/* This function is used to send a high-priority XON/XOFF character to the device  */
static void uart_send_xchar(struct tty_struct *tty, char ch)
/* This function is used to send a high-priority XON/XOFF character to the device  */
static void uart_send_xchar(struct tty_struct *tty, char ch)
{
	struct uart_state *state = tty->driver_data;
	struct uart_port *port = state->uart_port;
	unsigned long flags;
	if (port->ops->send_xchar)
		port->ops->send_xchar(port, ch);
	else {
		port->x_char = ch;
		if (ch) {
			spin_lock_irqsave(&port->lock, flags);
			port->ops->start_tx(port);
			spin_unlock_irqrestore(&port->lock, flags);
		}
	}
}