Backlight control does not work, but there are entries in /sys/class/backlight.

[Abdurrahman Çarkacıoğlu]

Backlight control does not work, but there are entries in /sys/class/backlight.

This may require the ACPI backlight driver to not take control so that a vendor specific driver will have a chance to register.

I wanto mention that this goes beyond just the applet not working. My data does change in Ubuntu for those entries and the acpi interface to the Linux Kernel is not able to use that changed data to change the hardware brightness setting.

ProblemType: Bug
DistroRelease: Ubuntu 12.04
Package: linux-image-3.2.0-37-generic 3.2.0-37.58
ProcVersionSignature: Ubuntu 3.2.0-37.58-generic 3.2.35
Uname: Linux 3.2.0-37-generic x86_64
AlsaVersion: Advanced Linux Sound Architecture Driver Version 1.0.24.
ApportVersion: 2.0.1-0ubuntu17.1
Architecture: amd64
AudioDevicesInUse:
 USER PID ACCESS COMMAND
 /dev/snd/controlC1: carkaci 1936 F.... pulseaudio
 /dev/snd/controlC0: carkaci 1936 F.... pulseaudio
CRDA:
 country AW:
  (2402 - 2482 @ 40), (N/A, 20)
  (5170 - 5250 @ 40), (N/A, 20)
  (5250 - 5330 @ 40), (N/A, 20), DFS
  (5490 - 5710 @ 40), (N/A, 27), DFS
Card0.Amixer.info:
 Card hw:0 'Intel'/'HDA Intel at 0xd0500000 irq 48'
   Mixer name : 'Cirrus Logic CS4206'
   Components : 'HDA:10134206,106b1800,00100301'
   Controls : 25
   Simple ctrls : 11
Card1.Amixer.info:
 Card hw:1 'Generic'/'HD-Audio Generic at 0xd0440000 irq 49'
   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: Mon Feb 4 21:53:10 2013
HibernationDevice: RESUME=UUID=2850be5d-9902-4a6d-8e97-3f9d34028e02
InstallationMedia: Ubuntu 12.04.1 LTS "Precise Pangolin" - Release amd64 (20120823.1)
MachineType: Apple Inc. iMac11,3
MarkForUpload: True
ProcEnviron:
 TERM=xterm
 PATH=(custom, no user)
 LANG=en_US.UTF-8
 SHELL=/bin/bash
ProcFB: 0 radeondrmfb
ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-3.2.0-37-generic root=UUID=83592388-7d5b-432f-94fe-74542604df39 ro acpi_osi=Linux quiet splash vt.handoff=7
PulseList:
 Error: command ['pacmd', 'list'] failed with exit code 1: Home directory /home/carkaci not ours.
 No PulseAudio daemon running, or not running as session daemon.
RelatedPackageVersions:
 linux-restricted-modules-3.2.0-37-generic N/A
 linux-backports-modules-3.2.0-37-generic N/A
 linux-firmware 1.79.1
SourcePackage: linux
UpgradeStatus: No upgrade log present (probably fresh install)
dmi.bios.date: 05/03/10
dmi.bios.vendor: Apple Inc.
dmi.bios.version: IM112.88Z.0057.B00.1005031455
dmi.board.name: Mac-F2238BAE
dmi.board.vendor: Apple Inc.
dmi.board.version: iMac11,3
dmi.chassis.type: 13
dmi.chassis.vendor: Apple Inc.
dmi.chassis.version: Mac-F2238BAE
dmi.modalias: dmi:bvnAppleInc.:bvrIM112.88Z.0057.B00.1005031455:bd05/03/10:svnAppleInc.:pniMac11,3:pvr1.0:rvnAppleInc.:rnMac-F2238BAE:rvriMac11,3:cvnAppleInc.:ct13:cvrMac-F2238BAE:
dmi.product.name: iMac11,3
dmi.product.version: 1.0
dmi.sys.vendor: Apple Inc.

[Brad Figg (brad-figg)]

This change was made by a bot.

[Joseph Salisbury (jsalisbury)]

Would it be possible for you to test the latest upstream kernel? Refer to https://wiki.ubuntu.com/KernelMainlineBuilds . Please test the latest v3.8 kernel[0] (Not a kernel in the daily directory) and install both the linux-image and linux-image-extra .deb packages.

