linux-kernel - Re: [PATCH 1/2] PM / Runtime: Add sysfs switch for disabling device run-time PM (rev. 2)

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Date:	Fri, 5 Feb 2010 07:27:19 +0100
From:	Pavel Machek <pavel@....cz>
To:	"Rafael J. Wysocki" <rjw@...k.pl>
Cc:	pm list <linux-pm@...ts.linux-foundation.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Jesse Barnes <jbarnes@...tuousgeek.org>,
	Matthew Garrett <mjg59@...f.ucam.org>,
	Alan Stern <stern@...land.harvard.edu>,
	Greg KH <greg@...ah.com>
Subject: Re: [PATCH 1/2] PM / Runtime: Add sysfs switch for disabling
	device run-time PM (rev. 2)


> > > + *	The default for all devices is "auto", which means that devices may be
> > > + *	subject to automatic power management, depending on their drivers.
> > 
> > Is it wise to specify 'auto' default value for devices without runtime
> > pm?
> 
> Yes, it is.  It means the user space doesn't care whether or not the device is
> power managed at run-time.

Well, defaulting to 'on' for drivers when runtime pm is experimental
seems logical. and there will be such drivers...

> > > +		len = cp - buf;
> > > +	if (len == sizeof ctrl_auto - 1 && strncmp(buf, ctrl_auto, len) == 0)
> > > +		pm_runtime_allow(dev);
> > 
> > parenthesis after sizeof?
> 
> This notation is used throughout this file too.

...but is inconsistent with rest of kernel.

> > Do I read it correctly that all of
> > 
> > "auto"
> > "auto\n"
> > "auto\non\nIm confused"
> > 
> > will switch to auto?
> 
> Perhaps it would, but what exactly is the problem with that?

That apps will start depending on such broken behaviour?
									Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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