Re: multi-domain PCI and sysfs

[Matthew Wilcox <willy@debian.org>]

On Tue, Sep 07, 2004 at 06:58:53PM -0400, Jon Smirl wrote:
> How many active VGA devices can I have in this system 1 or 4? If the
> answer is 4, how do I independently address each VGA card? If the
> answer is one, you can see why I want a pci0000 node to hold the
> attribute for turning it off and on.

Each root bridge has the ability to route the VGA memory space.  I imagine
only one has that bit set at a time.

> How many simultaneous VGA devices does this system allow?

I don't think HP supports a configuration other than having the VGA
device on the AGP bus, but there's no reason one couldn't put a VGA
device in every PCI-X slot, is there?

> Does a PCI domain imply separate PCI IO address spaces, or does it
> just mean separate PCI Config spaces?

It only requires separate config space.  In practice, you may well
get separate IO port space and/or memory space per domain, or even per
root bus.  On PA-RISC, we extend the IO port space to 24 bit and use
the top 8 bits to determine which PCI root bus we're talking to.

> Can an x86 machine use separate PCI IO address spaces?

I think some of the NUMAQ stuff can have separate IO port space, but
you'd have to ask someone familiar with the architecture like Martin
Bligh or Bill Irwin.

-- 
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