[Lenovo ThinkPad X220] Brightness control doesn't work

[narel]

After upgrading to Ubuntu 14.10 brightness control no longer works on Lenovo Thinkpad X220. Fn+Home/Fn+End doesn't work, the only way is to echo value to:

/sys/devices/pci0000:00/0000:00:02.0/drm/card0/card0-LVDS-1/intel_backlight/brightness

I use Awesome WM, but it doesn't seem to be related to Awesome.
---
ApportVersion: 2.14.7-0ubuntu8
Architecture: amd64
AudioDevicesInUse:
 USER PID ACCESS COMMAND
 /dev/snd/pcmC0D0p: narel 3706 F...m pulseaudio
 /dev/snd/controlC0: narel 3706 F.... pulseaudio
DistroRelease: Ubuntu 14.10
EcryptfsInUse: Yes
HibernationDevice: RESUME=UUID=0f22933e-6234-43cf-8687-1245585a3025
InstallationDate: Installed on 2014-01-03 (318 days ago)
InstallationMedia: Ubuntu 13.10 "Saucy Salamander" - Release amd64 (20131016.1)
MachineType: LENOVO 4290PB8
Package: linux (not installed)
ProcFB: 0 inteldrmfb
ProcKernelCmdLine: BOOT_IMAGE=/vmlinuz-3.16.0-24-generic root=/dev/mapper/ubuntu--vg-root ro acpi_backlight=vendor quiet splash vt.handoff=7
ProcVersionSignature: Ubuntu 3.16.0-24.32-generic 3.16.4
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
Tags: utopic
Uname: Linux 3.16.0-24-generic x86_64
UpgradeStatus: Upgraded to utopic on 2014-11-07 (10 days ago)
UserGroups: adm audio cdrom dialout dip libvirtd lpadmin plugdev pulse pulse-access remote sambashare sudo
_MarkForUpload: True
dmi.bios.date: 07/19/2012
dmi.bios.vendor: LENOVO
dmi.bios.version: 8DET63WW (1.33 )
dmi.board.asset.tag: Not Available
dmi.board.name: 4290PB8
dmi.board.vendor: LENOVO
dmi.board.version: Not Available
dmi.chassis.asset.tag: No Asset Information
dmi.chassis.type: 10
dmi.chassis.vendor: LENOVO
dmi.chassis.version: Not Available
dmi.modalias: dmi:bvnLENOVO:bvr8DET63WW(1.33):bd07/19/2012:svnLENOVO:pn4290PB8:pvrThinkPadX220:rvnLENOVO:rn4290PB8:rvrNotAvailable:cvnLENOVO:ct10:cvrNotAvailable:
dmi.product.name: 4290PB8
dmi.product.version: ThinkPad X220
dmi.sys.vendor: LENOVO

[penalvch (penalvch)]

narel, thank you for taking the time to report this bug and helping to make Ubuntu better. Please execute the following command, as it will automatically gather debugging information, in a terminal:
apport-collect 1391153

[narel (narel)]

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[narel (narel)]

I've just updated BIOS:

8DET69WW (1.39 )
07/18/2013

Unfortunately brightness control still doesn't work via hotkeys (echoing value to /sys still works).

Is there any way to check/modify action performed by hotkeys? I see that they are correctly regognized by xev as XF86MonBrightnessUp and XF86MonBrightnessDown.
If you point me to the right place maybe I will be able to investigate the problem?

[penalvch (penalvch)]

narel, 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-rc5

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.

[narel (narel)]

I tested on 3.18.0-031800rc5, but with no luck - the problem still exists.

[penalvch (penalvch)]

narel, the next step is to fully commit bisect from your prior working kernel to 3.16 in order to identify the last good kernel commit, followed immediately by the first bad one. This will allow for a more expedited analysis of the root cause of your issue. Could you please do this following https://wiki.ubuntu.com/Kernel/KernelBisection ? Please note, finding adjacent kernel versions is not fully commit bisecting.

Thank you for your understanding.

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

[narel (narel)]

Update - I just started 3.13.0-39-generic from Trusty (on which everything was OK). But now it doesn't work. I can control brightness before X is started, but when lighdm starts brightness control no longer works.
IMHO this is rather related to X server, not kernel, what do you think?

[penalvch (penalvch)]

narel, it would appear this is a userspace issue, versus a kernel one. For now, let this be placed in the Ubuntu general queue for a further review.

[Mark Baker (markashtonb)]

Had this problem on 14.04.1 running 3.13.0-40-generic kernel. Was working previous to update a zfew days ago.

Fix is to install the indicator applet

http://www.omgubuntu.co.uk/2013/04/brightness-control-ubuntu

This not only allows you to change the brightness from the indicataor panel but hot keys magically work again.