SUMMARY Changing the brightness on the battery applet or fn-keys doesn't change the screen brightness. Using xrandr works, but that seems to be a gamma change and not a change in the backlight. STEPS TO REPRODUCE 1. Start plasma 2. Change brightness OBSERVED RESULT No change in actual screen brightness EXPECTED RESULT Change in actual screen brightness SOFTWARE/OS VERSIONS Linux/KDE Plasma: KDE neon 5.21 (available in About System) KDE Plasma Version: 5.21.0 KDE Frameworks Version: 5.79.0 Qt Version: 5.12.2 ADDITIONAL INFORMATION
Can't reproduce on openSUSE Tumbleweed with Plasma 5.21; works for me.
Hmm could that be fallout from removing xrandr brightness? Can you provide the output of $ ls /sys/class/backlight/
ls /sys/class/backlight/ gives a directory called: acpi_video0
Okay, so that is the fallback driver I think, can you check the contents of "brightness" and "max_brightness" in that folder? Also, when you echo into brightness, does it change? e.g. echo 5 | sudo tee /sys/class/backlight/acpi_video0/brightness
cat /sys/class/backlight/acpi_video0/brightness 0 cat /sys/class/backlight/acpi_video0/max_brightness 100 echo 5 | sudo tee ls /sys/class/backlight/acpi_video0/brightness changes the file, but has no effect on screen brightness
So then there's not much Plasma can do unfortunately. What GPU is this? Perhaps report a kernel or driver bug.
I use an Nvidia 650m But it worked before the update to plasma 5.21 earlier today.
We removed the xrandr code path (which xrandr probably uses) for codd maintenance and because it wouldn't work on wayland anyway, sorry.
I found a solution by editing /etc/default/grub GRUB_CMDLINE_LINUX_DEFAULT="quiet splash" to GRUB_CMDLINE_LINUX_DEFAULT="quiet splash video.use_native_backlight=1" and updating grub
Glad you found a solution and sorry for the trouble but sometimes we gotta clean up our codebase to make it more maintainable and future-proof