Message-Id: <1334335720-3309-1-git-send-email-swarren@wwwdotorg.org>
Date:	Fri, 13 Apr 2012 10:48:40 -0600
From:	Stephen Warren <swarren@...dotorg.org>
To:	Linus Walleij <linus.walleij@...aro.org>
Cc:	linux-kernel@...r.kernel.org, Stephen Warren <swarren@...dia.com>
Subject: [PATCH V2] pinctrl: implement devm_pinctrl_get()/put()

From: Stephen Warren <swarren@...dia.com>

These functions allow the driver core to automatically clean up any
allocations made by drivers, thus leading to simplified drivers.

Signed-off-by: Stephen Warren <swarren@...dia.com>
---
v2:
* Updated documentation to describe and recommend using devm_* functions.
* Added devm_pinctrl_get_select() and devm_pinctrl_get_select_default() to
  consumer.h
---
 Documentation/pinctrl.txt        |   48 +++++++++++++++++++-------------
 drivers/pinctrl/core.c           |   56 ++++++++++++++++++++++++++++++++++++++
 include/linux/pinctrl/consumer.h |   44 +++++++++++++++++++++++++++++
 3 files changed, 129 insertions(+), 19 deletions(-)

diff --git a/Documentation/pinctrl.txt b/Documentation/pinctrl.txt
index 4431c3e..e40f4b4 100644
--- a/Documentation/pinctrl.txt
+++ b/Documentation/pinctrl.txt
@@ -945,13 +945,13 @@ case), we define a mapping like this:
 The result of grabbing this mapping from the device with something like
 this (see next paragraph):
 
-	p = pinctrl_get(dev);
+	p = devm_pinctrl_get(dev);
 	s = pinctrl_lookup_state(p, "8bit");
 	ret = pinctrl_select_state(p, s);
 
 or more simply:
 
-	p = pinctrl_get_select(dev, "8bit");
+	p = devm_pinctrl_get_select(dev, "8bit");
 
 Will be that you activate all the three bottom records in the mapping at
 once. Since they share the same name, pin controller device, function and
@@ -985,7 +985,7 @@ foo_probe()
 	/* Allocate a state holder named "foo" etc */
 	struct foo_state *foo = ...;
 
-	foo->p = pinctrl_get(&device);
+	foo->p = devm_pinctrl_get(&device);
 	if (IS_ERR(foo->p)) {
 		/* FIXME: clean up "foo" here */
 		return PTR_ERR(foo->p);
@@ -993,24 +993,17 @@ foo_probe()
 
 	foo->s = pinctrl_lookup_state(foo->p, PINCTRL_STATE_DEFAULT);
 	if (IS_ERR(foo->s)) {
-		pinctrl_put(foo->p);
 		/* FIXME: clean up "foo" here */
 		return PTR_ERR(s);
 	}
 
 	ret = pinctrl_select_state(foo->s);
 	if (ret < 0) {
-		pinctrl_put(foo->p);
 		/* FIXME: clean up "foo" here */
 		return ret;
 	}
 }
 
-foo_remove()
-{
-	pinctrl_put(state->p);
-}
-
 This get/lookup/select/put sequence can just as well be handled by bus drivers
 if you don't want each and every driver to handle it and you know the
 arrangement on your bus.
@@ -1022,6 +1015,11 @@ The semantics of the pinctrl APIs are:
   kernel memory to hold the pinmux state. All mapping table parsing or similar
   slow operations take place within this API.
 
+- devm_pinctrl_get() is a variant of pinctrl_get() that causes pinctrl_put()
+  to be called automatically on the retrieved pointer when the associated
+  device is removed. It is recommended to use this function over plain
+  pinctrl_get().
+
 - pinctrl_lookup_state() is called in process context to obtain a handle to a
   specific state for a the client device. This operation may be slow too.
 
