I am not able to set my screen brightness on my macbook running arch linux. The macbook is a 15 inch 2012 model and I am using Arch Linux 4.11.5-1. I have read up on arch linux wiki "backlight", "Mac", and different other forums and posts but I cant quite get it to work.
What is your Desktop environment? In the past I had many problems regarding screen brightness on LXDE desktop environment and changing to XFCE fixed all my problems.
If anyone stumbles upon this issue in the future, here is how I solved it. I just used
gmux_backlight +50000 and it worked perfectly.