2.6.28 regression: xbacklight broken on ThinkPad X61s

Hi,

xbacklight is broken as of 2.6.28 on my ThinkPad X61s. It works with 2.6.27(.8) The difference I can see between both kernels is that 2.6.27 has 2 backlight ACPI devices, whereas 2.6.28 only has one device. With 2.6.28, I can use xbacklight and see the values change in xbacklight -get, but the actual display brightness doesn't change.

Attached are 2 files with diagnostic output from 2.6.27 and 2.6.28. Any hints how to solve or debug this?

Regards,
Tino

dmesg:

acpi device:03: registered as cooling_device2
input: Video Bus as /class/input/input8
ACPI: Video Device [VID] (multi-head: yes rom: no post: no) acpi device:08: registered as cooling_device3
input: Video Bus as /class/input/input9
ACPI: Video Device [VID1] (multi-head: yes rom: no post: no)

xrandr --prop:

Screen 0: minimum 320 x 200, current 1024 x 768, maximum 1024 x 1024 VGA disconnected (normal left inverted right x axis y axis)
LVDS connected 1024x768+0+0 (normal left inverted right x axis y axis) 246mm x 185mm

	EDID_DATA:
		00ffffffffffff0030ae004000000000
		000f010380191278eaed7591574f8b26
		21505421080001010101010101010101
		01010101010128150040410026301888
		3600f6b900000018ed10004041002630
		18883600f6b9000000180000000f0061
		43326143280f01004ca3584a000000fe
		004c544e313231584a2d4c30370a0000
	PANEL_FITTING: full
		supported: center       full_aspect  full        
	BACKLIGHT_CONTROL: kernel
		supported: native       legacy       combination  kernel      
	BACKLIGHT: 10 (0x0000000a) range:  (0,15)
   1024x768       50.0*+   60.0     40.0  
   800x600        60.3  
   640x480        60.0     59.9

Xorg log:

(II) intel(0): found backlight control method /sys/class/backlight/acpi_video1

sysfs:

/sys/class/backlight/acpi_video0/subsystem/acpi_video1/bl_power:0 /sys/class/backlight/acpi_video0/subsystem/acpi_video1/brightness:10 /sys/class/backlight/acpi_video0/subsystem/acpi_video1/actual_brightness:10 /sys/class/backlight/acpi_video0/subsystem/acpi_video1/max_brightness:15 /sys/class/backlight/acpi_video0/subsystem/acpi_video1/power/wakeup:
/sys/class/backlight/acpi_video0/bl_power:0 /sys/class/backlight/acpi_video0/brightness:9 /sys/class/backlight/acpi_video0/actual_brightness:12 /sys/class/backlight/acpi_video0/max_brightness:15 /sys/class/backlight/acpi_video0/power/wakeup:
/sys/class/backlight/acpi_video1/subsystem/acpi_video0/bl_power:0 /sys/class/backlight/acpi_video1/subsystem/acpi_video0/brightness:9 /sys/class/backlight/acpi_video1/subsystem/acpi_video0/actual_brightness:12 /sys/class/backlight/acpi_video1/subsystem/acpi_video0/max_brightness:15 /sys/class/backlight/acpi_video1/subsystem/acpi_video0/power/wakeup:
/sys/class/backlight/acpi_video1/bl_power:0 /sys/class/backlight/acpi_video1/brightness:10 /sys/class/backlight/acpi_video1/actual_brightness:10 /sys/class/backlight/acpi_video1/max_brightness:15 /sys/class/backlight/acpi_video1/power/wakeup:

dmesg:

acpi device:03: registered as cooling_device2
input: Video Bus as /class/input/input7
ACPI: Video Device [VID] (multi-head: yes rom: no post: no)

xrandr --prop:

Screen 0: minimum 320 x 200, current 1024 x 768, maximum 1024 x 1024 VGA disconnected (normal left inverted right x axis y axis)
LVDS connected 1024x768+0+0 (normal left inverted right x axis y axis) 246mm x 185mm

	EDID_DATA:
		00ffffffffffff0030ae004000000000
		000f010380191278eaed7591574f8b26
		21505421080001010101010101010101
		01010101010128150040410026301888
		3600f6b900000018ed10004041002630
		18883600f6b9000000180000000f0061
		43326143280f01004ca3584a000000fe
		004c544e313231584a2d4c30370a0000
	PANEL_FITTING: full
		supported: center       full_aspect  full        
	BACKLIGHT_CONTROL: kernel
		supported: native       legacy       combination  kernel      
	BACKLIGHT: 5 (0x00000005) range:  (0,15)
   1024x768       50.0*+   60.0     40.0  
   800x600        60.3  
   640x480        60.0     59.9

Xorg log:

(II) intel(0): found backlight control method /sys/class/backlight/acpi_video0

sysfs:

/sys/class/backlight/acpi_video0/actual_brightness:5 /sys/class/backlight/acpi_video0/bl_power:0 /sys/class/backlight/acpi_video0/brightness:5 /sys/class/backlight/acpi_video0/max_brightness:15 /sys/class/backlight/acpi_video0/power/wakeup:
/sys/class/backlight/acpi_video0/subsystem/acpi_video0/bl_power:0 /sys/class/backlight/acpi_video0/subsystem/acpi_video0/brightness:5 /sys/class/backlight/acpi_video0/subsystem/acpi_video0/actual_brightness:5 /sys/class/backlight/acpi_video0/subsystem/acpi_video0/max_brightness:15 /sys/class/backlight/acpi_video0/subsystem/acpi_video0/power/wakeup:

hmm, this regression is caused by commit
22c13f9d8179f4c9caecfcb60a95214562b9addc

but the real problem is that the IGD OpRegion doesn't work well on this laptop.

please file a bug at bugzilla.kernel.org and attach the acpidump there.

thanks,
rui

I suspect that the issue is actually that the opregion code works fine but i915 interrupts are failing to work properly, which we've seen a couple of cases of. Jesse?

Matthew Garrett | [email protected]