https://bugs.freedesktop.org/show_bug.cgi?id=81382
--- Comment #17 from Patrick ps_mail@freenet.de --- (In reply to comment #14)
This could be true. I can control it via /sys/class/backlight/acpi_video0/brightness. If I change /sys/class/backlight/radeon_bl0/brightness then the display is nearly black and cannot be restored.
After reboot the following values are set: acpi_video0 = 7 radeon_bl0 = 0
I've attached a lspci -vvv to " lspci output for amilo" and the vbios to "vbios from Amilo"