driver-api/gpio/consumer.rst

6 it describes the new descriptor-based interface. For a description of the
7 deprecated integer-based GPIO interface please refer to legacy.rst.
23 - Simple compile coverage with e.g. COMPILE_TEST - it does not matter that
27 - Truly optional GPIOLIB support - where the driver does not really make use
28   of the GPIOs on certain compile-time configurations for certain systems, but
29   will use it under other compile-time configurations. In this case the
31   be met with console warnings that may be perceived as intimidating.
37 All the functions that work with the descriptor-based GPIO interface are
47 With the descriptor-based interface, GPIOs are identified with an opaque,
48 non-forgeable handler that must be obtained through a call to one of the
54 				    enum gpiod_flags flags)
61 					  enum gpiod_flags flags)
64 see Documentation/driver-api/gpio/board.rst
66 The flags parameter is used to optionally specify a direction and initial value
71 * GPIOD_IN to initialize the GPIO as input.
72 * GPIOD_OUT_LOW to initialize the GPIO as output with a value of 0.
73 * GPIOD_OUT_HIGH to initialize the GPIO as output with a value of 1.
74 * GPIOD_OUT_LOW_OPEN_DRAIN same as GPIOD_OUT_LOW but also enforce the line
76 * GPIOD_OUT_HIGH_OPEN_DRAIN same as GPIOD_OUT_HIGH but also enforce the line
83 The two last flags are used for use cases where open drain is mandatory, such
84 as I2C: if the line is not already configured as open drain in the mappings
89 with IS_ERR() (they will never return a NULL pointer). -ENOENT will be returned
96 instead of -ENOENT if no GPIO has been assigned to the requested function::
100 					     enum gpiod_flags flags)
105 						   enum gpiod_flags flags)
110 -ENOSYS return codes.  System integrators should however be careful to enable
117 					   enum gpiod_flags flags)
129 The following function returns NULL instead of -ENOENT if no GPIOs have been
134 						    enum gpiod_flags flags)
136 Device-managed variants of these functions are also defined::
139 					 enum gpiod_flags flags)
144 					       enum gpiod_flags flags)
148 						  enum gpiod_flags flags)
153 							enum gpiod_flags flags)
157 						enum gpiod_flags flags)
161 							 enum gpiod_flags flags)
175 The device-managed variants are, unsurprisingly::
186 -----------------
188 direction-setting flags have been given to gpiod_get*(), this is done by
197 for spinlock-safe GPIOs it is OK to use them before tasking is enabled, as part
214 Spinlock-Safe GPIO Access
215 -------------------------
217 don't need to sleep, and can safely be done from inside hard (non-threaded) IRQ
228 open-drain signaling and output latencies.
238 --------------------------
255 IRQ handler, and those accessors must be used instead of spinlock-safe
259 that can't be accessed from hardIRQ handlers, these calls act the same as the
260 spinlock-safe calls.
266 ---------------------------------------
267 As a consumer should not have to care about the physical line level, all of the
280 parameter "value" as "asserted" ("1") or "de-asserted" ("0"). The physical line
283 As an example, if the active low property for a dedicated GPIO is set, and the
302 but it should be avoided as much as possible, especially by system-agnostic drivers
308 -------------------------
313 The following set of calls ignore the active-low or open drain property of a GPIO and
333 -------------------------------------------------
378 	* array_size	- the number of array elements
379 	* desc_array	- an array of GPIO descriptors
380 	* array_info	- optional information obtained from gpiod_get_array()
381 	* value_bitmap	- a bitmap to store the GPIOs' values (get) or
390 	gpiod_set_array_value(my_gpio_descs->ndescs, my_gpio_descs->desc,
391 			      my_gpio_descs->info, my_gpio_value_bitmap);
408 banks as data I/O ports without much loss of performance.
413 values are stored in value_array rather than passed back as return value.
417 --------------------
418 GPIO lines can quite often be used as IRQs. You can get the IRQ number
424 done (most likely because that particular GPIO cannot be used as IRQ). It is an
425 unchecked error to use a GPIO that wasn't set up as an input using
429 Non-error values returned from gpiod_to_irq() can be passed to request_irq() or
431 by the board-specific initialization code. Note that IRQ trigger options are
432 part of the IRQ interface, e.g. IRQF_TRIGGER_FALLING, as are system wakeup
451 For details refer to Documentation/firmware-guide/acpi/gpio-properties.rst
457 integer-based interface. It is strongly recommended to update these to the new
460 and vice-versa::
465 The GPIO number returned by desc_to_gpio() can safely be used as a parameter of
466 the gpio\_*() functions for as long as the GPIO descriptor `desc` is not freed.