tulip_desc_t
tulip_desc_t *desc;
#define DESC_STATUS(di) (((volatile tulip_desc_t *)((di)->di_desc))->d_status)
tulip_desc_t *nextout;
size = count * sizeof(tulip_desc_t);
bzero(ri->ri_descs, sizeof(tulip_desc_t) * ri->ri_max);
tulip_desc_t *ri_descs;
tulip_desc_t *di_desc;