Re: [PATCH tty-linus] serial: Reduce spinlocked portion of uart_rs485_config()

[Lukas Wunner <lukas@wunner.de>]

On Thu, Sep 21, 2023 at 06:01:41PM +0300, Ilpo Järvinen wrote:
> On Thu, 21 Sep 2023, Lukas Wunner wrote:
> > --- a/drivers/tty/serial/serial_core.c
> > +++ b/drivers/tty/serial/serial_core.c
> > @@ -1404,12 +1404,18 @@ static void uart_set_rs485_termination(struct uart_port *port,
> >  static int uart_rs485_config(struct uart_port *port)
> >  {
> >  	struct serial_rs485 *rs485 = &port->rs485;
> > +	unsigned long flags;
> >  	int ret;
> >  
> > +	if (!(rs485->flags & SER_RS485_ENABLED))
> > +		return 0;
> > +
> >  	uart_sanitize_serial_rs485(port, rs485);
> 
> There's a subtle change in behavior here, uart_sanitize_serial_rs485() 
> memset()s rs485 if RS485 is not enabled but the early return above does 
> not.

The two callers of uart_rs485_config() only call it if
(!(uport->rs485.flags & SER_RS485_ENABLED)).

Adding that early return ensures that the behavior doesn't change.

So I don't quite see why you think there's a change in behavior?
Am I missing something?

Thanks,

Lukas