On Sat, 14 Oct 2023, Lino Sanfilippo wrote:
> On 13.10.23 12:24, Ilpo Järvinen wrote:
> > On Thu, 12 Oct 2023, Lino Sanfilippo wrote:
> >> On 12.10.23 15:10, Ilpo Järvinen wrote:
> >>> On Wed, 11 Oct 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 697c36dc7ec8..f4feebf8200f 100644
> >>>> --- a/drivers/tty/serial/serial_core.c
> >>>> +++ b/drivers/tty/serial/serial_core.c
> >>>> @@ -1370,19 +1370,27 @@ 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;
> >>>
> >>> So if neither of the flags is supported, what will happen? You might want
> >>> add if after that else?
> >>>
> >>
> >> I would consider this a bug in the driver, as at least one of both modes
> >> has to be supported. If the driver does not have at least one of both flags
> >> set in rs485_supported.flags we could print a warning though. Would you prefer that?
> >
> > 8250_exar.c needs to fixed then?
> I was taking these as things one can
> > "configure" even if when there's support only for a one of them there's
> > not that much to configure. As there was neither in 8250_exar's code, I
> > didn't add either flag.
>
> > But I suppose your interpretation of those flag makes more sense.
>
> IMHO this is consistent with what we have in uart_get_rs485_mode(). This function
> ensures that we have at least one RTS mode set (with default to RTS_ON_SEND). So
> concerning 8250_exar.c, I think it should be fixed (havent noticed the missing
> RTS mode though until you mentioned it). Would you like to provide a fix for this
> or shall I include one into the next version of this series?
Just create that fix yourself thank you and include it into your series,
I'm busy with other stuff currently.
--
i.
