I looked into the screen brightness issue a little bit a while back. The reason that the brightness gets set to maximum at boot is that the firmware doesn't initialize some state memory with the brightness at boot, so when the brightness is read from the firmware it gets back a value which corresponds to the maximum brightness. When Linux boots the acpi_video driver does some tests of various functionality which includes reading the current brightness and writing it back, which has the effect of setting the screen brightness to maximum.
What OS X seems to do is to write the screen brightness to an EFI variable, so either acpi_video would need to know to look for that variable or else acpi_video just shouldn't be used for brightness on Apple hardware. As a workaround you could pass acpi_backlight=vendor on the kernel command line to disable use of the ACPI backlight interface. Not sure about the keyboard backlight, but it could be something similar. -- 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/1279308 Title: [MacBook Air 6,2] screen backlight brightness and keyboard light turn into fully-on after Grub boot with i915 driver Status in “linux” package in Ubuntu: Incomplete Bug description: Problem: Both the screen backlight brightness and keyboard light are turned on during the booting as tested on ubuntu 12.04.3, 12.04.4, and 13.10. Due to installation problem on 12.04, it's only tested with the live system. What's expected: the brightness state before booting is preserved. Some trials: the problem should be on i915 driver even in single user mode. Tried "nomodeset" kerenel arguement can avoid the problem, but X will fail to start. --- ApportVersion: 2.12.5-0ubuntu2 Architecture: amd64 AudioDevicesInUse: USER PID ACCESS COMMAND /dev/snd/controlC0: john 1776 F.... pulseaudio /dev/snd/controlC1: john 1776 F.... pulseaudio DistroRelease: Ubuntu 13.10 InstallationDate: Installed on 2014-02-10 (1 days ago) InstallationMedia: Ubuntu 13.10 "Saucy Salamander" - Release amd64 (20131016.1) MachineType: Apple Inc. MacBookAir6,2 MarkForUpload: True NonfreeKernelModules: wl Package: linux (not installed) ProcFB: 0 inteldrmfb ProcKernelCmdLine: BOOT_IMAGE=/@/boot/vmlinuz-3.11.0-15-generic.efi.signed root=UUID=b52fef82-3749-4624-a352-bd750dcb7e65 ro rootflags=subvol=@ quiet splash vt.handoff=7 ProcVersionSignature: Ubuntu 3.11.0-15.25-generic 3.11.10 RelatedPackageVersions: linux-restricted-modules-3.11.0-15-generic N/A linux-backports-modules-3.11.0-15-generic N/A linux-firmware 1.116 Tags: saucy Uname: Linux 3.11.0-15-generic x86_64 UpgradeStatus: No upgrade log present (probably fresh install) UserGroups: adm cdrom dip lpadmin plugdev sambashare sudo dmi.bios.date: 11/12/2013 dmi.bios.vendor: Apple Inc. dmi.bios.version: MBA61.88Z.0099.B07.1311121319 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.B07.1311121319:bd11/12/2013: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. To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1279308/+subscriptions -- Mailing list: https://launchpad.net/~kernel-packages Post to : [email protected] Unsubscribe : https://launchpad.net/~kernel-packages More help : https://help.launchpad.net/ListHelp
