regression: backlight can't be adjusted on UX32VD with 3.19.0-12-generic kernel

[Matthew Haughton]

The keyboard buttons are working as I get the on screen notification. But it has no effect on the backlight itself.

I rebooted and switched back to 3.19.0-11-generic which works fine, rebooted and went back to 3.19.0-12-generic and it stopped working again, so very confident something broke in the new kernel version.

ProblemType: Bug
DistroRelease: Ubuntu 15.04
Package: linux-image-3.19.0-12-generic 3.19.0-12.12
ProcVersionSignature: Ubuntu 3.19.0-12.12-generic 3.19.3
Uname: Linux 3.19.0-12-generic x86_64
NonfreeKernelModules: nvidia
ApportVersion: 2.17-0ubuntu1
Architecture: amd64
AudioDevicesInUse:
 USER PID ACCESS COMMAND
 /dev/snd/controlC0: snafu109 2549 F.... pulseaudio
CurrentDesktop: XFCE
Date: Fri Apr 3 21:34:50 2015
HibernationDevice: RESUME=UUID=4e46a15c-d441-4b34-ae15-a93302da75a5
InstallationDate: Installed on 2012-12-26 (828 days ago)
InstallationMedia: Xubuntu 12.04.1 LTS "Precise Pangolin" - Release amd64 (20120817.3)
MachineType: ASUSTeK COMPUTER INC. UX32VD
ProcFB: 0 inteldrmfb
ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-3.19.0-12-generic root=UUID=687d7b6d-6fe2-413c-84c1-ed511edff5f9 ro quiet splash vt.handoff=7
RelatedPackageVersions:
 linux-restricted-modules-3.19.0-12-generic N/A
 linux-backports-modules-3.19.0-12-generic N/A
 linux-firmware 1.143
SourcePackage: linux
UpgradeStatus: Upgraded to vivid on 2015-03-10 (24 days ago)
dmi.bios.date: 01/29/2013
dmi.bios.vendor: American Megatrends Inc.
dmi.bios.version: UX32VD.214
dmi.board.asset.tag: ATN12345678901234567
dmi.board.name: UX32VD
dmi.board.vendor: ASUSTeK COMPUTER INC.
dmi.board.version: 1.0
dmi.chassis.asset.tag: No Asset Tag
dmi.chassis.type: 10
dmi.chassis.vendor: ASUSTeK COMPUTER INC.
dmi.chassis.version: 1.0
dmi.modalias: dmi:bvnAmericanMegatrendsInc.:bvrUX32VD.214:bd01/29/2013:svnASUSTeKCOMPUTERINC.:pnUX32VD:pvr1.0:rvnASUSTeKCOMPUTERINC.:rnUX32VD:rvr1.0:cvnASUSTeKCOMPUTERINC.:ct10:cvr1.0:
dmi.product.name: UX32VD
dmi.product.version: 1.0
dmi.sys.vendor: ASUSTeK COMPUTER INC.

[Brad Figg (brad-figg)]

This change was made by a bot.

[penalvch (penalvch)]

Matthew Haughton, thank you for reporting this and helping make Ubuntu better. Could you please test the latest upstream kernel available from the very top line at the top of the page (the release names are irrelevant for testing, and please do not test the daily folder) following https://wiki.ubuntu.com/KernelMainlineBuilds ? It will allow additional upstream developers to examine the issue.

If the test did not allow you to test to the issue (ex. you couldn't boot into the OS) please make a comment in your report about this, and continue to test the next most recent kernel version until you can test to the issue. Once you've tested the upstream kernel, please comment on which kernel version specifically you tested. If this bug is fixed in the mainline kernel, please add the following tags by clicking on the yellow circle with a black pencil icon, next to the word Tags, located at the bottom of the report description:
kernel-fixed-upstream
kernel-fixed-upstream-3.XY-rcZ

Where XY and Z are numbers corresponding to the kernel version.

If the mainline kernel does not fix this bug, please add the following tags:
kernel-bug-exists-upstream
kernel-bug-exists-upstream-3.XY-rcZ

Once testing of the upstream kernel is complete, please mark this bug's Status as Confirmed. Please let us know your results.

Thank you for your understanding.

[Marco Cè (marco89-7)]

I have the same issue on a Dell XPS 13 (L322X, Ivy Bridge model with 1080p display).
- With 3.19.0-11-generic backlight is working fine.
- With 3.19.0-12-generic, keyboard buttons produce notifications but the brightness is not changed. I can manually change it writing to '/sys/class/backlight/intel_backlight/brightness'.
- I tested 4.0.0-040000rc7-generic from kernel-ppa/mainline and it is working fine, as 3.19.0-11-generic.
With all kernels, when brightness is set to 0 the display (not only backlight) turn off, but I think it's another bug.

I'm available if more tests are needed to bisect the issue.

