linux-kernel - Re: [PATCH 1/3] PM: Introduce new top level suspend and hibernation callbacks (rev. 8)

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Message-Id: <1208120711.6958.52.camel@pasglop>
Date:	Mon, 14 Apr 2008 07:05:11 +1000
From:	Benjamin Herrenschmidt <benh@...nel.crashing.org>
To:	"Rafael J. Wysocki" <rjw@...k.pl>
Cc:	Greg KH <greg@...ah.com>,
	pm list <linux-pm@...ts.linux-foundation.org>,
	ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
	Alan Stern <stern@...land.harvard.edu>,
	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>,
	Nigel Cunningham <ncunningham@...a.org.au>,
	Jesse Barnes <jbarnes@...tuousgeek.org>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH 1/3] PM: Introduce new top level suspend and
	hibernation callbacks (rev. 8)


On Sun, 2008-04-13 at 15:33 +0200, Rafael J. Wysocki wrote:
> + *     The PM core executes @prepare() for all devices before starting to
> + *     execute suspend callbacks for any of them, so drivers may assume all of
> + *     the other devices to be present and functional while @prepare() is being
> + *     executed.  In particular, it is safe to make GFP_KERNEL memory
> + *     allocations from within @prepare().  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).  [To work around this limitation, drivers may
> + *     register suspend and hibernation notifiers that are executed before the
> + *     freezing of tasks.]

Can you tell me why you kept that limitation with user space ?

I don't see the point... On the contrary, prepare() is the pefect place
to implement handshaking with userspace for drivers that need to do so,
such as the DRM.

Ben.

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