Is someone else facing a similar issue of not able to adjust the screen brightness ? Both brightness control in Gnome GUI and Fn keys have stopped working. I am able to change the brightness by changing values manually in /cd /sys/class/backlight/intel_backlight/brightness. It used to work perfectly fine ever since fresh install (3 weeks back) till it stopped now.
I recently upgraded all the packages which included a move to Kernel 4.17.11-arch1 and linux-firmware 20180717.8d69bab-1. I noticed the error after the upgrade.