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@vger.kernel.org
Fixes: be2e2cb1d281 ("serial: Sanitize rs485_struct")
Signed-off-by: Lino Sanfilippo <l.sanfilippo@kunbus.com>
---
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;
+
+ dev_warn_ratelimited(port->dev,
+ "%s (%d): invalid RTS setting, using RTS_AFTER_SEND instead\n",
+ port->name, port->line);
+ }
+ }
uart_sanitize_serial_rs485_delays(port, rs485);
--
2.40.1
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@vger.kernel.org
> Fixes: be2e2cb1d281 ("serial: Sanitize rs485_struct")
> Signed-off-by: Lino Sanfilippo <l.sanfilippo@kunbus.com>
> ---
> 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.
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@vger.kernel.org
>> Fixes: be2e2cb1d281 ("serial: Sanitize rs485_struct")
>> Signed-off-by: Lino Sanfilippo <l.sanfilippo@kunbus.com>
>> ---
>> 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
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@vger.kernel.org
> >> Fixes: be2e2cb1d281 ("serial: Sanitize rs485_struct")
> >> Signed-off-by: Lino Sanfilippo <l.sanfilippo@kunbus.com>
> >> ---
> >> 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.
--
i.
Hi Ilpo,
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@vger.kernel.org
>>>> Fixes: be2e2cb1d281 ("serial: Sanitize rs485_struct")
>>>> Signed-off-by: Lino Sanfilippo <l.sanfilippo@kunbus.com>
>>>> ---
>>>> 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?
BR,
Lino
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@vger.kernel.org
> >>>> Fixes: be2e2cb1d281 ("serial: Sanitize rs485_struct")
> >>>> Signed-off-by: Lino Sanfilippo <l.sanfilippo@kunbus.com>
> >>>> ---
> >>>> 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.
On 16.10.23 12:05, Ilpo Järvinen wrote:
> 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@vger.kernel.org
>>>>>> Fixes: be2e2cb1d281 ("serial: Sanitize rs485_struct")
>>>>>> Signed-off-by: Lino Sanfilippo <l.sanfilippo@kunbus.com>
>>>>>> ---
>>>>>> 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.
>
>
Sure, will do.
BR,
Lino
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