I’ve had some difficulties when it came to the backlight on my arch linux installation.
Of course the first place to look for a solution was the arch wiki but I couldn’t find the right combination of kernel params to brighten the screen. It was kind of dark and the other possible mode was completely off.
After searching for a while I found a bug report having the same problem as I had so I had a look at it and checked to see if this works. My expectation was low given the fact that I thought that I’ve already tried everything but fortunately this helped.
Add the following line to GRUB_CMDLINE_LINUX_DEFAULT in /etc/default/grub and execute update-grub
Hope this helped you, too 🙂