@@ -1034,14 +1032,25 @@ The semantics of the pinctrl APIs are:
 
 - pinctrl_put() frees all information associated with a pinctrl handle.
 
+- devm_pinctrl_put() is a variant of pinctrl_put() that may be used to
+  explicitly destroy a pinctrl object returned by devm_pinctrl_get().
+  However, use of this function will be rare, due to the automatic cleanup
+  that will occur even without calling it.
+
+  pinctrl_get() must be paired with a plain pinctrl_put().
+  pinctrl_get() may not be paired with devm_pinctrl_put().
+  devm_pinctrl_get() can optionally be paired with devm_pinctrl_put().
+  devm_pinctrl_get() may not be paired with plain pinctrl_put().
+
 Usually the pin control core handled the get/put pair and call out to the
 device drivers bookkeeping operations, like checking available functions and
 the associated pins, whereas the enable/disable pass on to the pin controller
 driver which takes care of activating and/or deactivating the mux setting by
 quickly poking some registers.
 
-The pins are allocated for your device when you issue the pinctrl_get() call,
-after this you should be able to see this in the debugfs listing of all pins.
+The pins are allocated for your device when you issue the devm_pinctrl_get()
+call, after this you should be able to see this in the debugfs listing of all
+pins.
 
 NOTE: the pinctrl system will return -EPROBE_DEFER if it cannot find the
 requested pinctrl handles, for example if the pinctrl driver has not yet
@@ -1092,13 +1101,13 @@ it, disables and releases it, and muxes it in on the pins defined by group B:
 
 #include <linux/pinctrl/consumer.h>
 
-foo_switch()
-{
-	struct pinctrl *p;
-	struct pinctrl_state *s1, *s2;
+struct pinctrl *p;
+struct pinctrl_state *s1, *s2;
 
+foo_probe()
+{
 	/* Setup */
-	p = pinctrl_get(&device);
+	p = devm_pinctrl_get(&device);
 	if (IS_ERR(p))
 		...
 
@@ -1109,7 +1118,10 @@ foo_switch()
 	s2 = pinctrl_lookup_state(foo->p, "pos-B");
 	if (IS_ERR(s2))
 		...
+}
 
+foo_switch()
+{
 	/* Enable on position A */
 	ret = pinctrl_select_state(s1);
 	if (ret < 0)
@@ -1123,8 +1135,6 @@ foo_switch()
 	    ...
 
 	...
-
-	pinctrl_put(p);
 }
 
 The above has to be done from process context.
diff --git a/drivers/pinctrl/core.c b/drivers/pinctrl/core.c
index 59027ab..2eaa187 100644
--- a/drivers/pinctrl/core.c
+++ b/drivers/pinctrl/core.c
@@ -23,6 +23,7 @@
 #include <linux/sysfs.h>
 #include <linux/debugfs.h>
 #include <linux/seq_file.h>
+#include <linux/pinctrl/consumer.h>
 #include <linux/pinctrl/pinctrl.h>
 #include <linux/pinctrl/machine.h>
 #include "core.h"
@@ -801,6 +802,61 @@ int pinctrl_select_state(struct pinctrl *p, struct pinctrl_state *state)
 }
 EXPORT_SYMBOL_GPL(pinctrl_select_state);
 
