diff options
| -rw-r--r-- | Documentation/driver-api/gpio/consumer.rst (renamed from Documentation/gpio/consumer.txt) | 85 | ||||
| -rw-r--r-- | Documentation/driver-api/gpio/index.rst | 1 | ||||
| -rw-r--r-- | Documentation/gpio/00-INDEX | 2 |
3 files changed, 44 insertions, 44 deletions
diff --git a/Documentation/gpio/consumer.txt b/Documentation/driver-api/gpio/consumer.rst index d53e5b5cfc9c..c71a50d85b50 100644 --- a/Documentation/gpio/consumer.txt +++ b/Documentation/driver-api/gpio/consumer.rst @@ -1,3 +1,4 @@ +================================== GPIO Descriptor Consumer Interface ================================== @@ -30,10 +31,10 @@ warnings. These stubs are used for two use cases: be met with console warnings that may be perceived as intimidating. All the functions that work with the descriptor-based GPIO interface are -prefixed with gpiod_. The gpio_ prefix is used for the legacy interface. No -other function in the kernel should use these prefixes. The use of the legacy -functions is strongly discouraged, new code should use <linux/gpio/consumer.h> -and descriptors exclusively. +prefixed with ``gpiod_``. The ``gpio_`` prefix is used for the legacy +interface. No other function in the kernel should use these prefixes. The use +of the legacy functions is strongly discouraged, new code should use +<linux/gpio/consumer.h> and descriptors exclusively. Obtaining and Disposing GPIOs @@ -43,13 +44,13 @@ With the descriptor-based interface, GPIOs are identified with an opaque, non-forgeable handler that must be obtained through a call to one of the gpiod_get() functions. Like many other kernel subsystems, gpiod_get() takes the device that will use the GPIO and the function the requested GPIO is supposed to -fulfill: +fulfill:: struct gpio_desc *gpiod_get(struct device *dev, const char *con_id, enum gpiod_flags flags) If a function is implemented by using several GPIOs together (e.g. a simple LED -device that displays digits), an additional index argument can be specified: +device that displays digits), an additional index argument can be specified:: struct gpio_desc *gpiod_get_index(struct device *dev, const char *con_id, unsigned int idx, @@ -84,7 +85,7 @@ occurred while trying to acquire it. This is useful to discriminate between mere errors and an absence of GPIO for optional GPIO parameters. For the common pattern where a GPIO is optional, the gpiod_get_optional() and gpiod_get_index_optional() functions can be used. These functions return NULL -instead of -ENOENT if no GPIO has been assigned to the requested function: +instead of -ENOENT if no GPIO has been assigned to the requested function:: struct gpio_desc *gpiod_get_optional(struct device *dev, const char *con_id, @@ -101,14 +102,14 @@ This is helpful to driver authors, since they do not need to special case -ENOSYS return codes. System integrators should however be careful to enable gpiolib on systems that need it. -For a function using multiple GPIOs all of those can be obtained with one call: +For a function using multiple GPIOs all of those can be obtained with one call:: struct gpio_descs *gpiod_get_array(struct device *dev, const char *con_id, enum gpiod_flags flags) This function returns a struct gpio_descs which contains an array of -descriptors: +descriptors:: struct gpio_descs { unsigned int ndescs; @@ -116,13 +117,13 @@ descriptors: } The following function returns NULL instead of -ENOENT if no GPIOs have been -assigned to the requested function: +assigned to the requested function:: struct gpio_descs *gpiod_get_array_optional(struct device *dev, const char *con_id, enum gpiod_flags flags) -Device-managed variants of these functions are also defined: +Device-managed variants of these functions are also defined:: struct gpio_desc *devm_gpiod_get(struct device *dev, const char *con_id, enum gpiod_flags flags) @@ -149,11 +150,11 @@ Device-managed variants of these functions are also defined: const char *con_id, enum gpiod_flags flags) -A GPIO descriptor can be disposed of using the gpiod_put() function: +A GPIO descriptor can be disposed of using the gpiod_put() function:: void gpiod_put(struct gpio_desc *desc) -For an array of GPIOs this function can be used: +For an array of GPIOs this function can be used:: void gpiod_put_array(struct gpio_descs *descs) @@ -161,7 +162,7 @@ It is strictly forbidden to use a descriptor after calling these functions. It is also not allowed to individually release descriptors (using gpiod_put()) from an array acquired with gpiod_get_array(). -The device-managed variants are, unsurprisingly: +The device-managed variants are, unsurprisingly:: void devm_gpiod_put(struct device *dev, struct gpio_desc *desc) @@ -175,7 +176,7 @@ Setting Direction ----------------- The first thing a driver must do with a GPIO is setting its direction. If no direction-setting flags have been given to gpiod_get*(), this is done by -invoking one of the gpiod_direction_*() functions: +invoking one of the gpiod_direction_*() functions:: int gpiod_direction_input(struct gpio_desc *desc) int gpiod_direction_output(struct gpio_desc *desc, int value) @@ -189,7 +190,7 @@ of early board setup. For output GPIOs, the value provided becomes the initial output value. This helps avoid signal glitching during system startup. -A driver can also query the current direction of a GPIO: +A driver can also query the current direction of a GPIO:: int gpiod_get_direction(const struct gpio_desc *desc) @@ -206,7 +207,7 @@ Most GPIO controllers can be accessed with memory read/write instructions. Those don't need to sleep, and can safely be done from inside hard (non-threaded) IRQ handlers and similar contexts. -Use the following calls to access GPIOs from an atomic context: +Use the following calls to access GPIOs from an atomic context:: int