Public bug reported:
This is a system installed with 12.04.3.
Brightness can be controlled in "Systems Settings" > "Brightness and
Lock" > Brightness slider.
However there are three interfaces,
/sys/class/backlight$ ls
acpi_video0 acpi_video1 intel_backlight
By controlling each interfaces as following command:
$ sudo sh -c 'echo 80 > brightness'
here is the findings:
acpi_video*/brighness can be only controll by particular values like,
80, 40, 22, 12, 8, 5 ,3,1
intel_backlight/brightness can adjust from 0 to 4789.
three interfaces are not synchronized, this cause an issue for other
tools that uses acpi_video0 or acpi_video1 on this system.
ProblemType: Bug
DistroRelease: Ubuntu 12.04
Package: linux-image-3.8.0-35-generic 3.8.0-35.50~precise1
ProcVersionSignature: Ubuntu 3.8.0-35.50~precise1-generic 3.8.13.13
Uname: Linux 3.8.0-35-generic x86_64
AlsaVersion: Advanced Linux Sound Architecture Driver Version k3.8.0-35-generic.
ApportVersion: 2.0.1-0ubuntu17.6
Architecture: amd64
ArecordDevices:
**** List of CAPTURE Hardware Devices ****
card 1: PCH [HDA Intel PCH], device 0: ALC292 Analog [ALC292 Analog]
Subdevices: 1/1
Subdevice #0: subdevice #0
AudioDevicesInUse:
USER PID ACCESS COMMAND
/dev/snd/controlC1: ubuntu 1751 F.... pulseaudio
/dev/snd/controlC0: ubuntu 1751 F.... pulseaudio
CRDA: Error: [Errno 2] No such file or directory
Card0.Amixer.info:
Card hw:0 'MID'/'HDA Intel MID at 0xf2630000 irq 48'
Mixer name : 'Intel Haswell HDMI'
Components : 'HDA:80862807,80860101,00100000'
Controls : 21
Simple ctrls : 3
Card1.Amixer.info:
Card hw:1 'PCH'/'HDA Intel PCH at 0xf2634000 irq 49'
Mixer name : 'Realtek ALC292'
Components : 'HDA:10ec0292,17aa2210,00100001'
Controls : 22
Simple ctrls : 10
Card29.Amixer.info:
Card hw:29 'ThinkPadEC'/'ThinkPad Console Audio Control at EC reg 0x30, fw
unknown'
Mixer name : 'ThinkPad EC (unknown)'
Components : ''
Controls : 1
Simple ctrls : 1
Card29.Amixer.values:
Simple mixer control 'Console',0
Capabilities: pswitch pswitch-joined penum
Playback channels: Mono
Mono: Playback [on]
CurrentDmesg: [ 40.050791] type=1400 audit(1389947716.229:28):
apparmor="DENIED" operation="open" parent=1
profile="/usr/lib/telepathy/mission-control-5"
name="/usr/share/gvfs/remote-volume-monitors/" pid=1974 comm="mission-control"
requested_mask="r" denied_mask="r" fsuid=1000 ouid=0
Date: Fri Jan 17 03:40:35 2014
HibernationDevice: RESUME=UUID=619bafb8-b790-472c-9471-181ae33c4dd2
InstallationMedia: Ubuntu 12.04.3 LTS "Precise Pangolin" - Release amd64
(20130820.1)
IwConfig:
eth0 no wireless extensions.
lo no wireless extensions.
MachineType: LENOVO 20BFZ052US
MarkForUpload: True
ProcEnviron:
TERM=xterm
PATH=(custom, no user)
LANG=en_US.UTF-8
SHELL=/bin/bash
ProcFB: 0 inteldrmfb
ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-3.8.0-35-generic
root=UUID=4fde570e-2674-44ba-8c05-5626a382ef7b ro quiet splash thinkpad-acpi
brightness_enable=1 initcall_debug vt.handoff=7
RelatedPackageVersions:
linux-restricted-modules-3.8.0-35-generic N/A
linux-backports-modules-3.8.0-35-generic N/A
linux-firmware 1.79.6
SourcePackage: linux-lts-raring
UpgradeStatus: No upgrade log present (probably fresh install)
dmi.bios.date: 08/09/2013
dmi.bios.vendor: LENOVO
dmi.bios.version: GMET21WW (1.01 )
dmi.board.asset.tag: Not Available
dmi.board.name: 20BFZ052US
dmi.board.vendor: LENOVO
dmi.board.version: Win8 Pro DPK TPG
dmi.chassis.asset.tag: No Asset Information
dmi.chassis.type: 10
dmi.chassis.vendor: LENOVO
dmi.chassis.version: Not Available
dmi.modalias:
dmi:bvnLENOVO:bvrGMET21WW(1.01):bd08/09/2013:svnLENOVO:pn20BFZ052US:pvrThinkPadT540p:rvnLENOVO:rn20BFZ052US:rvrWin8ProDPKTPG:cvnLENOVO:ct10:cvrNotAvailable:
dmi.product.name: 20BFZ052US
dmi.product.version: ThinkPad T540p
dmi.sys.vendor: LENOVO
** Affects: linux-lts-raring (Ubuntu)
Importance: Undecided
Status: New
** Tags: 201309-14211 amd64 apport-bug blocks-hwcert precise
qa-kernel-lts-testing running-unity taipei-lab
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https://bugs.launchpad.net/bugs/1270079
Title:
[Lenovo T540p, W540] Backlight interfaces not fully working
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