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From: Jeremy Maitin-Shepard <jbms@cmu.edu>
To: david@lang.hm
Cc: "Rafael J. Wysocki" <rjw@sisk.pl>, Alan Stern <stern@rowland.harvard.edu>,
       LKML <linux-kernel@vger.kernel.org>,
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       Al Boldi <a1426z@gawab.com>
Subject: Re: Hibernation considerations
References: <Pine.LNX.4.44L0.0707171010490.3551-100000@iolanthe.rowland.org>
	<200707171802.30903.rjw@sisk.pl>
	<Pine.LNX.4.64.0707170959160.2467@asgard.lang.hm>
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	<Pine.LNX.4.64.0707171302430.2467@asgard.lang.hm>
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Date: Tue, 17 Jul 2007 16:39:17 -0400
In-Reply-To: <Pine.LNX.4.64.0707171302430.2467@asgard.lang.hm>
	(david@lang.hm's message of "Tue\, 17 Jul 2007 13\:18\:13 -0700 \(PDT\)")
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david@lang.hm writes:

[snip]

> the non-ACPI hibernate behaves very differently, and for some people (and I
> think I am one of them) it will meet their needs better then _any_ of the ACPI
> suspends.

It may have certain differences from the user point of view, but from
the implementation view, it seems that it is nearly exactly the same.
The only differences seem to be: 

 - rather than shutting down, do whatever is necessary to stick the
   system in S4 state.

 - make sure ACPI isn't initialized by the "load image" kernel

 - rather than "resume from hibernate" ACPI by initializing it normally,
   issue the special hibernate-related methods.

Thus, it seems that supporting ACPI S4 will have a very minimal affect
on the hibernate implementation.

-- 
Jeremy Maitin-Shepard