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[Bug 1069357] Re: [Dell Vostro V131] Hardware keys change backlight brightness in much larger increments/steps than expected


Rafał Ochmański, 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,
please just make a comment to this.

Also, could you please test the latest upstream kernel available (not the daily folder, but the one all the way at the bottom) 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:

where VERSION-NUMBER is the version number of the kernel you tested. For example:

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:

If the mainline kernel does not fix this bug, please add the following tags:

As well, please remove the tag:

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

** Changed in: linux (Ubuntu)
   Importance: Medium => Low

** Changed in: linux (Ubuntu)
       Status: Confirmed => Incomplete

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

Status in “linux” package in Ubuntu:

Bug description:
  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

  # lsb_release -rd
  Description:	Ubuntu 12.10
  Release:	12.10
  ApportVersion: 2.6.1-0ubuntu3
  Architecture: amd64
   /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)
   PATH=(custom, no user)
  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
   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.

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