duplicate of bug 501510 ***