[Joseph Salisbury (jsalisbury)]

Can folks affected by this bug please test the v4.0-rc1 kernel:
http://kernel.ubuntu.com/~kernel-ppa/mainline/v4.0-rc1-vivid/

[Matthew Haughton (snafu109)]

I just booted into 4.0-rc1. Backlight controls work again.

[Timo Aaltonen (tjaalton)]

does this kernel work?

http://kernel.ubuntu.com/~kernel-ppa/mainline/drm-intel-next/2015-01-31-vivid/

[Marco Cè (marco89-7)]

I confirm that backlight controls work both with 4.0-rc1 and 3.19.0-997.
However, with 3.19.0-997 the external usb mouse moves the pointer on the screen with a lag of the order of one second, being unusable. Probably this is unrelated.

[Timo Aaltonen (tjaalton)]

Thanks for testing. Yes the slow mouse is unrelated, fixed later in 4.0.

[Timo Aaltonen (tjaalton)]

the offending commit has been identified and will be reverted from 3.19.0-13

[Launchpad Janitor (janitor)]

This bug was fixed in the package linux - 3.19.0-13.13

---------------
linux (3.19.0-13.13) vivid; urgency=low

  [ Andy Whitcroft ]

  * [Packaging] initscripts need installing when making the package
  * [Packaging] initscripts work around bug in debhelper systemd support

  [ Jay Vosburgh ]

  * SAUCE: fan: Proof of concept implementation
    - LP: #1439706

  [ Leann Ogasawara ]

  * Release Tracking Bug
    - LP: #1442165

  [ Upstream Kernel Changes ]

  * Revert "drm: fix mismerge in drm_crtc.c"
    - LP: #1440270, #1440392
  * e1000e: initial support for i219
    - LP: #1400955
  * e1000e: fix obscure comments
    - LP: #1400955
  * e1000e: remove calls to ioremap/unmap for NVM addr
    - LP: #1400955
  * d-i: Enable usb modules on arm64
  * drm/amdkfd: Initialize only amdkfd's assigned pipelines
  * storvsc: use cmd_size to allocate per-command data
  * storvsc: in responce to a scan event, scan the host
  * storvsc: force discovery of LUNs that may have been removed.
  * storvsc: fix a bug in storvsc limits
  * Drivers: hv: vmbus: Use get_cpu() to get the current CPU
  * Tools: hv: address compiler warnings for hv_fcopy_daemon.c
  * Tools: hv: do not add redundant '/' in hv_start_fcopy()
  * Drivers: hv: hv_balloon: Make adjustments in computing the floor
  * Drivers: hv: hv_balloon: Fix a locking bug in the balloon driver
  * Drivers: hv: hv_balloon: Don't post pressure status from interrupt
    context
  * Drivers: hv: vmbus: Implement a clockevent device
  * Drivers: hv: vmbus: Fix a bug in vmbus_establish_gpadl()
  * Drivers: hv: vmbus: Support a vmbus API for efficiently sending page
    arrays
  * hv: hv_fcopy: drop the obsolete message on transfer failure
  * Drivers: hv: check vmbus_device_create() return value in
    vmbus_process_offer()
  * Drivers: hv: rename sc_lock to the more generic lock
  * Drivers: hv: vmbus: serialize Offer and Rescind offer
  * Drivers: hv: vmbus: hv_process_timer_expiration() can be static
  * hyperv: netvsc.c: match wait_for_completion_timeout return type
  * hyperv: fix sparse warnings
  * powerpc/powernv: Add OPAL soft-poweroff routine
    - LP: #1439562
  * drivers/sbus/char/envctrl.c: ignore orderly_poweroff return value
    - LP: #1439562
  * kernel/reboot.c: add orderly_reboot for graceful reboot
    - LP: #1439562
  * powerpc/powernv: reboot when requested by firmware
    - LP: #1439562
  * powerpc/kernel: Make syscall_exit a local label
    - LP: #1439562
  * powerpc: Remove old compile time disabled syscall tracing code
    - LP: #1439562
  * powerpc: Add a proper syscall for switching endianness
    - LP: #1439562
  * powerpc/powernv: Remove "opal" prefix from pr_xxx()s
    - LP: #1439562
  * powerpc/powernv: Separate function for OPAL IRQ setup
    - LP: #1439562
  * powerpc/powernv: Add OPAL message notifier unregister function
    - LP: #1439562
  * powerpc/powernv: Support OPAL requested heartbeat
    - LP: #1439562
  * device: Add dev_of_node() accessor
    - LP: #1439562
  * drivers/core/of: Add symlink to device-tree from devices with an OF
    node
    - LP: #1439562
  * ipv6: Don't reduce hop limit for an interface
    - LP: #1441103
    - CVE-2015-2922
  * x86/microcode/int...