Brightness controls not working on intel igfx

[Martin H]

Brightness controls not working for me in Vivid Vervet as of 1-2 weeks ago.
Was confirmed working on Utopic Unicorn.

Hotkeys for brightness up & down non-functioning,
Hotkey for display on/off still works.

Gnome control center (brightness & lock) does not show brightness slider.

What does work is
"echo $value > /sys/class/backlight/intel_backlight/brightness"
as root for any $value of 0 - 2047

Running on an Asus S400C Laptop.

kernel:
x86_64 3.16.0-24-generic

lspci:
00:02.0 VGA compatible controller: Intel Corporation 3rd Gen Core processor Graphics Controller (rev 09)

lsb_release:
Description: Ubuntu Vivid Vervet (development branch)
Release: 15.04

ProblemType: Bug
DistroRelease: Ubuntu 15.04
Package: linux-image-3.16.0-24-generic 3.16.0-24.32
ProcVersionSignature: Ubuntu 3.16.0-24.32-generic 3.16.4
Uname: Linux 3.16.0-24-generic x86_64
ApportVersion: 2.14.7-0ubuntu10
Architecture: amd64
AudioDevicesInUse:
 USER PID ACCESS COMMAND
 /dev/snd/controlC0: martin 1970 F.... pulseaudio
CurrentDesktop: Unity
Date: Wed Nov 12 16:06:27 2014
HibernationDevice: RESUME=UUID=a7b59988-1d75-4f19-8fd8-3c9a08c38e8d
InstallationDate: Installed on 2014-08-21 (83 days ago)
InstallationMedia: Ubuntu 14.10 "Utopic Unicorn" - Alpha amd64 (20140820)
MachineType: ASUSTeK COMPUTER INC. S400CA
ProcFB: 0 inteldrmfb
ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-3.16.0-24-generic.efi.signed root=UUID=e2aa386f-a710-4fb4-ba6e-5d233c6b7b25 ro quiet splash vt.handoff=7
RelatedPackageVersions:
 linux-restricted-modules-3.16.0-24-generic N/A
 linux-backports-modules-3.16.0-24-generic N/A
 linux-firmware 1.138
SourcePackage: linux
UpgradeStatus: No upgrade log present (probably fresh install)
dmi.bios.date: 01/27/2014
dmi.bios.vendor: American Megatrends Inc.
dmi.bios.version: S400CA.210
dmi.board.asset.tag: ATN12345678901234567
dmi.board.name: S400CA
dmi.board.vendor: ASUSTeK COMPUTER INC.
dmi.board.version: 1.0
dmi.chassis.asset.tag: No Asset Tag
dmi.chassis.type: 10
dmi.chassis.vendor: ASUSTeK COMPUTER INC.
dmi.chassis.version: 1.0
dmi.modalias: dmi:bvnAmericanMegatrendsInc.:bvrS400CA.210:bd01/27/2014:svnASUSTeKCOMPUTERINC.:pnS400CA:pvr1.0:rvnASUSTeKCOMPUTERINC.:rnS400CA:rvr1.0:cvnASUSTeKCOMPUTERINC.:ct10:cvr1.0:
dmi.product.name: S400CA
dmi.product.version: 1.0
dmi.sys.vendor: ASUSTeK COMPUTER INC.

[Brad Figg (brad-figg)]

This change was made by a bot.

[penalvch (penalvch)]

Martin H, thank you for reporting this and helping make Ubuntu better. Could you please test the latest upstream kernel available from the very top line at the top of the page (the release names are irrelevant for testing, and please do not test the daily folder) following https://wiki.ubuntu.com/KernelMainlineBuilds ? It will allow additional upstream developers to examine the issue.

If the test did not allow you to test to the issue (ex. you couldn't boot into the OS) please make a comment in your report about this, and continue to test the next most recent kernel version until you can test to the issue. 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 exactly shown as:
kernel-fixed-upstream-3.18-rc4

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.

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

[Martin H (n17r4m)]

Not a problem

uname -a
Linux GreenBanana 3.18.0-031800rc4-generic #201411091835 SMP Sun Nov 9 23:36:36 UTC 2014 x86_64 x86_64 x86_64 GNU/Linux

The problem still is happening, (no hotkey controls, no brightness slider in control center)

Once change I noticed with latest kernel is ...
/sys/class/backlight/intel_backlight/brightness
... now accepts values between 0 - 4882 (and does change brightness).

Values above 4882 give "write error: Invalid argument"

[Martin H (n17r4m)]

One other point of note, is after the "Turn off screen when inactive for:" duration specified in the brightness & lock settings has ellapsed, instead of turning off the screen, it goes black (without turning off), and the mouse cursor is still visible. Yet, the hotkey for screen on/off does still seem to work ok, oddly enough.

