[PATCH] gpio: add flags argument to gpiod_get*() functions

[Alexandre Courbot <acourbot@xxxxxxxxxx>]

The huge majority of GPIOs have their direction and initial value set
right after being obtained by one of the gpiod_get() functions. The
integer GPIO API had gpio_request_one() that took a convenience flags
parameter allowing to specify an direction and value applied to the
returned GPIO. This feature greatly simplifies client code and ensures
errors are always handled properly.

A similar feature has been requested for the gpiod API. Since setting
the direction of a GPIO is so often the very next action done after
obtaining its descriptor, we prefer to extend the existing functions
instead of introducing new functions that would raise the
number of gpiod getters to 16 (!).

The drawback of this approach is that all gpiod clients need to be
updated. To limit the pain, temporary macros are introduced that allow
gpiod_get*() to be called with or without the extra flags argument. They
will be removed once all consumer code has been updated.

Signed-off-by: Alexandre Courbot <acourbot@xxxxxxxxxx>
---
This dude can be applied harmlessly to the GPIO tree - then I will go
after every gpiod user to update the calls to gpiod_get*() before
removing the macros in consumer.h.

Formatting is not fixed everywhere but this is on purpose, to limit the
amount of noise in the temporary changes.

 Documentation/gpio/consumer.txt | 26 ++++++++++---
 drivers/gpio/devres.c           | 40 ++++++++++++--------
 drivers/gpio/gpiolib.c          | 67 +++++++++++++++++++++++-----------
 include/linux/gpio/consumer.h   | 81 +++++++++++++++++++++++++++++++++--------
 4 files changed, 155 insertions(+), 59 deletions(-)

diff --git a/Documentation/gpio/consumer.txt b/Documentation/gpio/consumer.txt
index d8abfc3..7654632 100644
--- a/Documentation/gpio/consumer.txt
+++ b/Documentation/gpio/consumer.txt
@@ -29,13 +29,24 @@ gpiod_get() functions. Like many other kernel subsystems, gpiod_get() takes the
 device that will use the GPIO and the function the requested GPIO is supposed to
 fulfill:
 
-	struct gpio_desc *gpiod_get(struct device *dev, const char *con_id)
+	struct gpio_desc *gpiod_get(struct device *dev, const char *con_id,
+				    enum gpiod_flags flags)
 
 If a function is implemented by using several GPIOs together (e.g. a simple LED
 device that displays digits), an additional index argument can be specified:
 
 	struct gpio_desc *gpiod_get_index(struct device *dev,
-					  const char *con_id, unsigned int idx)
+					  const char *con_id, unsigned int idx,
+					  enum gpiod_flags flags)
+
+The flags parameter is used to optionally specify a direction and initial value
+for the GPIO. Values can be:
+
+* GPIOD_ASIS or 0 to not initialize the GPIO at all. The direction must be set
+  later with one of the dedicated functions.
+* GPIOD_IN to initialize the GPIO as input.
+* GPIOD_OUT_LOW to initialize the GPIO as output with a value of 0.
+* GPIOD_OUT_HIGH to initialize the GPIO as output with a value of 1.
 
 Both functions return either a valid GPIO descriptor, or an error code checkable
 with IS_ERR() (they will never return a NULL pointer). -ENOENT will be returned
@@ -46,11 +57,13 @@ errors and an absence of GPIO for optional GPIO parameters.
 
 Device-managed variants of these functions are also defined:
 
-	struct gpio_desc *devm_gpiod_get(struct device *dev, const char *con_id)
+	struct gpio_desc *devm_gpiod_get(struct device *dev, const char *con_id,
+					 enum gpiod_flags flags)
 
 	struct gpio_desc *devm_gpiod_get_index(struct device *dev,
 					       const char *con_id,
-					       unsigned int idx)
+					       unsigned int idx,
+					       enum gpiod_flags flags)
 
 A GPIO descriptor can be disposed of using the gpiod_put() function:
 
