Hi,

I recently discovered that FreeBSD has agp support for amd64, and
wanted to port it to NetBSD (at least to give it a try).

http://www.freebsd.org/cgi/cvsweb.cgi/src/sys/pci/agp_amd64.c

After digging into the code, and specs, i noticed that this driver
needs to talk to some devices (one for each CPU) that may not be on
the same PCI bus as the AGP device.

pchb3 at pci0 dev 24 function 3
pchb3: Advanced Micro Devices AMD64 Miscellaneous configuration (rev. 0x00)
pchb7 at pci0 dev 25 function 3
pchb7: Advanced Micro Devices AMD64 Miscellaneous configuration (rev. 0x00)

pchb8 at pci4 dev 0 function 0
pchb8: Advanced Micro Devices AMD8151 AGP Device (rev. 0x13)

I'm not really familiar with dealing with multiple PCI buses/devices
at the same time, and prefer asking about the best way to handle
pci0 devices regs read/writes from another bus.

Any help will be appreciated.

-- 
Nicolas Joly

Biological Software and Databanks.
Institut Pasteur, Paris.