> BAT[UL] should have fixed size (currently, at least).

I mean that a port has a port-specific fixed size (mask).
BATU(vaddr, shft) and BATL(raddr, shft, wimg) are needed to support
other battable size.  Sorry for confusion.

(macppc has rather complex mapping:
00000000-		normal RAM
80000000-90000000?	PCI MEM
90000000-a0000000?	PCI MEM
f2000000-f2010000	PCI I/O
f3000000-f4000000	PCI MEM
f4000000-f4010000	PCI I/O
f5000000-f6000000	PCI MEM
ff800000-ff900000	Open Firmware
ffc00000-		AAPL,ROM

so it needed 256 or 1024 battable entries if we use BATs to map...)