@@ -67,8 +80,9 @@ Using GPIOs
 
 Setting Direction
 -----------------
-The first thing a driver must do with a GPIO is setting its direction. This is
-done by invoking one of the gpiod_direction_*() functions:
+The first thing a driver must do with a GPIO is setting its direction. If no
+direction-setting flags have been given to gpiod_get*(), this is done by
+invoking one of the gpiod_direction_*() functions:
 
 	int gpiod_direction_input(struct gpio_desc *desc)
 	int gpiod_direction_output(struct gpio_desc *desc, int value)
diff --git a/drivers/gpio/devres.c b/drivers/gpio/devres.c
index 65978cf..41b2f40 100644
--- a/drivers/gpio/devres.c
+++ b/drivers/gpio/devres.c
@@ -39,47 +39,53 @@ static int devm_gpiod_match(struct device *dev, void *res, void *data)
  * devm_gpiod_get - Resource-managed gpiod_get()
  * @dev:	GPIO consumer
  * @con_id:	function within the GPIO consumer
+ * @flags:	optional GPIO initialization flags
  *
  * Managed gpiod_get(). GPIO descriptors returned from this function are
  * automatically disposed on driver detach. See gpiod_get() for detailed
  * information about behavior and return values.
  */
-struct gpio_desc *__must_check devm_gpiod_get(struct device *dev,
-					      const char *con_id)
+struct gpio_desc *__must_check __devm_gpiod_get(struct device *dev,
+					      const char *con_id,
+					      enum gpiod_flags flags)
 {
-	return devm_gpiod_get_index(dev, con_id, 0);
+	return devm_gpiod_get_index(dev, con_id, 0, flags);
 }
-EXPORT_SYMBOL(devm_gpiod_get);
+EXPORT_SYMBOL(__devm_gpiod_get);
 
 /**
  * devm_gpiod_get_optional - Resource-managed gpiod_get_optional()
  * @dev: GPIO consumer
  * @con_id: function within the GPIO consumer
+ * @flags: optional GPIO initialization flags
  *
  * 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)
+struct gpio_desc *__must_check __devm_gpiod_get_optional(struct device *dev,
+						       const char *con_id,
+						       enum gpiod_flags flags)
 {
-	return devm_gpiod_get_index_optional(dev, con_id, 0);
+	return devm_gpiod_get_index_optional(dev, con_id, 0, flags);
 }
-EXPORT_SYMBOL(devm_gpiod_get_optional);
+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
  * @idx:	index of the GPIO to obtain in the consumer
+ * @flags:	optional GPIO initialization flags
  *
  * Managed gpiod_get_index(). GPIO descriptors returned from this function are
  * automatically disposed on driver detach. See gpiod_get_index() for detailed
  * information about behavior and return values.
  */
-struct gpio_desc *__must_check devm_gpiod_get_index(struct device *dev,
+struct gpio_desc *__must_check __devm_gpiod_get_index(struct device *dev,
 						    const char *con_id,
-						    unsigned int idx)
+						    unsigned int idx,
+						    enum gpiod_flags flags)
 {
 	struct gpio_desc **dr;
 	struct gpio_desc *desc;
@@ -89,7 +95,7 @@ struct gpio_desc *__must_check devm_gpiod_get_index(struct device *dev,
 	if (!dr)
 		return ERR_PTR(-ENOMEM);
 
-	desc = gpiod_get_index(dev, con_id, idx);
+	desc = gpiod_get_index(dev, con_id, idx, flags);
 	if (IS_ERR(desc)) {
 		devres_free(dr);
 		return desc;
@@ -100,26 +106,28 @@ struct gpio_desc *__must_check devm_gpiod_get_index(struct device *dev,
 
 	return desc;
 }
-EXPORT_SYMBOL(devm_gpiod_get_index);
+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
+ * @flags: optional GPIO initialization flags
  *
  * 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,
+struct gpio_desc *__must_check __devm_gpiod_get_index_optional(struct device *dev,
 							     const char *con_id,
-							     unsigned int index)
+							     unsigned int index,
+							 enum gpiod_flags flags)
 {
 	struct gpio_desc *desc;
 