If this bug is fixed in the mainline kernel, please add the following tag 'kernel-fixed-upstream'.

If the mainline kernel does not fix this bug, please add the tag: 'kernel-bug-exists-upstream'.

If you are unable to test the mainline kernel, for example it will not boot, please add the tag: 'kernel-unable-to-test-upstream'.
Once testing of the upstream kernel is complete, please mark this bug as "Confirmed".

Thanks in advance.

[0] http://kernel.ubuntu.com/~kernel-ppa/mainline/v3.8-rc6-raring/

[Abdurrahman Çarkacıoğlu (carkaci)]

I tried the new kernel than I added 'kernel-bug-exists-upstream' as a tag
to the bug.

On Mon, Feb 4, 2013 at 11:15 PM, Joseph Salisbury <
<email address hidden>> wrote:

> Would it be possible for you to test the latest upstream kernel? Refer
> to https://wiki.ubuntu.com/KernelMainlineBuilds . Please test the latest
> v3.8 kernel[0] (Not a kernel in the daily directory) and install both
> the linux-image and linux-image-extra .deb packages.
>
> If this bug is fixed in the mainline kernel, please add the following
> tag 'kernel-fixed-upstream'.
>
> If the mainline kernel does not fix this bug, please add the tag:
> 'kernel-bug-exists-upstream'.
>
> If you are unable to test the mainline kernel, for example it will not
> boot, please add the tag: 'kernel-unable-to-test-upstream'.
> Once testing of the upstream kernel is complete, please mark this bug as
> "Confirmed".
>
>
> Thanks in advance.
>
> [0] http://kernel.ubuntu.com/~kernel-ppa/mainline/v3.8-rc6-raring/
>
>
> ** Changed in: linux (Ubuntu)
> Importance: Undecided => Medium
>
> ** Changed in: linux (Ubuntu)
> Status: Confirmed => Incomplete
>
> --
> You received this bug notification because you are subscribed to the bug
> report.
> https://bugs.launchpad.net/bugs/1115555
>
> Title:
> Backlight control does not work, but there are entries in
> /sys/class/backlight.
>
> Status in “linux” package in Ubuntu:
> Incomplete
>
> Bug description:
> Backlight control does not work, but there are entries in
> /sys/class/backlight.
>
> This may require the ACPI backlight driver to not take control so that
> a vendor specific driver will have a chance to register.
>
> I wanto mention that this goes beyond just the applet not working. My
> data does change in Ubuntu for those entries and the acpi interface to
> the Linux Kernel is not able to use that changed data to change the
> hardware brightness setting.
>
> ProblemType: Bug
> DistroRelease: Ubuntu 12.04
> Package: linux-image-3.2.0-37-generic 3.2.0-37.58
> ProcVersionSignature: Ubuntu 3.2.0-37.58-generic 3.2.35
> Uname: Linux 3.2.0-37-generic x86_64
> AlsaVersion: Advanced Linux Sound Architecture Driver Version 1.0.24.
> ApportVersion: 2.0.1-0ubuntu17.1
> Architecture: amd64
> AudioDevicesInUse:
> USER PID ACCESS COMMAND
> /dev/snd/controlC1: carkaci 1936 F.... pulseaudio
> /dev/snd/controlC0: carkaci 1936 F.... pulseaudio
> CRDA:
> country AW:
> (2402 - 2482 @ 40), (N/A, 20)
> (5170 - 5250 @ 40), (N/A, 20)
> (5250 - 5330 @ 40), (N/A, 20), DFS
> (5490 - 5710 @ 40), (N/A, 27), DFS
> Card0.Amixer.info:
> Card hw:0 'Intel'/'HDA Intel at 0xd0500000 irq 48'
> Mixer name : 'Cirrus Logic CS4206'
> Components : 'HDA:10134206,106b1800,00100301'
> Controls : 25
> Simple ctrls : 11
> Card1.Amixer.info:
> Card hw:1 'Generic'/'HD-Audio Generic at 0xd0440000 irq 49'
> 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-j...

