path: root/Documentation/pinctrl.txt
diff options
authorStephen Warren <swarren@nvidia.com>2012-04-16 16:51:00 (GMT)
committerLinus Walleij <linus.walleij@linaro.org>2012-04-18 11:53:13 (GMT)
commit6d4ca1fb467932773da7b808c52f3d7ef4461ba0 (patch)
tree6e2055564dc75b2c44a3a41daf6ebfcfce326617 /Documentation/pinctrl.txt
parent2aeefe0233174015aef19dc06aac02a1119a44be (diff)
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 <swarren@nvidia.com> Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Diffstat (limited to 'Documentation/pinctrl.txt')
1 files changed, 29 insertions, 19 deletions
diff --git a/Documentation/pinctrl.txt b/Documentation/pinctrl.txt
index 4431c3e7..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;
- 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
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>
- struct pinctrl *p;
- struct pinctrl_state *s1, *s2;
+struct pinctrl *p;
+struct pinctrl_state *s1, *s2;
/* 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))
/* 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.

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