gpio: brcmstb: support gpio-line-names property

The default handling of the gpio-line-names property by the
gpiolib-of implementation does not work with the multiple
gpiochip banks per device structure used by the gpio-brcmstb
driver.

This commit adds driver level support for the device tree
property so that GPIO lines can be assigned friendly names.
Signed-off-by: Doug Berger <opendmb@gmail.com>
Link: https://lore.kernel.org/r/1583780521-45702-1-git-send-email-opendmb@gmail.comAcked-by: Gregory Fong <gregory.0xf0@gmail.com>
Acked-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

drivers/gpio/gpio-brcmstb.c

@@ -603,6 +603,49 @@ static const struct dev_pm_ops brcmstb_gpio_pm_ops = {
 	.resume_noirq = brcmstb_gpio_resume,
 };
 
+static void brcmstb_gpio_set_names(struct device *dev,
+				   struct brcmstb_gpio_bank *bank)
+{
+	struct device_node *np = dev->of_node;
+	const char **names;
+	int nstrings, base;
+	unsigned int i;
+
+	base = bank->id * MAX_GPIO_PER_BANK;
+
+	nstrings = of_property_count_strings(np, "gpio-line-names");
+	if (nstrings <= base)
+		/* Line names not present */
+		return;
+
+	names = devm_kcalloc(dev, MAX_GPIO_PER_BANK, sizeof(*names),
+			     GFP_KERNEL);
+	if (!names)
+		return;
+
+	/*
+	 * Make sure to not index beyond the end of the number of descriptors
+	 * of the GPIO device.
+	 */
+	for (i = 0; i < bank->width; i++) {
+		const char *name;
+		int ret;
+
+		ret = of_property_read_string_index(np, "gpio-line-names",
+						    base + i, &name);
+		if (ret) {
+			if (ret != -ENODATA)
+				dev_err(dev, "unable to name line %d: %d\n",
+					base + i, ret);
+			break;
+		}
+		if (*name)
+			names[i] = name;
+	}
+
+	bank->gc.names = names;
+}
+
 static int brcmstb_gpio_probe(struct platform_device *pdev)
 {
 	struct device *dev = &pdev->dev;
@@ -726,6 +769,7 @@ static int brcmstb_gpio_probe(struct platform_device *pdev)
 		need_wakeup_event |= !!__brcmstb_gpio_get_active_irqs(bank);
 		gc->write_reg(reg_base + GIO_MASK(bank->id), 0);
 
+		brcmstb_gpio_set_names(dev, bank);
 		err = gpiochip_add_data(gc, bank);
 		if (err) {
 			dev_err(dev, "Could not add gpiochip for bank %d\n",