Hi everyone,
I came here because of I have a strange problem with the control of my monitor’s backlight: There is no brightness slider in that drop down menu on the top right (‘control center’, I think?).
I run F42 KDE Spin, usually with the default SDDM / Plasma / Wayland Desktop, everything updated. But I am currently trying out GDM / Gnome / Wayland (because I simply want to). The hardware is a desktop computer:
- Mainboard AMD B650
- CPU Ryzen 7 7700 X
- GPU AMD Radeon RX 6700 XT
- Monitor Dell G2724D
- If you need more information, please ask, I would happily provide it!
First thought, ask Dr. Google. And, easy peasy, there seems to be a bug where the slider is only shown after one issues a dbus command once per session to change the brightness.
So I opened the terminal and c&p this command:
gdbus call --session --dest org.gnome.SettingsDaemon.Power --object-path /org/gnome/SettingsDaemon/Power --method org.freedesktop.DBus.Properties.Set org.gnome.SettingsDaemon.Power.Screen Brightness ‘<90>’
The result is:
Fehler: GDBus.Error:org.gtk.GDBus.UnmappedGError.Quark._gsd_5fpower_5fmanager_5ferror.Code1: No usable backlight could be found!
Fehler = German for error
A quick ls -a of /sys/class/backlight shows the usual ‘.’ and ‘..’ . Okay, that would be the perfect explanation. Except - when switching to Plasma, there is a f…ine brightness control slider. And it works perfectly. Has been doing so since I switched to Linux from Windows over a year ago. On Arch as well as on Fedora (wanted something easier after a couple of weeks 
and didn’t really like pacman).
There is so much documentation out in the internet, but everything I find describes and ‘solves’, rather works around, the bug I described above. Which should be resolved by the devs by now, anyway. So I am hitting a wall right now. Would someone be so kind to point me in the right direction? Thanks a lot!