I'm not so certian it is a kernel error now after some digging deeper. I've tried all of the following kernels:
3.11.10-03111015-generic 3.12.20-031220-generic 3.14.2-031402-generic 3.14.23-031423-generic 3.16.0-10-generic 3.16.0-14-generic 3.16.0-18-generic 3.16.0-23-generic 3.16.0-24-generic 3.17.2-031702-generic 3.18.0-031800rc4-generic I tried downloading and booting from the currently available Utopic iso, and as well as the latest daily image of Vivid. On the Utopic iso boot, running kernel 3.16.0-23-generic (according to uname -a), the brightness controls function absolutely fine. On the Vivid iso boot, the brightness controls no longer work. Booting my machine from the same kernel version as what was working on the iso, 3.16.0-23, the controls also still don't work. Additionally, I am noticing the following dmesg errors: On brightness down: [ 64.883616] ACPI Error: Method parse/execution failed [\_SB_.PCI0.GFX0.DWBL] (Node ffff88011a433500), AE_AML_UNINITIALIZED_ELEMENT (20140424/psparse-536) [ 64.883626] ACPI Error: Method parse/execution failed [\_SB_.PCI0.LPCB.EC0_._Q0E] (Node ffff88011a442c58), AE_AML_UNINITIALIZED_ELEMENT (20140424/psparse-536) On brightness up: [ 64.888952] ACPI Error: Method parse/execution failed [\_SB_.PCI0.GFX0.UPBL] (Node ffff88011a4334d8), AE_AML_UNINITIALIZED_ELEMENT (20140424/psparse-536) [ 64.888959] ACPI Error: Method parse/execution failed [\_SB_.PCI0.LPCB.EC0_._Q0F] (Node ffff88011a442c80), AE_AML_UNINITIALIZED_ELEMENT (20140424/psparse-536) Could there have been a userland change that is causing some mismatch or somesuch? ** Changed in: linux (Ubuntu) Status: Incomplete => Confirmed -- You received this bug notification because you are a member of Kernel Packages, which is subscribed to linux in Ubuntu. https://bugs.launchpad.net/bugs/1392101 Title: Brightness controls not working on intel igfx Status in “linux” package in Ubuntu: Confirmed Bug description: Brightness controls not working for me in Vivid Vervet as of 1-2 weeks ago. Was confirmed working on Utopic Unicorn. Hotkeys for brightness up & down non-functioning, Hotkey for display on/off still works. Gnome control center (brightness & lock) does not show brightness slider. What does work is "echo $value > /sys/class/backlight/intel_backlight/brightness" as root for any $value of 0 - 2047 Running on an Asus S400C Laptop. kernel: x86_64 3.16.0-24-generic lspci: 00:02.0 VGA compatible controller: Intel Corporation 3rd Gen Core processor Graphics Controller (rev 09) lsb_release: Description: Ubuntu Vivid Vervet (development branch) Release: 15.04 ProblemType: Bug DistroRelease: Ubuntu 15.04 Package: linux-image-3.16.0-24-generic 3.16.0-24.32 ProcVersionSignature: Ubuntu 3.16.0-24.32-generic 3.16.4 Uname: Linux 3.16.0-24-generic x86_64 ApportVersion: 2.14.7-0ubuntu10 Architecture: amd64 AudioDevicesInUse: USER PID ACCESS COMMAND /dev/snd/controlC0: martin 1970 F.... pulseaudio CurrentDesktop: Unity Date: Wed Nov 12 16:06:27 2014 HibernationDevice: RESUME=UUID=a7b59988-1d75-4f19-8fd8-3c9a08c38e8d InstallationDate: Installed on 2014-08-21 (83 days ago) InstallationMedia: Ubuntu 14.10 "Utopic Unicorn" - Alpha amd64 (20140820) MachineType: ASUSTeK COMPUTER INC. S400CA ProcFB: 0 inteldrmfb ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-3.16.0-24-generic.efi.signed root=UUID=e2aa386f-a710-4fb4-ba6e-5d233c6b7b25 ro quiet splash vt.handoff=7 RelatedPackageVersions: linux-restricted-modules-3.16.0-24-generic N/A linux-backports-modules-3.16.0-24-generic N/A linux-firmware 1.138 SourcePackage: linux UpgradeStatus: No upgrade log present (probably fresh install) dmi.bios.date: 01/27/2014 dmi.bios.vendor: American Megatrends Inc. dmi.bios.version: S400CA.210 dmi.board.asset.tag: ATN12345678901234567 dmi.board.name: S400CA 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.:bvrS400CA.210:bd01/27/2014:svnASUSTeKCOMPUTERINC.:pnS400CA:pvr1.0:rvnASUSTeKCOMPUTERINC.:rnS400CA:rvr1.0:cvnASUSTeKCOMPUTERINC.:ct10:cvr1.0: dmi.product.name: S400CA dmi.product.version: 1.0 dmi.sys.vendor: ASUSTeK COMPUTER INC. To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1392101/+subscriptions -- Mailing list: https://launchpad.net/~kernel-packages Post to : kernel-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~kernel-packages More help : https://help.launchpad.net/ListHelp