BUS_SPACE_RD4_MV2
u_int32_t outbound_tail = BUS_SPACE_RD4_MV2(outbound_tail);
u_int32_t outbound_head = BUS_SPACE_RD4_MV2(outbound_head);
u_int32_t inbound_head = BUS_SPACE_RD4_MV2(inbound_head);
u_int32_t msg = BUS_SPACE_RD4_MV2(outbound_msg);