[Virtual-pkg-base-maintainers] Bug#703134: base: Screen brightness dim on a Dell XPS M1710; can't change it

[Damien]

Package: base
Severity: important

Dear Maintainer,

I've been unable to change the screen brightness today, on a Dell XPS M1710 laptop.  It stays dim.  When changing from a virtual terminal to X, the screen is bright briefly, but immediately dims again.  During boot, the brightness is correct for Grub but dims during the boot process.

If I use the brightness keys to set the brighness to the minimum value, the screen doesn't brighten when I change to the graphical desktop from a text console (ie. ctrl+alt+f1), but when I set it to maximum it becomes bright for about 1/4 second when I change to the graphical desktop.

The brightness keys don't work, nor does writing to /sys/class/backlight/acpi_video0/backlight.

I've only seen this today, so maybe it's related to these package updates:

Start-Date: 2013-03-15  17:02:14
Upgrade: xserver-xorg-video-ati:amd64 (6.14.4-7, 6.14.4-8), gstreamer0.10-alsa:a
md64 (0.10.36-1, 0.10.36-1.1), linux-image-3.2.0-4-amd64:amd64 (3.2.35-2, 3.2.39
-2), linux-headers-3.2.0-4-amd64:amd64 (3.2.35-2, 3.2.39-2), linux-headers-3.2.0
-4-common:amd64 (3.2.35-2, 3.2.39-2), libgstreamer-plugins-base0.10-0:amd64 (0.1
0.36-1, 0.10.36-1.1), linux-libc-dev:amd64 (3.2.35-2, 3.2.39-2), xserver-xorg-vi
deo-radeon:amd64 (6.14.4-7, 6.14.4-8), gstreamer0.10-plugins-base:amd64 (0.10.36
-1, 0.10.36-1.1)
End-Date: 2013-03-15  17:03:02

I don't know whether the brightness controls worked before as the screen was always bright enough.

I think this is the relevant part of 'lshw':

           *-display
                description: VGA compatible controller
                product: G71 [GeForce Go 7950 GTX]
                vendor: NVIDIA Corporation
                physical id: 0
                bus info: pci at 0000:01:00.0
                version: a1
                width: 64 bits
                clock: 33MHz
                capabilities: pm msi pciexpress vga_controller bus_master cap_list rom
                configuration: driver=nouveau latency=0
                resources: irq:16 memory:ed000000-edffffff memory:d0000000-dfffffff memory:ee000000-eeffffff ioport:ef00(size=128) memory:efe00000-efe1ffff

Let me know if you need any more information.

-- System Information:
Debian Release: 7.0
  APT prefers testing
  APT policy: (500, 'testing')
Architecture: amd64 (x86_64)

Kernel: Linux 3.2.0-4-amd64 (SMP w/2 CPU cores)
Locale: LANG=en_AU.UTF-8, LC_CTYPE=en_AU.UTF-8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/dash