pinctrl: implement devm_pinctrl_get()/put()

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 <[e-mail]>
Signed-off-by: Linus Walleij <[e-mail]>

Documentation/driver-model/devres.txt

···
   devm_regulator_get()
   devm_regulator_put()
   devm_regulator_bulk_get()
+
+PINCTRL
+  devm_pinctrl_get()
+  devm_pinctrl_put()

Documentation/pinctrl.txt

···
 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
···
 	/* 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);
···
 
 	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
···
   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.
 
···
 
 - 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
···
 
 #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))
 		...
 
···
 	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)
···
 	    ...
 
 	...
-
-	pinctrl_put(p);
 }
 
 The above has to be done from process context.

drivers/pinctrl/core.c

···
 #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"
···
 	return ret;
 }
 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)

include/linux/pinctrl/consumer.h

···
 							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)
···
 	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(
···
 					struct device *dev)
 {
 	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