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-rw-r--r--Documentation/pinctrl.txt94
1 files changed, 51 insertions, 43 deletions
diff --git a/Documentation/pinctrl.txt b/Documentation/pinctrl.txt
index d97bccf..e40f4b4 100644
--- a/Documentation/pinctrl.txt
+++ b/Documentation/pinctrl.txt
@@ -152,11 +152,9 @@ static const struct foo_group foo_groups[] = {
};
-static int foo_list_groups(struct pinctrl_dev *pctldev, unsigned selector)
+static int foo_get_groups_count(struct pinctrl_dev *pctldev)
{
- if (selector >= ARRAY_SIZE(foo_groups))
- return -EINVAL;
- return 0;
+ return ARRAY_SIZE(foo_groups);
}
static const char *foo_get_group_name(struct pinctrl_dev *pctldev,
@@ -175,7 +173,7 @@ static int foo_get_group_pins(struct pinctrl_dev *pctldev, unsigned selector,
}
static struct pinctrl_ops foo_pctrl_ops = {
- .list_groups = foo_list_groups,
+ .get_groups_count = foo_get_groups_count,
.get_group_name = foo_get_group_name,
.get_group_pins = foo_get_group_pins,
};
@@ -186,13 +184,12 @@ static struct pinctrl_desc foo_desc = {
.pctlops = &foo_pctrl_ops,
};
-The pin control subsystem will call the .list_groups() function repeatedly
-beginning on 0 until it returns non-zero to determine legal selectors, then
-it will call the other functions to retrieve the name and pins of the group.
-Maintaining the data structure of the groups is up to the driver, this is
-just a simple example - in practice you may need more entries in your group
-structure, for example specific register ranges associated with each group
-and so on.
+The pin control subsystem will call the .get_groups_count() function to
+determine total number of legal selectors, then it will call the other functions
+to retrieve the name and pins of the group. Maintaining the data structure of
+the groups is up to the driver, this is just a simple example - in practice you
+may need more entries in your group structure, for example specific register
+ranges associated with each group and so on.
Pin configuration
@@ -606,11 +603,9 @@ static const struct foo_group foo_groups[] = {
};
-static int foo_list_groups(struct pinctrl_dev *pctldev, unsigned selector)
+static int foo_get_groups_count(struct pinctrl_dev *pctldev)
{
- if (selector >= ARRAY_SIZE(foo_groups))
- return -EINVAL;
- return 0;
+ return ARRAY_SIZE(foo_groups);
}
static const char *foo_get_group_name(struct pinctrl_dev *pctldev,
@@ -629,7 +624,7 @@ static int foo_get_group_pins(struct pinctrl_dev *pctldev, unsigned selector,
}
static struct pinctrl_ops foo_pctrl_ops = {
- .list_groups = foo_list_groups,
+ .get_groups_count = foo_get_groups_count,
.get_group_name = foo_get_group_name,
.get_group_pins = foo_get_group_pins,
};
@@ -640,7 +635,7 @@ struct foo_pmx_func {
const unsigned num_groups;
};
-static const char * const spi0_groups[] = { "spi0_1_grp" };
+static const char * const spi0_groups[] = { "spi0_0_grp", "spi0_1_grp" };
static const char * const i2c0_groups[] = { "i2c0_grp" };
static const char * const mmc0_groups[] = { "mmc0_1_grp", "mmc0_2_grp",
"mmc0_3_grp" };
@@ -663,11 +658,9 @@ static const struct foo_pmx_func foo_functions[] = {
},
};
-int foo_list_funcs(struct pinctrl_dev *pctldev, unsigned selector)
+int foo_get_functions_count(struct pinctrl_dev *pctldev)
{
- if (selector >= ARRAY_SIZE(foo_functions))
- return -EINVAL;
- return 0;
+ return ARRAY_SIZE(foo_functions);
}
const char *foo_get_fname(struct pinctrl_dev *pctldev, unsigned selector)
@@ -703,7 +696,7 @@ void foo_disable(struct pinctrl_dev *pctldev, unsigned selector,
}
struct pinmux_ops foo_pmxops = {
- .list_functions = foo_list_funcs,
+ .get_functions_count = foo_get_functions_count,
.get_function_name = foo_get_fname,
.get_function_groups = foo_get_groups,
.enable = foo_enable,
@@ -786,7 +779,7 @@ and spi on the second function mapping:
#include <linux/pinctrl/machine.h>
-static const struct pinctrl_map __initdata mapping[] = {
+static const struct pinctrl_map mapping[] __initconst = {
{
.dev_name = "foo-spi.0",
.name = PINCTRL_STATE_DEFAULT,
@@ -952,13 +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
@@ -992,7 +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);
@@ -1000,24 +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.
@@ -1029,6 +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.
@@ -1041,14 +1032,30 @@ 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
+registered. Thus make sure that the error path in your driver gracefully
+cleans up and is ready to retry the probing later in the startup process.
System pin control hogging
@@ -1094,13 +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))
...
@@ -1111,7 +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)
@@ -1125,8 +1135,6 @@ foo_switch()
...
...
-
- pinctrl_put(p);
}
The above has to be done from process context.