How to determine which ceddk api to use

Hi,
i have terribly confused about the choice of the following 2 apis
1) READ_PORT_UCHAR
2) READ_REGISTER_UCHAR

consider i have a pci device and i got both iobase and memory base
address.i will use consecutively the following functions

3)( HalTranslateBusAddress and/or MmMapIoSpace )
or
4) TransBusAddrToVirtual

In the above functions,a parameter is there called AddressSpace
which signifies that the address is memory address(AddressSpace =0) or
i/o address ( AddressSpace=1)

Q) So what is the criteria for giving physical base address
( iobase or memorybase )in the above ceddk fns( 3 & 4) ?
means which address i have to give as the input to the
above ceddk apis .
Q) so altogher based on which conditions,i have to choose the
above two memory access functions ( 1 & 2 )

Expecting that this muddy water will get cleared !


Thanking you


with regards
Sonu Thomas

.