> Well, one bit mask at the very least is a good thing: MI versus MD devices. 
> The former could be in a table in the MI part of the sys tree, and the
> latter in tables in the various arch trees.  This was my original thought
> wrt bit masks, and I added the "dynamic" space after the fact. 

How is this better than just starting the MI major device numbers at
zero and counting up, and starting the MD major device numbers at N
and counting down (where N is the maximum major device number)?

			       _MelloN_