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Message #44515
[Bug 1279569] Re: Backlight control suddenly stops working on ThinkPad T420
** Attachment added: "dmidecode.log"
https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1279569/+attachment/3979004/+files/dmidecode.log
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https://bugs.launchpad.net/bugs/1279569
Title:
Backlight control suddenly stops working on ThinkPad T420
Status in “linux” package in Ubuntu:
Confirmed
Bug description:
Backlight control with Fn+Home, Fn+End stopped working for me today
out of nothing. I am not aware of any changes that might have caused
it. I am installing updates as they come, so it could have been an
update.
I followed the guidelines at
https://wiki.ubuntu.com/Kernel/Debugging/Backlight
I can change brightness by writing to
/sys/class/backlight/intel_backlight/brightness, for example echo 1000
> /sys/class/backlight/intel_backlight/brightness
None of the kernel parameters changed the behavior..., not even
thinkpad-acpi.brightness_enable=1 acpi_backlight=vendor - that is even
with these parameters the brightness control shortcuts don't work and
changing brightness by writing to the above file does work. I am not
aware of any brightness changing applet I could try. I'm using Gnome
Shell if that matters.
Let me know what I can do, thank you.
ProblemType: Bug
DistroRelease: Ubuntu 13.10
Package: linux-image-3.11.0-15-generic 3.11.0-15.25
ProcVersionSignature: Ubuntu 3.11.0-15.25-generic 3.11.10
Uname: Linux 3.11.0-15-generic x86_64
ApportVersion: 2.12.5-0ubuntu2.2
Architecture: amd64
AudioDevicesInUse:
USER PID ACCESS COMMAND
/dev/snd/controlC1: jakub 2972 F.... pulseaudio
/dev/snd/controlC0: jakub 2972 F.... pulseaudio
Date: Wed Feb 12 23:10:06 2014
HibernationDevice: RESUME=UUID=9009e872-0f42-4632-bc0a-4a70931f9767
InstallationDate: Installed on 2011-06-06 (982 days ago)
InstallationMedia: Ubuntu 11.04 "Natty Narwhal" - Release amd64 (20110427.1)
MachineType: LENOVO 4180W1G
MarkForUpload: True
ProcFB: 0 inteldrmfb
ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-3.11.0-15-generic root=UUID=e79e9934-9ad4-4091-8b9d-2ef7b1dba68e ro video.use_bios_initial_backlight=0 quiet splash vt.handoff=7
RelatedPackageVersions:
linux-restricted-modules-3.11.0-15-generic N/A
linux-backports-modules-3.11.0-15-generic N/A
linux-firmware 1.116.1
SourcePackage: linux
UpgradeStatus: Upgraded to saucy on 2013-11-13 (91 days ago)
dmi.bios.date: 10/31/2011
dmi.bios.vendor: LENOVO
dmi.bios.version: 83ET66WW (1.36 )
dmi.board.asset.tag: Not Available
dmi.board.name: 4180W1G
dmi.board.vendor: LENOVO
dmi.board.version: Not Available
dmi.chassis.asset.tag: No Asset Information
dmi.chassis.type: 10
dmi.chassis.vendor: LENOVO
dmi.chassis.version: Not Available
dmi.modalias: dmi:bvnLENOVO:bvr83ET66WW(1.36):bd10/31/2011:svnLENOVO:pn4180W1G:pvrThinkPadT420:rvnLENOVO:rn4180W1G:rvrNotAvailable:cvnLENOVO:ct10:cvrNotAvailable:
dmi.product.name: 4180W1G
dmi.product.version: ThinkPad T420
dmi.sys.vendor: LENOVO
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