Re: multi-domain PCI and sysfs

Jesse Barnes
2004-09-08T04:17:01Z

On Tuesday, September 7, 2004 8:39 pm, Jon Smirl wrote:
> On Tue, 7 Sep 2004 16:11:40 -0700, David S. Miller <davem@davemloft.net>
wrote:
> > On Tue, 7 Sep 2004 18:58:53 -0400
> >
> > Jon Smirl <jonsmirl@gmail.com> 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.
> >
> > I don't know about the above but for a multi-domain system the
> > way it works is that the I/O ports are accessed using a different
> > base address for each domain.
>
> How does this work for IO ports in port space instead of memory mapped IO?

On sn2 at least, it's the same thing. Each PCI segment has a 'base address'
that can be used for legacy I/O. Just add the port you want to access to the
base and hope that a card responds before a master abort occurs.

Jesse