On Sat, 9 Dec 2023, Lino Sanfilippo wrote:
> Among other things uart_sanitize_serial_rs485() tests the sanity of the RTS
> settings in a RS485 configuration that has been passed by userspace.
> If RTS-on-send and RTS-after-send are both set or unset the configuration
> is adjusted and RTS-after-send is disabled and RTS-on-send enabled.
>
> This however makes only sense if both RTS modes are actually supported by
> the driver.
>
> With commit be2e2cb1d281 ("serial: Sanitize rs485_struct") the code does
> take the driver support into account but only checks if one of both RTS
> modes are supported. This may lead to the errorneous result of RTS-on-send
> being set even if only RTS-after-send is supported.
>
> Fix this by changing the implemented logic: First clear all unsupported
> flags in the RS485 configuration, then adjust an invalid RTS setting by
> taking into account which RTS mode is supported.
>
> Cc: stable@xxxxxxxxxxxxxxx
> Fixes: be2e2cb1d281 ("serial: Sanitize rs485_struct")
> Signed-off-by: Lino Sanfilippo <l.sanfilippo@xxxxxxxxxx>
> ---
> drivers/tty/serial/serial_core.c | 28 ++++++++++++++++++----------
> 1 file changed, 18 insertions(+), 10 deletions(-)
>
> diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c
> index c254e88c8452..4eae1406cb6c 100644
> --- a/drivers/tty/serial/serial_core.c
> +++ b/drivers/tty/serial/serial_core.c
> @@ -1371,19 +1371,27 @@ static void uart_sanitize_serial_rs485(struct uart_port *port, struct serial_rs4
> return;
> }
>
> + rs485->flags &= supported_flags;
> +
> /* Pick sane settings if the user hasn't */
> - if ((supported_flags & (SER_RS485_RTS_ON_SEND|SER_RS485_RTS_AFTER_SEND)) &&
> - !(rs485->flags & SER_RS485_RTS_ON_SEND) ==
> + if (!(rs485->flags & SER_RS485_RTS_ON_SEND) ==
> !(rs485->flags & SER_RS485_RTS_AFTER_SEND)) {
> - dev_warn_ratelimited(port->dev,
> - "%s (%d): invalid RTS setting, using RTS_ON_SEND instead\n",
> - port->name, port->line);
> - rs485->flags |= SER_RS485_RTS_ON_SEND;
> - rs485->flags &= ~SER_RS485_RTS_AFTER_SEND;
> - supported_flags |= SER_RS485_RTS_ON_SEND|SER_RS485_RTS_AFTER_SEND;
> - }
> + if (supported_flags & SER_RS485_RTS_ON_SEND) {
> + rs485->flags |= SER_RS485_RTS_ON_SEND;
> + rs485->flags &= ~SER_RS485_RTS_AFTER_SEND;
>
> - rs485->flags &= supported_flags;
> + dev_warn_ratelimited(port->dev,
> + "%s (%d): invalid RTS setting, using RTS_ON_SEND instead\n",
> + port->name, port->line);
> + } else {
> + rs485->flags |= SER_RS485_RTS_AFTER_SEND;
> + rs485->flags &= ~SER_RS485_RTS_ON_SEND;
> +
> + dev_warn_ratelimited(port->dev,
> + "%s (%d): invalid RTS setting, using RTS_AFTER_SEND instead\n",
> + port->name, port->line);
> + }
> + }
Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@xxxxxxxxxxxxxxx>
--
i.
