linux-kernel - Re: [PATCH] ACPI / PM: Traverse video_device

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Date:	Wed, 4 Aug 2010 13:00:23 +0200
From:	Matthias Hopf <mhopf@...e.de>
To:	Zhang Rui <rui.zhang@...el.com>
Cc:	Len Brown <lenb@...nel.org>, Matthew Garrett <mjg@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Julia Lawall <julia@...u.dk>, Oliver Neukum <oneukum@...e.de>,
	"linux-acpi@...r.kernel.org" <linux-acpi@...r.kernel.org>,
	"linux-pm@...ts.linux-foundation.org" 
	<linux-pm@...ts.linux-foundation.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] ACPI / PM: Traverse video_device_list for backlight
	restoration

On Aug 04, 10 09:27:29 +0800, Zhang Rui wrote:
> On Tue, 2010-08-03 at 18:11 +0800, Matthias Hopf wrote:
> > The .bind_info is later used in acpi_video_resume() to re-set the backlight
> > - but it's only evaluated on the active_list[], on which all .bind_info are
> > NULL by construction.
> why? .bind_info in active_list is initialized in acpi_video_device_bind.

Hm. Right. acpi_video_bus_get_one_device() is called after _enumerate().
Dunno why I didn't read this correctly.

> > I don't understand
> > why the list is (partially) transformed into an array in the first place,
> > especially as both the array *and* the list are used in the code...
> > 
> no, the active_list is an array in fact, which equals
> acpi_video_bus->attached_array. Maybe we need to change it to a more
> proper name.

:-)

> I'm still wondering why the patch works for you.

Same to me.

> could you please attach the acpidump output of this laptop?

Will do.

> please rebuild your kernel with CONFIG_ACPI_DEBUG=y, and reboot with
> kernel parameter "acpi.debug_layer=0x10 acpi.debug_level=0x400".
> and attach the dmesg output after resume, both w/ and w/o the patch you
> attached.

The most intriguing thing here is that the system starts writing to
/var/log/messages continuously, thus dmesg output is sort-of worthless.
This might be a reasonable side effect, it might be an indication of the
original issue.
I'll try to compile something for you.

Thanks

Matthias

-- 
Matthias Hopf <mhopf@...e.de>      __        __   __
Maxfeldstr. 5 / 90409 Nuernberg   (_   | |  (_   |__          mat@...opf.de
Phone +49-911-74053-715           __)  |_|  __)  |__  R & D   www.mshopf.de
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