The behavior is the lighting control works upon initial boot, but after leaving the computer on for multiple hours at some point the backlight ceases to respond and backlight controls are never regained until a shutdown or reboot of the system. I haven't tracked the exact pattern of actions that cause this. The on screen indicator shows the graphic of the dimming, but the actual behavior of reducing brightness does not function upon key press.
I noticed when the backlight was lost the following is added to dmesg, but I don't know how long before or after the loss that this message appeared: [ 9231.171766] usb 5-1: USB disconnect, device number 4 [11481.272220] perf interrupt took too long (2515 > 2500), lowering kernel.perf_event_max_sample_rate to 50000 [20859.513041] atkbd serio0: Unknown key pressed (translated set 2, code 0xab on isa0060/serio0). [20859.513049] atkbd serio0: Use 'setkeycodes e02b <keycode>' to make it known. [20859.533404] atkbd serio0: Unknown key released (translated set 2, code 0xab on isa0060/serio0). [20859.533413] atkbd serio0: Use 'setkeycodes e02b <keycode>' to make it known. [20859.832244] atkbd serio0: Unknown key pressed (translated set 2, code 0xab on isa0060/serio0). [20859.832253] atkbd serio0: Use 'setkeycodes e02b <keycode>' to make it known. Each press of the brightness key results in additional "atkbd serio0: Unknown key pressed (translated set 2, code 0xab on isa0060/serio0)...." values to be added to dmesg. May be related to resuming control after the screen goes blank after inactivity or other activity while idle? -- You received this bug notification because you are a member of Ubuntu Touch seeded packages, which is subscribed to xorg in Ubuntu. https://bugs.launchpad.net/bugs/1416186 Title: Periodically loss of backlight control Status in xorg package in Ubuntu: Incomplete Bug description: Periodically there is a loss of control of the backlight control where trying to brighten the screen or dim it with the keyboard controls does not function and remains in its current state. ProblemType: Bug DistroRelease: Ubuntu 14.10 Package: xorg 1:7.7+7ubuntu2 ProcVersionSignature: Ubuntu 3.16.0-29.39-generic 3.16.7-ckt2 Uname: Linux 3.16.0-29-generic x86_64 .tmp.unity.support.test.0: ApportVersion: 2.14.7-0ubuntu8.1 Architecture: amd64 CompizPlugins: No value set for `/apps/compiz-1/general/screen0/options/active_plugins' CompositorRunning: compiz CompositorUnredirectDriverBlacklist: '(nouveau|Intel).*Mesa 8.0' CompositorUnredirectFSW: true CurrentDesktop: Unity Date: Thu Jan 29 21:05:25 2015 DistUpgraded: Fresh install DistroCodename: utopic DistroVariant: ubuntu EcryptfsInUse: Yes ExtraDebuggingInterest: Yes, if not too technical GraphicsCard: Advanced Micro Devices, Inc. [AMD/ATI] Richland [Radeon HD 8650G] [1002:990b] (prog-if 00 [VGA controller]) Subsystem: Hewlett-Packard Company Device [103c:198a] Advanced Micro Devices, Inc. [AMD/ATI] Mars [Radeon HD 8670A/8670M/8750M] [1002:6600] (rev ff) (prog-if ff) InstallationDate: Installed on 2015-01-29 (0 days ago) InstallationMedia: Ubuntu 14.10 "Utopic Unicorn" - Alpha amd64 (20141015) MachineType: Hewlett-Packard HP ENVY TS 15 Notebook PC ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-3.16.0-29-generic.efi.signed root=UUID=1cc26cb0-3476-4abf-a12e-acac53ba8537 ro quiet splash vt.handoff=7 SourcePackage: xorg Symptom: display UpgradeStatus: No upgrade log present (probably fresh install) dmi.bios.date: 11/06/2014 dmi.bios.vendor: Insyde dmi.bios.version: F.18 dmi.board.asset.tag: Base Board Asset Tag dmi.board.name: 198A dmi.board.vendor: Hewlett-Packard dmi.board.version: KBC Version 03.14 dmi.chassis.asset.tag: 5CG32129MN dmi.chassis.type: 10 dmi.chassis.vendor: Hewlett-Packard dmi.chassis.version: Chassis Version dmi.modalias: dmi:bvnInsyde:bvrF.18:bd11/06/2014:svnHewlett-Packard:pnHPENVYTS15NotebookPC:pvr0888100000305B00000320000:rvnHewlett-Packard:rn198A:rvrKBCVersion03.14:cvnHewlett-Packard:ct10:cvrChassisVersion: dmi.product.name: HP ENVY TS 15 Notebook PC dmi.product.version: 0888100000305B00000320000 dmi.sys.vendor: Hewlett-Packard version.compiz: compiz 1:0.9.12+14.10.20140918-0ubuntu1 version.ia32-libs: ia32-libs N/A version.libdrm2: libdrm2 2.4.56-1 version.libgl1-mesa-dri: libgl1-mesa-dri 10.3.2-0ubuntu0.1 version.libgl1-mesa-dri-experimental: libgl1-mesa-dri-experimental N/A version.libgl1-mesa-glx: libgl1-mesa-glx 10.3.2-0ubuntu0.1 version.xserver-xorg-core: xserver-xorg-core 2:1.16.0-1ubuntu1.2 version.xserver-xorg-input-evdev: xserver-xorg-input-evdev 1:2.9.0-1ubuntu2 version.xserver-xorg-video-ati: xserver-xorg-video-ati 1:7.4.0-2ubuntu2 version.xserver-xorg-video-intel: xserver-xorg-video-intel 2:2.99.914-1~exp1ubuntu4.1 version.xserver-xorg-video-nouveau: xserver-xorg-video-nouveau 1:1.0.11-1ubuntu2 xserver.bootTime: Thu Jan 29 20:59:15 2015 xserver.configfile: default xserver.errors: RADEON(G0): [XvMC] Failed to initialize extension. xserver.logfile: /var/log/Xorg.0.log xserver.version: 2:1.16.0-1ubuntu1.2 xserver.video_driver: radeon To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/xorg/+bug/1416186/+subscriptions -- Mailing list: https://launchpad.net/~touch-packages Post to : touch-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~touch-packages More help : https://help.launchpad.net/ListHelp
