Bug#587014: screen brightness can't be modified on some Panasonic laptops

[Nicolas Limare]

I also received a message reportin for this bug on a Panasonic CF-52.

Can I in any way help this bug get more attention?

Just in case, I am at 27C3 now, with my laptop, so if anyone there
wants to directly investigate the issue just let me know.

--
Nicolas LIMARE
http://nicolas.limare.net/ pgp:0xFA423F4F

[Nicolas Limare]

The latest squeeze kernel (2.6.32-29) improved the situation. Now,
when the system boots, the backlight is not automatically set to its
maximum level. So, it is possible to set the backlight level
during the BIOS boot phase, and keep this level.

This is a big improvement since now the system is usable in a dark
environment, even is adjusting the backlight level requires a reboot.

Hotkeys still dont't work, and result in the following message in the
system console:
ACPI: Failed to switch the brightness

Playing with /sys/class/backlight/panasonic/brightness doewsn't work
either.

[Thomas Renninger]

On Wednesday 29 December 2010 16:24:28 Nicolas Limare wrote:
> I also received a message reportin for this bug on a Panasonic CF-52.
>
> Can I in any way help this bug get more attention?
>

What is Bug#587014? Do you have a link?

Panasonic is the only driver which will always try to use
native backlight switching (may conflict with video.ko?).

drivers/platform/x86/panasonic-laptop.c misses a line like:
if (acpi_video_backlight_support()

The reason panasonic was not changed to differ acpi/native
switching was because ACPI based switching resulted in 2 missing
backlight states. But this was fixed by better (more Windows compatible)
parsing the backlight ACPI states and they should be all availeable
with ACPI as well. Len Brown has/had such a machine.

> Just in case, I am at 27C3 now, with my laptop, so if anyone there
> wants to directly investigate the issue just let me know.

No idea whether it's above, there is not much info about the issue,
but you could try in this direction. Tell me if it helps or if
you need assistance to try things out.

Ah, and there is the "global methods execution is broken":
https://bugzilla.kernel.org/show_bug.cgi?id=19462
which very much affects Panasonics.
Make sure your kernel has the git commit mentioned in the
last comment.

Thomas

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[Nicolas Limare]

On Mon, Jan 03, 2011 at 10:40:03AM +0100, Thomas Renninger wrote:
> On Wednesday 29 December 2010 16:24:28 Nicolas Limare wrote:
> > I also received a message reportin for this bug on a Panasonic CF-52.
> >
> > Can I in any way help this bug get more attention?
> >
> What is Bug#587014? Do you have a link?

Debian bug report #587014
-> http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=587014

Linked to the Ubuntu bug report #588983
-> https://bugs.launchpad.net/ubuntu/+source/linux/+bug/588983

Thanks a lot for your help Thomas.
I can't confirm your diagnostics, because I'm not in a position to
recompile the kernel, but hopefully these hints will help others
resolve this bug.

[Cristopher Camacho]

No, there is no. Only the /sys/class/backlight/panasonic/ directory is present.

Cristopher

On Tue, Jan 4, 2011 at 5:33 AM, Matthew Garrett <mj...@srcf.ucam.org> wrote:
> Is there a /sys/class/backlight/acpi_video0 directory as well as the
> Panasonic one?
>
> --
> Matthew Garrett | mj...@srcf.ucam.org

[Matthew Garrett]

On Tue, Jan 04, 2011 at 06:14:40AM +0800, Cristopher Camacho wrote:
> No, there is no. Only the /sys/class/backlight/panasonic/ directory is present.

Can you attach the output of the acpidump command on your system?

[Matthew Garrett]

Well, that's odd. There's certainly support for ACPI backlight control
in your firmware, and it goes via opregion so it should work correctly.
I think the thing to do here is to have the panasonic driver bail if
there's ACPI backlight support, and then figure out why the ACPI video
driver isn't working for you.