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
