linux-kernel - Re: multiple drivers, single device (was Re: Announce: Linux-next (Or Andrew's dream :-)))

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Message-ID: <alpine.LFD.1.00.0802121027190.2920@woody.linux-foundation.org>
Date:	Tue, 12 Feb 2008 10:30:04 -0800 (PST)
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Jeff Garzik <jeff@...zik.org>
cc:	Greg KH <greg@...ah.com>, Stephen Rothwell <sfr@...b.auug.org.au>,
	LKML <linux-kernel@...r.kernel.org>, linux-next@...r.kernel.org,
	linux-arch@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: multiple drivers, single device (was Re: Announce: Linux-next
 (Or Andrew's dream  :-)))



On Tue, 12 Feb 2008, Jeff Garzik wrote:

> Greg KH wrote:
> > The work I'm doing here is for stupid PCI firmware engineers, who have
> > created devices that are different things, all bound up under the same
> > PCI device.  I'm thinking of watchdog timers and random number
> > generator and i2c controller on the same PCI device, or even the more
> > basic, frame buffer and DRM access to the same PCI video device.
> 
> Yes, that has a known solution:  have your driver register i2c, rng, watchdog,
> etc. functions.
> 
> Works just fine inside today's infrastructure, no changes needed.

Indeed. If you have a multi-function device that shows up as a single PCI 
function, just make it have its own "private bus", and make it show up as 
a "devices within a device".

Create the fake PCI subdevices that have no "real" counterpart, except as 
parts of the stupid device that couldn't be bothered to be seen as 
multiple _real_ functions.

That not only solves the infrastructure issues, it's actually The Truth 
with capital letters. It is, after all, how the device actually works 
internally.

			Linus
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