linux-kernel - Re: i915/kms/backlight-combo mode problem

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Message-Id: <201105081605.46617@rk-nord.at>
Date:	Sun, 8 May 2011 16:05:46 +0200
From:	Melchior FRANZ <melchior.franz@...il.com>
To:	"Joey Lee" <jlee@...ell.com>
Cc:	chris@...is-wilson.co.uk, dri-devel@...ts.freedesktop.org,
	tiwai@...e.de, linux-kernel@...r.kernel.org
Subject: Re: i915/kms/backlight-combo mode problem

* Joey Lee -- Sunday 08 May 2011:
> 於 六，2011-05-07 於 22:22 +0200，Melchior FRANZ 提到：
> > It has turned out that acpi key events seem to be handled correctly
> > and even the state of /sys/class/backlight/acer-wmi/brightness is
> 
> That's interesting for acer-wmi generated brightness interface when this
> machine declare acpi brightness interface in DSDT.

I'm sorry to give contradicting info. Yesterday I saw a subdir acer-wmi
(or acer_wmi) in /sys/class/backlight/ during one of my tests (with/without
acer_wmi, with/without acpi_osi=Linux). Now I left acpi_osi=Linux
away and allow acer_wmi, and it's subdir acpi_video0. Next time I'll
make notes.

> Does it work to you direct control brightness by access
> by /sys/class/backlight/acer-wmi/brightness ?

No. A number written to this virtual file is accepted and remembered,
but it doesn't actually change the brightness. It takes setpci to do
that. 

> As I remember, use setpci to control brightness is not recommended
> because BIOS or ACPI will also touch brightness level. That will be
> better control brightness by the function that was provided by BIOS. 
> e.g. ACPI or WMI interface, or direct control by EC.

Well, sounds plausible. And I wouldn't do it if it weren't the only
way at the moment.  :-)

> That means that will be better fix your Fn key control brightness like
> before, you just need press Fn key to change brightness and don't need
> have any workaround.

OK. I have added a lot of debug messages to intel_panel.c yesterday.
All it told me was that it seems to work correctly wiht acpi_osi=Linux.
Except that it doesn't actually change the brightness. Without acpi_osi
the functions aren't called at all and none of my messages showed up.

> Looks like current status is we try to fix bko#31522 but the patch
> causes your brightness no work by press Fn key even with acpi_osi=Linux.
> Does it right?

The history is: with acpi_osi=Linux everything worked with 2.6.38-rc8.
With 2.6.38 the screen stayed black. The patch that only ignored lbpc=0
worked (IIRC) including key adjustment. Later patches broke keys.

> 	replace acpi_osi=Linux by acpi_osi="!Windows 2006"
> 
> Does it also works to you for backlight control?

No, doesn't work.

m.
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