Keyboard backlight stopped working after upgrade to Wily

[Harry P]

I'm using a Samsung Ativ Book 9. Keyboard backlight worked OK under Vivid, seems to have stopped working since I installed Wily. Can't see any evidence of it in /sys/class.

Happy to do any further debugging if it helps.

ProblemType: Bug
DistroRelease: Ubuntu 15.10
Package: linux-image-4.2.0-18-generic 4.2.0-18.22
ProcVersionSignature: Ubuntu 4.2.0-18.22-generic 4.2.3
Uname: Linux 4.2.0-18-generic x86_64
ApportVersion: 2.19.1-0ubuntu5
Architecture: amd64
AudioDevicesInUse:
 USER PID ACCESS COMMAND
 /dev/snd/controlC1: harry 1635 F.... pulseaudio
 /dev/snd/controlC0: harry 1635 F.... pulseaudio
CurrentDesktop: GNOME
Date: Tue Nov 24 09:45:23 2015
EcryptfsInUse: Yes
HibernationDevice: RESUME=UUID=9a886cf6-b939-4fdc-9721-bbf214a10519
InstallationDate: Installed on 2015-10-15 (39 days ago)
InstallationMedia: Ubuntu-GNOME 15.10 "Wily Werewolf" - Alpha amd64 (20150924)
MachineType: SAMSUNG ELECTRONICS CO., LTD. 940X3G/930X3G
ProcFB: 0 inteldrmfb
ProcKernelCmdLine: BOOT_IMAGE=/vmlinuz-4.2.0-18-generic.efi.signed root=/dev/mapper/ubuntu--gnome--vg-root ro noprompt persistent quiet splash vt.handoff=7
RelatedPackageVersions:
 linux-restricted-modules-4.2.0-18-generic N/A
 linux-backports-modules-4.2.0-18-generic N/A
 linux-firmware 1.149.2
SourcePackage: linux
UdevLog: Error: [Errno 2] No such file or directory: '/var/log/udev'
UpgradeStatus: No upgrade log present (probably fresh install)
dmi.bios.date: 08/19/2014
dmi.bios.vendor: American Megatrends Inc.
dmi.bios.version: P05ACJ.128.140819.dg
dmi.board.asset.tag: No Asset Tag
dmi.board.name: NP940X3G-K05US
dmi.board.vendor: SAMSUNG ELECTRONICS CO., LTD.
dmi.board.version: SAMSUNG_SW_REVISION_1234567890ABCD
dmi.chassis.asset.tag: No Asset Tag
dmi.chassis.type: 9
dmi.chassis.vendor: SAMSUNG ELECTRONICS CO., LTD.
dmi.chassis.version: N/A
dmi.modalias: dmi:bvnAmericanMegatrendsInc.:bvrP05ACJ.128.140819.dg:bd08/19/2014:svnSAMSUNGELECTRONICSCO.,LTD.:pn940X3G/930X3G:pvrP05ACJ:rvnSAMSUNGELECTRONICSCO.,LTD.:rnNP940X3G-K05US:rvrSAMSUNG_SW_REVISION_1234567890ABCD:cvnSAMSUNGELECTRONICSCO.,LTD.:ct9:cvrN/A:
dmi.product.name: 940X3G/930X3G
dmi.product.version: P05ACJ
dmi.sys.vendor: SAMSUNG ELECTRONICS CO., LTD.

[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 v4.4 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'.

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/v4.4-rc2+cod1-wily/

[Harry P (hjwp2)]

Hi there,

I managed to install the new kernel (which was exciting! I've never done that before. Only nonobvious bit was uninstalling virtualbox-dkms first). It booted ok, this was my new uname -a:

  Linux harry-samsung 4.4.0-040400rc2-generic #201511231054 SMP Mon Nov 23 10:56:43 UTC 2015 x86_64 x86_64 x86_64 GNU/Linux

 But no change to the keyboard backlight situation.

I did see one error while installing the new kernel, which looked potentially pertinent:

W: Possible missing firmware /lib/firmware/i915/skl_guc_ver4.bin for module i915

What else might I be able to try? I think I saw something on the internets about EFI vs UEFI boots, or something like that?

[penalvch (penalvch)]

Harry P, the next step is to fully commit bisect from kernel 3.19 to 4.2 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

[Harry P (hjwp2)]

Hi Christopher,

I just installed 3.19.8-031908-generic and the backlight still doesn't work, which is mysterious. I'm now starting to worry if I misremember this keyboard backlight working in the past!

Will try and get a live cd of vivdi, and maybe one of trusty too, boot from them and see what I see...

[Harry P (hjwp2)]

Quick question in the meantime -- I have some vague notions that there are two different ways for an OS to boot, UEFI and the old bios way -- when I installed wily, I remember messing about trying to get EFI to work. Could that have made a difference?

[Harry P (hjwp2)]

So for one reason or another I ended up reinstalling the OS, and it's now booting in traditional BIOS mode rather than EFI, and sure enough the backlight works again. Not sure whether that means this should be marked against a different package?

[penalvch (penalvch)]

Harry P, this bug report is being closed due to your last comment https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1519282/comments/8 regarding this being fixed with a reinstall. For future reference you can manage the status of your own bugs by clicking on the current status in the yellow line and then choosing a new status in the revealed drop down box. You can learn more about bug statuses at https://wiki.ubuntu.com/Bugs/Status. Thank you again for taking the time to report this bug and helping to make Ubuntu better. Please submit any future bugs you may find.

[Harry P (hjwp2)]

Sorry Christopher, I'm not sure this should be closed. An Ubuntu install with UEFI boot consistently shows the problem. An install with old-style BIOS does not. So the problem is with Ubuntu's UEFI boot loader, which I'm sure the team would want to fix, since it's meant to be the preferred way of booting PCs these days?

This might mean you want to reassign the bug to a different package, rather than closing it?

[Harry P (hjwp2)]

I've changed it to "efibootmgr", which seems to be as close as anything might be?

[penalvch (penalvch)]

Harry P, to advise, one shouldn't change the package unless there is strong technical evidence to the package being at fault. Just because it has the word efi in it, doesn't mean it has anything to do with this problem.

Despite this, if you are going to use legacy boot going forward, and if you aren't going to continue providing logs and debugging this issue, then there isn't a reason to keep this open as updates filter down from the respective upstream projects into Ubuntu.

Hence, if you are going to do that, then yes, mark this Confirmed (not change the package).