Keyboard backlight no longer controllable via Fn keys within last week. Can still control via slider in battery/power applet in system tray. This worked up until the last one or two dups (which I run weekly).
Kernel 4.14.15-1-default (IIRC, did not work following upgrade to the one prior, either – again within the last week)
Has anyone else observed this? Any idea how to troubleshoot?
Start by sharing these details…
ls -l /sys/class/backlight
If you can demonstrate that booting from an older kernel results in brightness keys working as expected (via Grub > Advance options…) then a bug report is probably the best course of action.
Not clear to me if you are referring to the Video screen backlight not working, or the backlight LEDs under the keyboard not being controllable through Fn+F3, Fn+F4.
If the latter is the case, on a similar ASUS laptop I had to add an "acpi_osi= " including the trailing blank to the command line:
bruno@LT_B:~> cat /proc/cmdline
BOOT_IMAGE=/boot/vmlinuz-4.4.104-39-default root=UUID=fe8f.... ro **acpi_osi= **resume=/dev/disk/by-uuid/a9... splash=silent quiet showopts