MBOX_MSG_SEND
return (dir == MBOX_MSG_SEND) ?
dst_aeqn = (dir == MBOX_MSG_SEND) ?
MBOX_MSG_SEND, MBOX_MSG_ACK, &msg_info);
MBOX_MSG_SEND, MBOX_MSG_NO_ACK, &msg_info);
MBOX_MSG_SEND) ? true : false;