Brightness control at f11 & f12 is not working

[Jing]

@petsam

ls /sys/class/backlight/

lrwxrwxrwx 0 root 20 Feb 21:29 intel_backlight -> ../../devices/pci0000:00/0000:00:02.0/drm/card0/card0-eDP-1/intel_backlight

@petsam

find  /sys/class/backlight/*/*brightness -type f -printf "%f "  -exec cat {} \;
systemctl status systemd-backlight@backlight*

actual_brightness 5334
brightness 5334
max_brightness 26666
● systemd-backlight@backlight:intel_backlight.service - Load/Save Screen Backlight Brightness of backlight:intel_backlight
     Loaded: loaded (/usr/lib/systemd/system/systemd-backlight@.service; static)
     Active: active (exited) since Sat 2021-02-20 17:59:22 +08; 3h 32min ago
       Docs: man:systemd-backlight@.service(8)
    Process: 408 ExecStart=/usr/lib/systemd/systemd-backlight load backlight:intel_backlight (code=exited, status=0/SUCCESS)
   Main PID: 408 (code=exited, status=0/SUCCESS)

Feb 20 17:59:22 Jinglebell systemd[1]: Starting Load/Save Screen Backlight Brightness of backlight:intel_backlight...
Feb 20 17:59:22 Jinglebell systemd[1]: Finished Load/Save Screen Backlight Brightness of backlight:intel_backlight.```