[4.8 regression][ThinkPad X230] brightness change keys do not work any more

[Martin Pitt]

With yakkety's recent update from linux 4.4 to 4.8 my brightness keys stopped working. They are not handled in software via evdev events (on most platforms you just get a KEY_BRIGHTNESS{UP<DOWN}), but are hardwired in the kernel driver.

With both 4.4 and 4.8 dmesg shows:

[ 10.114072] thinkpad_acpi: This ThinkPad has standard ACPI backlight brightness control, supported by the ACPI video driver
[ 10.114073] thinkpad_acpi: Disabling thinkpad-acpi brightness events by default...

In 4.4 I have these two devices in /sys:

/sys/class/backlight/acpi_video0/:
-r--r--r-- 1 root root 4096 Sep 22 09:45 actual_brightness
-rw-r--r-- 1 root root 4096 Sep 22 09:45 bl_power
-rw-r--r-- 1 root root 4096 Sep 22 09:45 brightness
lrwxrwxrwx 1 root root 0 Sep 22 09:45 device -> ../../../0000:00:02.0
-r--r--r-- 1 root root 4096 Sep 22 09:45 max_brightness
drwxr-xr-x 2 root root 0 Sep 22 09:45 power
lrwxrwxrwx 1 root root 0 Sep 22 09:45 subsystem -> ../../../../../class/backlight
-r--r--r-- 1 root root 4096 Sep 22 09:45 type
-rw-r--r-- 1 root root 4096 Sep 22 09:45 uevent

/sys/class/backlight/intel_backlight/:
-r--r--r-- 1 root root 4096 Sep 22 09:46 actual_brightness
-rw-r--r-- 1 root root 4096 Sep 22 09:46 bl_power
-rw-r--r-- 1 root root 4096 Sep 22 09:46 brightness
lrwxrwxrwx 1 root root 0 Sep 22 09:46 device -> ../../card0-LVDS-1
-r--r--r-- 1 root root 4096 Sep 22 09:46 max_brightness
drwxr-xr-x 2 root root 0 Sep 22 09:46 power
lrwxrwxrwx 1 root root 0 Sep 22 09:46 subsystem -> ../../../../../../../class/backlight
-r--r--r-- 1 root root 4096 Sep 22 09:46 type
-rw-r--r-- 1 root root 4096 Sep 22 09:46 uevent

While in 4.8 I only have intel_backlight and acpi_video0 is missing completely.

I. e. in 4.4 this command works:

  echo 12 | sudo tee /sys/class/backlight/acpi_video0/brightness

and I suppose this is the moral equivalent of what happens when I press the brightness keys, i. e. these keys seem to be handled by the acpi_video0 driver instead of intel_backlight.

The intel driver still actually works, I can do

  echo 1000 | sudo tee /sys/class/backlight/intel_backlight/brightness

but this isn't connected to the keys any more.

ProblemType: Bug
DistroRelease: Ubuntu 16.10
Package: linux-image-4.8.0-11-generic 4.8.0-11.12
ProcVersionSignature: Ubuntu 4.8.0-11.12-generic 4.8.0-rc6
Uname: Linux 4.8.0-11-generic x86_64
ApportVersion: 2.20.3-0ubuntu7
Architecture: amd64
AudioDevicesInUse:
 USER PID ACCESS COMMAND
 /dev/snd/pcmC0D0c: martin 3049 F...m pulseaudio
 /dev/snd/pcmC0D0p: martin 3049 F...m pulseaudio
 /dev/snd/controlC0: martin 3049 F.... pulseaudio
Date: Thu Sep 22 09:42:56 2016
EcryptfsInUse: Yes
MachineType: LENOVO 2324CTO
ProcEnviron:
 TERM=linux
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=de_DE.UTF-8
 SHELL=/bin/bash
ProcFB: 0 inteldrmfb
ProcKernelCmdLine: BOOT_IMAGE=/@/boot/vmlinuz-4.8.0-11-generic.efi.signed root=UUID=f86539b0-3a1b-4372-83b0-acdd029ade68 ro rootflags=subvol=@ systemd.debug-shell
RelatedPackageVersions:
 linux-restricted-modules-4.8.0-11-generic N/A
 linux-backports-modules-4.8.0-11-generic N/A
 linux-firmware 1.161
SourcePackage: linux
UpgradeStatus: No upgrade log present (probably fresh install)
dmi.bios.date: 07/09/2013
dmi.bios.vendor: LENOVO
dmi.bios.version: G2ET95WW (2.55 )
dmi.board.asset.tag: Not Available
dmi.board.name: 2324CTO
dmi.board.vendor: LENOVO
dmi.board.version: 0B98401 Pro
dmi.chassis.asset.tag: No Asset Information
dmi.chassis.type: 10
dmi.chassis.vendor: LENOVO
dmi.chassis.version: Not Available
dmi.modalias: dmi:bvnLENOVO:bvrG2ET95WW(2.55):bd07/09/2013:svnLENOVO:pn2324CTO:pvrThinkPadX230:rvnLENOVO:rn2324CTO:rvr0B98401Pro:cvnLENOVO:ct10:cvrNotAvailable:
dmi.product.name: 2324CTO
dmi.product.version: ThinkPad X230
dmi.sys.vendor: LENOVO

[Brad Figg (brad-figg)]

This change was made by a bot.

[Colin Ian King (colin-king)]

OK, I've got an X230 where this works for me on 4.4 and 4.8, so if it's being handled by the ACPI driver then we may have some weird ACPI issue going on. Can you dump the acpi tables so I can sanity check these to see what is different from your X230 and mine?

Please install acpica-tools and run:

sudo acpidump > acpidump-x230.log

and attach that to the bug report

[Martin Pitt (pitti)]

So this did break with -10 and -11, but was fixed again in -14.