On 04.07.22 11:55, Ilpo Järvinen wrote:
> On Sun, 3 Jul 2022, Lino Sanfilippo wrote:
>
>> From: Lino Sanfilippo <l.sanfilippo@xxxxxxxxxx>
>>
>> In uart_get_rs485_mode() only try to get a termination GPIO if RS485 bus
>> termination is supported by the driver. This prevents from allocating
>> and holding a GPIO descriptor for the drivers lifetimg that will never be
>> used.
>>
>> Signed-off-by: Lino Sanfilippo <l.sanfilippo@xxxxxxxxxx>
>> ---
>>
>> NOTE:
>> This patch follows the design decision that "rs485_supported" is
>> set by the driver at initialization and cannot be modified
>> afterwards. However the better approach would be to let the serial
>> core modify the termination GPIO support setting based on the
>> existence of a termination GPIO. If "rs485_supported" is not a
>> read-only value any more in future the logic implemented in this
>> patch should be adjusted accordingly.
>>
>> drivers/tty/serial/serial_core.c | 10 ++++++++++
>> 1 file changed, 10 insertions(+)
>>
>> diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c
>> index 85ef7ef00b82..3768663dfa4d 100644
>> --- a/drivers/tty/serial/serial_core.c
>> +++ b/drivers/tty/serial/serial_core.c
>> @@ -3404,6 +3404,16 @@ int uart_get_rs485_mode(struct uart_port *port)
>> */
>> port->rs485_term_gpio = devm_gpiod_get_optional(dev, "rs485-term",
>> GPIOD_OUT_LOW);
>> +
>> + if (port->rs485_term_gpio &&
>> + !(port->rs485_supported->flags & SER_RS485_TERMINATE_BUS)) {
>> + dev_warn(port->dev,
>> + "%s (%d): RS485 termination gpio not supported by driver\n",
>> + port->name, port->line);
>> + devm_gpiod_put(dev, port->rs485_term_gpio);
>> + port->rs485_term_gpio = NULL;
>> + }
>> +
>> if (IS_ERR(port->rs485_term_gpio)) {
>> ret = PTR_ERR(port->rs485_term_gpio);
>> port->rs485_term_gpio = NULL;
>
> I sent a series to embed supported_rs485 to uart_port and manage
> SER_RS485_TERMINATE_BUS properly so I think this won't be necessary
> with that?
>
>
This is why I wrote the "NOTE" above. But yes, this patch is not needed
any more. I will drop it in the next version.
Regards,
Lino
