diff options
Diffstat (limited to 'Documentation/pinctrl.txt')
| -rw-r--r-- | Documentation/pinctrl.txt | 94 |
1 files changed, 51 insertions, 43 deletions
diff --git a/Documentation/pinctrl.txt b/Documentation/pinctrl.txt index d97bccf4614..e40f4b4e197 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. |