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>

1 files changed, 30 insertions, 0 deletions

diff --git a/drivers/gpio/gpiolib-devres.c b/drivers/gpio/gpiolib-devres.c
index f9591b5c9748..0acc2cc6e868 100644
--- a/drivers/gpio/gpiolib-devres.c
+++ b/drivers/gpio/gpiolib-devres.c
@@ -347,6 +347,36 @@ 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
  * @descs:	GPIO descriptor array to dispose of