linux-kernel - Re: [RFC][PATCH] PM: Introduce new top level suspend and hibernation callbacks (rev. 6)

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Date:	Wed, 2 Apr 2008 10:11:14 -0400 (EDT)
From:	Alan Stern <stern@...land.harvard.edu>
To:	"Rafael J. Wysocki" <rjw@...k.pl>
cc:	Nigel Cunningham <ncunningham@...a.org.au>,
	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>,
	Pavel Machek <pavel@....cz>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Oliver Neukum <oliver@...kum.org>
Subject: Re: [RFC][PATCH] PM: Introduce new top level suspend and hibernation
 callbacks (rev. 6)

On Tue, 1 Apr 2008, Rafael J. Wysocki wrote:

> > If the device is gone, it doesn't much matter what resume() returns.
> 
> Yes, it does.  In that cases, the error code would tell the PM core not to attempt
> to resume the device's children etc.

If the device is gone then so are its descendants, right?  So it 
doesn't matter whether the PM core tries to resume them.

>  Otherwise, it's quite meaningless to the
> PM core, because it really can mean anything and how's the PM core supposed
> to handle _that_?

Exactly.  This is the point I was trying to make a week or so ago.

> Either we decide that the error codes returned by ->resume() mean critical
> errors or there's no point in returning error codes from ->resume() at all
> (other than logging the errors by the core).
> 
> Well, that's getting confused.  I think I'll have to rework the patch not to
> really handle the errors returned by ->resume() and friends, after all, but
> I'll keep the reporting of them.
> 
> However, I'd like to add a recommendation that the _new_ "resume" callbacks
> should only return errors in critical situations as the indication to the PM
> core that something went _really_ wrong and the device in question is quite
> surely unusable.

Agreed.  The most important aspect is that drivers should _not_ return
an error if the device is working correctly.  We should fix the drivers 
which make this mistake.

Alan Stern

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