Looking at the driver for the sm712 graphics chip and noticed something that I just can get my head wrapped around...

Why is isaBase added to the index in smiWrite() when it is already added to each index when it is defined (i.e. #define SMI_INDX_C4 (pGD->isaBase + 0x03c4)) ? I figure I have to be missing something quite obvious since it has been this way for quite some time and no one seems to have mentioned it before.