Hi,
On 15.11.23 at 21:07, Tomas Paukrt wrote:
> This patch provides an option to enable the RS485 mode at boot time
> based on the state of a GPIO pin (DIP switch or configuration jumper).
> The GPIO is defined by the device tree property "rs485-mode-gpio".
This needs documentation in rs485.yaml.
>
> Signed-off-by: Tomas Paukrt <tomaspaukrt@xxxxxxxx>
> ---
> drivers/tty/serial/serial_core.c | 12 ++++++++++++
> 1 file changed, 12 insertions(+)
>
> diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c
> index f1348a5..444d7fd 100644
> --- a/drivers/tty/serial/serial_core.c
> +++ b/drivers/tty/serial/serial_core.c
> @@ -3603,6 +3603,18 @@ int uart_get_rs485_mode(struct uart_port *port)
> }
>
> /*
> + * Enable the RS485 mode based on the state of a GPIO pin.
> + */
> + desc = devm_gpiod_get_optional(dev, "rs485-mode", GPIOD_IN);
> + if (IS_ERR(desc))
> + return dev_err_probe(dev, PTR_ERR(desc), "Cannot get rs485-mode-gpio\n");
> + if (desc) {
> + if (gpiod_get_value(desc))
> + rs485conf->flags |= SER_RS485_ENABLED;
> + devm_gpiod_put(dev, desc);
> + }
So this means RS485 cannot be disabled any more after that. Then we must not allow
to unset SER_RS485_ENABLED if userspace tries to do so via TIOCSRS485.
Regards,
Lino
