From mboxrd@z Thu Jan  1 00:00:00 1970
From: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Subject: Re: [PATCH v3] gpio: of: make it possible to name GPIO lines
Date: Thu, 21 Apr 2016 10:06:15 -0700
Message-ID: <20160421170615.GA25466@dtor-ws>
References: <1461236901-28626-1-git-send-email-linus.walleij@linaro.org>
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To: Linus Walleij <linus.walleij@linaro.org>
Cc: linux-gpio@vger.kernel.org, Alexandre Courbot <acourbot@nvidia.com>, Johan Hovold <johan@kernel.org>, Michael Welling <mwelling@ieee.org>, Markus Pargmann <mpa@pengutronix.de>, Lee Campbell <leecam@google.com>, Bamvor Jian Zhang <bamvor.zhangjian@linaro.org>, Grant Likely <grant.likely@linaro.org>, Arnd Bergmann <arnd@arndb.de>, Mark Brown <broonie@kernel.org>, Greg Kroah-Hartman <gregkh@linuxfoundation.org>, Rob Herring <robh+dt@kernel.org>, Amit Kucheria <amit.kucheria@linaro.org>, David Mandala <david.mandala@linaro.org>, devicetree@vger.kernel.org

Hi Linus,

On Thu, Apr 21, 2016 at 01:08:21PM +0200, Linus Walleij wrote:
>  /**
> + * of_gpiochip_set_names() - set up the names of the lines
> + * @chip: GPIO chip whose lines should be named, if possible
> + */
> +static void of_gpiochip_set_names(struct gpio_chip *gc)
> +{
> +	struct gpio_device *gdev = gc->gpiodev;
> +	struct device_node *np = gc->of_node;
> +	int i;
> +	int nstrings;
> +
> +	/* Do we even have the "gpio-line-names" property */
> +	if (!of_property_read_bool(np, "gpio-line-names"))
> +		return;
> +
> +	nstrings = of_property_count_strings(np, "gpio-line-names");
> +	/*
> +	 * Make sure to not index beyond either the end of the
> +	 * "gpio-names" array nor the number of descriptors of
> +	 * the GPIO device.
> +	 */

I know you mentioned that it already been discussed much, but I am not
sure why we need to count the string (and validate that strings are
present by treating the property as boolean?), when we could do
something like this (relying on the fact that
of_property_read_string_index() returns 0 or negative error, no positive
return codes):

	for (i = 0; i < gdev->ngpio; i++) {
		const char *name;
		int error;

		error = of_property_read_string_index(np,
						      "gpio-line-names",
						      i,
						      &name);
		if (error) {
			if (error != -ENODATA)
				dev_err(&gdev->dev,
					"unable to name line %d: %d\n",
					i, error);
			/*
			 * Either no more strings (-ENODATA), or
			 * other error, in any case we are done naming.
			 */
			break;
		}

		gdev->descs[i].name = name;
	}

Thanks.

-- 
Dmitry