[PATCH 1/2] gpio: Add missing device-managed documentation

[PATCH 1/2] gpio: Add missing device-managed documentation

[Thierry Reding]

From: Thierry Reding <treding@nvidia.com>

Add the GPIO-related device-managed functions to the list of functions
in Documentation/driver-model/devres.txt.

Signed-off-by: Thierry Reding <treding@nvidia.com>
---
 Documentation/driver-model/devres.txt | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/Documentation/driver-model/devres.txt b/Documentation/driver-model/devres.txt
index a3477c3d69a2..7b7d1c4d06bf 100644
--- a/Documentation/driver-model/devres.txt
+++ b/Documentation/driver-model/devres.txt
@@ -310,3 +310,8 @@ SLAVE DMA ENGINE
 
 SPI
   devm_spi_register_master()
+
+GPIO
+  devm_gpiod_get()
+  devm_gpiod_get_index()
+  devm_gpiod_put()
-- 
1.9.2

[PATCH 2/2] gpio: Add helpers for optional GPIOs

[Thierry Reding]

From: Thierry Reding <treding@nvidia.com>

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>
---
 Documentation/driver-model/devres.txt |  2 ++
 drivers/gpio/devres.c                 | 43 +++++++++++++++++++++++++++++++++++
 drivers/gpio/gpiolib.c                | 43 +++++++++++++++++++++++++++++++++++
 include/linux/gpio/consumer.h         | 40 ++++++++++++++++++++++++++++++++
 4 files changed, 128 insertions(+)

diff --git a/Documentation/driver-model/devres.txt b/Documentation/driver-model/devres.txt
index 7b7d1c4d06bf..4796e2ab3349 100644
--- a/Documentation/driver-model/devres.txt
+++ b/Documentation/driver-model/devres.txt
@@ -314,4 +314,6 @@ SPI
 GPIO
   devm_gpiod_get()
   devm_gpiod_get_index()
+  devm_gpiod_get_optional()
+  devm_gpiod_get_index_optional()
   devm_gpiod_put()
diff --git a/drivers/gpio/devres.c b/drivers/gpio/devres.c
index 307464fd015f..65978cf85f79 100644
--- a/drivers/gpio/devres.c
+++ b/drivers/gpio/devres.c
@@ -52,6 +52,22 @@ struct gpio_desc *__must_check devm_gpiod_get(struct device *dev,
 EXPORT_SYMBOL(devm_gpiod_get);
 
 /**
+ * devm_gpiod_get_optional - Resource-managed gpiod_get_optional()
+ * @dev: GPIO consumer
+ * @con_id: function within the GPIO consumer
+ *
+ * Managed gpiod_get_optional(). GPIO descriptors returned from this function
+ * are automatically disposed on driver detach. See gpiod_get_optional() for
+ * detailed information about behavior and return values.
+ */
+struct gpio_desc *__must_check devm_gpiod_get_optional(struct device *dev,
+						       const char *con_id)
+{
+	return devm_gpiod_get_index_optional(dev, con_id, 0);
+}
+EXPORT_SYMBOL(devm_gpiod_get_optional);
+
+/**
  * devm_gpiod_get_index - Resource-managed gpiod_get_index()
  * @dev:	GPIO consumer
  * @con_id:	function within the GPIO consumer
@@ -87,6 +103,33 @@ struct gpio_desc *__must_check devm_gpiod_get_index(struct device *dev,
 EXPORT_SYMBOL(devm_gpiod_get_index);
 
 /**
+ * devm_gpiod_get_index_optional - Resource-managed gpiod_get_index_optional()
+ * @dev: GPIO consumer
+ * @con_id: function within the GPIO consumer
+ * @index: index of the GPIO to obtain in the consumer
+ *
+ * Managed gpiod_get_index_optional(). GPIO descriptors returned from this
+ * function are automatically disposed on driver detach. See
+ * gpiod_get_index_optional() for detailed information about behavior and
+ * return values.
+ */
+struct gpio_desc *__must_check devm_gpiod_get_index_optional(struct device *dev,
+							     const char *con_id,
+							     unsigned int index)
+{
+	struct gpio_desc *desc;
+
+	desc = devm_gpiod_get_index(dev, con_id, index);
+	if (IS_ERR(desc)) {
+		if (PTR_ERR(desc) == -ENOENT)
+			return NULL;
+	}
+
+	return desc;
+}
+EXPORT_SYMBOL(devm_gpiod_get_index_optional);
+
+/**
  * devm_gpiod_put - Resource-managed gpiod_put()
  * @desc:	GPIO descriptor to dispose of
  *
diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index f284e23c78ef..431fddb0dfec 100644
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -2732,6 +2732,22 @@ struct gpio_desc *__must_check gpiod_get(struct device *dev, const char *con_id)
 EXPORT_SYMBOL_GPL(gpiod_get);
 
