[Bug 518002] Re: lucid extensa 5635z backlight dimming not working at all

[Wolfgang Kufner]

** Description changed:

  [Workaround 1]
  For Acer Extensa 5635Z with bios version V0.3219 or newer adding acpi_osi=Linux acpi_backlight=legacy as boot parameter resolves the issue.
  
  [Workaround 2]
- See comment #28.
+ Write into the "Legacy Backlight Brightness" register (on [8086:2a42] hardware):
+ first make sure you have that hardware ([8086:2a42]) at that address (00:02.0) by looking at the output of lspci -nn|grep VGA
+ then try setpci -s 00:02.0 F4.B=a1 
+ Also see comments #28 and #32.
+ And be careful where you point that setpci command. It might even damage your hardware.
  
  [Report]
  ubuntu lucid-desktop-amd64 20100206 (booting the iso from hd via grub2 loopback) on acer extensa 5635z:
  the backlight settings are simply ignored. the keys work, the notification works (changing according to the key presses), but the display always stays at the same full brightness.
  
  boot with acpi=off:
  backlight dimming works. 10 levels are available. surprisingly there is no notification. (notification for sound is there)
  warning: a short press of the power button kills the power immediately!
  
  ProblemType: Bug
  AlsaVersion: Advanced Linux Sound Architecture Driver Version 1.0.21.
  Architecture: amd64
  ArecordDevices:
   **** List of CAPTURE Hardware Devices ****
   card 0: Intel [HDA Intel], device 0: CONEXANT Analog [CONEXANT Analog]
     Subdevices: 1/1
     Subdevice #0: subdevice #0
  AudioDevicesInUse:
   USER        PID ACCESS COMMAND
   /dev/snd/controlC0:  ubuntu     2832 F.... pulseaudio
  CRDA: Error: [Errno 2] No such file or directory
  Card0.Amixer.info:
   Card hw:0 'Intel'/'HDA Intel at 0xf0700000 irq 22'
     Mixer name	: 'Conexant CX20561 (Hermosa)'
     Components	: 'HDA:14f15051,10250253,00100000'
     Controls      : 14
     Simple ctrls  : 7
  Date: Sat Feb  6 11:04:34 2010
  DistroRelease: Ubuntu 10.04
  LiveMediaBuild: Ubuntu 10.04 "Lucid Lynx" - Alpha amd64 (20100206)
  MachineType: Acer Extensa 5635Z
  Package: linux-image-2.6.32-12-generic 2.6.32-12.17
  ProcCmdLine: BOOT_IMAGE=(loop)/casper/vmlinuz boot=casper iso-scan/filename=/boot/iso/hostname/lucid-desktop-amd64.iso noprompt --
  ProcEnviron:
   LANG=en_US.UTF-8
   SHELL=/bin/bash
  ProcVersionSignature: Ubuntu 2.6.32-12.17-generic
  Regression: No
  RelatedPackageVersions: linux-firmware 1.29
  Reproducible: Yes
  SourcePackage: linux
  TestedUpstream: No
  Uname: Linux 2.6.32-12-generic x86_64
  dmi.bios.date: 05/07/2009
  dmi.bios.vendor: Phoenix
  dmi.bios.version: V0.3213
  dmi.board.name: BA50-MV
  dmi.board.vendor: Acer
  dmi.board.version: Not Applicable
  dmi.chassis.type: 10
  dmi.chassis.vendor: Acer
  dmi.chassis.version: N/A
  dmi.modalias: dmi:bvnPhoenix:bvrV0.3213:bd05/07/2009:svnAcer:pnExtensa5635Z:pvrNotApplicable:rvnAcer:rnBA50-MV:rvrNotApplicable:cvnAcer:ct10:cvrN/A:
  dmi.product.name: Extensa 5635Z
  dmi.product.version: Not Applicable
  dmi.sys.vendor: Acer

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lucid extensa 5635z backlight dimming not working at all
https://bugs.launchpad.net/bugs/518002
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