linux-kernel - Re: [PATCH 7/8] serial: ar933x: Remove redundant assignment in rs485

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Date:   Thu, 30 Jun 2022 02:33:23 +0200
From:   Lino Sanfilippo <LinoSanfilippo@....de>
To:     Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jiri Slaby <jirislaby@...nel.org>, robh+dt@...nel.org,
        krzysztof.kozlowski+dt@...aro.org,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        vz@...ia.com, linux-arm-kernel@...ts.infradead.org,
        devicetree@...r.kernel.org,
        linux-serial <linux-serial@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>, lukas@...ner.de,
        p.rosenberger@...bus.com, Lino Sanfilippo <l.sanfilippo@...bus.com>
Subject: Re: [PATCH 7/8] serial: ar933x: Remove redundant assignment in
 rs485_config



On 27.06.22 10:14, Ilpo Järvinen wrote:
> On Sun, 26 Jun 2022, Lino Sanfilippo wrote:
>
>> On 25.06.22 at 12:14, Ilpo Järvinen wrote:
>>> On Wed, 22 Jun 2022, Lino Sanfilippo wrote:
>>>
>>>> From: Lino Sanfilippo <l.sanfilippo@...bus.com>
>>>>
>>>> In uart_set_rs485_config() the serial core already assigns the passed
>>>> serial_rs485 struct to the uart port.
>>>>
>>>> So remove the assignment in the drivers rs485_config() function to avoid
>>>> redundancy.
>>>>
>>>> Signed-off-by: Lino Sanfilippo <l.sanfilippo@...bus.com>
>>>> ---
>>>>  drivers/tty/serial/ar933x_uart.c | 1 -
>>>>  1 file changed, 1 deletion(-)
>>>>
>>>> diff --git a/drivers/tty/serial/ar933x_uart.c b/drivers/tty/serial/ar933x_uart.c
>>>> index ab2c5b2a1ce8..857e010d01dc 100644
>>>> --- a/drivers/tty/serial/ar933x_uart.c
>>>> +++ b/drivers/tty/serial/ar933x_uart.c
>>>> @@ -591,7 +591,6 @@ static int ar933x_config_rs485(struct uart_port *port,
>>>>  		dev_err(port->dev, "RS485 needs rts-gpio\n");
>>>>  		return 1;
>>>>  	}
>>>> -	port->rs485 = *rs485conf;
>>>>  	return 0;
>>>>  }
>>>
>>> Hmm, I realize that for some reason I missed cleaning up this particular
>>> driver after introducing the serial_rs485 sanitization. It shouldn't need
>>> that preceeding if block either because ar933x_no_rs485 gets applied if
>>> there's no rts_gpiod so the core clears SER_RS485_ENABLED.
>>
>> I think we still need that "if" in case that RS485 was not enabled at driver
>> startup (no rs485-enabled-at-boot-time) and no RTS GPIO was defined but then
>> RS485 is enabled via TIOCSRS485.
>>
>> Maybe in ar933x_uart_probe()
>>
>> 	if ((port->rs485.flags & SER_RS485_ENABLED) &&
>> 	    !up->rts_gpiod) {
>> 		dev_err(&pdev->dev, "lacking rts-gpio, disabling RS485\n");
>> 		port->rs485.flags &= ~SER_RS485_ENABLED;
>> 		port->rs485_supported = &ar933x_no_rs485;
>> 	}
>>
>> should rather be
>
> I think it would be better (and what I should have done while moving the
> check there in the first place but I missed it). In addition, however, it
> would be useful to not print unnecessarily:
>
>> 	if (!up->rts_gpiod) {
>
> if (port->rs485.flags & SER_RS485_ENABLED) {
>
>> 		dev_err(&pdev->dev, "lacking rts-gpio, disabling RS485\n");
>> 		port->rs485.flags &= ~SER_RS485_ENABLED;
>
> }


Right. I will send a fix for this with the new version of my series.

Regards,
Lino