diff options
Diffstat (limited to 'Documentation/gpio/consumer.txt')
| -rw-r--r-- | Documentation/gpio/consumer.txt | 26 |
1 files changed, 20 insertions, 6 deletions
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) |