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[Bug 1354710] Re: Backlight control does not work, but there are entries in /sys/class/backlight.


Workaround information

Reboot with only the kernel parameter acpi_backlight=vendor : 
no change

output of  ls /sys/class/backlight


output of ls -la /sys/class/backlight/intel_backlight/ > lslabacklight
as root

total 0
drwxr-xr-x 3 root root    0 Aug  8 23:17 .
drwxr-xr-x 4 root root    0 Aug  8 23:17 ..
-r--r--r-- 1 root root 4096 Aug  8 23:27 actual_brightness
-rw-r--r-- 1 root root 4096 Aug  8 23:27 bl_power
-rw-r--r-- 1 root root 4096 Aug  8 23:17 brightness
lrwxrwxrwx 1 root root    0 Aug  8 23:27 device -> ../../card0-LVDS-1
-r--r--r-- 1 root root 4096 Aug  8 23:17 max_brightness
drwxr-xr-x 2 root root    0 Aug  8 23:27 power
lrwxrwxrwx 1 root root    0 Aug  8 23:27 subsystem -> ../../../../../../../class/backlight
-r--r--r-- 1 root root 4096 Aug  8 23:17 type
-rw-r--r-- 1 root root 4096 Aug  8 23:17 uevent

echo 8 > /sys/class/backlight/intel_backlight/brightness
brightness changes

reboot with just kernel parameter video.use_native_backlight=1

keys still cannot be used for changing brightness

creating a new file in /usr/share/X11/xorg.conf.d/80-backlight.conf and
paste into it the following code:

Section "Device"
    Identifier  "Intel Graphics"
    Driver      "intel"
    Option      "AccelMethod"     "sna"
    Option      "Backlight"       "intel_backlight" # use your backlight that works here
    BusID       "PCI:0:2:0"

keys can now be used for changing brightness of backlight

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  Backlight control does not work, but there are entries in

Status in “linux” package in Ubuntu:

Bug description:
  Laptop model: Lenovo B570
  package version: Ubuntu 3.13.0-32.57-generic

  I expected the keys for changeing the backlight brightness to work
  they had no effect on the backlight

  further details in attatched Tar

  ProblemType: Bug
  DistroRelease: Ubuntu 14.04
  Package: linux-image-3.13.0-32-generic 3.13.0-32.57
  ProcVersionSignature: Ubuntu 3.13.0-32.57-generic
  Uname: Linux 3.13.0-32-generic i686
  ApportVersion: 2.14.1-0ubuntu3.3
  Architecture: i386
   /dev/snd/controlC0:  x321x321   1977 F.... pulseaudio
  Date: Sat Aug  9 16:11:34 2014
  HibernationDevice: RESUME=UUID=61c2c6a6-4b45-4af0-941a-dadf05ad0aba
  InstallationDate: Installed on 2014-07-31 (8 days ago)
  InstallationMedia: Xubuntu 14.04.1 LTS "Trusty Tahr" - Release i386 (20140723)
  MachineType: LENOVO 1068FJG
   PATH=(custom, no user)
  ProcFB: 0 inteldrmfb
  ProcKernelCmdLine: BOOT_IMAGE=/vmlinuz-3.13.0-32-generic root=/dev/mapper/xubuntu--vg-root ro quiet splash vt.handoff=7
   Error: command ['pacmd', 'list'] failed with exit code 1: Home directory not accessible: Permission denied
   No PulseAudio daemon running, or not running as session daemon.
   linux-restricted-modules-3.13.0-32-generic N/A
   linux-backports-modules-3.13.0-32-generic  N/A
   linux-firmware                             1.127.5
  SourcePackage: linux
  StagingDrivers: rts5139
  UpgradeStatus: No upgrade log present (probably fresh install)
  dmi.bios.date: 07/11/2011
  dmi.bios.vendor: LENOVO
  dmi.bios.version: 44CN36WW
  dmi.board.asset.tag: Base Board Asset Tag
  dmi.board.name: Emerald Lake
  dmi.board.vendor: LENOVO
  dmi.board.version: FAB1
  dmi.chassis.asset.tag: Asset Tag
  dmi.chassis.type: 10
  dmi.chassis.vendor: LENOVO
  dmi.chassis.version: 0.1
  dmi.modalias: dmi:bvnLENOVO:bvr44CN36WW:bd07/11/2011:svnLENOVO:pn1068FJG:pvrLenovoB570:rvnLENOVO:rnEmeraldLake:rvrFAB1:cvnLENOVO:ct10:cvr0.1:
  dmi.product.name: 1068FJG
  dmi.product.version: Lenovo B570
  dmi.sys.vendor: LENOVO

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