gpio: Add helpers for optional GPIOs

Introduce gpiod_get_optional() and gpiod_get_index_optional() helpers
that make it easier for drivers to handle optional GPIOs.

Currently in order to handle optional GPIOs, a driver needs to special
case error handling for -ENOENT, such as this:

	gpio = gpiod_get(dev, "foo");
	if (IS_ERR(gpio)) {
		if (PTR_ERR(gpio) != -ENOENT)
			return PTR_ERR(gpio);

		gpio = NULL;
	}

	if (gpio) {
		/* set up GPIO */
	}

With these new helpers the above is reduced to:

	gpio = gpiod_get_optional(dev, "foo");
	if (IS_ERR(gpio))
		return PTR_ERR(gpio);

	if (gpio) {
		/* set up GPIO */
	}

While at it, device-managed variants of these functions are also
provided.

Signed-off-by: Thierry Reding <treding@nvidia.com>
Reviewed-by: Alexandre Courbot <acourbot@nvidia.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

1 files changed, 40 insertions, 0 deletions

diff --git a/include/linux/gpio/consumer.h b/include/linux/gpio/consumer.h
index bed128e8f4b..6a37ef0dc59 100644
--- a/include/linux/gpio/consumer.h
+++ b/include/linux/gpio/consumer.h
@@ -23,6 +23,12 @@ struct gpio_desc *__must_check gpiod_get(struct device *dev,
 struct gpio_desc *__must_check gpiod_get_index(struct device *dev,
 					       const char *con_id,
 					       unsigned int idx);
+struct gpio_desc *__must_check gpiod_get_optional(struct device *dev,
+						  const char *con_id);
+struct gpio_desc *__must_check gpiod_get_index_optional(struct device *dev,
+							const char *con_id,
+							unsigned int index);
+
 void gpiod_put(struct gpio_desc *desc);
 
 struct gpio_desc *__must_check devm_gpiod_get(struct device *dev,
@@ -30,6 +36,12 @@ struct gpio_desc *__must_check devm_gpiod_get(struct device *dev,
 struct gpio_desc *__must_check devm_gpiod_get_index(struct device *dev,
 						    const char *con_id,
 						    unsigned int idx);
+struct gpio_desc *__must_check devm_gpiod_get_optional(struct device *dev,
+						       const char *con_id);
+struct gpio_desc *__must_check
+devm_gpiod_get_index_optional(struct device *dev, const char *con_id,
+			      unsigned int index);
+
 void devm_gpiod_put(struct device *dev, struct gpio_desc *desc);
 
 int gpiod_get_direction(const struct gpio_desc *desc);
@@ -73,6 +85,20 @@ static inline struct gpio_desc *__must_check gpiod_get_index(struct device *dev,
 {
 	return ERR_PTR(-ENOSYS);
 }
+
+static inline struct gpio_desc *__must_check
+gpiod_get_optional(struct device *dev, const char *con_id)
+{
+	return ERR_PTR(-ENOSYS);
+}
+
+static inline struct gpio_desc *__must_check
+gpiod_get_index_optional(struct device *dev, const char *con_id,
+			 unsigned int index)
+{
+	return ERR_PTR(-ENOSYS);
+}
+
 static inline void gpiod_put(struct gpio_desc *desc)
 {
 	might_sleep();
@@ -93,6 +119,20 @@ struct gpio_desc *__must_check devm_gpiod_get_index(struct device *dev,
 {
 	return ERR_PTR(-ENOSYS);
 }
+
+static inline struct gpio_desc *__must_check
+devm_gpiod_get_optional(struct device *dev, const char *con_id)
+{
+	return ERR_PTR(-ENOSYS);
+}
+
+static inline struct gpio_desc *__must_check
+devm_gpiod_get_index_optional(struct device *dev, const char *con_id,
+			      unsigned int index)
+{
+	return ERR_PTR(-ENOSYS);
+}
+
 static inline void devm_gpiod_put(struct device *dev, struct gpio_desc *desc)
 {
 	might_sleep();