[PATCH v2] gpio: merrifield: check the return value of devm_kstrdup()

[xkernel.wang@foxmail.com]

From: Xiaoke Wang <xkernel.wang@foxmail.com>

devm_kstrdup() returns pointer to allocated string on success, NULL on
failure. So it is better to check the return value of it.

Before, if devm_kstrdup() fails, pinctrl_dev_name will be NULL, then the
retval below will be a negative error-code(inside gpiochip_add_pin_range(),
pinctrl_find_and_add_gpio_range()->get_pinctrl_dev_from_devname() will
finally check pinctrl_dev_name and return error), so the failure of
devm_kstrdup() can be only implicitly caught after a long call chain.
While this patch is to explicitly catch the failure in time.
> retval = gpiochip_add_pin_range(&priv->chip, pinctrl_dev_name,
>				  range->gpio_base,
>				  range->pin_base,
>				  range->npins);
> if (retval) {
> 	dev_err(priv->dev, "failed to add GPIO pin range\n");
> 	return retval;
> }

Signed-off-by: Xiaoke Wang <xkernel.wang@foxmail.com>
---
Changelogs:
v1 -> v2: update the commit message.
 drivers/gpio/gpio-merrifield.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/gpio/gpio-merrifield.c b/drivers/gpio/gpio-merrifield.c
index 42c4d9d..f3d1bae 100644
--- a/drivers/gpio/gpio-merrifield.c
+++ b/drivers/gpio/gpio-merrifield.c
@@ -409,6 +409,9 @@ static int mrfld_gpio_add_pin_ranges(struct gpio_chip *chip)
 	int retval;
 
 	pinctrl_dev_name = mrfld_gpio_get_pinctrl_dev_name(priv);
+	if (!pinctrl_dev_name)
+		return -ENOMEM;
+
 	for (i = 0; i < ARRAY_SIZE(mrfld_gpio_ranges); i++) {
 		range = &mrfld_gpio_ranges[i];
 		retval = gpiochip_add_pin_range(&priv->chip, pinctrl_dev_name,
--