[Lenovo B470e] Backlight interface does not working

[Yung Shen]

Brightness Keys does not work on this system with 12.04.4.

Brightness slider in "Settings > Brightness and Lock" does not function as well.

There is two backlight interfaces under /sys/class/backlight/ :
lrwxrwxrwx 1 root root 0 Apr 10 05:19 ideapad -> ../../devices/platform/ideapad/backlight/ideapad
lrwxrwxrwx 1 root root 0 Apr 10 05:19 intel_backlight -> ../../devices/pci0000:00/0000:00:02.0/drm/card0/card0-LVDS-1/intel_backlight

Trying to modify brightness value directly in the control file, but only intel_backlight/brighness works here.

Further investigating by trying older kernel versions,
brightness hot keys and backlight interfaces works just fine with 3.2, 3.5, 3.8 .
Verified with:
linux-image-3.2.0-60-generic 3.2.0-60.91
linux-image-3.5.0-48-generic 3.5.0-48.72~precise1 linux-image-3.8.0-38-generic 3.8.0-38.56~precise1

ProblemType: Bug
DistroRelease: Ubuntu 12.04
Package: linux-image-3.11.0-15-generic 3.11.0-15.25~precise1 [modified: boot/vmlinuz-3.11.0-15-generic]
ProcVersionSignature: Ubuntu 3.11.0-15.25~precise1-generic 3.11.10
Uname: Linux 3.11.0-15-generic x86_64
AlsaVersion: Advanced Linux Sound Architecture Driver Version k3.11.0-15-generic.
ApportVersion: 2.0.1-0ubuntu17.6
Architecture: amd64
ArecordDevices:
 **** List of CAPTURE Hardware Devices ****
 card 0: PCH [HDA Intel PCH], device 0: ALC272 Analog [ALC272 Analog]
   Subdevices: 1/1
   Subdevice #0: subdevice #0
AudioDevicesInUse:
 USER PID ACCESS COMMAND
 /dev/snd/controlC0: ubuntu 1850 F.... pulseaudio
CRDA: Error: [Errno 2] No such file or directory
Card0.Amixer.info:
 Card hw:0 'PCH'/'HDA Intel PCH at 0x90600000 irq 44'
   Mixer name : 'Intel CougarPoint HDMI'
   Components : 'HDA:10ec0272,17aa6012,00100001 HDA:80862805,80860101,00100000'
   Controls : 28
   Simple ctrls : 10
Date: Thu Apr 10 05:22:31 2014
HibernationDevice: RESUME=UUID=cfc777d4-9050-434e-8ea9-a22ea054c001
InstallationMedia: Ubuntu 12.04.4 LTS "Precise Pangolin" - Release amd64 (20140204)
MachineType: LENOVO HuronRiver Platform
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-3.11.0-15-generic root=UUID=74ea0650-a72e-4186-9064-5d3ad2e480d6 ro quiet splash acpi_backlight=vendor initcall_debug 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 1.79.9
SourcePackage: linux-lts-saucy
StagingDrivers: rts5139
UpgradeStatus: No upgrade log present (probably fresh install)
dmi.bios.date: 02/16/2012
dmi.bios.vendor: LENOVO
dmi.bios.version: 43CN45WW
dmi.board.asset.tag: Base Board Asset Tag
dmi.board.name: Emerald Lake
dmi.board.vendor: LENOVO
dmi.board.version: FAB1
dmi.chassis.asset.tag: Asset Tag
dmi.chassis.type: 10
dmi.chassis.vendor: LENOVO
dmi.chassis.version: 0.1
dmi.modalias: dmi:bvnLENOVO:bvr43CN45WW:bd02/16/2012:svnLENOVO:pnHuronRiverPlatform:pvrLenovoB470e:rvnLENOVO:rnEmeraldLake:rvrFAB1:cvnLENOVO:ct10:cvr0.1:
dmi.product.name: HuronRiver Platform
dmi.product.version: Lenovo B470e
dmi.sys.vendor: LENOVO

[Anthony Wong (anthonywong)]

@Yung Shen
According to https://wiki.ubuntu.com/Kernel/LTSEnablementStack, the Saucy HWE stack should already be EOL'd, should we close this bug?

[Launchpad Janitor (janitor)]

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

[Yung Shen (kaxing)]

Still having this issue on 12.04.5 with linux-image-3.13.0-46-generic.