Laptop backlight control disappears

Hi all,

I have an issue with the backlight brightness slider in Gnome’s top-right panel menu. When I first boot my laptop, the slider is there and works fine. But at some point it disappears and I can no longer control screen brightness.

I was searching for this issue and found that both /sys/class/backlight/intel_backlight/brightness and /sys/class/backlight/nvidia_0/brightness (I have a laptop with a dGPU) seem to be fine. They still exist even though the slider disappeared, and I can even use them to control the backlight from command-line. So H/W and drivers seems to be fine, it’s just Gnome that has decided to hide the brightness slider. Furthermore the keyboard hotkeys also do not work so I cannot use the brightness keys (F5 and F6) to control brightness…

The only thing I can do is logout and log back into Gnome (no reboot necessary) and everything works fine again (the slider is back and I can control brighness with it as well as the keyboard keys).

Does anyone have any suggestions on how to debug Gnome’s behaviour about that slider? Is there something I can “reset” to make Gnome re-detect the slider without a logout/login (this would be a useful workaround).

The slider is currently working, but I would like to know what I can do next time this happens…

I had the same issue after upgrading to Gnome 48, but I’m not sure if it’s the same as yours. When running echo 255 | sudo tee /sys/class/backlight/intel_backlight/brightness the brightness slider suddenly reappeared.

After a reboot, the slider is back to being hidden:

Running the command above again makes it reappear, so at least it’s reproducible:

What you are seeing is Display backlight slider in Quick Settings won't show up until brightness adjusted by keyboard (#867) · Issues · GNOME / gnome-settings-daemon · GitLab. This however couldn’t be the cause of the problem originally posted here, because the commit that introduced the bug was only merged after the post.

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Ah, thanks for pointing me to the right issue, and sorry for making some noise in the wrong thread!

same issue for me on fedora 42