Bug 15631

Summary:	Brightness function is unresponsive on a HP DV3-2105TU laptop
Product:	Drivers	Reporter:	Michael (michael_matkovic)
Component:	Platform	Assignee:	Zhang Rui (rui.zhang)
Status:	RESOLVED PATCH_ALREADY_AVAILABLE
Severity:	normal	CC:	rui.zhang
Priority:	P1
Hardware:	All
OS:	Linux
Kernel Version:	2.6.32-17-generic	Subsystem:
Regression:	No	Bisected commit-id:
Bug Depends on:
Bug Blocks:	56331
Attachments:	output of acpidump

Description Michael 2010-03-25 22:03:33 UTC

Screen brightness is unresponsive to Fn+F7 and Fn+F8 key presses, however the values in the following paths do change accordingly:

/proc/acpi/video/OVGA/DD03/brightness
/sys/class/backlight/acpi_video0/brightness

I found an error message in /var/log/messages which may be a bug in the kernel module drivers/acpi/video.ko

[Firmware Bug]: ACPI: ACPI brightness control misses _BQC function

The laptop uses Intel GMA 4500MHD.
Please advise what information / output you require to debug this issue.

Comment 1 Zhang Rui 2010-03-26 02:22:42 UTC

please attach the acpidump output of this laptop.

Comment 2 Michael 2010-03-26 05:55:58 UTC

Created attachment 25720 [details]
output of acpidump

Comment 3 Zhang Rui 2010-03-29 07:31:57 UTC

please set CONFIG_ACPI_WMI and see if it helps.

Comment 4 Michael 2010-03-29 08:29:07 UTC

(In reply to comment #3)
> please set CONFIG_ACPI_WMI and see if it helps.

In the current (Ubuntu 2.6.32-17-generic) kernel it's already set:
CONFIG_ACPI_WMI=y


I'm not sure if this will help, but I had a look in the kernel source and found comments which may possibly be related to the "ACPI brightness control misses _BQC function" message I get in dmesg.
In drivers/acpi/video.c there is a comment regarding _BCQ as opposed to _BQC which says:

/* Some buggy BIOS uses _BCQ instead of _BQC */

which appears in the acpi_video_device_cap struct.

Could it be likely this BIOS may be doing similar?

Comment 5 Michael 2010-05-08 03:08:02 UTC

My current kernel is now 2.6.32-22-generic. Unfortunately the problem remains. Is there an update to this problem? It's been a while.

Comment 6 Michael 2010-06-04 04:43:58 UTC

I found the fix here:
https://bugs.launchpad.net/ubuntu/+source/linux/+bug/568611/comments/11

Technically it addressed a fault with brightness functionality for a Dell Studio 1558, however once I installed the two .deb files as directed (and rebooted), the brightness function worked.

Kamal stated this was a preliminary test fix. It'd be good to have it progress to be integrated with the next kernel release. As he suggested, it's for '...Dell Studios or any other i915-based systems."

Comment 7 Michael 2010-06-04 04:46:13 UTC

On 2nd thought, since he released 3 patches, I'll mark this as RESOLVED PATCH_ALREADY_AVAILABLE