On Tue, Sep 19, 2023 at 07:26:40PM -0700, Max Filippov wrote:
> uart_get_baud_rate has input parameters 'min' and 'max' limiting the
> range of acceptable baud rates from the caller's perspective. If neither
> current or old termios structures have acceptable baud rate setting and
> 9600 is not in the min/max range either the function returns 0 and
> issues a warning.
> However for a UART that does not support speed of 9600 baud this is
> expected behavior.
> Clarify that 0 can be (and always could be) returned from the
> uart_get_baud_rate. Don't issue a warning in that case.
> Move the warinng to the uart_get_divisor instead, which is often called
> with the uart_get_baud_rate return value.
>
> Signed-off-by: Max Filippov <jcmvbkbc@xxxxxxxxx>
> ---
> drivers/tty/serial/serial_core.c | 5 ++---
> 1 file changed, 2 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c
> index 7bdc21d5e13b..a8e2915832e8 100644
> --- a/drivers/tty/serial/serial_core.c
> +++ b/drivers/tty/serial/serial_core.c
> @@ -431,7 +431,7 @@ EXPORT_SYMBOL(uart_update_timeout);
> * baud.
> *
> * If the new baud rate is invalid, try the @old termios setting. If it's still
> - * invalid, we try 9600 baud.
> + * invalid, we try 9600 baud. If that is also invalid 0 is returned.
> *
> * The @termios structure is updated to reflect the baud rate we're actually
> * going to be using. Don't do this for the case where B0 is requested ("hang
> @@ -515,8 +515,6 @@ uart_get_baud_rate(struct uart_port *port, struct ktermios *termios,
> max - 1, max - 1);
> }
> }
> - /* Should never happen */
> - WARN_ON(1);
I'm ok with this removal, but:
> return 0;
> }
> EXPORT_SYMBOL(uart_get_baud_rate);
> @@ -539,6 +537,7 @@ uart_get_divisor(struct uart_port *port, unsigned int baud)
> {
> unsigned int quot;
>
> + WARN_ON(baud == 0);
Why is this needed? If this isn't happening today, then there's no need
to check for this here. Or if it can happen, we should return an error,
not cause a possible reboot of the system if panic-on-warn is enabled.
thanks,
greg k-h
