| Message ID | 20200711045441.19464-1-u.kleine-koenig@pengutronix.de |
|---|---|
| State | New |
| Headers | show |
| Series | [v2,RFC] dt-bindings: gpio: introduce hog properties with less ambiguity | expand |
On Sat, Jul 11, 2020 at 7:57 AM Uwe Kleine-König <u.kleine-koenig@pengutronix.de> wrote: > > For active low lines the semantic of output-low and output-high is hard > to grasp because there is a double negation involved and so output-low > is actually a request to drive the line high (aka inactive). > > So introduce output-inactive and output-active with the same semantic as > output-low and output-high respectively have today, but with a more > sensible name. I guess someone needs to proofread the GPIO in-kernel documentation and update it accordingly. We have a lot of references to logical vs. physical state AFAIR.
On Sat, Jul 11, 2020 at 6:54 AM Uwe Kleine-König <u.kleine-koenig@pengutronix.de> wrote: > For active low lines the semantic of output-low and output-high is hard > to grasp because there is a double negation involved and so output-low > is actually a request to drive the line high (aka inactive). > > So introduce output-inactive and output-active with the same semantic as > output-low and output-high respectively have today, but with a more > sensible name. > > Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de> > --- > Hello, > > compared to (implicit) v1, changed to ..asserted from ...active as Linus > Walleij suggested. I'm fine to apply this but would prefer if I can apply it back-to-back with a patch adding support to the kernel. I know the bindings and the OS should be decoupled in theory but ... feels better for me. Yours, Linus Walleij
diff --git a/Documentation/devicetree/bindings/gpio/gpio.txt b/Documentation/devicetree/bindings/gpio/gpio.txt index a8895d339bfe..1061c346a619 100644 --- a/Documentation/devicetree/bindings/gpio/gpio.txt +++ b/Documentation/devicetree/bindings/gpio/gpio.txt @@ -196,11 +196,16 @@ Only one of the following properties scanned in the order shown below. This means that when multiple properties are present they will be searched in the order presented below and the first match is taken as the intended configuration. -- input: A property specifying to set the GPIO direction as input. -- output-low A property specifying to set the GPIO direction as output with - the value low. -- output-high A property specifying to set the GPIO direction as output with - the value high. +- input: A property specifying to set the GPIO direction as input. +- output-deasserted: A property specifying to set the GPIO direction as output + with the inactive value (depending on the line's polarity, + which is active-high by default) +- output-asserted: A property specifying to set the GPIO direction as output + with the active value. + +For backwards compatibility "output-low" and "output-high" should be supported +as aliases for "output-deasserted" and "output-asserted" respectively. Their +usage is misleading for active-low outputs, so their use is discouraged. Optional properties: - line-name: The GPIO label name. If not present the node name is used.
For active low lines the semantic of output-low and output-high is hard to grasp because there is a double negation involved and so output-low is actually a request to drive the line high (aka inactive). So introduce output-inactive and output-active with the same semantic as output-low and output-high respectively have today, but with a more sensible name. Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de> --- Hello, compared to (implicit) v1, changed to ..asserted from ...active as Linus Walleij suggested. Best regards Uwe Documentation/devicetree/bindings/gpio/gpio.txt | 15 ++++++++++----- 1 file changed, 10 insertions(+), 5 deletions(-)