Samsung 900X4C laptop boots with display backlight off

[Andrew Glen-Young]

After upgrading to 3.5.0-15 on Quantal my Samsung 900X4C boots with it's display backlight off.

The backlight is turned off immediately after grub and before the kernel messages start. The display remains off and the keyboard keys assigned to adjust the brightness do not change the display.

The previous kernel (3.5.0-14) does not display these symptoms.

Workarounds:

1) Create a script which runs at boot time to turn the display on. I do this by running a reboot cronjob to set the display brightness.

    /etc/cron.d/fix-backlight:
    @reboot root echo 2040 > /sys/class/backlight/intel_backlight/brightness

   A initscript would be able to do the job as well, or better.

2) Use an earlier kernel (3.5.0-14)

ProblemType: Bug
DistroRelease: Ubuntu 12.10
Package: linux-image-3.5.0-15-generic 3.5.0-15.22
ProcVersionSignature: Ubuntu 3.5.0-15.22-generic 3.5.4
Uname: Linux 3.5.0-15-generic x86_64
ApportVersion: 2.5.2-0ubuntu4
Architecture: amd64
AudioDevicesInUse:
 USER PID ACCESS COMMAND
 /dev/snd/controlC0: agy 2182 F.... pulseaudio
Date: Mon Sep 24 16:45:57 2012
EcryptfsInUse: Yes
HibernationDevice: RESUME=UUID=e58f26d0-910f-4f85-a240-cd9d404f38ca
InstallationMedia: Ubuntu 12.04 LTS "Precise Pangolin" - Release amd64 (20120425)
MachineType: SAMSUNG ELECTRONICS CO., LTD. 900X3C/900X4C/900X4D
ProcEnviron:
 TERM=screen
 PATH=(custom, no user)
 LANG=en_US.UTF-8
 SHELL=/bin/bash
ProcFB: 0 inteldrmfb
ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-3.5.0-15-generic root=UUID=b281cccd-7e4d-4f82-9888-61890b3bafe4 ro quiet splash vt.handoff=7
RelatedPackageVersions:
 linux-restricted-modules-3.5.0-15-generic N/A
 linux-backports-modules-3.5.0-15-generic N/A
 linux-firmware 1.93
SourcePackage: linux
UpgradeStatus: Upgraded to quantal on 2012-09-14 (10 days ago)
dmi.bios.date: 04/26/2012
dmi.bios.vendor: Phoenix Technologies Ltd.
dmi.bios.version: P01AAC
dmi.board.asset.tag: Base Board Asset Tag
dmi.board.name: SAMSUNG_NP1234567890
dmi.board.vendor: SAMSUNG ELECTRONICS CO., LTD.
dmi.board.version: FAB1
dmi.chassis.asset.tag: No Asset Tag
dmi.chassis.type: 9
dmi.chassis.vendor: SAMSUNG ELECTRONICS CO., LTD.
dmi.chassis.version: 0.1
dmi.modalias: dmi:bvnPhoenixTechnologiesLtd.:bvrP01AAC:bd04/26/2012:svnSAMSUNGELECTRONICSCO.,LTD.:pn900X3C/900X4C/900X4D:pvr0.1:rvnSAMSUNGELECTRONICSCO.,LTD.:rnSAMSUNG_NP1234567890:rvrFAB1:cvnSAMSUNGELECTRONICSCO.,LTD.:ct9:cvr0.1:
dmi.product.name: 900X3C/900X4C/900X4D
dmi.product.version: 0.1
dmi.sys.vendor: SAMSUNG ELECTRONICS CO., LTD.

[Joseph Salisbury (jsalisbury)]

Would it be possible for you to test the latest upstream kernel? Refer to https://wiki.ubuntu.com/KernelMainlineBuilds . Please test the latest v3.6 kernel[0] (Not a kernel in the daily directory) and install both the linux-image and linux-image-extra .deb packages.

Once you've tested the upstream kernel, please remove the 'needs-upstream-testing' tag. Please only remove that one tag and leave the other tags. This can be done by clicking on the yellow pencil icon next to the tag located at the bottom of the bug description and deleting the 'needs-upstream-testing' text.

If this bug is fixed in the mainline kernel, please add the following tag 'kernel-fixed-upstream'.

If the mainline kernel does not fix this bug, please add the tag: 'kernel-bug-exists-upstream'.

If you are unable to test the mainline kernel, for example it will not boot, please add the tag: 'kernel-unable-to-test-upstream'.
Once testing of the upstream kernel is complete, please mark this bug as "Confirmed".

Thanks in advance.

[0] http://kernel.ubuntu.com/~kernel-ppa/mainline/v3.6-rc7-quantal/

[Launchpad Janitor (janitor)]

[Expired for linux (Ubuntu) because there has been no activity for 60 days.]