Description:
After system upgrade (linux-pae 3.0.7-1 -> 3.4.4-3, xorg-server 1.11.4-1 -> 1.12.3-1, xf86-video-nouveau 0.0.16_git20120210-1 -> 1.0.1-1)
I don't have any more control on backlight from X session programs such as xrandr, xbacklight or xfce4 brightness plugin.
Since I have /sys/class/backlight/acpi_video0/brightness I still can "echo $value >..." to it in a root shell and it actually adjusts LCD backlight level, so it works fine at kernel level.
xrandr shows no backlight control in properties (though it was before upgrade);
Also I have seen that /proc/acpi/video/... has disappeared in the new kernel;
So I don't know whether it's xorg-server which wasn't adapted to a new ACPI backlight kernel interface, or the nouveau driver which doesn't "publish" the randr properties... anyway it seems like one of the two is responsible.


Additional info:
* package version(s)
xf86-video-nouveau 1.0.1-1
xorg-server 1.12.3-1
xorg-xbacklight 1.1.2-3
xorg-xrandr 1.3.5-1
libxrandr 1.3.2-2
linux-pae 3.4.4-3
* config and/or log files etc.
/etc/X11/xorg.conf.d/nvidia-gt330m.conf
Section "Device"
Identifier "Card0"
Driver "nouveau"
BusID "PCI:1:0:0"
EndSection


Steps to reproduce:
It's hardware related;
This laptop is a Sony VPCF11E4E, it has a NVidia GT330M as sole video card (NO Optimus).
Probably this could be reproduced on another laptop with a nvidia card supported by nouveau, which would set backlight through ACPI.