[Asus UL30VT] Backlight control does not work

[RK]

The backlight control on my Asus UL30VT has not worked for quite a while. It used to work, a few ubuntu versions ago. The backlight control bubble does show up when the function keys on the laptop are pressed.

ProblemType: Bug
DistroRelease: Ubuntu 14.04
Package: linux-image-3.13.0-39-generic 3.13.0-39.66
ProcVersionSignature: Ubuntu 3.13.0-39.66-generic 3.13.11.8
Uname: Linux 3.13.0-39-generic x86_64
ApportVersion: 2.14.1-0ubuntu3.5
Architecture: amd64
AudioDevicesInUse:
 USER PID ACCESS COMMAND
 /dev/snd/controlC1: lina 2081 F.... pulseaudio
 /dev/snd/controlC0: lina 2081 F.... pulseaudio
CurrentDesktop: Unity
Date: Wed Nov 12 20:20:31 2014
EcryptfsInUse: Yes
HibernationDevice: RESUME=UUID=c8002bb0-2b05-4952-bc8b-bfcd29ac6117
InstallationDate: Installed on 2013-02-26 (623 days ago)
InstallationMedia: This
MachineType: ASUSTeK Computer Inc. UL30VT
ProcFB: 0 inteldrmfb
ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-3.13.0-39-generic root=UUID=ff44dc17-e11a-4d44-8ab6-bf188f64ed83 ro quiet splash acpi_backlight=vendor vt.handoff=7
RelatedPackageVersions:
 linux-restricted-modules-3.13.0-39-generic N/A
 linux-backports-modules-3.13.0-39-generic N/A
 linux-firmware 1.127.8
SourcePackage: linux
UpgradeStatus: Upgraded to trusty on 2014-07-20 (115 days ago)
dmi.bios.date: 07/14/2010
dmi.bios.vendor: American Megatrends Inc.
dmi.bios.version: 211
dmi.board.asset.tag: ATN12345678901234567
dmi.board.name: UL30VT
dmi.board.vendor: ASUSTeK Computer Inc.
dmi.board.version: 1.0
dmi.chassis.asset.tag: ATN12345678901234567
dmi.chassis.type: 10
dmi.chassis.vendor: ASUSTeK Computer Inc.
dmi.chassis.version: 1.0
dmi.modalias: dmi:bvnAmericanMegatrendsInc.:bvr211:bd07/14/2010:svnASUSTeKComputerInc.:pnUL30VT:pvr1.0:rvnASUSTeKComputerInc.:rnUL30VT:rvr1.0:cvnASUSTeKComputerInc.:ct10:cvr1.0:
dmi.product.name: UL30VT
dmi.product.version: 1.0
dmi.sys.vendor: ASUSTeK Computer Inc.

[Brad Figg (brad-figg)]

This change was made by a bot.

[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 v3.18 kernel[0].

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/v3.18-rc4-vivid/

[RK (shandolad)]

Hi,
I've tested the new 3.18 kernel
($ uname -a
Linux lina-UL30VT 3.18.0-031800rc4-generic #201411091835 SMP Sun Nov 9 23:36:36 UTC 2014 x86_64 x86_64 x86_64 GNU/Linux)

However, the bug persists. Backlight control does not work.

Furthermore, the touchpad control cannot be turned off with the hotkey, nor does the indicator bubble pop up (I understand that this perhaps should be reported as a separate bug)

Still, the indicator bubble for backlight control does pop up, but has no effect on actual backlight.

[penalvch (penalvch)]

RK, the next step is to fully commit bisect from your prior working release to Trusty in order to identify the last good kernel commit, followed immediately by the first bad one. This will allow for a more expedited analysis of the root cause of your issue. Could you please do this following https://wiki.ubuntu.com/Kernel/KernelBisection ? Please note, finding adjacent kernel versions is not fully commit bisecting.

Thank you for your understanding.

Helpful bug reporting tips:
https://wiki.ubuntu.com/ReportingBugs

[RK (shandolad)]

Hi,
I have now gone back and tested kernels back to 2.6.32, the kernel that was used in Ubuntu when this laptop was released. It seems I remembered incorrectly, backlight control has never worked properly on this laptop.

Backlight control did not work on any of the kernels I tested. I tested the following kernels:

- 2.6.32-69-generic
- 2.6.38-02063808-generic
- 3.0.1-030001-generic
- 3.11.0-12-generic
- 3.11.0-26-generic
- 3.13.0-32-generic
- 3.13.0-34-generic
- 3.13.0-37-generic
- 3.13.0-37-generic
- 3.18.0-031800rc4-generic

It is possible that the problem is the same as for the UL-80VT:
https://bugzilla.kernel.org/show_bug.cgi?id=66501

[penalvch (penalvch)]

RK, could you please test the latest mainline kernel via 3.18-rc6 and advise to the results?

[RK (shandolad)]

I have now tested the very latest kernel, version 3.19 rc 1 (from http://kernel.ubuntu.com/~kernel-ppa/mainline/v3.19-rc1-vivid/), and backlight control still does not work.

The indicator does pop up and indicates increase and decrease in the correct way, but the actual backlight level on the laptop screen does not change.

Furthermore, the function key to turn off the touchpad does not work, and doesn't even show an indicator bubble.

[penalvch (penalvch)]

RK, do any of the WORKAROUNDs mentioned in https://wiki.ubuntu.com/Kernel/Debugging/Backlight let you adjust the backlight with your keyboard (for now, don't worry about attaching the debugging information mentioned in the article).

[RK (shandolad)]

Hi Christopher,
thanks for your continued help.

The command
"echo 8 > /sys/class/backlight/intel_backlight/brightness"
does set the brightness to a very low value (basically completely black). This was done with the "acpi_backlight=vendor" kernel parameter in use.

Rebooting "with just kernel parameter video.use_bios_initial_backlight=0" does not change anything (indicator bubble pops up, backlight level doesn't actually change).

Rebooting "with just kernel parameter video.use_native_backlight=1" does not change anything (indicator bubble pops up, backlight level doesn't actually change).

This did work: "Creating a new file in /usr/share/X11/xorg.conf.d/80-backlight.conf and pasting into it the following code:

Section "Device"
    Identifier "Intel Graphics"
    Driver "intel"
    Option "AccelMethod" "sna"
    Option "Backlight" "intel_backlight" # use your backlight that works here
    BusID "PCI:0:2:0"
EndSection
"
The backlight control now works properly (indicator bubble and proper backlight change). Furthermore, it is now possible to turn off the touchpad by using the function key (the indicator bubble does show up).

[penalvch (penalvch)]

RK, in order to upstream this, could you please test the latest mainline kernel (4.4) and advise to the results?