[Dell Vostro V131] Hardware keys change backlight brightness in much larger increments/steps than expected

[Rafał Ochmański]

SInce the upgrade to Ubuntu 12.10, hardware keys for regulating backlight brightness (fn+f4, fn+f5) change brightness in large increments, even though much finer control is available both through the Brightness and Lock dialog in Settings and by just setting the value in /sys/class/backlight/acpi_video0/brightness, for example:

# echo 1 > /sys/class/backlight/acpi_video0/brightness

/sys/class/backlight/acpi_video0/brightness accepts values 0-15, the default step seems to be 3 instead of 1 as expected, and as it was in Ubuntu 12.04.

Partial workaround is to disable brightness switch

# echo -n 0 > /sys/module/video/parameters/brightness_switch_enabled

which cuts the step to 2. Moreover, adding kernel parameters "acpi_osi=Linux acpi_backlight=legacy" allows for even finer control in the Brightness and Lock dialog in Settings (finer than those 16 settings, including completely turning the backlight via the brightness slider) but breaks the hardware keys functionality completely.

# lsb_release -rd
Description: Ubuntu 12.10
Release: 12.10
---
ApportVersion: 2.6.1-0ubuntu3
Architecture: amd64
AudioDevicesInUse:
 USER PID ACCESS COMMAND
 /dev/snd/controlC0: rmo 1897 F.... pulseaudio
DistroRelease: Ubuntu 12.10
HibernationDevice: RESUME=UUID=7c82e11d-4211-4789-90b6-7a20abd8aa82
InstallationMedia: Ubuntu 12.10 "Quantal Quetzal" - Release amd64 (20121017.5)
MachineType: Dell Inc. Vostro V131
Package: linux (not installed)
ProcEnviron:
 TERM=xterm-256color
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=en_US.UTF-8
 SHELL=/bin/bash
ProcFB: 0 inteldrmfb
ProcKernelCmdLine: BOOT_IMAGE=/vmlinuz-3.5.0-17-generic root=/dev/mapper/ubuntu-root ro
ProcVersionSignature: Ubuntu 3.5.0-17.28-generic 3.5.5
RelatedPackageVersions:
 linux-restricted-modules-3.5.0-17-generic N/A
 linux-backports-modules-3.5.0-17-generic N/A
 linux-firmware 1.95
Tags: quantal running-unity
Uname: Linux 3.5.0-17-generic x86_64
UpgradeStatus: No upgrade log present (probably fresh install)
UserGroups: adm cdrom dip lpadmin plugdev sambashare sudo
dmi.bios.date: 10/24/2011
dmi.bios.vendor: Dell Inc.
dmi.bios.version: A03
dmi.board.name: 0X3GJK
dmi.board.vendor: Dell Inc.
dmi.board.version: A03
dmi.chassis.type: 8
dmi.chassis.vendor: Dell Inc.
dmi.chassis.version: Not Specified
dmi.modalias: dmi:bvnDellInc.:bvrA03:bd10/24/2011:svnDellInc.:pnVostroV131:pvrNotSpecified:rvnDellInc.:rn0X3GJK:rvrA03:cvnDellInc.:ct8:cvrNotSpecified:
dmi.product.name: Vostro V131
dmi.product.version: Not Specified
dmi.sys.vendor: Dell Inc.

[papukaija (papukaija)]

Thank you for taking the time to report this bug and helping to make Ubuntu better. We need some more information from you before we can start working on this bug.

Please run the following command which will attach necessary information:

apport-collect 1069357

Bear in mind that you may need to install the python-launchpadlib package from the universe repository with 'sudo apt-get install python-launchpadlib'. Additionally, when prompted to give apport-collect permissions for Launchpad you will need to give it at least the ability to "Change Non-Private" data as it will be adding information to your bug report.

If you are using an older release or cannot use apport please at least add the following information (pay attention to lspci's additional options):
First run the following commands:
1) uname -a > uname-a.log
2) dmesg > dmesg.log
3) sudo lspci -vvnn > lspci-vvnn.log
4) cat /proc/version_signature > version.log
then attach the files separately to the bug report (not pasted into comments or tar/zip-ed).

For your reference, the full description of procedures for kernel-related bug reports is available at https://wiki.ubuntu.com/KernelTeam/KernelTeamBugPolicies. Thanks in advance!

