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

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Date:	Wed, 2 Apr 2008 12:42:15 -0400 (EDT)
From:	Alan Stern <stern@...land.harvard.edu>
To:	Oliver Neukum <oliver@...kum.org>
cc:	"Rafael J. Wysocki" <rjw@...k.pl>,
	Nigel Cunningham <ncunningham@...a.org.au>,
	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>
Subject: Re: [RFC][PATCH] PM: Introduce new top level suspend and hibernation
 callbacks (rev. 6)

On Wed, 2 Apr 2008, Oliver Neukum wrote:

> Am Mittwoch, 2. April 2008 17:13:11 schrieb Alan Stern:
> > Basically yes.  Subsystems and drivers are allowed to keep devices
> > suspended if they were suspended before the system went to sleep.  
> > Remember, the purpose of the resume method is to let drivers know that
> > the system is now awake, not to force them to put their devices into a
> > high-power state.
> 
> Well, sometimes it is exactly that what we desire, eg. as a side effect
> of lsusb. Should the callbacks have different semantics depending on
> the reason you call them? And how should that information be transferred?

Which callbacks are you referring to?  When lsusb opens a device and
does an autoresume, it does not call the same routine as the PM core
does when resuming from a system sleep.  lsusb ends up calling
usb_autoresume_device() whereas the PM core ends up calling
usb_resume(), which is the function you quoted earlier.

Alan Stern

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