Hi, 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? Regards, Lino