-	desc = devm_gpiod_get_index(dev, con_id, index);
+	desc = devm_gpiod_get_index(dev, con_id, index, flags);
 	if (IS_ERR(desc)) {
 		if (PTR_ERR(desc) == -ENOENT)
 			return NULL;
@@ -127,7 +135,7 @@ struct gpio_desc *__must_check devm_gpiod_get_index_optional(struct device *dev,
 
 	return desc;
 }
-EXPORT_SYMBOL(devm_gpiod_get_index_optional);
+EXPORT_SYMBOL(__devm_gpiod_get_index_optional);
 
 /**
  * devm_gpiod_put - Resource-managed gpiod_put()
diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index 18b069e..70c48d4 100644
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -1578,38 +1578,43 @@ static struct gpio_desc *gpiod_find(struct device *dev, const char *con_id,
  * gpiod_get - obtain a GPIO for a given GPIO function
  * @dev:	GPIO consumer, can be NULL for system-global GPIOs
  * @con_id:	function within the GPIO consumer
+ * @flags:	optional GPIO initialization flags
  *
  * Return the GPIO descriptor corresponding to the function con_id of device
  * dev, -ENOENT if no GPIO has been assigned to the requested function, or
  * another IS_ERR() code if an error occured while trying to acquire the GPIO.
  */
-struct gpio_desc *__must_check gpiod_get(struct device *dev, const char *con_id)
+struct gpio_desc *__must_check __gpiod_get(struct device *dev, const char *con_id,
+					 enum gpiod_flags flags)
 {
-	return gpiod_get_index(dev, con_id, 0);
+	return gpiod_get_index(dev, con_id, 0, flags);
 }
-EXPORT_SYMBOL_GPL(gpiod_get);
+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
+ * @flags: optional GPIO initialization flags
  *
  * 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)
+struct gpio_desc *__must_check __gpiod_get_optional(struct device *dev,
+						  const char *con_id,
+						  enum gpiod_flags flags)
 {
-	return gpiod_get_index_optional(dev, con_id, 0);
+	return gpiod_get_index_optional(dev, con_id, 0, flags);
 }
-EXPORT_SYMBOL_GPL(gpiod_get_optional);
+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
  * @idx:	index of the GPIO to obtain in the consumer
+ * @flags:	optional GPIO initialization flags
  *
  * This variant of gpiod_get() allows to access GPIOs other than the first
  * defined one for functions that define several GPIOs.
@@ -1618,23 +1623,24 @@ EXPORT_SYMBOL_GPL(gpiod_get_optional);
  * requested function and/or index, or another IS_ERR() code if an error
  * occured while trying to acquire the GPIO.
  */
-struct gpio_desc *__must_check gpiod_get_index(struct device *dev,
+struct gpio_desc *__must_check __gpiod_get_index(struct device *dev,
 					       const char *con_id,
-					       unsigned int idx)
+					       unsigned int idx,
+					       enum gpiod_flags flags)
 {
 	struct gpio_desc *desc = NULL;
 	int status;
-	enum gpio_lookup_flags flags = 0;
+	enum gpio_lookup_flags lookupflags = 0;
 
 	dev_dbg(dev, "GPIO lookup for consumer %s\n", con_id);
 
 	/* Using device tree? */
 	if (IS_ENABLED(CONFIG_OF) && dev && dev->of_node) {
 		dev_dbg(dev, "using device tree for GPIO lookup\n");
-		desc = of_find_gpio(dev, con_id, idx, &flags);
+		desc = of_find_gpio(dev, con_id, idx, &lookupflags);
 	} else if (IS_ENABLED(CONFIG_ACPI) && dev && ACPI_HANDLE(dev)) {
 		dev_dbg(dev, "using ACPI for GPIO lookup\n");
-		desc = acpi_find_gpio(dev, con_id, idx, &flags);
+		desc = acpi_find_gpio(dev, con_id, idx, &lookupflags);
 	}
 
