On Thu, Jul 8, 2021 at 5:21 PM Hannu Hartikainen <hannu@xxxxxxx> wrote: > > I was confused about the gpiod_flags values and thought that > GPIOD_OUT_LOW and GPIOD_OUT_HIGH set the line to be active low / active > high. This is not true, but I got the misconception because the flags > GPIOD_OUT_*_OPEN_DRAIN do change line configuration and there's a > subchapter about *active low* and *open drain* semantics. > > Add an explicit mention that the initial value is a logical value (and > not the line configuration or physical line level). Also add a mention > of the function gpiod_toggle_active_low which was previously missing > from this document. > > Signed-off-by: Hannu Hartikainen <hannu@xxxxxxx> > --- > Documentation/driver-api/gpio/consumer.rst | 10 +++++++++- > 1 file changed, 9 insertions(+), 1 deletion(-) > > 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. > -- > 2.32.0 > Makes sense, applied! Bartosz
