[Status]
Fix for Natty and Maverick exists in https://launchpad.net/~kamalmostafa/+archive/linux-kamal-mjgbacklight .
Happens on Maverick. Tested with 2.6.36 and 2.6.38 (see comment #37) kernel. Tested with 2.6.39rc.
Happens on Lucid.
[Workaround/Fix 0]
Install the patched kernel and gnome-power-manager from https://launchpad.net/~kamalmostafa/+archive/linux-kamal-mjgbacklight by adding that ppa to your sources and upgrading your system (for maverick and natty).
[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]
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
(a1 in the above line is just one example for a brightness value; you can use any two digit hexadecimal value, e.g:
80 for something like half brightness
ff for full
better avoid 00 or be prepared for pitch black)
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
On karmic it did not work either, but could be worked around by switching to other methods:
e.g.:
xrandr --output LVDS --set BACKLIGHT_CONTROL native
xrandr --prop shows the available methods:
BACKLIGHT_CONTROL: native
supported: native legacy combination kernel
BACKLIGHT: 10867 (0x00002a73) range: (0,10867)
set the level with:
xrandr --output LVDS --set BACKLIGHT 500
The LED backlight really has 10000 levels. Absolutely smooth dimming is possible!
On lucid (with KMS) other methods are no longer available. And kernel method never worked, even in karmic.