 	/*
@@ -1643,7 +1649,7 @@ struct gpio_desc *__must_check gpiod_get_index(struct device *dev,
 	 */
 	if (!desc || desc == ERR_PTR(-ENOENT)) {
 		dev_dbg(dev, "using lookup tables for GPIO lookup");
-		desc = gpiod_find(dev, con_id, idx, &flags);
+		desc = gpiod_find(dev, con_id, idx, &lookupflags);
 	}
 
 	if (IS_ERR(desc)) {
@@ -1656,16 +1662,33 @@ struct gpio_desc *__must_check gpiod_get_index(struct device *dev,
 	if (status < 0)
 		return ERR_PTR(status);
 
-	if (flags & GPIO_ACTIVE_LOW)
+	if (lookupflags & GPIO_ACTIVE_LOW)
 		set_bit(FLAG_ACTIVE_LOW, &desc->flags);
-	if (flags & GPIO_OPEN_DRAIN)
+	if (lookupflags & GPIO_OPEN_DRAIN)
 		set_bit(FLAG_OPEN_DRAIN, &desc->flags);
-	if (flags & GPIO_OPEN_SOURCE)
+	if (lookupflags & GPIO_OPEN_SOURCE)
 		set_bit(FLAG_OPEN_SOURCE, &desc->flags);
 
+	/* No particular flag request, return here... */
+	if (flags & GPIOD_FLAGS_BIT_DIR_SET)
+		return desc;
+
+	/* Process flags */
+	if (flags & GPIOD_FLAGS_BIT_DIR_OUT)
+		status = gpiod_direction_output(desc,
+					      flags & GPIOD_FLAGS_BIT_DIR_VAL);
+	else
+		status = gpiod_direction_input(desc);
+
+	if (status < 0) {
+		dev_dbg(dev, "setup of GPIO %s failed\n", con_id);
+		gpiod_put(desc);
+		return ERR_PTR(status);
+	}
+
 	return desc;
 }
-EXPORT_SYMBOL_GPL(gpiod_get_index);
+EXPORT_SYMBOL_GPL(__gpiod_get_index);
 
 /**
  * gpiod_get_index_optional - obtain an optional GPIO from a multi-index GPIO
@@ -1673,18 +1696,20 @@ EXPORT_SYMBOL_GPL(gpiod_get_index);
  * @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
+ * @flags: optional GPIO initialization flags
  *
  * 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,
+struct gpio_desc *__must_check __gpiod_get_index_optional(struct device *dev,
 							const char *con_id,
-							unsigned int index)
+							unsigned int index,
+							enum gpiod_flags flags)
 {
 	struct gpio_desc *desc;
 
-	desc = gpiod_get_index(dev, con_id, index);
+	desc = gpiod_get_index(dev, con_id, index, flags);
 	if (IS_ERR(desc)) {
 		if (PTR_ERR(desc) == -ENOENT)
 			return NULL;
@@ -1692,7 +1717,7 @@ struct gpio_desc *__must_check gpiod_get_index_optional(struct device *dev,
 
 	return desc;
 }
-EXPORT_SYMBOL_GPL(gpiod_get_index_optional);
+EXPORT_SYMBOL_GPL(__gpiod_get_index_optional);
 
 /**
  * gpiod_put - dispose of a GPIO descriptor
diff --git a/include/linux/gpio/consumer.h b/include/linux/gpio/consumer.h
index 05e53cc..b7ce0c6 100644
--- a/include/linux/gpio/consumer.h
+++ b/include/linux/gpio/consumer.h
@@ -18,30 +18,79 @@ struct gpio_desc;
 
