Any Rules for Behavior of bus numbers changing?

["Collins, Edward H" <edward.collins@unisys.com>]

We are seeing some cards Windows drivers not work because
their bus number has changed between boot cycles, for instance
when a card with a bridge on it is installed and enumerated before
the card in question. 

Is there anything in the spec about how a driver should be able
to respond when it's card gets located on a different bus than the
one it was on during it's installation?

thanks,  

Ed Collins - Unisys Server Development
25725 Jeronimo,    Mission Viejo, 92691
Phone 949.380.5816      Net2 656.5816
Pager  949.587.2076