UARTn_STATE_TX_FULL
return (status & UARTn_STATE_TX_FULL) ? 0 : TIOCSER_TEMT;
while (mps2_uart_read8(port, UARTn_STATE) & UARTn_STATE_TX_FULL)
while (readb(port->membase + UARTn_STATE) & UARTn_STATE_TX_FULL)