DESC_BUFPTR
desc_addr_get(desc + DESC_BUFPTR),
desc_addr_set(desc + DESC_BUFPTR, buf);
#define DESC_CMDSTS (DESC_BUFPTR + HW_ADDR_LEN/4)
desc_addr_set(desc + DESC_BUFPTR, buf);
dma_addr_t bufptr = desc_addr_get(desc + DESC_BUFPTR);
addr = desc_addr_get(desc + DESC_BUFPTR);