linux-kernel - Re: [PATCH] - race-free suspend. Was: Re: [linux-pm] [PATCH 0/8] Suspend block api (version 8)

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Message-ID: <20100602233243.GA27666@core.coreip.homeip.net>
Date:	Wed, 2 Jun 2010 16:32:44 -0700
From:	Dmitry Torokhov <dmitry.torokhov@...il.com>
To:	Florian Mickler <florian@...kler.org>
Cc:	Neil Brown <neilb@...e.de>,
	Arve Hjønnevåg <arve@...roid.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	"Rafael J. Wysocki" <rjw@...k.pl>,
	Alan Stern <stern@...land.harvard.edu>,
	Felipe Balbi <felipe.balbi@...ia.com>,
	Peter Zijlstra <peterz@...radead.org>,
	"Paul@...p1.linux-foundation.org" <Paul@...p1.linux-foundation.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Linux OMAP Mailing List <linux-omap@...r.kernel.org>,
	Linux PM <linux-pm@...ts.linux-foundation.org>,
	Alan Cox <alan@...rguk.ukuu.org.uk>,
	James Bottomley <James.Bottomley@...e.de>
Subject: Re: [PATCH] - race-free suspend. Was: Re: [linux-pm] [PATCH 0/8]
 Suspend block api (version 8)

On Wed, Jun 02, 2010 at 09:05:21PM +0200, Florian Mickler wrote:
> On Wed, 2 Jun 2010 21:02:24 +1000
> Neil Brown <neilb@...e.de> wrote:
> > 
> > And this decision (to block suspend) really needs to be made in the driver,
> > not in userspace?
> 
> Well, it fits. The requirement is a direct consequence of the intimate
> knowledge the driver has about the driven devices.

That is not really true. A driver does have intimate knowledge of the
device, however it does not necessarily have an idea about the data read
from the device. Consider the gpio_matrix driver: Arve says that it has
to continue scanning matrix once first interrupt arrvies. But it really
depends on what key has been pressed - if user pressed KEY_SUSPEND or
KEY_POWER it cmight be better if we did not wait for key release but
initiated the action right away. The decision on how system reacts to a
key press does not belong to the driver but really to userspace.
 
-- 
Dmitry
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