Bug 40862

Have you tried "echo <number> > /sys/class/backlight/acpi_video0/brightness"?

Please attach the output of acpidump and dmesg.

(In reply to comment #1)
> Have you tried "echo <number> > /sys/class/backlight/acpi_video0/brightness"?

No, it does not work.

> Please attach the output of acpidump and dmesg.

I will add attachments of both.

Created attachment 68592 [details]
acpidump

Created attachment 68602 [details]
dmesg output

I think you can bisect bisect between 2.6.37 or earlier and 3.0.1 to identify whether the bug is a regression.

Same problem in reported bug 41112

I don't think this is a regression.

Vasileios and Pali,
Can you please verify if the problem still exists in the latest upstream
kernel?

I have linux kernel
Linux Pali-EliteBook 3.2.0-4-generic #10-Ubuntu SMP Wed Dec 14 02:11:20 UTC 2011 x86_64 x86_64 x86_64 GNU/Linux
and problem is still not fixed. All versions which I tested (2.6.35 to 3.2) have this problem.

More info: This problem seems to be on new EliteBooks 8x60 which have Radeon graphics card. Model with integrated Intel have no problem. Writing any value to "/sys/class/backlight/acpi_video0/brightness" has no effect. And some people said that this problem is only with open source radeon kms driver - when they used fglrx there was no brightness problem. See http://www.linlap.com/wiki/hp+elitebook+8460p

See also thread on linux-acpi where I reported this problem: http://www.spinics.net/lists/linux-acpi/msg33107.html

*** Bug 41112 has been marked as a duplicate of this bug. ***

More info is here: http://www.mail-archive.com/platform-driver-x86@vger.kernel.org/msg02862.html
Brightness control maybe need to be implemented in radeon driver...

Hi any news about this problem? What other info do you need?

Just upgraded my system from kernel-3.3.5 (gentoo-sources) to 3.4.0. The problem persisted in both 3.3 and now in 3.4 series kernels.

What more info can we provide in order to help debug this issue?

I also would like to offer my help. That I have to reboot my laptop every time I want to change the brightness of the display isn't a really "workaround".
kr
rb

this issue is in NEEDINFO state - what additional information is needed ?
maybe i can provide it

What information do you need? Is not info in this thread enought?
http://www.mail-archive.com/platform-driver-x86@vger.kernel.org/msg02862.html

Also, maybe this new code for radeon driver is relevant:
http://lists.freedesktop.org/archives/dri-devel/2012-July/025517.html

Ok, I tested patches from this post:
http://lists.freedesktop.org/archives/dri-devel/2012-July/025535.html

And it really can change brighntes on HP EliteBook 8460p (with Radeon 6470M) via file:
/sys/class/backlight/radeon_bl/brightness

(In reply to comment #17)
> Ok, I tested patches from this post:
> http://lists.freedesktop.org/archives/dri-devel/2012-July/025535.html
> 
> And it really can change brighntes on HP EliteBook 8460p (with Radeon 6470M)
> via file:
> /sys/class/backlight/radeon_bl/brightness

Ok, we seem to have some progress here. Against which kernel version did you try the patch?

Not being able to reduce the brightness is an issue. I'm sitting at my balcony with 30°C and the full brightness is really annoying. Not to mention it attracts many mosquitoes. :-)

to me, the problem seems to be that
1) ACPI backlight control does not work
2) we're missing the backlight control from Radeon DRM driver.

Is there any progress regarding this issue? I'm already on kernel 3.6.8 and this is a big issue. Not to mention that I replaced the faulty screen (it did not light up at all) a couple of days ago and I'm wondering if my issue had to do with the 100% full brightness setting at all times.

Great news. I just booted with kernel 3.7.0 (Gentoo box) in my laptop and the brightness control keys work fine! The screen brightness is reduced/increased as needed.

So, I guess from kernel 3.7.0 this bug can be considered closed.

Yes, above patches are in 3.7, so bug is fixed.

commit 9e05b2f49eb9484e857e9b6c70dea3bbbe564290
Author: Alex Deucher <alexander.deucher@amd.com>
Date:   Wed Jul 18 13:28:52 2012 -0400

    drm/radeon: add new AMD ACPI header and update relevant code (v2)
    
    Add a new header that defines the AMD ACPI interface used
    for laptops, PowerXpress, and chipset specific functionality
    and update the current code to use it.
    
    Todo:
    - properly verify the ACPI interfaces
    - hook up and handle ACPI notifications
    - make PX code more robust
    - implement PCIe Gen and width switching using ACPI
    
    v2: fix typo in header
    
    Signed-off-by: Alex Deucher <alexander.deucher@amd.com>