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

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Message-Id: <1207078467.23143.96.camel@nigel-laptop>
Date:	Wed, 02 Apr 2008 06:34:27 +1100
From:	Nigel Cunningham <ncunningham@...a.org.au>
To:	Alan Stern <stern@...land.harvard.edu>
Cc:	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	"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)

Hi.

On Tue, 2008-04-01 at 10:31 -0400, Alan Stern wrote:
> 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.

Then that should be mentioned here so that drivers authors can know that
it is possible to request firmware, allocate memory and so on at a stage
when you can still rely on userspace being alive.

Regards,

Nigel

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