Comment # 17 on bug 81382 from Patrick

(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"