Comment 11 for bug 1363623

The above patch causes a problem on my Amilo Xi 2550 (RadeonHD 2600).

The behaviour for kernel-3.14.8-100.fc19 (without patch):

The value of /sys/class/backlight/radeon_bl0/brightness is 0.
Whenever I write something (0-255) to /sys/class/backlight/radeon_bl0/brightness,
the backlight is turned off, and I am not able to turn on the backlight again.
However, I can still shutdown the system (Ctr+Alt+Fx, login as root, and give a
shutdown command.

I can control the backlight by writing values 0-7 to /sys/class/backlight/acpi_video0/brightness.

The behaviour for kernel-3.14.17-100.fc19 (with patch):

The backlight is turned off during the boot up process, when the kernel switches into
graphics mode.
I commented out the lines 233-234 in drivers/gpu/drm/radeon/atombios_encoders.c,
and then, the problem disappeared, i.e., the backlight stays on when the kernel switches
into graphics mode.

Best regards,
Daniel