linux-kernel - Re: [PATCH] x86, pci: Fix all early PCI scans to check the vendor ID first

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Date:	Mon, 13 Aug 2012 15:58:14 -0600
From:	Betty Dall <betty.dall@...com>
To:	Andi Kleen <ak@...ux.intel.com>
Cc:	"H. Peter Anvin" <hpa@...or.com>, Andi Kleen <andi@...stfloor.org>,
	x86@...nel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] x86, pci: Fix all early PCI scans to check the vendor
 ID first

On Sat, 2012-08-11 at 03:43 -0700, Andi Kleen wrote:
> On Fri, Aug 10, 2012 at 04:57:02PM -0700, H. Peter Anvin wrote:
> > On 08/09/2012 03:34 PM, Betty Dall wrote:
> > > 
> > > I thought this should be a break instead of a continue since the code
> > > does a break if the class is 0xffffffff. If the function does not have a
> > > valid VENDOR_ID, then the remaining function numbers do not have to be
> > > scanned because functions are required to be implemented in order (no
> > > skipping a function number.)
> > > 
> > 
> > Is that true?  This is certainly not true in PCI in general: there is
> > required to be a function 0, but there is no guarantee that functions
> > 1-7 don't have gaps.
> 
> These scans are for special known devices, presumably true for them.
> 
> Anwyays if you don't like it please use v1 of the patch.
> 
> -Andi

I checked the PCI specification, and Peter is right that function
numbers can be sparse. Please go with version 1 of the patch, as Andi
suggested. I will follow up by looking at why the three scans are not
consistent and send a patch, if appropriate. The scans could be improved
by stopping the function scan if function 0 does not exist because
function 0 is required, and if it is not there then none of the other
functions will be implemented.

-Betty

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