+static void devm_pinctrl_release(struct device *dev, void *res)
+{
+	pinctrl_put(*(struct pinctrl **)res);
+}
+
+/**
+ * struct devm_pinctrl_get() - Resource managed pinctrl_get()
+ * @dev: the device to obtain the handle for
+ *
+ * If there is a need to explicitly destroy the returned struct pinctrl,
+ * devm_pinctrl_put() should be used, rather than plain pinctrl_put().
+ */
+struct pinctrl *devm_pinctrl_get(struct device *dev)
+{
+	struct pinctrl **ptr, *p;
+
+	ptr = devres_alloc(devm_pinctrl_release, sizeof(*ptr), GFP_KERNEL);
+	if (!ptr)
+		return ERR_PTR(-ENOMEM);
+
+	p = pinctrl_get(dev);
+	if (!IS_ERR(p)) {
+		*ptr = p;
+		devres_add(dev, ptr);
+	} else {
+		devres_free(ptr);
+	}
+
+	return p;
+}
+EXPORT_SYMBOL_GPL(devm_pinctrl_get);
+
+static int devm_pinctrl_match(struct device *dev, void *res, void *data)
+{
+	struct pinctrl **p = res;
+
+	return *p == data;
+}
+
+/**
+ * devm_pinctrl_put() - Resource managed pinctrl_put()
+ * @p: the pinctrl handle to release
+ *
+ * Deallocate a struct pinctrl obtained via devm_pinctrl_get(). Normally
+ * this function will not need to be called and the resource management
+ * code will ensure that the resource is freed.
+ */
+void devm_pinctrl_put(struct pinctrl *p)
+{
+	WARN_ON(devres_destroy(p->dev, devm_pinctrl_release,
+			       devm_pinctrl_match, p));
+	pinctrl_put(p);
+}
+EXPORT_SYMBOL_GPL(devm_pinctrl_put);
+
 int pinctrl_register_map(struct pinctrl_map const *maps, unsigned num_maps,
 			 bool dup, bool locked)
 {
diff --git a/include/linux/pinctrl/consumer.h b/include/linux/pinctrl/consumer.h
index 191e726..6dd96fb 100644
--- a/include/linux/pinctrl/consumer.h
+++ b/include/linux/pinctrl/consumer.h
@@ -36,6 +36,9 @@ extern struct pinctrl_state * __must_check pinctrl_lookup_state(
 							const char *name);
 extern int pinctrl_select_state(struct pinctrl *p, struct pinctrl_state *s);
 
+extern struct pinctrl * __must_check devm_pinctrl_get(struct device *dev);
+extern void devm_pinctrl_put(struct pinctrl *p);
+
 #else /* !CONFIG_PINCTRL */
 
 static inline int pinctrl_request_gpio(unsigned gpio)
@@ -79,6 +82,15 @@ static inline int pinctrl_select_state(struct pinctrl *p,
 	return 0;
 }
 
+static inline struct pinctrl * __must_check devm_pinctrl_get(struct device *dev)
+{
+	return NULL;
+}
+
+static inline void devm_pinctrl_put(struct pinctrl *p)
+{
+}
+
 #endif /* CONFIG_PINCTRL */
 
 static inline struct pinctrl * __must_check pinctrl_get_select(
@@ -113,6 +125,38 @@ static inline struct pinctrl * __must_check pinctrl_get_select_default(
 	return pinctrl_get_select(dev, PINCTRL_STATE_DEFAULT);
 }
 
+static inline struct pinctrl * __must_check devm_pinctrl_get_select(
+					struct device *dev, const char *name)
+{
+	struct pinctrl *p;
+	struct pinctrl_state *s;
+	int ret;
+
+	p = devm_pinctrl_get(dev);
+	if (IS_ERR(p))
+		return p;
+
+	s = pinctrl_lookup_state(p, name);
+	if (IS_ERR(s)) {
+		devm_pinctrl_put(p);
+		return ERR_PTR(PTR_ERR(s));
+	}
+
+	ret = pinctrl_select_state(p, s);
+	if (ret < 0) {
+		devm_pinctrl_put(p);
+		return ERR_PTR(ret);
+	}
+
+	return p;
+}
+
+static inline struct pinctrl * __must_check devm_pinctrl_get_select_default(
+					struct device *dev)
+{
+	return devm_pinctrl_get_select(dev, PINCTRL_STATE_DEFAULT);
+}
+
 #ifdef CONFIG_PINCONF
 
 extern int pin_config_get(const char *dev_name, const char *name,
-- 
1.7.0.4

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