gpio: Add devm_gpiod_unhinge()

This adds a function named devm_gpiod_unhinge() that removes
the resource management from a GPIO descriptor.

I am not sure if this is the best anglosaxon name for the
function, no other managed resources have an equivalent
currently, but I chose "unhinge" as the closest intuitive
thing I could imagine that fits Rusty Russell's API design
criterions "the obvious use is the correct one" and
"the name tells you how to use it".

The idea came out of a remark from Mark Brown that it should
be possible to handle over management of a resource from
devres to the regulator core, and indeed we can do that.

Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Reviewed-by: Marek Szyprowski <m.szyprowski@samsung.com>
Tested-by: Marek Szyprowski <m.szyprowski@samsung.com>
Reviewed-by: Charles Keepax <ckeepax@opensource.cirrus.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

diff --git a/Documentation/driver-model/devres.txt b/Documentation/driver-model/devres.txt
index 43681ca0837f8d7c78fa576831c029a50e730203..fc4cc24dfb9767e38760295ac157adba3b88b182 100644 (file)
--- a/Documentation/driver-model/devres.txt
+++ b/Documentation/driver-model/devres.txt
@@ -254,6 +254,7 @@ GPIO
   devm_gpiod_get_index_optional()
   devm_gpiod_get_optional()
   devm_gpiod_put()
+  devm_gpiod_unhinge()
   devm_gpiochip_add_data()
   devm_gpiochip_remove()
   devm_gpio_request()

diff --git a/drivers/gpio/gpiolib-devres.c b/drivers/gpio/gpiolib-devres.c
index f9591b5c974856559565a531a9029057aee608e9..0acc2cc6e868fdefec661540d97513959e00575e 100644 (file)
--- a/drivers/gpio/gpiolib-devres.c
+++ b/drivers/gpio/gpiolib-devres.c
@@ -346,6 +346,36 @@ void devm_gpiod_put(struct device *dev, struct gpio_desc *desc)
 }
 EXPORT_SYMBOL(devm_gpiod_put);
 
+/**
+ * devm_gpiod_unhinge - Remove resource management from a gpio descriptor
+ * @dev:       GPIO consumer
+ * @desc:      GPIO descriptor to remove resource management from
+ *
+ * Remove resource management from a GPIO descriptor. This is needed when
+ * you want to hand over lifecycle management of a descriptor to another
+ * mechanism.
+ */
+
+void devm_gpiod_unhinge(struct device *dev, struct gpio_desc *desc)
+{
+       int ret;
+
+       if (IS_ERR_OR_NULL(desc))
+               return;
+       ret = devres_destroy(dev, devm_gpiod_release,
+                            devm_gpiod_match, &desc);
+       /*
+        * If the GPIO descriptor is requested as nonexclusive, we
+        * may call this function several times on the same descriptor
+        * so it is OK if devres_destroy() returns -ENOENT.
+        */
+       if (ret == -ENOENT)
+               return;
+       /* Anything else we should warn about */
+       WARN_ON(ret);
+}
+EXPORT_SYMBOL(devm_gpiod_unhinge);
+
 /**
  * devm_gpiod_put_array - Resource-managed gpiod_put_array()
  * @dev:       GPIO consumer

diff --git a/include/linux/gpio/consumer.h b/include/linux/gpio/consumer.h
index 348885f2f3d3b92173f090bed2cb2649bf0f3d84..8aebcf822082ea84ecbd7dafeecde7be662d1f00 100644 (file)
--- a/include/linux/gpio/consumer.h
+++ b/include/linux/gpio/consumer.h
@@ -104,6 +104,7 @@ struct gpio_descs *__must_check
 devm_gpiod_get_array_optional(struct device *dev, const char *con_id,
                              enum gpiod_flags flags);
 void devm_gpiod_put(struct device *dev, struct gpio_desc *desc);
+void devm_gpiod_unhinge(struct device *dev, struct gpio_desc *desc);
 void devm_gpiod_put_array(struct device *dev, struct gpio_descs *descs);
 
 int gpiod_get_direction(struct gpio_desc *desc);
@@ -249,6 +250,15 @@ static inline void gpiod_put(struct gpio_desc *desc)
        WARN_ON(1);
 }
 
+static inline void devm_gpiod_unhinge(struct device *dev,
+                                     struct gpio_desc *desc)
+{
+       might_sleep();
+
+       /* GPIO can never have been requested */
+       WARN_ON(1);
+}
+
 static inline void gpiod_put_array(struct gpio_descs *descs)
 {
        might_sleep();