linux-kernel - Re: [PATCH 1/8] serial: core: only get RS485 termination gpio if supported

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Date:   Thu, 23 Jun 2022 22:19:23 +0200
From:   Lino Sanfilippo <LinoSanfilippo@....de>
To:     Andy Shevchenko <andy.shevchenko@...il.com>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jiri Slaby <jirislaby@...nel.org>,
        Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Vladimir Zapolskiy <vz@...ia.com>,
        linux-arm Mailing List <linux-arm-kernel@...ts.infradead.org>,
        devicetree <devicetree@...r.kernel.org>,
        "open list:SERIAL DRIVERS" <linux-serial@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Lukas Wunner <lukas@...ner.de>, p.rosenberger@...bus.com,
        Lino Sanfilippo <l.sanfilippo@...bus.com>
Subject: Re: [PATCH 1/8] serial: core: only get RS485 termination gpio if
 supported

On 23.06.22 at 18:32, Andy Shevchenko wrote:

>>
>> Ok I see the point. So what about changing it to:
>
> You mean adding below after the existing code in the module?

Right, to be more precise between getting the gpio and the error check:


	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;
		return dev_err_probe(dev, ret, "Cannot get rs485-term-gpios\n");
	}

Regards,
Lino

>
>> 	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;
>> 	}
>>
>> This would also be consistent to the warnings we print in uart_sanitize_serial_rs485() for invalid
>> RS485 settings.
>
> Probably it's okay, but I dunno we have much on this to gain. Users may start
> complaining of this (harmless) warning. I leave it to others to comment.
>