linux-kernel - Re: [PATCH -mm 6/7] PM: Remove power_state.event checks from suspend core code

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Message-Id: <200706172126.31301.rjw@sisk.pl>
Date:	Sun, 17 Jun 2007 21:26:30 +0200
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Alan Stern <stern@...land.harvard.edu>
Cc:	David Brownell <david-b@...bell.net>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Greg KH <greg@...ah.com>, LKML <linux-kernel@...r.kernel.org>,
	Pavel Machek <pavel@....cz>
Subject: Re: [PATCH -mm 6/7] PM: Remove power_state.event checks from suspend core code

On Friday, 15 June 2007 23:57, Rafael J. Wysocki wrote:
> On Friday, 15 June 2007 04:00, Alan Stern wrote:
> > On Fri, 15 Jun 2007, Rafael J. Wysocki wrote:
> > 
> > > On Thursday, 14 June 2007 16:21, David Brownell wrote:
> > > > On Wednesday 13 June 2007, Rafael J. Wysocki wrote:
> > > > > From: Rafael J. Wysocki <rjw@...k.pl>
> > > > > 
> > > > > The suspend routines should be called for every device during a system sleep
> > > > > transition, regardless of the device's state, so that drivers can regard these
> > > > > method calls as notifications that the system is about to go to sleep, rather
> > > > > than as directives to put their devices into the 'off' state.
> > > > 
> > > > Did you audit all the drivers to make sure this won't break things?
> > > > Like for example through inappropriate pci_save_state() calls?
> > > 
> > > I did, but not very carefully.
> > > 
> > > > I'd really expect this patch would break things...
> > > 
> > > Well, in that case I'll have a closer look at them.
> > 
> > It might not be all that bad.  One would expect problems to occur only 
> > in cases where devices were already suspended at the time of a system 
> > sleep transition.  Since relatively few drivers currently implement 
> > runtime PM -- and those that do are likely to be more careful about 
> > not blindly making state changes -- there might not be too much 
> > trouble.
> 
> Yes, in fact I've had no problems related to that so far (tested the patch on
> four different machines).

It seems the drivers for which that could be relevant do the checks as needed.

Greetings,
Rafael


-- 
"Premature optimization is the root of all evil." - Donald Knuth
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