Re: [PATCH v2 1/2] dt-bindings: gpio: introduce hog properties with less ambiguity

[Alexander Stein <alexander.stein@ew.tq-group.com>]

Hi,

Am Dienstag, 30. Mai 2023, 17:19:45 CEST schrieb Uwe Kleine-König:
> 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>
> ---
>  Documentation/devicetree/bindings/gpio/gpio.txt | 16 +++++++++++-----
>  1 file changed, 11 insertions(+), 5 deletions(-)
> 
> diff --git a/Documentation/devicetree/bindings/gpio/gpio.txt
> b/Documentation/devicetree/bindings/gpio/gpio.txt index
> d82c32217fff..2f037bbd3ffa 100644
> --- a/Documentation/devicetree/bindings/gpio/gpio.txt
> +++ b/Documentation/devicetree/bindings/gpio/gpio.txt
> @@ -209,15 +209,21 @@ Required properties:
>  - gpios:      Store the GPIO information (id, flags, ...) for each GPIO to
>  	      affect. Shall contain an integer multiple of the number of 
cells
>  	      specified in its parent node (GPIO controller node).
> +
>  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-inactive:   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-active:     A property specifying to set the GPIO direction as
> output +		     with the active value.

I know this is essentially just renaming currently existing properties.
But these mutual exclusive (boolean) properties make it impossible to change 
them in DT overlay. Any ideas how to support changing the output level onGPIO 
hogs in DT overlay?

Despite that, this change looks sensible to me.

Best regards,
Alexander

> +For backwards compatibility "output-low" and "output-high" are supported as
> +aliases for "output-inactive" and "output-active" 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.


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