[PATCH v3 4/6] gpiolib: acpi: Export acpi_get_gpiod()

[Daniel Scally <djrscally@gmail.com>]

I need to be able to translate GPIO resources in an ACPI device's _CRS
into GPIO descriptor array. Those are represented in _CRS as a pathname
to a GPIO device plus the pin's index number: this function is perfect
for that purpose.

As it's currently only used internally within the GPIO layer, provide and
export a wrapper function that additionally holds a reference to the GPIO
device.

Signed-off-by: Daniel Scally <djrscally@gmail.com>
---
Changes in v3:

	- Having realised that it wasn't taking a reference to the GPIO device,
	  I decided the best thing to do was leave the existing function as-is
	  (apart from renaming) and provide a wrapper that simply passes
	  through to the original and takes a reference before returning the
	  struct gpio_desc

	  Because of the change to that functionality, I dropped the R-b's from
	  the last version.

 drivers/gpio/gpiolib-acpi.c   | 36 +++++++++++++++++++++++++++++++----
 include/linux/gpio/consumer.h |  7 +++++++
 2 files changed, 39 insertions(+), 4 deletions(-)

diff --git a/drivers/gpio/gpiolib-acpi.c b/drivers/gpio/gpiolib-acpi.c
index e4d728fda982..0cc7cc327757 100644
--- a/drivers/gpio/gpiolib-acpi.c
+++ b/drivers/gpio/gpiolib-acpi.c
@@ -102,7 +102,8 @@ static int acpi_gpiochip_find(struct gpio_chip *gc, void *data)
 }
 
 /**
- * acpi_get_gpiod() - Translate ACPI GPIO pin to GPIO descriptor usable with GPIO API
+ * __acpi_get_gpiod() - Translate ACPI GPIO pin to GPIO descriptor usable with
+ *			GPIO API
  * @path:	ACPI GPIO controller full path name, (e.g. "\\_SB.GPO1")
  * @pin:	ACPI GPIO pin number (0-based, controller-relative)
  *
@@ -111,7 +112,7 @@ static int acpi_gpiochip_find(struct gpio_chip *gc, void *data)
  * controller does not have GPIO chip registered at the moment. This is to
  * support probe deferral.
  */
-static struct gpio_desc *acpi_get_gpiod(char *path, int pin)
+static struct gpio_desc *__acpi_get_gpiod(char *path, int pin)
 {
 	struct gpio_chip *chip;
 	acpi_handle handle;
@@ -128,6 +129,33 @@ static struct gpio_desc *acpi_get_gpiod(char *path, int pin)
 	return gpiochip_get_desc(chip, pin);
 }
 
+/**
+ * acpi_get_gpiod() - Translate ACPI GPIO pin to GPIO descriptor usable with
+ *		      GPIO API, and hold a refcount to the GPIO device.
+ * @path:	ACPI GPIO controller full path name, (e.g. "\\_SB.GPO1")
+ * @pin:	ACPI GPIO pin number (0-based, controller-relative)
+ * @label:	Label to pass to gpiod_request()
+ *
+ * This function is a simple pass-through to __acpi_get_gpiod(), except that as
+ * it is intended for use outside of the GPIO layer (in a similar fashion to
+ * gpiod_get_index() for example) it also holds a reference to the GPIO device.
+ */
+struct gpio_desc *acpi_get_gpiod(char *path, int pin, char *label)
+{
+	struct gpio_desc *gpio = __acpi_get_gpiod(path, pin);
+	int ret;
+
+	if (IS_ERR(gpio))
+		return gpio;
+
+	ret = gpiod_request(gpio, label);
+	if (ret)
+		return ERR_PTR(ret);
+
+	return gpio;
+}
+EXPORT_SYMBOL_GPL(acpi_get_gpiod);
+
 static irqreturn_t acpi_gpio_irq_handler(int irq, void *data)
 {
 	struct acpi_gpio_event *event = data;
@@ -689,8 +717,8 @@ static int acpi_populate_gpio_lookup(struct acpi_resource *ares, void *data)
 		if (pin_index >= agpio->pin_table_length)
 			return 1;
 
-		lookup->desc = acpi_get_gpiod(agpio->resource_source.string_ptr,
-					      agpio->pin_table[pin_index]);
+		lookup->desc = __acpi_get_gpiod(agpio->resource_source.string_ptr,
+						agpio->pin_table[pin_index]);
 		lookup->info.pin_config = agpio->pin_config;
 		lookup->info.debounce = agpio->debounce_timeout;
 		lookup->info.gpioint = gpioint;
diff --git a/include/linux/gpio/consumer.h b/include/linux/gpio/consumer.h
index ef49307611d2..6eee751f44dd 100644
--- a/include/linux/gpio/consumer.h
+++ b/include/linux/gpio/consumer.h
@@ -690,6 +690,8 @@ int devm_acpi_dev_add_driver_gpios(struct device *dev,
 				   const struct acpi_gpio_mapping *gpios);
 void devm_acpi_dev_remove_driver_gpios(struct device *dev);
 
+struct gpio_desc *acpi_get_gpiod(char *path, int pin, char *label);
+
 #else  /* CONFIG_GPIOLIB && CONFIG_ACPI */
 
 struct acpi_device;
@@ -708,6 +710,11 @@ static inline int devm_acpi_dev_add_driver_gpios(struct device *dev,
 }
 static inline void devm_acpi_dev_remove_driver_gpios(struct device *dev) {}
 
+struct gpio_desc *acpi_get_gpiod(char *path, int pin, char *label)
+{
+	return NULL;
+}
+
 #endif /* CONFIG_GPIOLIB && CONFIG_ACPI */
 
 
-- 
2.25.1