linux-kernel - Re: -mm: pnp-do-not-stop-start-devices-in-suspend-resume-path.patch breaks resuming isapnp cards

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Date:	Tue, 15 Jan 2008 08:51:35 +0100 (CET)
From:	Jaroslav Kysela <perex@...ex.cz>
To:	Bjorn Helgaas <bjorn.helgaas@...com>
cc:	Rene Herman <rene.herman@...access.nl>,
	Andrew Morton <akpm@...l.org>,
	"Rafael J. Wysocki" <rjw@...k.pl>,
	Pierre Ossman <drzeus@...eus.cx>, Pavel Machek <pavel@...e.cz>,
	Ondrej Zary <linux@...nbow-software.org>,
	ALSA development <alsa-devel@...a-project.org>,
	Linux Kernel <linux-kernel@...r.kernel.org>,
	Takashi Iwai <tiwai@...e.de>,
	linux-pm@...ts.linux-foundation.org
Subject: Re: -mm: pnp-do-not-stop-start-devices-in-suspend-resume-path.patch
 breaks resuming isapnp cards

On Mon, 14 Jan 2008, Bjorn Helgaas wrote:

> On Saturday 12 January 2008 11:13:35 pm Rene Herman wrote:
> > ... And, now that I have your attention, while it's 
> > not important to the issue anymore with the tests removed as the submitted 
> > patch did, do you have an opinion on (include/linux/pnp.h):
> > 
> > /* pnp driver flags */
> > #define PNP_DRIVER_RES_DO_NOT_CHANGE    0x0001  /* do not change the state 
> > of the device */
> > #define PNP_DRIVER_RES_DISABLE          0x0003  /* ensure the device is 
> > disabled */
> > 
> > I find DISABLE including DO_NOT_CHANGE rather unexpected...
> 
> I don't know the history of those flags, but I wish they didn't exist.

Ok, something to explain. These flags exists to allow drivers to 
manually configure (override) PnP resources at init time - we know - for 
example in ALSA - that some combinations simply does not work for all 
soundcards.

The DISABLE flags simply tells core PnP layer - driver will handle 
resource allocation itself, don't do anything, just disable hw physically 
and do not change (allocate) any resources. Value 0x03 is valid in this 
semantics.

Unfortunately, suspend / resume complicates things a bit, but PnP core can 
handle DO_NOT_CHANGE flag. But it will just mean - _preserve_ resource 
allocation from last suspend state for this device and enable hw 
physically before calling resume() callback.

					Jaroslav

-----
Jaroslav Kysela <perex@...ex.cz>
Linux Kernel Sound Maintainer
ALSA Project, Red Hat, Inc.

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