Hardware state saving & X

From: Pavel Machek <pavel-AlSwsSmVLrQ@public.gmane.org>
To: Patrick Mochel <mochel-3NddpPZAyC0@public.gmane.org>
Cc: Karol Kozimor <sziwan-DETuoxkZsSqrDJvtcaxF/A@public.gmane.org>,
	Ducrot Bruno <ducrot-kk6yZipjEM5g9hUCZPvPmw@public.gmane.org>,
	Alan Hourihane
	<alanh-ASBjxr/nLg+TY6FTCsQk+9Bc4/FLrbF6@public.gmane.org>,
	acpi-devel-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org
Subject: Hardware state saving & X
Date: Wed, 15 Oct 2003 01:52:41 +0200	[thread overview]
Message-ID: <20031014235240.GD20789@elf.ucw.cz> (raw)
In-Reply-To: <Pine.LNX.4.44.0310141556320.803-100000-L1xM/EEGAB4@public.gmane.org>

Hi!

> > > It's also unncessary for X to do a full save/restore of the video card on 
> > > every VT switch. I personally find it annoying to wait a second or two 
> > > when switching from X to the console. 
> > 
> > ??
> > 
> > What if game or another X server is running on different console.
> 
> Is it really the current X server's responsibility to provide for what
> ever may be running on what ever console the user switches to? That seems
> backwards - the application that is being switched to should save the
> state of that which it's switching from. This is an X question, though, 
> and not fodder for this list.. 

Well, each application should do 

	* save state
	* reinitialize everything

when it is switched to, and 

	* shutdown everything
	* restore state

when it is being switched from. That includes random game, and that
includes X.

Well, its not quite X question... Its more fbcon question or
something. We are dictating interface X uses.

> > Patch looks reasonable, but:
> > 
> > STATE= should really be more finegrained. ACPI s3 is really differnent
> > from apm -s, and it looks to me like you'll only tell userspace 'mem'.
> 
> Well, it depends on what X (and in general userspace) needs to know on a 
> power-state transition. Alan, how does/will X behave differently for each 
> power state that we can enter? 

Different scripts should run on apm -s (BIOS saves most of hw state)
and S3 (we have to save most of hw state).

> > Kernel waiting for userspace to finish with pm_sem held... If that
> > code tries to do "echo platform > disk" in the meantime, you get ugly
> > deadlock.
> 
> Then, that would be a bug, and would be fixed in early stages of testing. 
> :) 

Userspace will be able to cause D-stated processes, which is ugly, but
perhaps it is reasonable. But at least document it somewhere.

								Pavel
-- 
When do you have a heart between your knees?
[Johanka's followup: and *two* hearts?]

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