linux-kernel - Re: [PATCH] Re: NAK new drivers without proper power management?

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Message-ID: <20070211211038.GD15445@elf.ucw.cz>
Date:	Sun, 11 Feb 2007 22:10:38 +0100
From:	Pavel Machek <pavel@....cz>
To:	Willy Tarreau <w@....eu>
Cc:	Matthew Garrett <mjg59@...f.ucam.org>,
	"Rafael J. Wysocki" <rjw@...k.pl>,
	Daniel Barkalow <barkalow@...ervon.org>,
	nigel@...el.suspend2.net, Robert Hancock <hancockr@...w.ca>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	Jeff Garzik <jeff@...zik.org>,
	pm list <linux-pm@...ts.osdl.org>
Subject: Re: [PATCH] Re: NAK new drivers without proper power management?

Hi!

> > > instead of modifying all drivers to explicitly state that they don't support
> > > it, we should start with a test of the NULL pointer for .suspend which should
> > > mean exactly the same without modifying the drivers. I find it obvious that
> > > a driver which does provide a suspend function will not support it. And if
> > > some drivers (eg /dev/null) can support it anyway, it's better to change
> > > *those* drivers to explicitly mark them as compatible.
> > 
> > No, that doesn't work. In the absence of suspend/resume methods, the PCI 
> > layer will implement basic PM itself. In some cases, this works. In 
> > others, it doesn't. There's no way to automatically determine which is 
> > which without modifying the drivers.
> 
> Then change the PCI layer to do the basic PM only for known compatible
> drivers, and modify only the known-compatible drivers to mark them
> explicitly compatible. IMHO, it generally is a bad idea to require that
> any driver explicitly states what it *does not* support. It's the reason
> why users encounter problem on new features with old drivers. For instance,
> do you know if the old ISA NE2000 driver breaks suspend ? I don't know,
> but I would at least expect it not to support it by default. It's best
> to announce what *is* supported and consider everything unimplemented
> otherwise explicitly stated.

Actually, ne2k driver is okay. ne2k cards are notoriously buggy, so it
responds with "****, that damn card has just locked up again, lets
reset it". Ok, it takes timeout to realize card is "locked up",
so it could be improved...

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