PUTCTRL
PUTCTRL(ring, prod, len | OP_PACKET | HW_OWNER | EOP);
PUTCTRL(ring, cons, port->p_framesize | OP_PACKET | HW_OWNER);
PUTCTRL(ring, cons, control);
PUTCTRL(ring, prod, port->p_framesize | OP_PACKET | HW_OWNER);