TOTAL_RX_BD_PER_PAGE
#define USABLE_RX_BD_PER_PAGE (TOTAL_RX_BD_PER_PAGE - 1)
#define MAX_RX_BD_AVAIL (MAX_RX_PAGES * TOTAL_RX_BD_PER_PAGE)
#define TOTAL_RX_BD_ALLOC (TOTAL_RX_BD_PER_PAGE * sc->rx_pages)