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

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Message-ID: <20070211121339.GB4204@srcf.ucam.org>
Date:	Sun, 11 Feb 2007 12:13:40 +0000
From:	Matthew Garrett <mjg59@...f.ucam.org>
To:	Willy Tarreau <w@....eu>
Cc:	"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>, Pavel Machek <pavel@....cz>,
	pm list <linux-pm@...ts.osdl.org>
Subject: Re: [PATCH] Re: NAK new drivers without proper power management?

On Sun, Feb 11, 2007 at 07:54:04AM +0100, Willy Tarreau wrote:

> 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.

-- 
Matthew Garrett | mjg59@...f.ucam.org
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