[Rafał Ochmański (rmopl)]

apport information

[Rafał Ochmański (rmopl)]

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[Rafał Ochmański (rmopl)]

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[Rafał Ochmański (rmopl)]

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[Rafał Ochmański (rmopl)]

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[Rafał Ochmański (rmopl)]

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[Rafał Ochmański (rmopl)]

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[Rafał Ochmański (rmopl)]

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[Rafał Ochmański (rmopl)]

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[Rafał Ochmański (rmopl)]

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[Rafał Ochmański (rmopl)]

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[Rafał Ochmański (rmopl)]

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[Rafał Ochmański (rmopl)]

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[Rafał Ochmański (rmopl)]

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[Rafał Ochmański (rmopl)]

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[James M. Leddy (jm-leddy)]

I've been looking in to this recently as I have the same problem with my thinkpad and we're currently dealing with Lenovo on this. The problem on the thinkpad side is pretty well understood, it's probably exactly the same here. The reason we can increment and decrement by 3 but not by 1 is that we have 3 different devices that control the brigthness of these:

from dmesg:

[936941.841019] thinkpad_acpi: detected a 8-level brightness capable ThinkPad
[936941.851964] input: ThinkPad Extra Buttons as /devices/platform/thinkpad_acpi/input/input90

This causes two "XF86MonBrignessUp" events to happen, g-s-d responds accordingly. The one additional is brightness_switch_enabled, which is the kernel responding to brightness events and setting the brightness before the key events ever reach g-s-d.

Something I'd like to test is if this is the same situation on the vostro. One way to try it out is to kill gnome-settings-damon and then use xev to confirm that you are in fact getting two key events from xev.

[James M. Leddy (jm-leddy)]

We defintely have these keys responding as input devices based on bootdmesg:

[ 27.522660] input: Dell WMI hotkeys as /devices/virtual/input/input7

One thing that's confusing me is that you said this works well on 12.04, when in fact this has been a problem for a long time. Unless you installed off a Dell provided pre-install CD/image it's unlikely anything changed between 12.04 and 12.10

[Rafał Ochmański (rmopl)]

It worked perfectly (ie. incremented by one from 0 to 15) in regular 12.04 installed from alternate cd from Ubuntu's website. The computer came with Windows pre-installed.

More than that, it still works perfectly during boot, before the graphical interface comes up. I have whole-disk encryption enabled and it seems to be working on the screen for password entry.

Let me know what other info I can provide, or what I should double-check. I can boot 12.04 from a pendrive too, if that helps somehow.

[Rafał Ochmański (rmopl)]

OK, here's output from xev. I pressed the increase brightness combination twice, and decrease combination once. It seems that the first increase resulted in one even but all further presses resulted in two events:

MappingNotify event, serial 40, synthetic NO, window 0x0,
    request MappingKeyboard, first_keycode 8, count 248

MappingNotify event, serial 41, synthetic NO, window 0x0,
    request MappingKeyboard, first_keycode 8, count 248

MappingNotify event, serial 42, synthetic NO, window 0x0,
    request MappingKeyboard, first_keycode 8, count 248

MappingNotify event, serial 43, synthetic NO, window 0x0,
    request MappingKeyboard, first_keycode 8, count 248

MappingNotify event, serial 44, synthetic NO, window 0x0,
    request MappingKeyboard, first_keycode 8, count 248

HTH

[Julio Medrano (thejuliomedrano)]

i have the same issue and i notice that this is only happening when the gnome-settings-daemon is running, maybe the problem appeared after the upgrade of gnome 3.4 to gnome 3.6?

i can see that because when im in the lightdm, the brightness control works fine

I really dont know much but this is what happening in my pc, i have a Dell Inspiron N5050 with Windows 7 pre-installed

sorry if my english is not too good

[Hydro Hu (hu-hydro)]

# echo -n 0 > /sys/module/video/parameters/brightness_switch_enabled
this works for me,

Thank you

[Rafał Ochmański (rmopl)]

Bug persists in raring.

[Julio Medrano (thejuliomedrano)]

same here, the bug persist in raring

[Joonas Saarinen (jza)]

My testing has shown this bug to be present in various different laptops. It is very ubiquitous.

Brightness is changed in two steps instead of one. At some point I thought it was an actual design decision from Ubuntu team.

[Launchpad Janitor (janitor)]

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

[Rafał Ochmański (rmopl)]

I just upgraded to Ubuntu 13.10, kernel 3.11.0-13-generic and the bug is still there.

[jalon (jalonwong)]

I have the same issue in Ubuntu 12.04.3. My laptop is Dell Latitude 3540.

[jalon (jalonwong)]

I reinstall my OS, I can adjust brightness befor I user "acpi_backlight=vendor".

[jalon (jalonwong)]

After I user "acpi_backlight=vendor", Brightness is 3 steps.

[penalvch (penalvch)]

Jalon, please do not post attachments to this report. Instead, so your hardware may be tracked, please file a new report via a terminal:
ubuntu-bug linux

[Launchpad Janitor (janitor)]

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

[Rafał Ochmański (rmopl)]

The bug is still here in Ubuntu 13.10 with latest updates.

[penalvch (penalvch)]

Rafał Ochmański, could you please test the latest upstream kernel available (not the daily folder) following https://wiki.ubuntu.com/KernelMainlineBuilds ? It will allow additional upstream developers to examine 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. For example:
kernel-fixed-upstream-3.14-rc2

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

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.

[Launchpad Janitor (janitor)]

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