linux-kernel - Re: [linux-pm] [RFC] PCI: Runtime power management

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Message-Id: <200908152321.53283.rjw@sisk.pl>
Date:	Sat, 15 Aug 2009 23:21:53 +0200
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Matthew Garrett <mjg59@...f.ucam.org>
Cc:	Alan Stern <stern@...land.harvard.edu>, linux-usb@...r.kernel.org,
	linux-pci@...r.kernel.org, Greg KH <gregkh@...e.de>,
	LKML <linux-kernel@...r.kernel.org>,
	"Linux-pm mailing list" <linux-pm@...ts.linux-foundation.org>
Subject: Re: [linux-pm] [RFC] PCI: Runtime power management

On Saturday 15 August 2009, Matthew Garrett wrote:
> On Sat, Aug 15, 2009 at 10:54:23PM +0200, Rafael J. Wysocki wrote:
> 
> > runtime_wakeup - if set, the device is allowed to do remote wakeup at run time
> >   That could be represented as 'runtime_wakeup' under 'power' with the
> >   following values:
> >   * no value (empty file) is 'runtime' is 'disabled'
> >   * 'enabled'
> >   * 'disabled'
> >   To set/unset the user space writes 'enabled'/'disabled' to it, respectively.
> >   The default is set.
> 
> Why would you ever want runtime_wakeup to be false unless 
> runtime_forbidden is true? Surely the point of runtime power management 
> is to be transparent to the user, in which case remote wakeup is 
> required?

Well, this was exactly my point previously. :-)

Still, although for the majority of devices 'runtime_wakeup' disabled would
mean no runtime PM at all IMO, there may be devices that actually work without
remote wakeup, although they support it in general.

I can even imagine a scenario where this setting might be useful, like when
we don't want a network adapter to be woken up from the outside.

Thanks,
Rafael
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