TX_BD_USABLE_PER_PAGE
#define TX_BD_USABLE (TX_BD_USABLE_PER_PAGE * TX_BD_NUM_PAGES)
((((x) & TX_BD_USABLE_PER_PAGE) == (TX_BD_USABLE_PER_PAGE - 1)) ? \
#define TX_BD_PAGE(x) (((x) & ~TX_BD_USABLE_PER_PAGE) >> 8)
#define TX_BD_IDX(x) ((x) & TX_BD_USABLE_PER_PAGE)