UART_DRAIN_TRANSMITTER
#define UART_FLUSH_TRANSMITTER UART_DRAIN_TRANSMITTER
ns8250_drain(bas, UART_DRAIN_TRANSMITTER);
if (what & UART_DRAIN_TRANSMITTER) {
drain |= UART_DRAIN_TRANSMITTER;
error = ns8250_drain(bas, UART_DRAIN_TRANSMITTER);
error = ns8250_drain(bas, UART_DRAIN_RECEIVER|UART_DRAIN_TRANSMITTER);