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

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Date:	Wed, 02 Apr 2008 08:38:06 +1100
From:	Nigel Cunningham <ncunningham@...a.org.au>
To:	Alan Stern <stern@...land.harvard.edu>
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>,
	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)

Hi.

On Tue, 2008-04-01 at 16:56 -0400, Alan Stern wrote:
> On Tue, 1 Apr 2008, Rafael J. Wysocki wrote:
> 
> > > Does ..._ext_... mean extended? (external?) If 'extended' (or if not),
> > > does that imply that they're mutually exclusive alternatives for drivers
> > > to use?
> > 
> > 'ext' means 'extended'.  The idea is that the 'extended' version will be used
> > by bus types / driver types that don't need to implement the _noirq callbacks.
> 
> Something's wrong here.  This seems to say that the "extended" version
> has _fewer_ method pointers -- in which case it should be called 
> "restricted" instead.

Agreed.

> > > So drivers can never validly fail to resume. That sounds fair enough. If
> > > the hardware has gone away while in lower power mode (USB, say), should
> > > the driver then just printk an error and return success?
> > 
> > I think so.
> > 
> > IMO, an error code returned by a driver's ->resume() should mean "the device
> > hasn't resumed and is presumably dead".  Otherwise, ->resume() should return
> > success.
> 
> If the device is gone, it doesn't much matter what resume() returns.

What if the same driver is handling multiple instances and only some of
them fail to resume?

Regards,

Nigel

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