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[Stefan Burnicki <stefan.burnicki@xxxxxxxxxxxx>]

The default ubuntu kernel (currently 3.19.0-16) does not work for me.
In /sys/class/backlight there is only

intel_backlight ->
../../devices/pci0000:00/0000:00:02.0/drm/card0/card0-eDP-1/intel_backlight

However, with 4.1-rc3 there is

acpi_video0 -> ../../devices/pci0000:00/0000:00:01.0/0000:01:00.0/backlight/acpi_video0
acpi_video1 -> ../../devices/pci0000:00/0000:00:02.0/backlight/acpi_video1
intel_backlight -> ../../devices/pci0000:00/0000:00:02.0/drm/card0/card0-eDP-1/intel_backlight

The first one can be used to control my LCD backlight.

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https://bugs.launchpad.net/bugs/1454207

Title:
  Samsung 730U3E LCD backlight brightness control doesn't work

Status in linux package in Ubuntu:
  Incomplete

Bug description:
  Fn-shortcuts work and the value in /sys/class/backlight/intel_backlight/brightness changes, but is has no physical effect.
  Only setting /sys/class/backlight/intel_backlight/brightness to 0 turns the LCD off, changing it to any other value turns it on again.

  I tried to set different boot parameters in /etc/defaults/grub
  GRUB_CMDLINE_LINUX_DEFAULT="quiet splash video.use_native_backlight=1"
  GRUB_CMDLINE_LINUX_DEFAULT="quiet splash video.use_native_backlight=0"
  GRUB_CMDLINE_LINUX_DEFAULT="quiet splash acpi_backlight=vendor"
  GRUB_CMDLINE_LINUX_DEFAULT="quiet splash acpi_osi=Linux acpi_backlight=vendor"
  GRUB_CMDLINE_LINUX_DEFAULT="quiet splash video.use_bios_initial_backlight=0"

  For each change, I called update-grub, restarted, and verfied the
  settings with /proc/cmdline. Nothing worked for me.

  I also tested this with the newest mainline kernel (4.1-rc2), but the
  bug still exists.

  It work with trusty and stopped working with utopic. I thought this
  issue would may be fixed in vivid, but it isn't.

  Please tell me what other information you need in order to fix this.

  ProblemType: Bug
  DistroRelease: Ubuntu 15.04
  Package: linux-image-3.19.0-16-generic 3.19.0-16.16
  ProcVersionSignature: Ubuntu 3.19.0-16.16-generic 3.19.3
  Uname: Linux 3.19.0-16-generic x86_64
  ApportVersion: 2.17.2-0ubuntu1
  Architecture: amd64
  AudioDevicesInUse:
   USER        PID ACCESS COMMAND
   /dev/snd/controlC0:  stefan     1383 F.... pulseaudio
  CurrentDesktop: KDE
  Date: Tue May 12 13:08:51 2015
  HibernationDevice: RESUME=UUID=34e06653-f31c-45ef-80ca-9eddcae5134f
  InstallationDate: Installed on 2015-03-10 (62 days ago)
  InstallationMedia: Kubuntu-Plasma-5 14.10 "Utopic Unicorn" - Release amd64 (20141022)
  MachineType: SAMSUNG ELECTRONICS CO., LTD. 730U3E/740U3E
  ProcFB:
   0 inteldrmfb
   1 radeondrmfb
  ProcKernelCmdLine: BOOT_IMAGE=/vmlinuz-3.19.0-16-generic root=/dev/mapper/kubuntu--plasma--5--vg-root ro quiet splash video.use_bios_initial_backlight=0
  RelatedPackageVersions:
   linux-restricted-modules-3.19.0-16-generic N/A
   linux-backports-modules-3.19.0-16-generic  N/A
   linux-firmware                             1.143
  SourcePackage: linux
  UpgradeStatus: Upgraded to vivid on 2015-04-26 (16 days ago)
  dmi.bios.date: 05/30/2013
  dmi.bios.vendor: American Megatrends Inc.
  dmi.bios.version: P05ABW.060.130530.dg
  dmi.board.asset.tag: No Asset Tag
  dmi.board.name: NP730U3E-S03DE
  dmi.board.vendor: SAMSUNG ELECTRONICS CO., LTD.
  dmi.board.version: SEC_SW_REVISION_1234567890ABCD
  dmi.chassis.asset.tag: No Asset Tag
  dmi.chassis.type: 9
  dmi.chassis.vendor: SAMSUNG ELECTRONICS CO., LTD.
  dmi.chassis.version: N/A
  dmi.modalias: dmi:bvnAmericanMegatrendsInc.:bvrP05ABW.060.130530.dg:bd05/30/2013:svnSAMSUNGELECTRONICSCO.,LTD.:pn730U3E/740U3E:pvrP05ABW:rvnSAMSUNGELECTRONICSCO.,LTD.:rnNP730U3E-S03DE:rvrSEC_SW_REVISION_1234567890ABCD:cvnSAMSUNGELECTRONICSCO.,LTD.:ct9:cvrN/A:
  dmi.product.name: 730U3E/740U3E
  dmi.product.version: P05ABW
  dmi.sys.vendor: SAMSUNG ELECTRONICS CO., LTD.

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