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Re: x86 pcitag_t change proposal/patch

On Fri, Apr 26, 2013 at 11:16:22AM +0900, Masanobu SAITOH wrote:
> Hi, Jonathan
> (2012/12/05 11:59), Jonathan A. Kollasch wrote:
> >
> >I'd like feedback on the attached patch.
> >
> >Commit message would be approximately as follows:
> >
> >Separate the implementation of PCI Configuration Access Mode 1 and
> >Mode 2 from the x86 pcitag_t.  This is desirable so that any tags
> >possibly created prior to parsing of the ACPI MCFG table(s) can be
> >used with a memory-mapped configuration space mechanism afterwards.
> >
> >     Jonathan Kollasch
> >
>  What's the current status of this work? I'd like to access to the PCIe
> extended configuration space (from 0x100 to 0xfff) for debugging purpose.
> There are a lot of important informations in it...

I've been sitting on a revised pcitag_t adjustment patch for months,
it can be found attached.

I should point out - for the naysayers that think having the BDF in bits
23-8 is better - on x86 there are dedicated sub-registers for accessing
bits 15-0, 15-8, and 7-0 of a register word, while there are not for
bits 23-16 or 31-16, so it turns out that putting the B:DF in bits
15-8:7-0 works out pretty well for elegant and compact generated
assembly code.

Also, my thought is, that if we ever have to use the 16-bit PCI domain
number from ACPI, that we can stuff it in bits 31-16 of the pcitag_t,
rather than have the complexity of introducing a chipset tag for each

Anyway (assuming nothing more important comes up) I'd be happy to resume
work on using the ACPI MCFG info for config space access today.

        Jonathan Kollasch

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