This machine supports the standard ACPI backlight interface, but using it has no effect on the screen brightness. The only known way to adjust screen brightness on this machine is via the gmux device, but this is not currently supported under Linux. The details of the gmux backlight interface are known, so it's a matter of getting driver support into the kernel.
ProblemType: Bug
DistroRelease: Ubuntu 12.04
Package: linux-image-3.2.0-12-generic 3.2.0-12.21
ProcVersionSignature: Ubuntu 3.2.0-12.21-generic 3.2.2
Uname: Linux 3.2.0-12-generic x86_64
AlsaVersion: Advanced Linux Sound Architecture Driver Version 1.0.24.
ApportVersion: 1.91-0ubuntu1
Architecture: amd64
AudioDevicesInUse:
USER PID ACCESS COMMAND
/dev/snd/controlC1: ubuntu 1743 F.... pulseaudio
/dev/snd/controlC0: ubuntu 1743 F.... pulseaudio
Card0.Amixer.info:
Card hw:0 'PCH'/'HDA Intel PCH at 0xb0900000 irq 47'
Mixer name : 'Cirrus Logic CS4206'
Components : 'HDA:10134206,106b1d00,00100302'
Controls : 24
Simple ctrls : 10
Card1.Amixer.info:
Card hw:1 'Generic'/'HD-Audio Generic at 0xb0840000 irq 48'
Mixer name : 'ATI R6xx HDMI'
Components : 'HDA:1002aa01,00aa0100,00100200'
Controls : 6
Simple ctrls : 1
Card1.Amixer.values:
Simple mixer control 'IEC958',0
Capabilities: pswitch pswitch-joined penum
Playback channels: Mono
Mono: Playback [on]
Date: Thu Feb 2 09:55:21 2012
HibernationDevice: RESUME=UUID=13594e7c-281a-4c68-afc8-7ef8aae830c9
InstallationMedia: Ubuntu 12.04 LTS "Precise Pangolin" - Alpha amd64+mac (20111208)
MachineType: Apple Inc. MacBookPro8,2
ProcEnviron:
PATH=(custom, no user)
LANG=en_US.UTF-8
SHELL=/bin/bash
ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-3.2.0-12-generic root=UUID=b914ccd7-a73e-4a8b-97b2-4b23a1d3d39c ro acpi_backlight=vendor quiet splash vt.handoff=7
RelatedPackageVersions:
linux-restricted-modules-3.2.0-12-generic N/A
linux-backports-modules-3.2.0-12-generic N/A
linux-firmware 1.68
SourcePackage: linux
StagingDrivers: mei
UpgradeStatus: No upgrade log present (probably fresh install)
dmi.bios.date: 09/28/11
dmi.bios.vendor: Apple Inc.
dmi.bios.version: MBP81.88Z.0047.B22.1109281426
dmi.board.asset.tag: Base Board Asset Tag#
dmi.board.name: Mac-94245A3940C91C80
dmi.board.vendor: Apple Inc.
dmi.board.version: MacBookPro8,2
dmi.chassis.type: 10
dmi.chassis.vendor: Apple Inc.
dmi.chassis.version: Mac-94245A3940C91C80
dmi.modalias: dmi:bvnAppleInc.:bvrMBP81.88Z.0047.B22.1109281426:bd09/28/11:svnAppleInc.:pnMacBookPro8,2:pvr1.0:rvnAppleInc.:rnMac-94245A3940C91C80:rvrMacBookPro8,2:cvnAppleInc.:ct10:cvrMac-94245A3940C91C80:
dmi.product.name: MacBookPro8,2
dmi.product.version: 1.0
dmi.sys.vendor: Apple Inc.
I've got a patch adding support for gmux backlight control to the apple_bl driver and am currently working to get it tested on a variety of Apple machines. So far the results are positive.