linux-kernel - Re: [patch update 3] PM: Introduce core framework for run-time PM of I/O devices

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Date:	Mon, 22 Jun 2009 12:28:14 -0400 (EDT)
From:	Alan Stern <stern@...land.harvard.edu>
To:	"Rafael J. Wysocki" <rjw@...k.pl>
cc:	Oliver Neukum <oliver@...kum.org>,
	Magnus Damm <magnus.damm@...il.com>,
	<linux-pm@...ts.linux-foundation.org>,
	ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
	Ingo Molnar <mingo@...e.hu>,
	LKML <linux-kernel@...r.kernel.org>, Greg KH <gregkh@...e.de>
Subject: Re: [patch update 3] PM: Introduce core framework for run-time PM
 of I/O devices

On Mon, 22 Jun 2009, Rafael J. Wysocki wrote:

> > Again, this boils down to how drivers decide to use the async 
> > interface.  I can see justifications for both pm_request_resume_get 
> > (which would always increment the counter) and pm_request_resume (which 
> > would increment the counter only if a work item had to be queued).
> 
> OK, so this means we should provide both at the core level and let the drivers
> decide which one to use.
> 
> I think in both cases the caller would be responsible for decrementing the
> counter?

Sure.  They could call pm_runtime_put just once at the end of their
runtime_resume method (assuming they used pm_request_resume), or they
could call it at every place where some deferred work was finished 
(assuming they used pm_request_resume_get).

> > Okay, we don't need it then.  I forgot to mention in the previous
> > message that there also has to be a pm_runtime_del() routine, which
> > should cancel pending workqueue items and set the counter to some high
> > value so that no new items are added.
> 
> Should that be called by device_pm_remove()?  I think so.

Yes.  I suppose it could be named pm_runtime_remove.  Either would be 
okay.

Alan Stern

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