Brightness bar worked with acpi_backlight=video
xubuntu@xubuntu:/sys/class/backlight/radeon_bl0$ cd .. xubuntu@xubuntu:/sys/class/backlight$ ls acpi_video0 radeon_bl0 xubuntu@xubuntu:/sys/class/backlight$
Brightness bar worked with acpi_backlight= video
xubuntu@ xubuntu: /sys/class/ backlight/ radeon_ bl0$ cd .. xubuntu: /sys/class/ backlight$ ls xubuntu: /sys/class/ backlight$
xubuntu@
acpi_video0 radeon_bl0
xubuntu@