[MacBook Pro 8,2] Unable to adjust display brightness

Bug #925544 reported by Seth Forshee on 2012-02-02
This bug affects 2 people
Affects Status Importance Assigned to Milestone
linux (Ubuntu)
Seth Forshee

Bug Description

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
 /dev/snd/controlC1: ubuntu 1743 F.... pulseaudio
 /dev/snd/controlC0: ubuntu 1743 F.... pulseaudio
 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
 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
 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
 PATH=(custom, no user)
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
 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.

Seth Forshee (sforshee) wrote :
Seth Forshee (sforshee) wrote :

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.

Brad Figg (brad-figg) on 2012-02-02
Changed in linux (Ubuntu):
status: New → Confirmed
Seth Forshee (sforshee) on 2012-02-02
Changed in linux (Ubuntu):
status: Confirmed → In Progress
Launchpad Janitor (janitor) wrote :

This bug was fixed in the package linux - 3.2.0-18.29

linux (3.2.0-18.29) precise; urgency=low

  [ Andy Whitcroft ]

  * [Config] restore build-% shortcut
  * SAUCE: ata_piix: defer disks to the Hyper-V drivers by default
    - LP: #929545, #942316

  [ Eugeni Dodonov ]

  * SAUCE: drm: give up on edid retries when i2c bus is not responding
    - LP: #855124

  [ Seth Forshee ]

  * SAUCE: (drop after 3.3) platform/x86: Add driver for Apple gmux device
    - LP: #925544

  [ Upstream Kernel Changes ]

  * bsg: fix sysfs link remove warning
    - LP: #946928
  * regset: Prevent null pointer reference on readonly regsets
    - LP: #949905
    - CVE-2012-1097
  * regset: Return -EFAULT, not -EIO, on host-side memory fault
    - LP: #949905
    - CVE-2012-1097

  [ Wu Fengguang ]

  * SAUCE: (drop after 3.4) ALSA: hda - add id for Atom Cedar Trail HDMI
 -- Leann Ogasawara <email address hidden> Fri, 09 Mar 2012 07:56:11 -0800

Changed in linux (Ubuntu):
status: In Progress → Fix Released

The verification of this Stable Release Update has completed successfully and the package has now been released to -updates. Subsequently, the Ubuntu Stable Release Updates Team is being unsubscribed and will not receive messages about this bug report. In the event that you encounter a regression using the package from -updates please report a new bug using ubuntu-bug and tag the bug report regression-update so we can easily find any regresssions.

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