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[Po-Hsu Lin <po-hsu.lin@xxxxxxxxxxxxx>]

Brightness control works with "video.use_native_backlight=1" added into
grub

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https://bugs.launchpad.net/bugs/1348020

Title:
  [Dell Latitude 3540] Unable to control brightness

Status in “linux” package in Ubuntu:
  New

Bug description:
  CIDL 201306-13866 Dell Latitude 3540

  The brightness control does not work on this system

  Steps:
  1. Install 14.04 + update (3.13.0-32), boot to desktop
  2. Try to change the brightness by using the hotkeys
  3. Try to change the brightness by using the "Brightness and Lock" applet

  Expect result:
  * Brightness control works fine

  Actual result:
  * Brightness level indicator changes with the hotkey, but not the brightness.
  * Brightness cannot be changed by the applet

  Debugging information:
  ubuntu@201306-13866:~$ ls /sys/class/backlight
  acpi_video0  intel_backlight

  ubuntu@201306-13866:~$ grep -r . /proc/acpi
  /proc/acpi/battery/BAT1/alarm:alarm:                   unsupported
  /proc/acpi/battery/BAT1/state:present:                 yes
  /proc/acpi/battery/BAT1/state:capacity state:          ok
  /proc/acpi/battery/BAT1/state:charging state:          charged
  /proc/acpi/battery/BAT1/state:present rate:            1 mA
  /proc/acpi/battery/BAT1/state:remaining capacity:      5900 mAh
  /proc/acpi/battery/BAT1/state:present voltage:         12972 mV
  /proc/acpi/battery/BAT1/info:present:                 yes
  /proc/acpi/battery/BAT1/info:design capacity:         5900 mAh
  /proc/acpi/battery/BAT1/info:last full capacity:      5900 mAh
  /proc/acpi/battery/BAT1/info:battery technology:      rechargeable
  /proc/acpi/battery/BAT1/info:design voltage:          11100 mV
  /proc/acpi/battery/BAT1/info:design capacity warning: 590 mAh
  /proc/acpi/battery/BAT1/info:design capacity low:     177 mAh
  /proc/acpi/battery/BAT1/info:cycle count:		  0
  /proc/acpi/battery/BAT1/info:capacity granularity 1:  264 mAh
  /proc/acpi/battery/BAT1/info:capacity granularity 2:  3780 mAh
  /proc/acpi/battery/BAT1/info:model number:            DELL G019Y35H
  /proc/acpi/battery/BAT1/info:serial number:           0C45
  /proc/acpi/battery/BAT1/info:battery type:            Li-Ion
  /proc/acpi/battery/BAT1/info:OEM info:                SDI
  /proc/acpi/button/lid/LID0/state:state:      open
  /proc/acpi/wakeup:Device	S-state	  Status   Sysfs node
  /proc/acpi/wakeup:P0P1	  S4	*disabled
  /proc/acpi/wakeup:LID0	  S3	*enabled 
  /proc/acpi/wakeup:EHC1	  S0	*enabled   pci:0000:00:1d.0
  /proc/acpi/wakeup:XHC	  S0	*enabled   pci:0000:00:14.0
  /proc/acpi/wakeup:PXSX	  S4	*disabled
  /proc/acpi/wakeup:RP03	  S3	*disabled  pci:0000:00:1c.0
  /proc/acpi/wakeup:PEG0	  S4	*disabled
  /proc/acpi/wakeup:PEGP	  S4	*disabled
  /proc/acpi/wakeup:PEG1	  S4	*disabled
  /proc/acpi/wakeup:PEG2	  S4	*disabled

  ubuntu@201306-13866:~$ dmesg | grep 'ACPI: Video' 
  [   11.036337] ACPI: Video Device [GFX0] (multi-head: yes  rom: no  post: no)

  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 3.13.11.4
  Uname: Linux 3.13.0-32-generic x86_64
  ApportVersion: 2.14.1-0ubuntu3.2
  Architecture: amd64
  AudioDevicesInUse:
   USER        PID ACCESS COMMAND
   /dev/snd/controlC0:  ubuntu     1586 F.... pulseaudio
  CRDA:
   country TW:
   	(2402 - 2472 @ 40), (3, 27)
   	(5270 - 5330 @ 40), (3, 17), DFS
   	(5735 - 5815 @ 40), (3, 30)
  CurrentDesktop: Unity
  Date: Wed Jul 23 23:35:09 2014
  HibernationDevice: RESUME=UUID=bce2a764-eac9-4044-b879-caa497463b91
  InstallationDate: Installed on 2014-07-24 (0 days ago)
  InstallationMedia: Ubuntu 14.04 LTS "Trusty Tahr" - Release amd64 (20140417)
  MachineType: Dell Inc. Latitude 3540
  ProcFB: 0 inteldrmfb
  ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-3.13.0-32-generic.efi.signed root=UUID=1dd2f74b-d1f1-42e1-9c35-6675a578b71e ro quiet splash vt.handoff=7
  RelatedPackageVersions:
   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: 08/06/2013
  dmi.bios.vendor: Dell Inc.
  dmi.bios.version: A01
  dmi.board.name: 0992HC
  dmi.board.vendor: Dell Inc.
  dmi.board.version: X01
  dmi.chassis.type: 8
  dmi.chassis.vendor: Dell Inc.
  dmi.chassis.version: A01
  dmi.modalias: dmi:bvnDellInc.:bvrA01:bd08/06/2013:svnDellInc.:pnLatitude3540:pvrA01:rvnDellInc.:rn0992HC:rvrX01:cvnDellInc.:ct8:cvrA01:
  dmi.product.name: Latitude 3540
  dmi.product.version: A01
  dmi.sys.vendor: Dell Inc.

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