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

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Date:	Tue, 12 Feb 2008 13:31:50 -0500
From:	Jeff Garzik <jeff@...zik.org>
To:	Greg KH <greg@...ah.com>
CC:	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>,
	Linus <torvalds@...ux-foundation.org>
Subject: Re: multiple drivers, single device (was Re: Announce: Linux-next
 (Or Andrew's dream  :-)))

Greg KH wrote:
> Except that the individual drivers are a lot of the time written by
> different people, live in different portions of the tree, and are
> combined into different combinations depending on the chipset.

Yes -- the worst case is that people have to work together, and it 
tweaks people who like to organize source files nicely into directories :)

> For i2c devices, I see the scx200_acb, i2c-elektor, i2c-sis5595, and
> i2c-sis630 drivers needing this.  The last one happens to share the pci
> device with a video driver, that doesn't always need to be / want to be
> loaded by users just so they can read the temperature of their
> processors.

Sure.  Reasonable request, and doable within today's APIs.

> Oh, the EDAC code also needs this, and I know that no one wants to merge
> that stuff into their individual drivers :)

So people have to work together...  darn :)  most drivers these days are 
organized nicely into nicely modular units anyway, making it easy to 
write a "shell" driver that simply registers each sub-driver, and helps 
arbitrate/provide resources to sub-units.

Consider, for example, a PCI driver that loads, and then fills in 
platform_data to provide a specific set of resources to a platform 
driver (a common idiom).  You would need to create parented struct 
devices (parent: pci_dev's device), but everything else should work within

I could even forsee a future where most drivers are written in a generic 
platform-driver style, and PCI|sbus|embedded-bus|blah are simply 
bus-specific shells that fill in platform data.

All of this should be nicely possible within the existing usage of 
struct device, platform drivers, generic DMA API, iomap, etc.

	Jeff

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