diff options
Diffstat (limited to 'Documentation/gpio')
| -rw-r--r-- | Documentation/gpio/board.txt | 2 | ||||
| -rw-r--r-- | Documentation/gpio/consumer.txt | 26 | ||||
| -rw-r--r-- | Documentation/gpio/driver.txt | 25 |
3 files changed, 44 insertions, 9 deletions
diff --git a/Documentation/gpio/board.txt b/Documentation/gpio/board.txt index ba169faad5c6..4452786225b8 100644 --- a/Documentation/gpio/board.txt +++ b/Documentation/gpio/board.txt @@ -60,7 +60,7 @@ Platform Data Finally, GPIOs can be bound to devices and functions using platform data. Board files that desire to do so need to include the following header: - #include <linux/gpio/driver.h> + #include <linux/gpio/machine.h> GPIOs are mapped by the means of tables of lookups, containing instances of the gpiod_lookup structure. Two macros are defined to help declaring such mappings: diff --git a/Documentation/gpio/consumer.txt b/Documentation/gpio/consumer.txt index d8abfc31abbe..76546324e968 100644 --- a/Documentation/gpio/consumer.txt +++ b/Documentation/gpio/consumer.txt @@ -29,13 +29,24 @@ 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: - struct gpio_desc *gpiod_get(struct device *dev, const char *con_id) + 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: struct gpio_desc *gpiod_get_index(struct device *dev, - const char *con_id, unsigned int idx) + const char *con_id, unsigned int idx, + enum gpiod_flags flags) + +The flags parameter is used to optionally specify a direction and initial value +for the GPIO. Values can be: + +* GPIOD_ASIS or 0 to not initialize the GPIO at all. The direction must be set + later with one of the dedicated functions. +* GPIOD_IN to initialize the GPIO as input. +* GPIOD_OUT_LOW to initialize the GPIO as output with a value of 0. +* GPIOD_OUT_HIGH to initialize the GPIO as output with a value of 1. Both functions return either a valid GPIO descriptor, or an error code checkable with IS_ERR() (they will never return a NULL pointer). -ENOENT will be returned @@ -46,11 +57,13 @@ errors and an absence of GPIO for optional GPIO parameters. Device-managed variants of these functions are also defined: - struct gpio_desc *devm_gpiod_get(struct device *dev, const char *con_id) + struct gpio_desc *devm_gpiod_get(struct device *dev, const char *con_id, + enum gpiod_flags flags) struct gpio_desc *devm_gpiod_get_index(struct device *dev, const char *con_id, - unsigned int idx) + unsigned int idx, + enum gpiod_flags flags) A GPIO descriptor can be disposed of using the gpiod_put() function: @@ -67,8 +80,9 @@ Using GPIOs Setting Direction ----------------- -The first thing a driver must do with a GPIO is setting its direction. This is -done by invoking one of the gpiod_direction_*() functions: +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: int gpiod_direction_input(struct gpio_desc *desc) int gpiod_direction_output(struct gpio_desc *desc, int value) diff --git a/Documentation/gpio/driver.txt b/Documentation/gpio/driver.txt index fa9a0a8b3734..18790c237977 100644 --- a/Documentation/gpio/driver.txt +++ b/Documentation/gpio/driver.txt @@ -157,13 +157,34 @@ Locking IRQ usage Input GPIOs can be used as IRQ signals. When this happens, a driver is requested to mark the GPIO as being used as an IRQ: - int gpiod_lock_as_irq(struct gpio_desc *desc) + int gpio_lock_as_irq(struct gpio_chip *chip, unsigned int offset) This will prevent the use of non-irq related GPIO APIs until the GPIO IRQ lock is released: - void gpiod_unlock_as_irq(struct gpio_desc *desc) + void gpio_unlock_as_irq(struct gpio_chip *chip, unsigned int offset) When implementing an irqchip inside a GPIO driver, these two functions should typically be called in the .startup() and .shutdown() callbacks from the irqchip. + + +Requesting self-owned GPIO pins +------------------------------- + +Sometimes it is useful to allow a GPIO chip driver to request its own GPIO +descriptors through the gpiolib API. Using gpio_request() for this purpose +does not help since it pins the module to the kernel forever (it calls +try_module_get()). A GPIO driver can use the following functions instead +to request and free descriptors without being pinned to the kernel forever. + + int gpiochip_request_own_desc(struct gpio_desc *desc, const char *label) + + void gpiochip_free_own_desc(struct gpio_desc *desc) + +Descriptors requested with gpiochip_request_own_desc() must be released with +gpiochip_free_own_desc(). + +These functions must be used with care since they do not affect module use +count. Do not use the functions to request gpio descriptors not owned by the +calling driver. |