PCI Driver Read in Linux

Hi,
I have SBC 104+ which has installed White Dwarf Linux.
I have another DSP board which is stacked on this SBC.
That board has PCI & ISA slots are interfaced with SBC.
I want to read external data of DSP Board from SBC using PCI Slot.
White Dwarf linux has already written PCI Device Driver.
I would like to develop a application code using PCI Driver API's ,
So I can read external data of DSP Board.
I have written some basic code, But how to exactly read external data
Through pci about that I have little bit problem.
Please, Reply as soon as possible. A positive reply awaited from u.

Thanks,
Sumeet