 /**
+ * gpiod_get_optional - obtain an optional GPIO for a given GPIO function
+ * @dev: GPIO consumer, can be NULL for system-global GPIOs
+ * @con_id: function within the GPIO consumer
+ *
+ * This is equivalent to gpiod_get(), except that when no GPIO was assigned to
+ * the requested function it will return NULL. This is convenient for drivers
+ * that need to handle optional GPIOs.
+ */
+struct gpio_desc *__must_check gpiod_get_optional(struct device *dev,
+						  const char *con_id)
+{
+	return gpiod_get_index_optional(dev, con_id, 0);
+}
+EXPORT_SYMBOL_GPL(gpiod_get_optional);
+
+/**
  * gpiod_get_index - obtain a GPIO from a multi-index GPIO function
  * @dev:	GPIO consumer, can be NULL for system-global GPIOs
  * @con_id:	function within the GPIO consumer
@@ -2794,6 +2810,33 @@ struct gpio_desc *__must_check gpiod_get_index(struct device *dev,
 EXPORT_SYMBOL_GPL(gpiod_get_index);
 
 /**
+ * gpiod_get_index_optional - obtain an optional GPIO from a multi-index GPIO
+ *                            function
+ * @dev: GPIO consumer, can be NULL for system-global GPIOs
+ * @con_id: function within the GPIO consumer
+ * @index: index of the GPIO to obtain in the consumer
+ *
+ * This is equivalent to gpiod_get_index(), except that when no GPIO with the
+ * specified index was assigned to the requested function it will return NULL.
+ * This is convenient for drivers that need to handle optional GPIOs.
+ */
+struct gpio_desc *__must_check gpiod_get_index_optional(struct device *dev,
+							const char *con_id,
+							unsigned int index)
+{
+	struct gpio_desc *desc;
+
+	desc = gpiod_get_index(dev, con_id, index);
+	if (IS_ERR(desc)) {
+		if (PTR_ERR(desc) == -ENOENT)
+			return NULL;
+	}
+
+	return desc;
+}
+EXPORT_SYMBOL_GPL(gpiod_get_index_optional);
+
+/**
  * gpiod_put - dispose of a GPIO descriptor
  * @desc:	GPIO descriptor to dispose of
  *
diff --git a/include/linux/gpio/consumer.h b/include/linux/gpio/consumer.h
index bed128e8f4b1..6a37ef0dc59c 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();
-- 
1.9.2

Re: [PATCH 2/2] gpio: Add helpers for optional GPIOs

[Alexandre Courbot]

On Sat, Apr 26, 2014 at 12:10 AM, Thierry Reding
<thierry.reding@gmail.com> wrote:
> From: Thierry Reding <treding@nvidia.com>
>
> 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.

Patch is sound and the introduced functions are useful indeed.

Reviewed-by: Alexandre Courbot <acourbot@nvidia.com>

It makes me wonder whether this should not have been the behavior of
gpiod_get() directly... My aversion for IS_ERR_OR_NULL drove the
current design, which may not have been optimal.

Oh, well.

Re: [PATCH 2/2] gpio: Add helpers for optional GPIOs

[Linus Walleij]

On Fri, Apr 25, 2014 at 5:10 PM, Thierry Reding
<thierry.reding@gmail.com> wrote:

> From: Thierry Reding <treding@nvidia.com>
>
> Introduce gpiod_get_optional() and gpiod_get_index_optional() helpers
> that make it easier for drivers to handle optional GPIOs.

Excellent Thierry, patch applied with Alexandre's review tag.

Can you *please* also produce a patch to
Documentation/gpio/consumer.txt
explaining the new interface to potential users?

Yours,
Linus Walleij

Re: [PATCH 1/2] gpio: Add missing device-managed documentation

[Linus Walleij]

On Fri, Apr 25, 2014 at 8:10 AM, Thierry Reding
<thierry.reding@gmail.com> wrote:

> From: Thierry Reding <treding@nvidia.com>
>
> Add the GPIO-related device-managed functions to the list of functions
> in Documentation/driver-model/devres.txt.
>
> Signed-off-by: Thierry Reding <treding@nvidia.com>

Patch applied.

Yours,
Linus Walleij