A few days ago, I did a fresh install of Arch Linux and decided to go minimal by only installing the plasma-desktop package.
Right after installing, I noticed something pretty cool—I could adjust the brightness of both my laptop screen and my external monitor. Before, I could only control my laptop screen, so this felt like a great improvement.
A couple of days later, I installed the full Plasma package group (plasma in Arch), and after rebooting, my brightness settings got reset. That’s when things started acting weird:
- I could only adjust the brightness of my external monitor through KDE settings.
- To change my laptop screen’s brightness, I had to use the keyboard shortcuts.
- Using the keyboard shortcuts changed the brightness of both screens at the same time, according to the on-screen notification.
Then, after another reboot:
- KDE settings only let me control my laptop screen’s brightness.
- Running
kscreen-doctor -o showed that my external monitor doesn’t support brightness control anymore.
Output: 1 eDP-1
enabled
connected
priority 2
Panel
Modes: 1:1920x1080@144*! 2:1920x1080@60 3:1280x1024@60 4:1024x768@60 5:1280x800@60 6:1920x1080@60 7:1600x900@60 8:1368x768@60 9:1280x720@60
Geometry: 1920,0 1920x1080
Scale: 1
Rotation: 1
Overscan: 0
Vrr: incapable
RgbRange: Automatic
HDR: incapable
Wide Color Gamut: incapable
ICC profile: none
Color profile source: sRGB
Brightness control: supported, set to 100%
Output: 2 HDMI-A-1
enabled
connected
priority 1
HDMI
Modes: 10:1920x1080@60! 11:1920x1080@120* 12:1920x1080@120 13:1920x1080@100 14:1920x1080@100 15:1920x1080@85 16:1920x1080@60 17:1920x1080@50 18:1680x1050@60 19:1280x1024@75 20:1280x1024@60 21:1440x900@60 22:1280x960@60 23:1280x800@60 24:1152x864@75 25:1280x720@60 26:1280x720@60 27:1280x720@50 28:1024x768@75 29:1024x768@70 30:1024x768@60 31:800x600@75 32:800x600@72 33:800x600@60 34:800x600@56 35:720x576@50 36:720x480@60 37:640x480@75 38:640x480@60 39:640x480@60
Geometry: 0,0 1920x1080
Scale: 1
Rotation: 1
Overscan: 0
Vrr: incapable
RgbRange: unknown
HDR: incapable
Wide Color Gamut: incapable
ICC profile: none
Color profile source: sRGB
Brightness control: unsupported
But here’s the weird part
Even though kscreen-doctor says my external monitor doesn’t support brightness control, running ddcutil does change the brightness:
sudo ddcutil --display 1 setvcp 10 + 10
Seems like something broke after installing the full Plasma package set. Maybe it’s related to this bug?
https://bugs.kde.org/show_bug.cgi?id=482713
Any ideas on what’s going on?
Hi! I can’t personally reproduce, but just to check - when the broader KDE Plasma metapackage was installed and the issue began, were any existing installed packages (like ddcutil or powerdevil, most specifically) perhaps also updated at that same time?
Hi, I am experiencing this issue also with different setup. The NEC monitor on the dual head desktop setup sometimes is shown and sometimes not in brightness control. It’s brightness can no longer be changed via brightness control either.
If it’s intermittently unavailable, then I do believe it would be worth following the bug that was linked to in @MaEscalanteHe 's first post here, since there seems to be some investigation happening there 
When installing the plasma-desktop package, powerdevil 6.2.5-1 and ddcutil 2.1.4-2 were installed with it.
When installing the plasma package group, only the powerdevil package was reinstalled. The next reboot of performing the installation of the package group installation was that I noticed the error.
I just reinstalled my system again to help with the bug fix search.
Only by installing the plasma-desktop package can I change the brightness of my two monitors (laptop monitor and external monitor).
I then installed the nvidia drivers (the nvidia, nvidia-utils and egl-wayland packages) and I can still change the brightness of my external monitor.
