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>

1 files changed, 29 insertions, 19 deletions

diff --git a/Documentation/pinctrl.txt b/Documentation/pinctrl.txt
index 4431c3e727ba..e40f4b4e1977 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.