[Martin H (n17r4m)]

I'm not so certian it is a kernel error now after some digging deeper.
I've tried all of the following kernels:

3.11.10-03111015-generic
3.12.20-031220-generic
3.14.2-031402-generic
3.14.23-031423-generic
3.16.0-10-generic
3.16.0-14-generic
3.16.0-18-generic
3.16.0-23-generic
3.16.0-24-generic
3.17.2-031702-generic
3.18.0-031800rc4-generic

I tried downloading and booting from the currently available Utopic iso, and as well as the latest daily image of Vivid.

On the Utopic iso boot, running kernel 3.16.0-23-generic (according to uname -a), the brightness controls function absolutely fine.

On the Vivid iso boot, the brightness controls no longer work.

Booting my machine from the same kernel version as what was working on the iso, 3.16.0-23, the controls also still don't work.

Additionally, I am noticing the following dmesg errors:

On brightness down:
[ 64.883616] ACPI Error: Method parse/execution failed [\_SB_.PCI0.GFX0.DWBL] (Node ffff88011a433500), AE_AML_UNINITIALIZED_ELEMENT (20140424/psparse-536)
[ 64.883626] ACPI Error: Method parse/execution failed [\_SB_.PCI0.LPCB.EC0_._Q0E] (Node ffff88011a442c58), AE_AML_UNINITIALIZED_ELEMENT (20140424/psparse-536)

On brightness up:
[ 64.888952] ACPI Error: Method parse/execution failed [\_SB_.PCI0.GFX0.UPBL] (Node ffff88011a4334d8), AE_AML_UNINITIALIZED_ELEMENT (20140424/psparse-536)
[ 64.888959] ACPI Error: Method parse/execution failed [\_SB_.PCI0.LPCB.EC0_._Q0F] (Node ffff88011a442c80), AE_AML_UNINITIALIZED_ELEMENT (20140424/psparse-536)

Could there have been a userland change that is causing some mismatch or somesuch?

[Florian Boucault (fboucault)]

I have exactly the same issue on my Macbook11,1 starting a couple of weeks ago with Vivid. It does not seem to be a kernel issue and the /sys brightness interfaces are present and working fine.

[penalvch (penalvch)]

Florian Boucault, thank you for your comment. So your hardware and problem may be tracked, could you please file a new report with Ubuntu by executing the following in a terminal while booted into the default Ubuntu kernel (not a mainline one) via:
ubuntu-bug linux

For more on this, please read the official Ubuntu documentation:
Ubuntu Bug Control and Ubuntu Bug Squad: https://wiki.ubuntu.com/Bugs/BestPractices#X.2BAC8-Reporting.Focus_on_One_Issue
Ubuntu Kernel Team: https://wiki.ubuntu.com/KernelTeam/KernelTeamBugPolicies#Filing_Kernel_Bug_reports
https://wiki.ubuntu.com/Kernel/Policies/DuplicateBugs
Ubuntu Community: https://help.ubuntu.com/community/ReportingBugs#Bug_reporting_etiquette

When opening up the new report, please feel free to subscribe me to it.

As well, please do not announce in this report you created a new bug report.

Thank you for your understanding.

Helpful bug reporting tips:
https://wiki.ubuntu.com/ReportingBugs

[Miles Lane (miles-lane)]

I am testing the Linus GIT development kernel. Currently, my kernel build is 3.18.0-rc5+.
With this kernel, I get the following:

root@Wobbly:~# echo 938 > /sys/class/backlight/intel_backlight/brightness
bash: echo: write error: Invalid argument

root@Wobbly:~# echo 937 > /sys/class/backlight/intel_backlight/brightness

As you can see, 937 is the highest value that does not give an error.

[Miles Lane (miles-lane)]

Also, I also do not see the brightness slider control in the "Brightness and Lock" control panel section. This is with today's updated Vivid.

[penalvch (penalvch)]

Miles Lane, thank you for your comment. So your hardware and problem may be tracked, could you please file a new report with Ubuntu by executing the following in a terminal while booted into the default Ubuntu kernel (not a mainline one) via:
ubuntu-bug linux

For more on this, please read the official Ubuntu documentation:
Ubuntu Bug Control and Ubuntu Bug Squad: https://wiki.ubuntu.com/Bugs/BestPractices#X.2BAC8-Reporting.Focus_on_One_Issue
Ubuntu Kernel Team: https://wiki.ubuntu.com/KernelTeam/KernelTeamBugPolicies#Filing_Kernel_Bug_reports
https://wiki.ubuntu.com/Kernel/Policies/DuplicateBugs
Ubuntu Community: https://help.ubuntu.com/community/ReportingBugs#Bug_reporting_etiquette

When opening up the new report, please feel free to subscribe me to it.

As well, please do not announce in this report you created a new bug report.

Thank you for your understanding.

Helpful bug reporting tips:
https://wiki.ubuntu.com/ReportingBugs

[Martin H (n17r4m)]

Sweet galloping unicorns!

After doing an apt-get upgrade today, the screen brightness bug seems to have resolved itself.

Marking as resolved.