Here are the details of the powerdevil and ddcutil packages:
$ pacman -Qi powerdevil
Name : powerdevil
Version : 6.3.0-1
Description : Manages the power consumption settings of a Plasma Shell
Architecture : x86_64
URL : https://kde.org/plasma-desktop/
Licenses : LGPL-2.0-or-later
Groups : plasma
Provides : None
Depends On : ddcutil gcc-libs glibc plasma-activities kauth kcmutils
kconfig kcoreaddons kcrash kdbusaddons kglobalaccel
ki18n kidletime kirigami kitemmodels knotifications
kservice ksvg kwindowsystem kxmlgui libkscreen libplasma
libxcb plasma-workspace qcoro qt6-base qt6-declarative
qt6-wayland solid systemd-libs wayland
Optional Deps : kinfocenter: for the Energy Information KCM
power-profiles-daemon: power profiles support
tlp: alternative power profiles support
Required By : plasma-desktop
Optional For : None
Conflicts With : None
Replaces : None
Installed Size : 4.70 MiB
Packager : Antonio Rojas <arojas@archlinux.org>
Build Date : Sat 08 Feb 2025 05:27:01 AM -04
Install Date : Sun 16 Feb 2025 09:54:42 PM -04
Install Reason : Installed as a dependency for another package
Install Script : No
Validated By : Signature
$ pacman -Qi ddcutil
Name : ddcutil
Version : 2.1.4-2
Description : Query and change Linux monitor settings using DDC/CI and USB.
Architecture : x86_64
URL : http://ddcutil.com/
Licenses : GPL2
Groups : None
Provides : None
Depends On : glib2 i2c-tools libusb libdrm jansson
Optional Deps : None
Required By : powerdevil
Optional For : None
Conflicts With : None
Replaces : None
Installed Size : 1903.15 KiB
Packager : Felix Yan <felixonmars@archlinux.org>
Build Date : Thu 19 Sep 2024 04:01:42 PM -04
Install Date : Sun 16 Feb 2025 09:54:42 PM -04
Install Reason : Installed as a dependency for another package
Install Script : No
Validated By : Signature
Curiously, by installing the plasma group of packages I’m still able to modify the brightness of my monitor.
When I run kscreen-doctor again this is the output:
Output: 1 eDP-1
(Same as above)
Output: 2 HDMI-A-1
enabled
connected
priority 1
HDMI
...
Brightness control: supported, set to 50% and dimming to 100%
What I noticed is that if I start the system without the HDMI connected and proceed to connect the monitor, I can no longer change the brightness until I reboot completely.
Just adding for what it’s worth, this might be a relevant bug as well - 493329 – Monitors attached after startup do not appear in the brightness applet unless Powerdevil is manually restarted (X11) - although the commit mentioned at the end was merged for 6.3, so its effects should already be in place on an up-to-date Arch device.
Similar issue here. EndeavourOS, Kernel 6.13.5-arch1-1, Plasma 6.3.2. Updated yesterday and now brightness adjustment for my only monitor is not showing up in power management settings. Issue is consistent, not random.
Here’s my kscreen doctor --outputs:
Output: 1 DP-2
enabled
connected
priority 1
DisplayPort
Modes: 1:1920x1080@144*! 2:1920x1080@120 3:1920x1080@75 4:1920x1080@60 5:1920x1080@60 6:1680x1050@144 7:1280x1024@75 8:1440x900@144 9:1280x800@144 10:1280x720@60 11:1280x720@60 12:1024x768@120 13:1024x768@75 14:1024x768@60 15:800x600@120 16:800x600@75 17:800x600@60 18:640x480@120 19:640x480@75 20:640x480@60 21:640x480@60 22:1280x1024@60 23:1024x768@60 24:1280x800@60 25:1920x1080@60 26:1600x900@60 27:1368x768@60 28:1280x720@60
Geometry: 0,0 1920x1080
Scale: 1
Rotation: 1
Overscan: 0
Vrr: incapable
RgbRange: unknown
HDR: disabled
Wide Color Gamut: disabled
ICC profile: none
Color profile source: sRGB
Color power preference: prefer efficiency and performance
Brightness control: supported, set to 100% and dimming to 100%
The brightness control field says it still supports it.
Update: The slider no longer appears in the settings page where it used to, but it does show up in the brightness and color applet in the tray.
