[Dell Latitude 2110] Clicking brightness key once increments brightness as if pressed multiple times

[Ben Harris]

According to <https://wiki.ubuntu.com/Hotkeys/Troubleshooting>, "If the events are reported by more than one input device then report a kernel bug (Ubuntu linux package) because it should only send the event on one device." On my Latitude 2110, the brightness control keys (Fn+Up and Fn+Down) seem to appear through two different devices, /dev/input/event3 ("AT Translated Set 2 keyboard") and /dev/input/event4 ("Video Bus"). The keys also control the screen brightness, even in a text console.

ProblemType: Bug
DistroRelease: Ubuntu 14.04
Package: linux-image-3.16.0-25-generic 3.16.0-25.33~14.04.2
ProcVersionSignature: Ubuntu 3.16.0-25.33~14.04.2-generic 3.16.7
Uname: Linux 3.16.0-25-generic i686
ApportVersion: 2.14.1-0ubuntu3.5
Architecture: i386
CurrentDesktop: Unity
Date: Sun Nov 30 17:02:52 2014
DistributionChannelDescriptor:
 # This is a distribution channel descriptor
 # For more information see http://wiki.ubuntu.com/DistributionChannelDescriptor
 canonical-oem-motts-20100121-3
EcryptfsInUse: Yes
InstallationDate: Installed on 2010-06-09 (1635 days ago)
InstallationMedia: Ubuntu GNU/Linux 9.10 "Karmic" - Build i386 LIVE Binary 20100121-21:52
SourcePackage: linux-lts-utopic
UpgradeStatus: Upgraded to trusty on 2014-08-15 (106 days ago)
---
ApportVersion: 2.14.1-0ubuntu3.5
Architecture: i386
AudioDevicesInUse:
 USER PID ACCESS COMMAND
 /dev/snd/controlC0: bjh21 2495 F.... pulseaudio
CurrentDesktop: Unity
DistributionChannelDescriptor:
 # This is a distribution channel descriptor
 # For more information see http://wiki.ubuntu.com/DistributionChannelDescriptor
 canonical-oem-motts-20100121-3
DistroRelease: Ubuntu 14.04
EcryptfsInUse: Yes
HibernationDevice: RESUME=UUID=5f11e886-4c98-43d9-8d51-6ab48f0bff3f
InstallationDate: Installed on 2010-06-09 (1636 days ago)
InstallationMedia: Ubuntu GNU/Linux 9.10 "Karmic" - Build i386 LIVE Binary 20100121-21:52
MachineType: Dell Inc. Latitude 2110
Package: linux (not installed)
ProcFB: 0 inteldrmfb
ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-3.16.0-25-generic root=UUID=a7f66818-5a12-4932-922a-b05d92593b24 ro quiet splash crashkernel=384M-:128M crashkernel=384M-:128M vt.handoff=7
ProcVersionSignature: Ubuntu 3.16.0-25.33~14.04.2-generic 3.16.7
RelatedPackageVersions:
 linux-restricted-modules-3.16.0-25-generic N/A
 linux-backports-modules-3.16.0-25-generic N/A
 linux-firmware 1.127.8
StagingDrivers: rts5208
Tags: trusty staging
Uname: Linux 3.16.0-25-generic i686
UpgradeStatus: Upgraded to trusty on 2014-08-15 (108 days ago)
UserGroups: adm admin cdrom dialout lpadmin plugdev sambashare wireshark
WifiSyslog:
 Dec 1 21:57:47 sole kernel: [ 713.837172] init: systemd-logind main process (504) killed by TERM signal
 Dec 1 21:57:58 sole kernel: [ 724.781339] systemd-udevd[5391]: starting version 204
_MarkForUpload: True
dmi.bios.date: 03/09/2010
dmi.bios.vendor: Dell Inc.
dmi.bios.version: A00
dmi.board.name: 0N61H4
dmi.board.vendor: Dell Inc.
dmi.chassis.type: 8
dmi.chassis.vendor: Dell Inc.
dmi.modalias: dmi:bvnDellInc.:bvrA00:bd03/09/2010:svnDellInc.:pnLatitude2110:pvr:rvnDellInc.:rn0N61H4:rvr:cvnDellInc.:ct8:cvr:
dmi.product.name: Latitude 2110
dmi.sys.vendor: Dell Inc.

