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From: "Rafael J. Wysocki" <rjw@sisk.pl>
To: Johannes Berg <johannes@sipsolutions.net>
Subject: Re: suspend2 merge (was Re: [Suspend2-devel] Re: CFS and suspend2: hang in atomic copy)
Date: Fri, 27 Apr 2007 12:18:05 +0200
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Cc: Pavel Machek <pavel@ucw.cz>,
       Linus Torvalds <torvalds@linux-foundation.org>,
       Nigel Cunningham <nigel@nigel.suspend2.net>,
       Nick Piggin <npiggin@suse.de>, suspend2-devel@lists.suspend2.net,
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       Con Kolivas <kernel@kolivas.org>,
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On Friday, 27 April 2007 11:41, Johannes Berg wrote:
> On Thu, 2007-04-26 at 21:02 +0200, Rafael J. Wysocki wrote:
> 
> > Yes.  That's because we want to be able to repeat creating the image
> > without closing the fd in some situations.
> 
> Oh yeah, I just checked and it's not in fact necessary. I'm just
> confused.
> 
> > Still, we could use a global var 'platform_hibernation' or something like this,
> > I think.  Then, we can do
> > 
> > #define platform_hibernation	0
> > 
> > on the architectures that don't need it and make ACPI use it instead of this
> > "dynamic linking".
> 
> No, because acpi doesn't know at build time whether it can actually do
> S4 or not.

That's not a problem, I think.

1) We define platform_hibernation if CONFIG_ACPI is set.

2) In the ACPI code we do

if (can do S4)
	platform_hibernation = 1;

3) We have functions arch_platform_prepare()/finish()/enter() that are defined
to be noops for anything but ACPI systems and for ACPI systems they are
defined like this:

int arch_platform_enter(void)
{
	if (!platform_hibernation)
		return 0;

	...
}

I think it should work.

Greetings,
Rafael