 #ifdef CONFIG_GPIOLIB
 
+#define GPIOD_FLAGS_BIT_DIR_SET		BIT(0)
+#define GPIOD_FLAGS_BIT_DIR_OUT		BIT(1)
+#define GPIOD_FLAGS_BIT_DIR_VAL		BIT(2)
+
+/**
+ * Optional flags that can be passed to one of gpiod_* to configure direction
+ * and output value. These values cannot be OR'd.
+ */
+enum gpiod_flags {
+	GPIOD_ASIS	= 0,
+	GPIOD_IN	= GPIOD_FLAGS_BIT_DIR_SET,
+	GPIOD_OUT_LOW	= GPIOD_FLAGS_BIT_DIR_SET | GPIOD_FLAGS_BIT_DIR_OUT,
+	GPIOD_OUT_HIGH	= GPIOD_FLAGS_BIT_DIR_SET | GPIOD_FLAGS_BIT_DIR_OUT |
+			  GPIOD_FLAGS_BIT_DIR_VAL,
+};
+
 /* Acquire and dispose GPIOs */
-struct gpio_desc *__must_check gpiod_get(struct device *dev,
-					 const char *con_id);
-struct gpio_desc *__must_check gpiod_get_index(struct device *dev,
+struct gpio_desc *__must_check __gpiod_get(struct device *dev,
+					 const char *con_id,
+					 enum gpiod_flags flags);
+#define __gpiod_get(dev, con_id, flags, ...) __gpiod_get(dev, con_id, flags)
+#define gpiod_get(varargs...) __gpiod_get(varargs, 0)
+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,
+					       unsigned int idx,
+					       enum gpiod_flags flags);
+#define __gpiod_get_index(dev, con_id, index, flags, ...)		\
+	__gpiod_get_index(dev, con_id, index, flags)
+#define gpiod_get_index(varargs...) __gpiod_get_index(varargs, 0)
+struct gpio_desc *__must_check __gpiod_get_optional(struct device *dev,
+						  const char *con_id,
+						  enum gpiod_flags flags);
+#define __gpiod_get_optional(dev, con_id, flags, ...)			\
+	__gpiod_get_optional(dev, con_id, flags)
+#define gpiod_get_optional(varargs...) __gpiod_get_optional(varargs, 0)
+struct gpio_desc *__must_check __gpiod_get_index_optional(struct device *dev,
 							const char *con_id,
-							unsigned int index);
+							unsigned int index,
+							enum gpiod_flags flags);
+#define __gpiod_get_index_optional(dev, con_id, index, flags, ...)	\
+	__gpiod_get_index_optional(dev, con_id, index, flags)
+#define gpiod_get_index_optional(varargs...)				\
+	__gpiod_get_index_optional(varargs, 0)
 
 void gpiod_put(struct gpio_desc *desc);
 
-struct gpio_desc *__must_check devm_gpiod_get(struct device *dev,
-					      const char *con_id);
-struct gpio_desc *__must_check devm_gpiod_get_index(struct device *dev,
+struct gpio_desc *__must_check __devm_gpiod_get(struct device *dev,
+					      const char *con_id,
+					      enum gpiod_flags flags);
+#define __devm_gpiod_get(dev, con_id, flags, ...)			\
+	__devm_gpiod_get(dev, con_id, flags)
+#define devm_gpiod_get(varargs...) __devm_gpiod_get(varargs, 0)
+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);
+						    unsigned int idx,
+						    enum gpiod_flags flags);
+#define __devm_gpiod_get_index(dev, con_id, index, flags, ...)		\
+	__devm_gpiod_get_index(dev, con_id, index, flags)
+#define devm_gpiod_get_index(varargs...) __devm_gpiod_get_index(varargs, 0)
+struct gpio_desc *__must_check __devm_gpiod_get_optional(struct device *dev,
+						       const char *con_id,
+						       enum gpiod_flags flags);
+#define __devm_gpiod_get_optional(dev, con_id, flags, ...)		\
+	__devm_gpiod_get_optional(dev, con_id, flags)
+#define devm_gpiod_get_optional(varargs...)				\
+	__devm_gpiod_get_optional(varargs, 0)
 struct gpio_desc *__must_check
-devm_gpiod_get_index_optional(struct device *dev, const char *con_id,
-			      unsigned int index);
+__devm_gpiod_get_index_optional(struct device *dev, const char *con_id,
+			      unsigned int index, enum gpiod_flags flags);
+#define __devm_gpiod_get_index_optional(dev, con_id, index, flags, ...)	\
+	__devm_gpiod_get_index_optional(dev, con_id, index, flags)
+#define devm_gpiod_get_index_optional(varargs...)			\
+	__devm_gpiod_get_index_optional(varargs, 0)
 
 void devm_gpiod_put(struct device *dev, struct gpio_desc *desc);
 
-- 
2.0.2

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