[Mike Ferreira (mafoelffen)]

Had been working with this user on forum thread:
http://ubuntuforums.org/showthread.php?t=2112027

I've confirmed that his /sys/class/backlight/acpi_video0/brightness data can be changed, but those changes do not get picked up.

What he didn't mention yet... is that if he does reboot to MAC OSX, changes the brightness setting there, then reboots the hardware back into Ubuntu, the MAC OSX changed setting is retained.

He has a functional workaround, but it is outside Ubuntu and the Linux kernel. Changes within Ubuntu do not make affect.

[Damir Butmir (d4m1r2)]

FYI, I am using a 2013 13" MBP and I was able to get my screen brightness controls to work automatically but using;

echo 5 | sudo tee /sys/......

instead of

sudo echo 5 > /sys/.....

[penalvch (penalvch)]

Abdurrahman Çarkacıoğlu, could you please confirm this issue exists with the latest development release of Ubuntu? ISO images are available from http://cdimage.ubuntu.com/daily-live/current/ . If the issue remains, could you please run the following command in the development release from a Terminal (Applications->Accessories->Terminal), as it will automatically gather and attach updated debug information to this report:

apport-collect -p linux <replace-with-bug-number>

Also, could you please test the latest upstream kernel available following https://wiki.ubuntu.com/KernelMainlineBuilds ? It will allow additional upstream developers to examine the issue. Please do not test the daily folder, but the one all the way at the bottom. Once you've tested the upstream kernel, please comment on which kernel version specifically you tested. If this bug is fixed in the mainline kernel, please add the following tags:
kernel-fixed-upstream
kernel-fixed-upstream-VERSION-NUMBER

where VERSION-NUMBER is the version number of the kernel you tested. For example:
kernel-fixed-upstream-v3.11-rc3

This can be done by clicking on the yellow circle with a black pencil icon next to the word Tags located at the bottom of the bug description. As well, please remove the tag:
needs-upstream-testing

If the mainline kernel does not fix this bug, please add the following tags:
kernel-bug-exists-upstream
kernel-bug-exists-upstream-VERSION-NUMBER

As well, please remove the tag:
needs-upstream-testing

If you are unable to test the mainline kernel, please comment as to why specifically you were unable to test it and add the following tags:
kernel-unable-to-test-upstream
kernel-unable-to-test-upstream-VERSION-NUMBER

Once testing of the upstream kernel is complete, please mark this bug's Status as Confirmed. Please let us know your results. Thank you for your understanding.

[Gaele Strootman (gaele)]

This bug is affecting me since Wily. In Vivid all was working well.

Macbook Pro 11,3 with nouveau.

/sys/class/backlight/gmux_backlight$ grep . *
actual_brightness:16777215
bl_power:0
brightness:400
grep: device: Is a directory
max_brightness:-1
grep: power: Is a directory
grep: subsystem: Is a directory
type:platform

[Gaele Strootman (gaele)]

Further info:

Hotkeys don't work,
no brightness indicator is displayed
there's no scrollbar in the "Brightness and Lock" applet.

[Gaele Strootman (gaele)]

Nothing changes after changing the brightness in MacOSX and rebooting back into Ubuntu. I'm still at maximum brightness.

[Gaele Strootman (gaele)]

If I enable the nvidia driver I get a brightness indicator and a scrollbar in the "Brightness and Lock" applet. However neither hotkeys nor the scrollbar have any effect.

/sys/class/backlight/gmux_backlight$ grep . *
actual_brightness:16777215
bl_power:0
brightness:1023
grep: device: Is a directory
max_brightness:1023
grep: power: Is a directory
grep: subsystem: Is a directory
type:platform
gaele@mozzy:/sys/class/backlight/gmux_backlight$

<Move the scrollbar to minimum brightness>

/sys/class/backlight/gmux_backlight$ grep . *
actual_brightness:16777215
bl_power:0
brightness:0
grep: device: Is a directory
max_brightness:1023
grep: power: Is a directory
grep: subsystem: Is a directory
type:platform

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[penalvch (penalvch)]

Gaele Strootman, it will help immensely if you filed a new report via a terminal:
ubuntu-bug linux

Please feel free to subscribe me to it.

[Launchpad Janitor (janitor)]

[Expired for linux (Ubuntu) because there has been no activity for 60 days.]