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Subject[PATCH V2] pinctrl: implement devm_pinctrl_get()/put()
Date
From: Stephen Warren <swarren@nvidia.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@nvidia.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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