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

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Date:	Wed, 02 Apr 2008 09:32:18 +1100
From:	Nigel Cunningham <ncunningham@...a.org.au>
To:	"Rafael J. Wysocki" <rjw@...k.pl>
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)

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:
> > > 'ext' means 'extended'.  The idea is that the 'extended' version will be used
> > > by bus types / driver types that don't need to implement the _noirq callbacks.
> > > Both the platform and PCI bus types generally allow drivers to use _noirq
> > > callbacks, so they use 'struct pm_ext_ops', as well as their corresponding
> > > driver types.
> > 
> > Do you mean to say in the first sentence "...that _do_ need to implement..."?
> 
> Yes, sorry.

Okay. Thanks!

> > If not, then extended sounds like a misnomer and the two 
> > sentences seem to contradict one another.
> > 
> > [...]
> > 
> > > > > + *	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?
 
> > 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...

Nigel

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