linux-kernel - Re: [PATCH DON'T APPLY v2 3/7] serial: 8250: Support rs485 bus termination GPIO

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Date:   Mon, 30 Mar 2020 17:51:02 +0300
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     Heiko Stuebner <heiko@...ech.de>
Cc:     gregkh@...uxfoundation.org, jslaby@...e.com,
        matwey.kornilov@...il.com, linux-serial@...r.kernel.org,
        linux-kernel@...r.kernel.org, lukas@...ner.de,
        christoph.muellner@...obroma-systems.com,
        giulio.benetti@...ronovasrl.com
Subject: Re: [PATCH DON'T APPLY v2 3/7] serial: 8250: Support rs485 bus
 termination GPIO

On Thu, Mar 26, 2020 at 12:14:18AM +0100, Heiko Stuebner wrote:
> From: Lukas Wunner <lukas@...ner.de>
> 
> Amend the serial core to retrieve the rs485 bus termination GPIO from
> the device tree (or ACPI table) and amend the default ->rs485_config()
> callback for 8250 drivers to change the GPIO on request from user space.

> +	port->rs485_term_gpio = devm_gpiod_get(dev, "rs485-term",
> +					       GPIOD_FLAGS_BIT_DIR_OUT);
> +	if (IS_ERR(port->rs485_term_gpio)) {
> +		ret = PTR_ERR(port->rs485_term_gpio);
> +		port->rs485_term_gpio = NULL;
> +		if (ret != -ENOENT) {
> +			if (ret != -EPROBE_DEFER)
> +				dev_err(dev, "Cannot get rs485-term-gpios\n");
> +			return ret;
> +		}

NIH of gpiod_get_optional().

> +	} else {
> +		ret = gpiod_get_value(port->rs485_term_gpio);
> +		if (ret < 0) {
> +			dev_err(dev, "Cannot get rs485-term-gpios value\n");
> +			return ret;
> +		}
> +		if (ret)
> +			rs485conf->flags |= SER_RS485_TERMINATE_BUS;
> +	}

-- 
With Best Regards,
Andy Shevchenko