[penalvch (penalvch)]

Ben Harris, thank you for reporting this and helping make Ubuntu better. Could you please execute the following command, as it will automatically gather debugging information, in a terminal:
apport-collect 1397699

[Ben Harris (bjh21.me.uk)]

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[Ben Harris (bjh21.me.uk)]

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[Ben Harris (bjh21.me.uk)]

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[Ben Harris (bjh21.me.uk)]

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[Ben Harris (bjh21.me.uk)]

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[Ben Harris (bjh21.me.uk)]

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[Ben Harris (bjh21.me.uk)]

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[Ben Harris (bjh21.me.uk)]

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[Ben Harris (bjh21.me.uk)]

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[Ben Harris (bjh21.me.uk)]

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[Ben Harris (bjh21.me.uk)]

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[Ben Harris (bjh21.me.uk)]

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[Ben Harris (bjh21.me.uk)]

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[Ben Harris (bjh21.me.uk)]

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[Ben Harris (bjh21.me.uk)]

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[Ben Harris (bjh21.me.uk)]

I've run the command as requested.

[Brad Figg (brad-figg)]

This change was made by a bot.

[penalvch (penalvch)]

Ben Harris, 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-rc7

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.

[Ben Harris (bjh21.me.uk)]

I've tested with the latest upstream kernel, and the bug exists there too.

bjh21@sole:~$ uname -a
Linux sole 3.18.0-031800rc7-generic #201411302035 SMP Mon Dec 1 01:58:20 UTC 2014 i686 i686 i686 GNU/Linux

[penalvch (penalvch)]

Ben Harris, did this problem not occur in a release prior to Trusty?

[Ben Harris (bjh21.me.uk)]

I've just tested in Precise (kernel 3.2.0-72-generic) and the same problem occurs there as well. So the problem did occur in prior releases.

[penalvch (penalvch)]

Ben Harris, just to clarify, are you able to adjust the brightness at all in any of the releases/kernels tested so far?

If not, could you please advise if you have a WORKAROUND following https://wiki.ubuntu.com/Kernel/Debugging/Backlight#Testing_for_a_work_around ? For now, don't worry about providing the debugging information requested in that article.

[Ben Harris (bjh21.me.uk)]

Yes, I can adjust brightness. The brightness slider in the "Brightness and Lock" page of System Settings works perfectly. The brightness-up and brightness-down keys (Fn+Up and Fn+Down) work, but they usually change the brightness by multiple steps. It seems that this duplication of keypresses across multiple input devices may be one of the causes of this problem.

[penalvch (penalvch)]

Ben Harris, the issue you are reporting is an upstream one. Could you please report this problem to the appropriate mailing list (linux-acpi) by following the instructions _verbatim_ at https://wiki.ubuntu.com/Bugs/Upstream/kernel ?

Please provide a direct URL to your e-mail to the mailing list once you have made it so that it may be tracked.

Thank you for your understanding.

[Ben Harris (bjh21.me.uk)]

Reported upstream: http://article.gmane.org/gmane.linux.acpi.devel/72409

[Ben Harris (bjh21.me.uk)]

A workaround: the extra key events can be disabled by creating /etc/udev/hwdb.d/70-keyboard.hwdb containing:

keyboard:dmi:bvn*:bvr*:bd*:svnDell*:pnLatitude*2110:pvr*
 KEYBOARD_KEY_85=unknown # Brightness Down, also emitted by acpi-video, ignore
 KEYBOARD_KEY_86=unknown # Brightness Up, also emitted by acpi-video, ignore

This is based on the existing rules for the Dell Inspiron 1520. If I also disable video.brightness_switch_enabled, then I get a backlight that changes brightness by one step for each keypress. I have had two rather worrying hangs while testing this, though.

[Po-Hsu Lin (cypressyew)]

Closing this bug with Won't fix as this kernel / release is no longer supported.
Please feel free to open a new bug report if you're still experiencing this on a newer release (Bionic 18.04.3 / Disco 19.04)
Thanks!