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

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Message-ID: <Pine.LNX.4.44L0.0804011029010.3993-100000@iolanthe.rowland.org>
Date:	Tue, 1 Apr 2008 10:31:44 -0400 (EDT)
From:	Alan Stern <stern@...land.harvard.edu>
To:	Benjamin Herrenschmidt <benh@...nel.crashing.org>
cc:	Nigel Cunningham <ncunningham@...a.org.au>,
	"Rafael J. Wysocki" <rjw@...k.pl>,
	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>, Oliver Neukum <oliver@...kum.org>
Subject: Re: [RFC][PATCH] PM: Introduce new top level suspend and hibernation
 callbacks (rev. 6)

On Tue, 1 Apr 2008, Benjamin Herrenschmidt wrote:

> On Tue, 2008-04-01 at 19:15 +1100, Nigel Cunningham wrote:
> > > + *   However, drivers may NOT assume anything about the availability of the
> > > + *   user space at that time and it is not correct to request firmware from
> > > + *   within @prepare() (it's too late to do that).
> > 
> > That doesn't sound good. It would be good to be able to get drivers to
> > request firmware early in the process.
> 
> Agreed. Prepare() should still allow request_firmware and full userspace
> communication / helper usage.

Pepare() is called after userspace has been frozen.  (Of course, once 
the freezer goes away this won't matter any more.)

There is a separate notifier chain which drivers can subscribe to;
notifications about impending sleeps are sent out while userspace is
still alive.  Drivers can use that for request_firmware, memory
allocation, and other things.

Alan Stern

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