I am pretty sure this is kernel bug. as root echo 1 > /sys/class/backlight/acpi_video0/brightness has no effect and xbacklight still works as described at the end of https://wiki.archlinux.org/index.php/backlight#sysfs_modified_but_no_brightness_change
I am pretty sure this is kernel bug. backlight/ acpi_video0/ brightness /wiki.archlinux .org/index. php/backlight# sysfs_modified_ but_no_ brightness_ change
as root
echo 1 > /sys/class/
has no effect and xbacklight still works as described at the end of https:/