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Diffstat (limited to 'Documentation/driver-api/gpio/consumer.rst')
| -rw-r--r-- | Documentation/driver-api/gpio/consumer.rst | 10 |
1 files changed, 9 insertions, 1 deletions
diff --git a/Documentation/driver-api/gpio/consumer.rst b/Documentation/driver-api/gpio/consumer.rst index 3366a991b4aa..47869ca8ccf0 100644 --- a/Documentation/driver-api/gpio/consumer.rst +++ b/Documentation/driver-api/gpio/consumer.rst @@ -72,6 +72,10 @@ for the GPIO. Values can be: * GPIOD_OUT_HIGH_OPEN_DRAIN same as GPIOD_OUT_HIGH but also enforce the line to be electrically used with open drain. +Note that the initial value is *logical* and the physical line level depends on +whether the line is configured active high or active low (see +:ref:`active_low_semantics`). + The two last flags are used for use cases where open drain is mandatory, such as I2C: if the line is not already configured as open drain in the mappings (see board.txt), then open drain will be enforced anyway and a warning will be @@ -252,6 +256,8 @@ that can't be accessed from hardIRQ handlers, these calls act the same as the spinlock-safe calls. +.. _active_low_semantics: + The active low and open drain semantics --------------------------------------- As a consumer should not have to care about the physical line level, all of the @@ -309,9 +315,11 @@ 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 and toggled using the +following calls:: int gpiod_is_active_low(const struct gpio_desc *desc) + void gpiod_toggle_active_low(struct gpio_desc *desc) Note that these functions should only be used with great moderation; a driver should not have to care about the physical line level or open drain semantics. |