gpiod_get_value(const struct gpio_desc *desc); void gpiod_set_value(struct gpio_desc *desc, int value); @@ -231,11 +232,11 @@ head of a queue to transmit a command and get its response. This requires sleeping, which can't be done from inside IRQ handlers. Platforms that support this type of GPIO distinguish them from other GPIOs by -returning nonzero from this call: +returning nonzero from this call:: int gpiod_cansleep(const struct gpio_desc *desc) -To access such GPIOs, a different set of accessors is defined: +To access such GPIOs, a different set of accessors is defined:: int gpiod_get_value_cansleep(const struct gpio_desc *desc) void gpiod_set_value_cansleep(struct gpio_desc *desc, int value) @@ -271,23 +272,23 @@ As an example, if the active low property for a dedicated GPIO is set, and the gpiod_set_(array)_value_xxx() passes "asserted" ("1"), the physical line level will be driven low. -To summarize: - -Function (example) line property physical line -gpiod_set_raw_value(desc, 0); don't care low -gpiod_set_raw_value(desc, 1); don't care high -gpiod_set_value(desc, 0); default (active high) low -gpiod_set_value(desc, 1); default (active high) high -gpiod_set_value(desc, 0); active low high -gpiod_set_value(desc, 1); active low low -gpiod_set_value(desc, 0); default (active high) low -gpiod_set_value(desc, 1); default (active high) high -gpiod_set_value(desc, 0); open drain low -gpiod_set_value(desc, 1); open drain high impedance -gpiod_set_value(desc, 0); open source high impedance -gpiod_set_value(desc, 1); open source high - -It is possible to override these semantics using the *set_raw/'get_raw functions +To summarize:: + + Function (example) line property physical line + gpiod_set_raw_value(desc, 0); don't care low + gpiod_set_raw_value(desc, 1); don't care high + gpiod_set_value(desc, 0); default (active high) low + gpiod_set_value(desc, 1); default (active high) high + gpiod_set_value(desc, 0); active low high + gpiod_set_value(desc, 1); active low low + gpiod_set_value(desc, 0); default (active high) low + gpiod_set_value(desc, 1); default (active high) high + gpiod_set_value(desc, 0); open drain low + gpiod_set_value(desc, 1); open drain high impedance + gpiod_set_value(desc, 0); open source high impedance + gpiod_set_value(desc, 1); open source high + +It is possible to override these semantics using the set_raw/get_raw functions but it should be avoided as much as possible, especially by system-agnostic drivers which should not need to care about the actual physical line level and worry about the logical value instead. @@ -300,7 +301,7 @@ their device will actually receive, no matter what lies between it and the GPIO line. The following set of calls ignore the active-low or open drain property of a GPIO and -work on the raw line value: +work on the raw line value:: int gpiod_get_raw_value(const struct gpio_desc *desc) void gpiod_set_raw_value(struct gpio_desc *desc, int value) @@ -308,7 +309,7 @@ work on the raw line value: void gpiod_set_raw_value_cansleep(struct gpio_desc *desc, int value) int gpiod_direction_output_raw(struct gpio_desc *desc, int value) -The active low state of a GPIO can also be queried using the following call: +The active low state of a GPIO can also be queried using the following call:: int gpiod_is_active_low(const struct gpio_desc *desc) @@ -318,7 +319,7 @@ should not have to care about the physical line level or open drain semantics. Access multiple GPIOs with a single function call ------------------------------------------------- -The following functions get or set the values of an array of GPIOs: +The following functions get or set the values of an array of GPIOs:: int gpiod_get_array_value(unsigned int array_size, struct gpio_desc **desc_array, @@ -361,7 +362,7 @@ The functions take three arguments: The descriptor array can be obtained using the gpiod_get_array() function or one of its variants. If the group of descriptors returned by that function matches the desired group of GPIOs, those GPIOs can be accessed by simply using -the struct gpio_descs returned by gpiod_get_array(): +the struct gpio_descs returned by gpiod_get_array():: struct gpio_descs *my_gpio_descs = gpiod_get_array(...); gpiod_set_array_value(my_gpio_descs->ndescs, my_gpio_descs->desc, @@ -384,7 +385,7 @@ values are stored in value_array rather than passed back as return value. GPIOs mapped to IRQs -------------------- GPIO lines can quite often be used as IRQs. You can get the IRQ number -corresponding to a given GPIO using the following call: +corresponding to a given GPIO using the following call:: int gpiod_to_irq(const struct gpio_desc *desc) @@ -424,7 +425,7 @@ Interacting With the Legacy GPIO Subsystem Many kernel subsystems still handle GPIOs using the legacy integer-based interface. Although it is strongly encouraged to upgrade them to the safer descriptor-based API, the following two functions allow you to convert a GPIO -descriptor into the GPIO integer namespace and vice-versa: +descriptor into the GPIO integer namespace and vice-versa:: int desc_to_gpio(const struct gpio_desc *desc) struct gpio_desc *gpio_to_desc(unsigned gpio) diff --git a/Documentation/driver-api/gpio/index.rst b/Documentation/driver-api/gpio/index.rst index fd22c0d1419e..6ba9e0043310 100644 --- a/Documentation/driver-api/gpio/index.rst +++ b/Documentation/driver-api/gpio/index.rst @@ -9,6 +9,7 @@ Contents: intro driver + consumer legacy Core diff --git a/Documentation/gpio/00-INDEX b/Documentation/gpio/00-INDEX index 64cf61245861..f960fc00a3ef 100644 --- a/Documentation/gpio/00-INDEX +++ b/Documentation/gpio/00-INDEX @@ -1,7 +1,5 @@ 00-INDEX - This file -consumer.txt - - How to obtain and use GPIOs in a driver drivers-on-gpio.txt: - Drivers in other subsystems that can use GPIO to provide more complex functionality. |