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 01:00:13 +0200
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Nigel Cunningham <ncunningham@...a.org.au>
Cc:	pm list <linux-pm@...ts.linux-foundation.org>,
	ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
	Alan Stern <stern@...land.harvard.edu>,
	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>,
	Oliver Neukum <oliver@...kum.org>
Subject: Re: [RFC][PATCH] PM: Introduce new top level suspend and hibernation callbacks (rev. 6)

On Wednesday, 2 of April 2008, Nigel Cunningham wrote:
> Hi.
> 
> On Tue, 2008-04-01 at 23:57 +0200, Rafael J. Wysocki wrote:
> > On Tuesday, 1 of April 2008, Nigel Cunningham wrote:
> > > Hi Rafael etc.
> > > 
> > > On Tue, 2008-04-01 at 22:12 +0200, Rafael J. Wysocki wrote:
[--snip--]
> > > 
> > > > > > + *	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.
> > > > 
> > > > That will be possible when we drop the freezer.
> > > 
> > > Yeah, but right now, it seems to me to be a bogus limitation for drivers
> > > to have no way of automatically loading firmware when you're about to
> > > hibernate. (Of course I've since been reminded of the notifier chain -
> > > that should probably be mentioned here as the way of achieving this).
> > 
> > This is a tricky stuff, though, because the notifier is used for disabling the
> > user mode helpers too ...
> 
> Hmm. Yet another notifier?

Well, perhaps it's better to disable user mode helpers directly from
freeze_processes().

Still, let's do one thing at a time. :-)

> > > By the way, I'm going to go on record now as saying I think dropping the
> > > freezer is a silly idea. I'm therefore currently considering including
> > > the freezer in TuxOnice from the time it gets dropped from mainline. I
> > > know that will only make it less likely that TuxOnIce gets merged, but
> > > I've given up caring about that anyway - caring about merging is
> > > pointless when the people who decide if it gets merged don't care.
> > 
> > Well, I'm just not sure if dropping the freezer entirely will actually work,
> > but we won't know that if we don't try.
> > 
> > There's been a lot of pressure on going into this direction recently and
> > in principle it seems to be doable at least for suspend.  Hibernation is
> > another issue, but IMO it's better to focus on suspend first.
> 
> For suspend, I agree with dropping its use. For hibernation...

I'm not sure and that's why I added the comment about the availability of
the user space during ->prepare().

Besides, for now, the freezer is necessary anyway, even for suspend.

Thanks,
Rafael
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