3.19.0-12.12 brightness regression

[Andy Whitcroft]

I am seeing lack of brightness control in unity when using the -12.12 kernel, booting back to -11.11 resolves the issue.

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: wl
ApportVersion: 2.17-0ubuntu1
Architecture: amd64
AudioDevicesInUse:
 USER PID ACCESS COMMAND
 /dev/snd/controlC0: apw 3666 F.... pulseaudio
CurrentDesktop: Unity
Date: Tue Apr 7 12:01:19 2015
EcryptfsInUse: Yes
HibernationDevice: RESUME=UUID=56f0e078-c76d-4cf9-a3ef-3b30e0c1a78b
InstallationDate: Installed on 2013-06-20 (655 days ago)
InstallationMedia: Ubuntu 13.10 "Saucy Salamander" - Alpha amd64 (20130618)
MachineType: Intel Corporation 2012 Client Platform
ProcFB: 0 inteldrmfb
ProcKernelCmdLine: BOOT_IMAGE=/vmlinuz-3.19.0-12-generic root=/dev/mapper/ubuntu--vg-root ro quiet splash nomdmonddf nomdmonisw nomdmonddf nomdmonisw nomdmonddf nomdmonisw 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 2013-11-10 (512 days ago)
dmi.bios.date: 07/30/2012
dmi.bios.vendor: American Megatrends Inc.
dmi.bios.version: ACRVMBY1.86C.0094.P02.1207301240
dmi.board.asset.tag: To be filled by O.E.M.
dmi.board.name: Latexo FFRD
dmi.board.vendor: Intel Corporation
dmi.board.version: To be filled by O.E.M.
dmi.chassis.asset.tag: To Be Filled By O.E.M.
dmi.chassis.type: 9
dmi.chassis.vendor: To Be Filled By O.E.M.
dmi.chassis.version: To Be Filled By O.E.M.
dmi.modalias: dmi:bvnAmericanMegatrendsInc.:bvrACRVMBY1.86C.0094.P02.1207301240:bd07/30/2012:svnIntelCorporation:pn2012ClientPlatform:pvrTobefilledbyO.E.M.:rvnIntelCorporation:rnLatexoFFRD:rvrTobefilledbyO.E.M.:cvnToBeFilledByO.E.M.:ct9:cvrToBeFilledByO.E.M.:
dmi.product.name: 2012 Client Platform
dmi.product.version: To be filled by O.E.M.
dmi.sys.vendor: Intel Corporation

[Andy Whitcroft (apw)]

Note that the hotkeys work up and down, and the visual slider moves, and no brightness change is reflected in the display.