After suspend/resume, screen brightness can only be switched between 0 and 100%

[Chris Cowan]

I have the same issue as described in https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1197482. I have a macbook running Ubuntu 15.04, and if I suspend and then unsuspend, then my screen turns off when I set the brightness to to below 85%ish (4 presses of the brightness down key from full), and it's at full brightness when it's anywhere above that. Brightness controls work perfectly fine after booting before I ever suspend.

ProblemType: Bug
DistroRelease: Ubuntu 15.04
Package: linux-image-3.19.0-21-generic 3.19.0-21.21
ProcVersionSignature: Ubuntu 3.19.0-21.21-generic 3.19.8
Uname: Linux 3.19.0-21-generic x86_64
NonfreeKernelModules: wl
ApportVersion: 2.17.2-0ubuntu1.1
Architecture: amd64
AudioDevicesInUse:
 USER PID ACCESS COMMAND
 /dev/snd/controlC1: chris 1861 F.... pulseaudio
 /dev/snd/controlC0: chris 1861 F.... pulseaudio
CurrentDesktop: Unity
Date: Sun Jul 5 19:46:00 2015
EcryptfsInUse: Yes
InstallationDate: Installed on 2015-06-08 (28 days ago)
InstallationMedia: Ubuntu 15.04 "Vivid Vervet" - Release amd64 (20150422)
MachineType: Apple Inc. MacBookAir6,2
ProcFB: 0 inteldrmfb
ProcKernelCmdLine: BOOT_IMAGE=/vmlinuz-3.19.0-21-generic.efi.signed root=UUID=fa0b84b0-1cfd-4da2-963e-8fc448a0b636 ro rootflags=subvol=@ noprompt persistent quiet splash vt.handoff=7
RelatedPackageVersions:
 linux-restricted-modules-3.19.0-21-generic N/A
 linux-backports-modules-3.19.0-21-generic N/A
 linux-firmware 1.143.1
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: 01/07/2015
dmi.bios.vendor: Apple Inc.
dmi.bios.version: MBA61.88Z.0099.B18.1501071032
dmi.board.asset.tag: Base Board Asset Tag#
dmi.board.name: Mac-7DF21CB3ED6977E5
dmi.board.vendor: Apple Inc.
dmi.board.version: MacBookAir6,2
dmi.chassis.type: 10
dmi.chassis.vendor: Apple Inc.
dmi.chassis.version: Mac-7DF21CB3ED6977E5
dmi.modalias: dmi:bvnAppleInc.:bvrMBA61.88Z.0099.B18.1501071032:bd01/07/2015:svnAppleInc.:pnMacBookAir6,2:pvr1.0:rvnAppleInc.:rnMac-7DF21CB3ED6977E5:rvrMacBookAir6,2:cvnAppleInc.:ct10:cvrMac-7DF21CB3ED6977E5:
dmi.product.name: MacBookAir6,2
dmi.product.version: 1.0
dmi.sys.vendor: Apple Inc.

[Brad Figg (brad-figg)]

This change was made by a bot.

[penalvch (penalvch)]

Chris Cowan, 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/Kernel/MainlineBuilds ? 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-X.Y-rcZ

Where X, Y, 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-X.Y-rcZ

Please note, an error to install the kernel does not fit the criteria of kernel-bug-exists-upstream.

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.

[Launchpad Janitor (janitor)]

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

[Chris Cowan (macil)]

I've just tested 4.3-wily (4.3.0-040300-generic #201511020949) in Ubuntu 15.10 and I still see this issue.

[penalvch (penalvch)]

Chris Cowan, could you please provide the missing information following https://wiki.ubuntu.com/DebuggingKernelSuspend ?