linux-kernel - [PATCH 09/13 v2] gpio: Add devm_gpiod

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Message-Id: <20181201154151.14890-10-linus.walleij@linaro.org>
Date:   Sat,  1 Dec 2018 16:41:47 +0100
From:   Linus Walleij <linus.walleij@...aro.org>
To:     Liam Girdwood <lgirdwood@...il.com>,
        Mark Brown <broonie@...nel.org>
Cc:     linux-kernel@...r.kernel.org,
        Charles Keepax <ckeepax@...nsource.cirrus.com>,
        Bartosz Golaszewski <bgolaszewski@...libre.com>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        Linus Walleij <linus.walleij@...aro.org>
Subject: [PATCH 09/13 v2] 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.

Cc: Bartosz Golaszewski <bgolaszewski@...libre.com>
Signed-off-by: Linus Walleij <linus.walleij@...aro.org>
---
ChangeLog v1->v2:
- New patch to be able to hand over GPIO descriptors to
  the regulator core.
- Mark: feel free to apply this to the regulator tree with
  the regulator tree with the rest.
---
 Documentation/driver-model/devres.txt |  1 +
 drivers/gpio/gpiolib-devres.c         | 17 +++++++++++++++++
 include/linux/gpio/consumer.h         | 10 ++++++++++
 3 files changed, 28 insertions(+)

diff --git a/Documentation/driver-model/devres.txt b/Documentation/driver-model/devres.txt
index 43681ca0837f..fc4cc24dfb97 100644
--- 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 01959369360b..5864e758d7f2 100644
--- a/drivers/gpio/gpiolib-devres.c
+++ b/drivers/gpio/gpiolib-devres.c
@@ -320,6 +320,23 @@ 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)
+{
+	WARN_ON(devres_destroy(dev, devm_gpiod_release,
+			       devm_gpiod_match, desc));
+}
+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 348885f2f3d3..8aebcf822082 100644
--- 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();
-- 
2.19.1