MCR_LOOPBACK
mcr |= MCR_LOOPBACK;
mcr &= ~MCR_LOOPBACK;
return ti_do_config(port, UMPC_SET_CLR_LOOPBACK, mcr & MCR_LOOPBACK);
mcr |= MCR_LOOPBACK;
mcr &= ~MCR_LOOPBACK;
mcr &= ~MCR_LOOPBACK;
mcr |= MCR_LOOPBACK;
| ((mcr & MCR_LOOPBACK) ? TIOCM_LOOP : 0)