> In message: <20090710024528.ec36959...@thoreau.thistledown.com.au> > Simon Burge <sim...@netbsd.org> writes: > : Christoph Egger wrote: > : > : > Michael Lorenz wrote: > : > > : > > +/* > : > > + * NetBSD's userland has a /dev/pci* entry for each bus but > userland has no way > : > > + * to tell if a bus is a subordinate of another one or if it's on a > different > : > > + * host bridge. > : > > : > I have a patch which introduces support for PCI domains. It allows the > : > userland to distinguish between them by checking if the pci bus > belongs > : > to the same PCI domain. > : > : What exactly is a "PCI domain"? A quick google seems to suggest that > : this is a Linux concept as opposed to a PCI concept. In a previous > : life we used NetBSD on a number of different machines of various > : architectures that had multiple PCI host bridges, although admittedly we > : didn't need to know the topology of the PCI bus layout. > > PCI domains, as implemented by Linux and FreeBSD are separate host > bridges. Each bus complex behind the host bridge has independent > numbering. Each of these bus complexes are in a different domain. > > Not all systems with multiple host bridges have separate numbering > domains, but many do.
PCI domains are part of the PCI host bridge specification. It is a 16bit-wide number. Christoph