unsigned int uart_get_baud_rate
(struct uart_port * port, struct termios * termios, struct termios * old, unsigned int min, unsigned int max);
uart_port structure describing the port in question.
desired termios settings.
old termios (or NULL)
minimum acceptable baud rate
maximum acceptable baud rate
Decode the termios structure into a numeric baud rate, taking account of the magic 38400 baud rate (with spd_* flags), and mapping the B0
rate to 9600 baud.
If the new baud rate is invalid, try the old termios setting. If it's still invalid, we try 9600 baud.
Update the termios structure to reflect the baud rate we're actually going to be using.