As the title says, I am unable to configure the brightness of the screen, both through fn+up and down keys, and through the sliders in the Gnome top bar. This happened after I booted into windows and then back to Linux. The brightness set itself to max and I am completely unable to change it.
I recently installed new updates that became available today, but this was not the first time i rebooted after the updates, but the first time I booted into windows after the updates.
It says “No outputs have backlight property”. I didn’t expect this to work though, as I am using wayland and this sounds like it’s exclusive to Xorg
You can edit kernel parameter with sudo nano /etc/default/grub and add this parameter to the line GRUB_CMDLINE_LINUX_DEFAULT="" or GRUB_CMDLINE_LINUX="". Do not remove existing parameters.
When you are done you need to run sudo update-grub and reboot.
I will not share my grub file as I don’t use quiet splash and it could be misleading for you.
Be aware that you may have from time to time a *.pacnew file and you will have to merge it partially or not to keep you settings.
I was facing a similar issue. After I turned on my laptop today I noticed that my screen was at full brightness and the keys didn’t work.
I followed your instructions and added the i915.enable_dpcd_backlight=0 line, updated grub and restarted the laptop. GRUB_CMDLINE_LINUX="i915.enable_dpcd_backlight=0"
Now the brightness keys are working again. Thanks vcottineau for providing the solution and JoelEng for making a thread.