is PCITAG big enough for future expansion?

[Egbert Eich]

Dave Airlie writes:
 > I'm not fully up on the PCI spec, but what are the defined sizes for the
 > 
 > domain, bus, device and function
 > 
 > can these become larger than 255? we munge them all into an unsigned
 > long PCITAG is it big enough for future expansion.. I think the PCITAG
 > thing is a bit of an ugly hack, its not as if passing a pointer to a
 > PciBusId instead of the unsigned long is really going to make a huge
 > performance difference to the X server...

The PCITAG is a leftover from the days where XFree86 was i386 only.
It is the PCI encoding used of direct IO access doing CFG space access
using mechanism 1. 
It used to be a benefit at one point in distant history but turned 
more into a nuisance since then as we often have to pull the individual 
pieces from this one tag.
It was kept around largely for compatibility reasons. Maybe we should
do away with it altogether - apart from the consideration about the size.

Egbert.