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From: "Grover, Andrew" <andrew.grover@intel.com>
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Date: Fri, 20 Sep 2002 11:26:03 -0700
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Subject: [acpi-jp 1838] RE: ACPI Question
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(I figured I'd just respond to your original mail :)

> From: John Baldwin [mailto:jhb@freebsd.org] 
> Ok, I have a question.  Do all Host-PCI bridges have to be enumerated
> by ACPI?

Yes.

>  From my reading of the ACPI 2.0a spec, I'm not sure.  I know
> that ACPI doesn't have to enumerate devices that can be found through
> other standard means unless it is overriding standard behavior.
> However, it also says that all Host-PCI bridges need a _PRT.  Hence
> my confusion.  If anyone could enlighten me I would appreciate it.

Host-PCI bridges cannot be enumerated today, without making the assumption
that there is a bus 0. I don't know about FBSD but Linux, pre-ACPI, both
assumes a PCI bus 0, and does a "peer bus trick" to find other peer root
bridges.

With ACPI, this assumption is no longer necessary, because pci root bridges
are explicitly enumerated, and _BBN gives the base bus number if it is not
0.

I'm not clear on how _PRT relates to this...

Regards -- Andy
