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

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Message-Id: <200804012359.54031.rjw@sisk.pl>
Date:	Tue, 1 Apr 2008 23:59:52 +0200
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Nigel Cunningham <ncunningham@...a.org.au>
Cc:	Alan Stern <stern@...land.harvard.edu>,
	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 Tuesday, 1 of April 2008, Nigel Cunningham wrote:
> 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.

This was a mistake explained in another message.  The "don't" should not be
present in the above sentence.

> > > > 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?

->resume() will be called separately for each of them.

Thanks,
Rafael
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