Can't change brightness on kde-plasma

I have rog strix g15 running fedora. I can’t change brightness with default method(keybinds, widget, etc). The issue is related to plasma only since I tried it on fedora as well as neon and it failed, but it worked on mint cinnamon. currently i am using “light” to change my brightness but i can have osd of brightness change and some other things.

Check if you have ddcutil installed

yeah, it was already installed

Assuming you’re talking about the internal laptop display, ddcutil is irrelevant here. For reading and adjusting laptop display brightness, KDE’s power management service uses the backlight devices directly that the Linux kernel exposes.

There have been a number of improvements as part of Bug 399646, but a few edge cases still remain unsolved. Short version, this stuff is hard and if your system advertises multiple backlight devices, it’s possible that Plasma picks the wrong one(s).

In the medium term, we can try to tweak the selection algorithm some more so it behaves more like systemd and its brightness restoration code. At the risk of breaking setups that were already fixed earlier. In the long term, the Linux kernel is looking at improving their brightness API so that user-space software such as Plasma doesn’t have to fumble and make poor guesses.

Sorry to hear that you’re one of those that are affected by this.

1 Like

Can’t We(Plasma Team) set fallback to brightnessctl/light because it seems to be working fine.

I looked at brightnessctl and it’s using a fairly primitive method of determining which backlight device to use. Switching to that would perhaps fix your use case, but break others that we’ve already fixed.

I have to look at light to see if it does anything better. However, it also seems the official repository at or has been removed and the AUR package for Arch Linux (at the time of writing) simply uses a mirror of the last release? Apart from not having made it into official repositories, I’m not sure that’s the kind of stable underpinning that Plasma should rely on.

But also, it’s infeasible to rely on an executable for brightness control if it doesn’t support brightness animations, we can’t create a new process for every frame of a standard 60 FPS animation and expect a smooth brightness transition. I think the effort in designing a fallback that can coexist with the current functionality, and getting the various distros to provide this as an optional dependency, would be better invested in improving the code in Plasma itself. Especially if all of this will be moot in a few years’ time when the new kernel APIs get available.

Well if plasma changes values at /sys/class/backlight/ something/brightness then we can so that it does it via making a symlink in $HOME/.config/kbrightness to that file so if the user wants to manually change it all he/she needs to do is modify the symlink location