I'm currently working on driver design in Windows CE using OSK5912
development board together with Mistral QVGA LCD module. The driver will
map and control the input and output of the GPIO pins. 

The problem is that I have difficulty in mapping the GPIO registers to the
OS. When I tried to map it using the given physical address i.e 0xFFFBE400,
the return value is NULL. I believe that GPIO is a shared peripheral
between MPU and DSP unit. But I'm not sure in detail on how that thing
works. Can anybody help me with this? 

Thanx in advance.