linux-kernel - Re: [Patch v2] Make PCI extended config space (MMCONFIG) a driver opt-in

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Date:	Tue, 29 Jan 2008 07:29:51 -0800
From:	Arjan van de Ven <arjan@...radead.org>
To:	tcamuso@...hat.com
Cc:	Greg KH <greg@...ah.com>, Matthew Wilcox <matthew@....cx>,
	Grant Grundler <grundler@...isc-linux.org>,
	Loic Prylli <loic@...i.com>, Adrian Bunk <bunk@...nel.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Ivan Kokshaysky <ink@...assic.park.msu.ru>,
	Greg KH <gregkh@...e.de>, linux-kernel@...r.kernel.org,
	Jeff Garzik <jeff@...zik.org>,
	linux-pci@...ey.karlin.mff.cuni.cz, Martin Mares <mj@....cz>
Subject: Re: [Patch v2] Make PCI extended config space (MMCONFIG) a driver
 opt-in

On Tue, 29 Jan 2008 10:15:45 -0500
Tony Camuso <tcamuso@...hat.com> wrote:

> Arjan van de Ven wrote:
> > On Tue, 29 Jan 2008 09:15:02 -0500
> > Tony Camuso <tcamuso@...hat.com> wrote:
> > 
> >> Greg,
> >>
> >> The problem with Arjan's patch, if I understand it correctly, is
> >> that it requires drivers to make a call to access extended PCI
> >> config space.
> >>
> >> And, IIRC, Arjan's patch encumbers drivers for all arch's, even
> >> those that have no MMCONFIG problems.
> >>
> >> The patches proposed by Loic, Ivan, Matthew, and myself, all
> >> address the problem in an x86-specific manner that is transparent
> >> to the drivers.
> > 
> > this is not quite correct; the patches from Loic, Ivan, Matthew and
> > you are for a different problem statement.
> > 
> > Your patch problem statement is "need to fix mmconfig", my patch
> > problem statement is "need to not make users who don't need it
> > suffer". These are orthogonal problems.
> > 
> > 
> 
> Yes, but your patch also makes users who need extended PCI config
> space suffer.
> 
> Right now, that isn't a lot of people in x86 land, but your patch
> encumbers drivers for non-x86 archs with an additional call to access
> space that they've never had a problem with.

lets say s/x86/x86, IA64 and architectures that use intel, amd or via chipsets/



> As more PCI express drivers start to take advantage of AER and other
> advanced express capabilities, the extra call to address a condition
> specific to legacy x86 hardware is, IMNSHO, a kludge.

in addition to pci_enable(), pci_enable_msi(), pci_enable_busmaster() they already need to do
to enable various features?


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