The new (2.6.39+) samsung_laptop kernel module causes serious backlight flickering - makes the desktop unusable
Affects | Status | Importance | Assigned to | Milestone | |
---|---|---|---|---|---|
linux (Ubuntu) |
Fix Released
|
High
|
Seth Forshee | ||
Oneiric |
Fix Released
|
High
|
Seth Forshee |
Bug Description
== SRU Justification ==
Impact: Many Samsung notebook models require a quirk for adjusting the screen brightness, but on some models the quirk detection fails and the wrong backlight adjustment method is used.
Fix: Upstream cherry pick to fix quirk detection.
Test Case: Verified on LP #810093 on the Samsung N220P.
---
*** Workaround in #26 ***
(A patched kernel module. Please test)
Original bug report:
I have a Samsung N220 plus. The backlight of the laptop often starts flickering (switching very fast between 2 brightness levels) when gnome tries to reduce the screen brightness (automatically after some time) to save power. This problem also occurs if you press more and less screen brightness at the same time.
I think it could be a problem with the sabi Bios interaction (samsung-laptop.c), because "linux on my samsung" also had this Problem with theier samsung-backlight module:
http://
and they solved it by interfacing the backlight via pci.
I tried to enable debug modus of samsung-laptop module, but I didn't get any more output on error. Dmesg only says (a lot of times):
ACPI: Failed to switch the brightness
I'll provide more informations if needed.
ProblemType: Bug
DistroRelease: Ubuntu 11.10
Package: linux-image-
ProcVersionSign
Uname: Linux 3.0.0-5-generic i686
NonfreeKernelMo
AlsaVersion: Advanced Linux Sound Architecture Driver Version 1.0.24.
AplayDevices:
**** List of PLAYBACK Hardware Devices ****
card 0: Intel [HDA Intel], device 0: ALC269 Analog [ALC269 Analog]
Subdevices: 1/1
Subdevice #0: subdevice #0
Architecture: i386
ArecordDevices:
**** List of CAPTURE Hardware Devices ****
card 0: Intel [HDA Intel], device 0: ALC269 Analog [ALC269 Analog]
Subdevices: 1/1
Subdevice #0: subdevice #0
AudioDevicesInUse:
USER PID ACCESS COMMAND
/dev/snd/
CRDA: Error: [Errno 2] Datei oder Verzeichnis nicht gefunden
Card0.Amixer.info:
Card hw:0 'Intel'/'HDA Intel at 0xf0400000 irq 47'
Mixer name : 'Realtek ALC269'
Components : 'HDA:10ec0269,
Controls : 14
Simple ctrls : 9
Date: Wed Jul 13 20:56:28 2011
HibernationDevice: RESUME=
InstallationMedia: Ubuntu 11.10 "Oneiric Ocelot" - Alpha i386 (20110705.1)
MachineType: SAMSUNG ELECTRONICS CO., LTD. N150P/N210P/N220P
ProcEnviron:
LANGUAGE=de:en
PATH=(custom, user)
LANG=de_DE.UTF-8
LC_MESSAGES=
SHELL=/bin/bash
ProcKernelCmdLine: BOOT_IMAGE=
RelatedPackageV
linux-
linux-
linux-firmware 1.56
SourcePackage: linux
StagingDrivers: brcmsmac brcmutil
UpgradeStatus: No upgrade log present (probably fresh install)
dmi.bios.date: 04/30/2010
dmi.bios.vendor: Phoenix Technologies Ltd.
dmi.bios.version: 01KY.M008.
dmi.board.
dmi.board.name: N150P/N210P/N220P
dmi.board.vendor: SAMSUNG ELECTRONICS CO., LTD.
dmi.board.version: Not Applicable
dmi.chassis.
dmi.chassis.type: 10
dmi.chassis.vendor: SAMSUNG ELECTRONICS CO., LTD.
dmi.chassis.
dmi.modalias: dmi:bvnPhoenixT
dmi.product.name: N150P/N210P/N220P
dmi.product.
dmi.sys.vendor: SAMSUNG ELECTRONICS CO., LTD.
Related branches
Changed in linux (Ubuntu): | |
status: | New → Confirmed |
tags: | added: bitesize hw-specific kernel-graphics usability |
Changed in linux (Ubuntu): | |
status: | Incomplete → Confirmed |
tags: | added: patch |
Changed in linux (Ubuntu): | |
status: | Confirmed → Triaged |
tags: | added: metabug regression-release |
tags: | added: backlight |
tags: | added: kernel-bug-exists-upstream |
tags: |
added: verification-failed-oneiric removed: verification-done-oneiric |
This bug is caused by the new samsung_laptop kernel module which was introduced in kernel 2.6.39. I haven't found any documentation for it but it sems to be written for at least the netbooks. If the module is enabled, the flickering starts on desktop load and can be stopped by changing the baclight brigtness. However, the only available modes are 0%, 10%(estimate) and 100%. The two lowest values are too dark for my eyes and the full backlight uses too much battery power.
WORKAROUND:
Disable the kernel module by adding:
blacklist samsung_laptop
to : /etc/modprobe. d/blacklist. conf