linux-kernel - Re: [PATCH v5 7/7] serial: 8250_exar: Set missing rs485

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Date:   Wed, 13 Dec 2023 12:18:50 +0200 (EET)
From:   Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
To:     Lino Sanfilippo <l.sanfilippo@...bus.com>
cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jiri Slaby <jirislaby@...nel.org>,
        u.kleine-koenig@...gutronix.de, shawnguo@...nel.org,
        s.hauer@...gutronix.de, mcoquelin.stm32@...il.com,
        alexandre.torgue@...s.st.com, cniedermaier@...electronics.com,
        hugo@...ovil.com, LKML <linux-kernel@...r.kernel.org>,
        linux-serial <linux-serial@...r.kernel.org>,
        LinoSanfilippo@....de, Lukas Wunner <lukas@...ner.de>,
        p.rosenberger@...bus.com, stable@...r.kernel.org
Subject: Re: [PATCH v5 7/7] serial: 8250_exar: Set missing rs485_supported
 flag

On Sat, 9 Dec 2023, Lino Sanfilippo wrote:

> The UART supports an auto-RTS mode in which the RTS pin is automatically
> activated during transmission. So mark this mode as being supported even
> if RTS is not controlled by the driver but the UART.
> 
> Also the serial core expects now at least one of both modes rts-on-send or
> rts-after-send to be supported. This is since during sanitization
> unsupported flags are deleted from a RS485 configuration set by userspace.
> However if the configuration ends up with both flags unset, the core prints
> a warning since it considers such a configuration invalid (see
> uart_sanitize_serial_rs485()).
> 
> Cc: stable@...r.kernel.org
> Signed-off-by: Lino Sanfilippo <l.sanfilippo@...bus.com>
> ---
>  drivers/tty/serial/8250/8250_exar.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/tty/serial/8250/8250_exar.c b/drivers/tty/serial/8250/8250_exar.c
> index 6085d356ad86..23366f868ae3 100644
> --- a/drivers/tty/serial/8250/8250_exar.c
> +++ b/drivers/tty/serial/8250/8250_exar.c
> @@ -480,7 +480,7 @@ static int sealevel_rs485_config(struct uart_port *port, struct ktermios *termio
>  }
>  
>  static const struct serial_rs485 generic_rs485_supported = {
> -	.flags = SER_RS485_ENABLED,
> +	.flags = SER_RS485_ENABLED | SER_RS485_RTS_ON_SEND,
>  };
>  
>  static const struct exar8250_platform exar8250_default_platform = {
> @@ -524,7 +524,8 @@ static int iot2040_rs485_config(struct uart_port *port, struct ktermios *termios
>  }
>  
>  static const struct serial_rs485 iot2040_rs485_supported = {
> -	.flags = SER_RS485_ENABLED | SER_RS485_RX_DURING_TX | SER_RS485_TERMINATE_BUS,
> +	.flags = SER_RS485_ENABLED | SER_RS485_RTS_ON_SEND |
> +		 SER_RS485_RX_DURING_TX | SER_RS485_TERMINATE_BUS,
>  };
>  
>  static const struct property_entry iot2040_gpio_properties[] = {

Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>

(I assume you picked the correct flag among the two alternatives).

-- 
 i.