Hi Matwey,

On 11/07/2015 05:09 AM, Matwey V. Kornilov wrote:
> When 8250 driver doesn't have its own hardware RS485 support and doesn't
> want to override rs485_config callback, then default
> serial8250_rs485_config is used. It just stores supplied by user-space
> config.
> 
> Signed-off-by: Matwey V. Kornilov <[email protected]>
> ---
>  drivers/tty/serial/8250/8250_core.c | 10 ++++++++++
>  1 file changed, 10 insertions(+)
> 
> diff --git a/drivers/tty/serial/8250/8250_core.c 
> b/drivers/tty/serial/8250/8250_core.c
> index 3912646..8f292da 100644
> --- a/drivers/tty/serial/8250/8250_core.c
> +++ b/drivers/tty/serial/8250/8250_core.c
> @@ -395,6 +395,12 @@ static void serial8250_release_rsa_resource(struct 
> uart_8250_port *up)
>       }
>  }
>  #endif
> +static int serial8250_rs485_config(struct uart_port *port,
> +                             struct serial_rs485 *rs485)
> +{
> +     port->rs485 = *rs485;
> +     return 0;
> +}
>  
>  static const struct uart_ops *base_ops;
>  static struct uart_ops univ8250_port_ops;
> @@ -990,6 +996,10 @@ int serial8250_register_8250_port(struct uart_8250_port 
> *up)
>               uart->port.rs485        = up->port.rs485;
>               uart->dma               = up->dma;
>  
> +             /* Use software RS485 support when hardware one is not 
> available */
> +             if (!(uart->capabilities & UART_CAP_HW485) && 
> !uart->port.rs485_config)
> +                     uart->port.rs485_config = serial8250_rs485_config;

To setup a default 8250 port function,
1. define the default 8250 port function in 8250/8250_port.c
2. add the port function to the dispatch table (serial8250_pops)
3. add a test for 8250 sub-driver override in serial8250_register_8250_port()
   Eg.,

                if (up->port.rs485_config)
                        uart->port.rs485_config = up->port.rs485_config;

Regards,
Peter Hurley

>               /* Take tx_loadsz from fifosize if it wasn't set separately */
>               if (uart->port.fifosize && !uart->tx_loadsz)
>                       uart->tx_loadsz = uart->port.fifosize;
> 

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