diff options
Diffstat (limited to 'Documentation/pinctrl.txt')
| -rw-r--r-- | Documentation/pinctrl.txt | 48 |
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. |