I spoke a bit too soon it seems.

It had been working fine. Just now I left my laptop for ~5 minutes (it
was on, screen open, brightness on full when I left).

I came back and found the brightness stuck on minimum (and my session
had timed out, prompting me for my password - presumably something that
happened as part of the time out is what triggered this bug and thus the
brightness to be stuck on minimum).

Echoing 0 to /sys/class/backlight/intel_backlight/brightness did not fix
it. Suspending and unsuspending the laptop did fix it - the brightness
was back at full when I unsuspended, and I have control again.

I seem to recall reading either further up on here or elsewhere that the
root cause is/was a race condition. I know next to nothing about things
at this level (my current expertise is in Android and at the SDK level)
but what I saw just now seemed like it could be explained in terms of a
race condition.

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  backlight brightness not adjustable by default on Dell XPS 13

Status in Dell Sputnik:
Status in “linux” package in Ubuntu:
  Fix Released
Status in “linux” source package in Precise:
  In Progress
Status in “linux” source package in Quantal:
  In Progress
Status in “linux” source package in Raring:
  Fix Released

Bug description:
  The backlight brightness is not changeable by default on a Dell XPS 13 
running Precise beta 1 (or later). If I run the following command as root, I 
can adjust the brightness:
      /bin/echo 0 > /sys/class/baclight/intel_backlight/brightness
  However, I must do this whenever I turn on the computer or resume it from 

  ProblemType: Bug
  DistroRelease: Ubuntu 12.04
  Package: xserver-xorg-video-intel 2:2.17.0-1ubuntu4
  ProcVersionSignature: Ubuntu 3.2.0-18.29-generic 3.2.9
  Uname: Linux 3.2.0-18-generic x86_64
  ApportVersion: 1.94.1-0ubuntu2
  Architecture: amd64
  CompositorRunning: None
  Date: Tue Mar 13 20:56:36 2012
  DistUpgraded: Fresh install
  DistroCodename: precise
  DistroVariant: ubuntu
  ExtraDebuggingInterest: Yes, whatever it takes to get this fixed in Ubuntu
   Intel Corporation 2nd Generation Core Processor Family Integrated Graphics 
Controller [8086:0116] (rev 09) (prog-if 00 [VGA controller])
     Subsystem: Dell Device [1028:052e]
  InstallationMedia: Ubuntu 12.04 LTS "Precise Pangolin" - Beta amd64 (20120301)
  MachineType: Dell Inc. Dell System XPS L321X
  ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-3.2.0-18-generic 
root=UUID=6a0a6c9c-fb29-446a-8806-e431d38c95e8 ro quiet splash 
i915.i915_enable_fbc=1 i915.i915_enable_rc6=1 pcie_aspm=force vt.handoff=7
  SourcePackage: xserver-xorg-video-intel
  UpgradeStatus: No upgrade log present (probably fresh install)
  dmi.bios.date: 01/30/2012
  dmi.bios.vendor: Dell Inc.
  dmi.bios.version: A02
  dmi.board.name: 085X6F
  dmi.board.vendor: Dell Inc.
  dmi.board.version: A00
  dmi.chassis.type: 8
  dmi.chassis.vendor: Dell Inc.
  dmi.chassis.version: 0.1
  dmi.product.name: Dell System XPS L321X
  dmi.sys.vendor: Dell Inc.
  version.compiz: compiz 1:
  version.ia32-libs: ia32-libs N/A
  version.libdrm2: libdrm2 2.4.30-1ubuntu1
  version.libgl1-mesa-dri: libgl1-mesa-dri 8.0.1-0ubuntu2
  version.libgl1-mesa-dri-experimental: libgl1-mesa-dri-experimental N/A
  version.libgl1-mesa-glx: libgl1-mesa-glx 8.0.1-0ubuntu2
  version.xserver-xorg-core: xserver-xorg-core 2:1.11.4-0ubuntu6
  version.xserver-xorg-input-evdev: xserver-xorg-input-evdev 
  version.xserver-xorg-video-ati: xserver-xorg-video-ati 
  version.xserver-xorg-video-intel: xserver-xorg-video-intel 2:2.17.0-1ubuntu4
  version.xserver-xorg-video-nouveau: xserver-xorg-video-nouveau 

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