Backlight control does not work and there are no entries in /sys/class/backlight. When I boot my system with the option GRUB_CMDLINE_LINUX_DEFAULT="acpi_backlight=vendor" I can change the brightness with the command xrandr on a terminal. I attach all the system information about this problem. ProblemType: Bug DistroRelease: Ubuntu 17.10 Package: linux-image-4.13.0-37-generic 4.13.0-37.42 ProcVersionSignature: Ubuntu 4.13.0-37.42-generic 4.13.13 Uname: Linux 4.13.0-37-generic x86_64 ApportVersion: 2.20.7-0ubuntu3.7 Architecture: amd64 AudioDevicesInUse: USER PID ACCESS COMMAND /dev/snd/controlC0: victor 2932 F.... pulseaudio CurrentDesktop: ubuntu:GNOME Date: Sat Mar 24 07:22:05 2018 InstallationDate: Installed on 2018-03-04 (19 days ago) InstallationMedia: Ubuntu 17.10 "Artful Aardvark" - Release amd64 (20180105.1) MachineType: Apple Inc. MacBookAir3,2 ProcEnviron: TERM=xterm-256color PATH=(custom, no user) XDG_RUNTIME_DIR=<set> LANG=es_ES.UTF-8 SHELL=/bin/bash ProcFB: 0 nouveaufb ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-4.13.0-37-generic.efi.signed root=UUID=dd2bcce2-7d14-4df7-b7c8-6aea4fbb9c13 ro acpi_backlight=vendor RelatedPackageVersions: linux-restricted-modules-4.13.0-37-generic N/A linux-backports-modules-4.13.0-37-generic N/A linux-firmware 1.169.3 SourcePackage: linux UpgradeStatus: No upgrade log present (probably fresh install) dmi.bios.date: 11/18/10 dmi.bios.vendor: Apple Inc. dmi.bios.version: MBA31.88Z.0061.B01.1011181342 dmi.board.asset.tag: Base Board Asset Tag# dmi.board.name: Mac-942C5DF58193131B dmi.board.vendor: Apple Inc. dmi.board.version: MacBookAir3,2 dmi.chassis.type: 10 dmi.chassis.vendor: Apple Inc. dmi.chassis.version: Mac-942C5DF58193131B dmi.modalias: dmi:bvnAppleInc.:bvrMBA31.88Z.0061.B01.1011181342:bd11/18/10:svnAppleInc.:pnMacBookAir3,2:pvr1.0:rvnAppleInc.:rnMac-942C5DF58193131B:rvrMacBookAir3,2:cvnAppleInc.:ct10:cvrMac-942C5DF58193131B: dmi.product.family: MacBook dmi.product.name: MacBookAir3,2 dmi.product.version: 1.0 dmi.sys.vendor: Apple Inc. More info: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1758496
IMO, you should file this bug against freedesktop.org, and we have graphics expert there to help you. But anyway, I can check why ACPI backlight does not work for you if you can attach the acpidump output, although I don't think this helps a lot.
Created attachment 276419 [details] acpidump from MacBookAir3,2 acpidump from MacBookAir3,2
Thanks, Zhang! I'll file this bug against freedesktop.org too.
(In reply to victor from comment #3) > Thanks, Zhang! I'll file this bug against freedesktop.org too. https://bugs.freedesktop.org/show_bug.cgi?id=106869
I checked your BIOS and it is confirmed that there is no _BCM/_BQC method, which means that ACPI backlight control is not available. So I guess we indeed need the native backlight control on this platform. Bug closed.
Thansk, Zhang! Excuseme, but I have a _BCL method in my DSDT.dat file, see line: Method (_BCL, 0, NotSerialized) // _BCL: Brightness Control Levels You can see it in the attached file https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1758496/+attachment/5088858/+files/dsdt.dsl Is it the name of the method the problem?
_BCL provides the available backlight levels, but _BCM is the control method to set the backlight level. There is ACPI backlight control when both _BCL and _BCM exist.
Ok Zang, I understand. Is possible you help me to implement this methods? In my hand, I have firmware tools in my ubuntu distro.
the ACPI control methods are written by BIOS engineers, and Linux kernel is just the consumer of these methods. Sorry that I can not help you here as it is not a kernel ACPI bug. Again, I'd propose you to keep tracking the freedesktop bug report, as the graphics driver has its own way to set backlight. Bug closed. Please feel free to reopen it if you still have any questions.
Thank you anyway. That's right, I already did, here it is https://bugs.freedesktop.org/show_bug.cgi?id=106869