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[Artem Grunichev <gluk@xxxxxxxxxxx>]

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

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https://bugs.launchpad.net/bugs/1205694

Title:
  Taichi 21 external screen is not working properly (probably due
  backlight)

Status in “linux” package in Ubuntu:
  Confirmed

Bug description:
  First of all, I'd like to say that both screen are recognized by xrandr: The internal as eDP1 and the external as DP1. 
  The external screen works under some circumstances, but without backlight. 

  If the computer is off, and I turn on with the lid closed, the external screen "works" 
  If the computer is turned on, on linux, and I restart, the external screen keeps "working".

  If the computer is off and I turn on with the lid opened or the
  computer is on windows, using the external screen, and I restart to
  linux, I can't use the external screen: The image keeps "off".
  Although, the screen is recognized by xrandr, but no setting turns the
  screen on (not even xrandr --output DP1 --auto)

  In the situations that the external screen works, the backlight has no effect on it: 
  When I adjust the backlight (either by the hotkeys, or by echo 50 > /sys/class/backlight/acpi_video0/brightness, or echo 3000 > /sys/class/backlight/intel_backlight/brightness), it just adjusts the internal screen
  When I use the hotkey to turn off the screen, it just turn off the internal screen

  Also, if I use xrandr to turn off the external screen, or suspend the
  computer, the external screen is turned off. When I try again to turn
  on, or resume it doesn't work.

  I tried to boot with acpi_backlight=vendor, and again just the internal screen worked properly. The hotkey to change the backlight didn't work, but  echo 3000 > /sys/class/backlight/intel_backlight/brightness worked
  I tried to boot with video.use_bios_initial_backlight=0 and the backlight worked just for the internal screen again
  I tried to boot with acpi_osi="!Windows 2012", the same thing

  By running dmesg | grep 'ACPI: Video', I get:
  [    4.981826] ACPI: Video Device [GFX0] (multi-head: yes  rom: no  post: no)

  And lspci |  grep VGA shows:
  00:02.0 VGA compatible controller: Intel Corporation 3rd Gen Core processor Graphics Controller (rev 09)

  I don't know if I should get 2 results in them, since I have two
  screens, but in DSDT, I just see one device with methods _DOS, _DOD,
  so I guess it is right.  There is an if in the BCL, checking if it is
  Windows 8, but I believe acpi_osi="!Windows 2012", should "fix" it if
  that was the problem

  I believe that solving the backlight problem when I'm able to turn on
  the screen might solve the screen not turning on with the lid open.

  I tried to use the current Mainline kernel (3.11.0-999, or something
  like that), but after the boot the external screen was off and the
  internal was on, not showing anything but a black screen.

  I followed the Kernel/Debugging/Backlight page and I'll submit all the
  files that it generated.

  Thank you for your help!

  ProblemType: Bug
  DistroRelease: Ubuntu 13.04
  Package: linux-image-3.8.0-26-generic 3.8.0-26.38
  ProcVersionSignature: Ubuntu 3.8.0-26.38-generic 3.8.13.2
  Uname: Linux 3.8.0-26-generic x86_64
  ApportVersion: 2.9.2-0ubuntu8.1
  Architecture: amd64
  AudioDevicesInUse:
   USER        PID ACCESS COMMAND
   /dev/snd/controlC0:  joao       2437 F.... pulseaudio
  Date: Sat Jul 27 12:44:02 2013
  HibernationDevice: RESUME=UUID=8c6201ab-045c-4bb7-b20d-c4650cca8821
  InstallationDate: Installed on 2013-07-23 (4 days ago)
  InstallationMedia: Ubuntu 13.04 "Raring Ringtail" - Release amd64 (20130424)
  MachineType: ASUSTeK COMPUTER INC. TAICHI21
  MarkForUpload: True
  ProcEnviron:
   TERM=xterm
   PATH=(custom, no user)
   XDG_RUNTIME_DIR=<set>
   LANG=en_US.UTF-8
   SHELL=/bin/bash
  ProcFB: 0 inteldrmfb
  ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-3.8.0-26-generic root=UUID=1b4e19b1-47cc-4068-a6d6-b73868b3c9d8 ro quiet splash vt.handoff=7
  RelatedPackageVersions:
   linux-restricted-modules-3.8.0-26-generic N/A
   linux-backports-modules-3.8.0-26-generic  N/A
   linux-firmware                            1.106
  SourcePackage: linux
  UpgradeStatus: No upgrade log present (probably fresh install)
  dmi.bios.date: 01/08/2013
  dmi.bios.vendor: American Megatrends Inc.
  dmi.bios.version: TAICHI21.208
  dmi.board.asset.tag: ATN12345678901234567
  dmi.board.name: TAICHI21
  dmi.board.vendor: ASUSTeK COMPUTER INC.
  dmi.board.version: 1.0
  dmi.chassis.asset.tag: No Asset Tag
  dmi.chassis.type: 10
  dmi.chassis.vendor: ASUSTeK COMPUTER INC.
  dmi.chassis.version: 1.0
  dmi.modalias: dmi:bvnAmericanMegatrendsInc.:bvrTAICHI21.208:bd01/08/2013:svnASUSTeKCOMPUTERINC.:pnTAICHI21:pvr1.0:rvnASUSTeKCOMPUTERINC.:rnTAICHI21:rvr1.0:cvnASUSTeKCOMPUTERINC.:ct10:cvr1.0:
  dmi.product.name: TAICHI21
  dmi.product.version: 1.0
  dmi.sys.vendor: ASUSTeK COMPUTER INC.

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