UART_FLUSH_TRANSMITTER
case UART_FLUSH_TRANSMITTER:
ns8250_flush(bas, UART_FLUSH_RECEIVER|UART_FLUSH_TRANSMITTER);
if (what & UART_FLUSH_TRANSMITTER)
if (((lsr & LSR_THRE) == 0) && (what & UART_FLUSH_TRANSMITTER))
ns8250_bus_flush(sc, UART_FLUSH_RECEIVER|UART_FLUSH_TRANSMITTER);
if (what & UART_FLUSH_TRANSMITTER) {