linux-kernel - Re: ACPI: Idle Processor PM Improvements

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Message-ID: <20060914091849.GA15102@elf.ucw.cz>
Date:	Thu, 14 Sep 2006 11:18:49 +0200
From:	Pavel Machek <pavel@....cz>
To:	Jim Gettys <jg@...top.org>
Cc:	Jordan Crouse <jordan.crouse@....com>,
	"Brown, Len" <len.brown@...el.com>,
	Linux Kernel ML <linux-kernel@...r.kernel.org>,
	Dominik Brodowski <linux@...inikbrodowski.net>,
	ACPI ML <linux-acpi@...r.kernel.org>,
	Adam Belay <abelay@...ell.com>,
	"Pallipadi, Venkatesh" <venkatesh.pallipadi@...el.com>,
	Arjan van de Ven <arjan@...ux.intel.com>, devel@...top.org,
	Bjorn Helgaas <bjorn.helgaas@...com>
Subject: Re: ACPI: Idle Processor PM Improvements

On Tue 2006-09-12 14:14:30, Jim Gettys wrote:
> On Tue, 2006-09-12 at 11:21 +0200, Pavel Machek wrote:
> 
> > Ok, so what is needed is message to X "we are suspending", and X needs
> > to respond "okay, I'm ready, no need for console switch".
> 
> This presumes an external agent to X controlling the fast
> suspend/resume, with messages having to flow to and from X, and to and
> from the kernel, with the kernel in the middle.
> 
> Another simpler option is X itself just telling the kernel to suspend
> without console switch, as the handoff of the display to the DCON chip
> has to be done with X and with an interrupt signaling completion of the
> handoff.  This would be triggered by an inactivity timeout in the X
> server.

Whoa... that's a hack.. but yes, you can probably do that, and I think
kernel even has neccessary interfaces already. (They were needed for
uswsusp).

> > Alternatively, hack kernel to take control from X without actually
> > switching consoles. That should be possible even with current
> > interface.
> 
> This would require saving/restoring all graphics state in the kernel
> (and X already has that state internally).  Feasible, but seems like

Hmm, save/restore graphics state from the kernel would of course be
clean solution, but you should have that anyway... what if someone
suspends without X running?

And of course you can just cheat, and not do kernel save-state on your
system.

									Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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