linux-kernel - Re: [PATCH 4/7] PM / Domains: Rework system suspend callback routines

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Message-Id: <201202172201.07274.rjw@sisk.pl>
Date:	Fri, 17 Feb 2012 22:01:07 +0100
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Pavel Machek <pavel@....cz>
Cc:	Linux PM list <linux-pm@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	"Linux-sh list" <linux-sh@...r.kernel.org>,
	Magnus Damm <magnus.damm@...il.com>,
	Guennadi Liakhovetski <g.liakhovetski@....de>,
	Kevin Hilman <khilman@...com>, jean.pihet@...oldbits.com
Subject: Re: [PATCH 4/7] PM / Domains: Rework system suspend callback routines

On Friday, February 17, 2012, Pavel Machek wrote:
> On Mon 2011-11-07 01:08:11, Rafael J. Wysocki wrote:
> > From: Rafael J. Wysocki <rjw@...k.pl>
> > 
> > The current generic PM domains code attempts to use the generic
> > system suspend operations along with the domains' device stop/start
> > routines, which requires device drivers to assume that their
> > system suspend/resume (and hibernation/restore) callbacks will always
> > be used with generic PM domains.  However, in theory, the same
> > hardware may be used in devices that don't belong to any PM domain,
> > in which case it would be necessary to add "fake" PM domains to
> > satisfy the above assumption.  Also, the domain the hardware belongs
> > to may not be handled with the help of the generic code.
> > 
> > To allow device drivers that may be used along with the generic PM
> > domains code of more flexibility, add new device callbacks, .freeze(),
> > .freeze_late(), .thaw_early() and .thaw(), that can be supplied by
> > the drivers in addition to their "standard" system suspend and
> > hibernation callbacks.  These new callbacks, if defined, will be used
> > by the generic PM domains code for the handling of system suspend and
> > hibernation instead of the "standard" ones.  This will allow drivers
> > to be designed to work with generic PM domains as well as without
> > them.
> 
> Should this go to Documentation/ somewhere? May concern is that we
> have way too many callbacks these days. Why is fake PM domain such a
> bad thing?

I'm not sure what you mean, really.  This particular patch only affects
the generic PM domains framework, which only has a few users now.

Thanks,
Rafael
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