linux-kernel - Re: [RFC][PATCH 1/3] PM: Introduce new top level suspend and hibernation callbacks

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Message-ID: <Pine.LNX.4.44L0.0803181103410.1476-100000@netrider.rowland.org>
Date:	Tue, 18 Mar 2008 11:10:05 -0400 (EDT)
From:	Alan Stern <stern@...land.harvard.edu>
To:	Pavel Machek <pavel@....cz>
cc:	"Rafael J. Wysocki" <rjw@...k.pl>,
	pm list <linux-pm@...ts.linux-foundation.org>,
	ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
	Greg KH <greg@...ah.com>, Len Brown <lenb@...nel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Alexey Starikovskiy <astarikovskiy@...e.de>,
	David Brownell <david-b@...bell.net>
Subject: Re: [RFC][PATCH 1/3] PM: Introduce new top level suspend and
 hibernation callbacks

On Tue, 18 Mar 2008, Pavel Machek wrote:

> > + * @complete: Undo the changes made by @prepare().  This method is executed for
> > + *	all kinds of resume transitions, immediately following one of the resume
> > + *	callbacks: @resume(), @thaw(), @restore(), or @recover().  Also executed
> > + *	if a suspend callback (@suspend(), @freeze(), @poweroff(), @quiesce())
> > + *	immediately following a successful @prepare() fails OR if a new child
> > + *	of the device has been registered during @prepare().

"during a successful call to @prepare()"?

> So... we do prepare() but it detects new child, so it returns -EAGAIN.
>   so we call complete() based on description above
> ...and then we call prepare() to suspend again?

You misunderstood (maybe the comment needs to be clarified as above).  

If prepare() returns any error (including -EAGAIN) then complete() does
not get called.  If prepare() returns successfully but the PM core
detects that a new child was added while prepare() was running, then we
call complete(), suspend the child, and call prepare() again.

> > + * @suspend: Executed before putting the system into a sleep state in which the
> > + *	contents of main memory are preserved.  Quiesce the device, put it into
> 
> content....is?

It's okay to use "contents" -- analogous to the table of contents in a
book.  It's one of those weird corner cases where either alternative is
acceptable.

Alan Stern

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