Aurora (Universal Blue) 42.20251019.1.
I have a laptop. Fairly often (daily), backlight controls on it stops working. I haven’t found a way to force it on-demand yet.
The key combinations to raise/lower the brightness still make the bar appear and it goes left and right, but the backlight stays unchanged. Likewise nothing happens if I drag the slider in the brightness panel widget.
The systemd journal has this to say when I try to change the brightness at this point;
okt 21 00:28:07 x1 systemd[1]: Started dbus-:1.3-org.kde.powerdevil.backlighthelper@16.service.
okt 21 00:28:07 x1 org_kde_powerdevil[2882]: org.kde.powerdevil: [BacklightBrightness]: Failed to set screen brightness ""
okt 21 00:28:15 x1 org_kde_powerdevil[2882]: org.kde.powerdevil: [BacklightBrightness]: Failed to set screen brightness ""
okt 21 00:28:16 x1 org_kde_powerdevil[2882]: org.kde.powerdevil: [BacklightBrightness]: Failed to set screen brightness ""
okt 21 00:28:16 x1 org_kde_powerdevil[2882]: org.kde.powerdevil: [BacklightBrightness]: Failed to set screen brightness ""
okt 21 00:28:16 x1 org_kde_powerdevil[2882]: org.kde.powerdevil: [BacklightBrightness]: Failed to set screen brightness ""
okt 21 00:28:17 x1 org_kde_powerdevil[2882]: org.kde.powerdevil: [BacklightBrightness]: Failed to set screen brightness ""
okt 21 00:28:17 x1 org_kde_powerdevil[2882]: org.kde.powerdevil: [BacklightBrightness]: Failed to set screen brightness ""
okt 21 00:28:17 x1 org_kde_powerdevil[2882]: org.kde.powerdevil: [BacklightBrightness]: Failed to set screen brightness ""
okt 21 00:28:17 x1 org_kde_powerdevil[2882]: org.kde.powerdevil: [BacklightBrightness]: Failed to set screen brightness ""
okt 21 00:28:17 x1 org_kde_powerdevil[2882]: org.kde.powerdevil: [BacklightBrightness]: Failed to set screen brightness ""
okt 21 00:28:17 x1 org_kde_powerdevil[2882]: org.kde.powerdevil: [BacklightBrightness]: Failed to set screen brightness ""
okt 21 00:28:18 x1 org_kde_powerdevil[2882]: org.kde.powerdevil: [BacklightBrightness]: Failed to set screen brightness ""
okt 21 00:28:28 x1 systemd[1]: dbus-:1.3-org.kde.powerdevil.backlighthelper@16.service: Deactivated successfully.
If I restart plasma-powerdevil.service, the backlight control disappears completely. The key combinations no longer do anything and the slider in the brightness widget is no longer there.
From the journal as I restart the service;
okt 21 00:32:37 x1 systemd[2369]: Starting plasma-powerdevil.service - Powerdevil...
okt 21 00:32:37 x1 org_kde_powerdevil[258582]: Starting libddcutil. library built Sep 5 2025 at 00:00:00. stdout_stderr_redirected=true
okt 21 00:32:38 x1 org_kde_powerdevil[258582]: Initializing libddcutil. ddcutil version: 2.2.1, shared library: /usr/lib64/libddcutil.so.5.3.0
okt 21 00:32:38 x1 org_kde_powerdevil[258582]: [258582] Options passed from client:
okt 21 00:32:38 x1 org_kde_powerdevil[258582]: [258582] Applying combined libddcutil options:
okt 21 00:32:39 x1 org_kde_powerdevil[258582]: Library initialization complete.
okt 21 00:32:39 x1 org_kde_powerdevil[258582]: Watching for DPMS state changes unimplemented
okt 21 00:32:39 x1 org_kde_powerdevil[258582]: [258582] Watching for DPMS state changes unimplemented
okt 21 00:32:39 x1 org_kde_powerdevil[258582]: [258582] Watching for display connection changes, resolved watch mode = Watch_Mode_Xevent, poll loop interval = 100 millisec
okt 21 00:32:39 x1 org_kde_powerdevil[258582]: [258582] extra_stabilization_millisec: 0, stabilization_poll_millisec: 100
okt 21 00:32:39 x1 org_kde_powerdevil[258582]: [258582] libddcutil recheck thread 0x55cd0b125c40 started
okt 21 00:32:39 x1 org_kde_powerdevil[258582]: [258582] libddcutil watch thread 0x55cd0b133fd0 started
okt 21 00:32:39 x1 org_kde_powerdevil[258582]: [258705] (dw_recheck_displays_func) Recheck interval: Sleeping for 200 milliseconds
okt 21 00:32:39 x1 systemd[1]: Started dbus-:1.3-org.kde.powerdevil.discretegpuhelper@1.service.
okt 21 00:32:39 x1 systemd[1]: Started dbus-:1.3-org.kde.powerdevil.chargethresholdhelper@1.service.
okt 21 00:32:39 x1 systemd[1]: Started dbus-:1.3-org.kde.powerdevil.backlighthelper@18.service.
okt 21 00:32:39 x1 org_kde_powerdevil[258582]: org.kde.powerdevil: org.kde.powerdevil.discretegpuhelper.hasdualgpu failed
okt 21 00:32:39 x1 org_kde_powerdevil[258582]: org.kde.powerdevil: org.kde.powerdevil.chargethresholdhelper.getthreshold failed ""
okt 21 00:32:39 x1 org_kde_powerdevil[258582]: org.kde.powerdevil: org.kde.powerdevil.backlighthelper.brightness failed
okt 21 00:32:39 x1 org_kde_powerdevil[258582]: org.kde.powerdevil: failed to inhibit systemd powersave handling
okt 21 00:32:39 x1 systemd[2369]: Started plasma-powerdevil.service - Powerdevil.
okt 21 00:32:39 x1 flatpak[3373]: PowerDevil found on DBus
okt 21 00:32:39 x1 org_kde_powerdevil[258582]: org.kde.powerdevil: Handle button events action could not check for screen configuration
okt 21 00:32:39 x1 org_kde_powerdevil[258582]: org.kde.powerdevil: org.kde.powerdevil.chargethresholdhelper.getthreshold failed ""
okt 21 00:32:49 x1 systemd[1]: dbus-:1.3-org.kde.powerdevil.discretegpuhelper@1.service: Deactivated successfully.
okt 21 00:32:49 x1 systemd[1]: dbus-:1.3-org.kde.powerdevil.chargethresholdhelper@1.service: Deactivated successfully.
okt 21 00:32:49 x1 systemd[1]: dbus-:1.3-org.kde.powerdevil.backlighthelper@18.service: Deactivated successfully.
If I restart sddm and log back in, backlight control returns. So I don’t need to do a full reboot, but a restart of Powerdevil alone is not enough.
At all times I can manually change brightness via /sys/class/backlight/intel-backlight/brightness, so backlight control itself doesn’t seem to be broken on some kernel level.
What can I do?
Operating System: Aurora 42
KDE Plasma Version: 6.4.5
KDE Frameworks Version: 6.19.0
Qt Version: 6.9.2
Kernel Version: 6.16.8-200.fc42.x86_64 (64-bit)
Graphics Platform: Wayland
Processors: 12 × 13th Gen Intel® Core™ i7-1365U
Memory: 34 GB of RAM (33,3 GB usable)
Graphics Processor: Intel® Iris® Xe Graphics