Re: [PATCH 3/4] gpio: dt-bindings: Declare gpio-hog optional for GPIO subnodes

[Rob Herring <robh@kernel.org>]

On Tue, Feb 23, 2016 at 08:54:48AM +0100, Markus Pargmann wrote:
> Reuse the GPIO hogging DT bindings for more generic specifications of
> the GPIO. Therefore gpio-hog is declared optional.

Before extending this binding further, we need to consider other cases 
that have been discussed recently such as gpio switch binding and 
whether it should fit in with this.

My biggest issue with this binding is whether the DT changes because 
today we don't have a driver for some GPIO line and tomorrow we do.

That said, some specific comments below:

> Signed-off-by: Markus Pargmann <mpa@pengutronix.de>
> ---
>  Documentation/devicetree/bindings/gpio/gpio.txt | 28 ++++++++++++++++++-------
>  1 file changed, 21 insertions(+), 7 deletions(-)
> 
> diff --git a/Documentation/devicetree/bindings/gpio/gpio.txt b/Documentation/devicetree/bindings/gpio/gpio.txt
> index 069cdf6f9dac..820898e0649c 100644
> --- a/Documentation/devicetree/bindings/gpio/gpio.txt
> +++ b/Documentation/devicetree/bindings/gpio/gpio.txt
> @@ -155,13 +155,25 @@ gpio-controller@00000000 {
>  	ngpios = <18>;
>  }
>  
> -The GPIO chip may contain GPIO hog definitions. GPIO hogging is a mechanism
> -providing automatic GPIO request and configuration as part of the
> -gpio-controller's driver probe function.
> +The GPIO chip may contain subnodes describing specific GPIOs of this
> +controller. These GPIO nodes can be used to define GPIO hogging or define GPIO
> +names.
> +GPIO hogging is a mechanism providing automatic GPIO request and configuration
> +as part of the gpio-controller's driver probe function.

Linux driver details don't belong in binding descriptions.

> -Each GPIO hog definition is represented as a child node of the GPIO controller.
> +Each GPIO node consists of the following properties:
>  Required properties:
> +- gpios:      Store the GPIO information (id, flags, ...). Shall contain the
> +	      number of cells specified in its parent node (GPIO controller
> +	      node).
> +
> +Optional properties:
> +- line-name:  The GPIO name. If not present the node name is used.

I'd like to deprecate line-name in favor of the standard property 
for user visible names "label".

>  - gpio-hog:   A property specifying that this child node represent a GPIO hog.
> +
> +For GPIO hogging which is specified by the "gpio-hog" property the following
> +additional properties are required.
> +Required properties for GPIO hogging:
>  - gpios:      Store the GPIO information (id, flags, ...). Shall contain the

This doesn't make sense. gpios is always required and already listed 
above.

>  	      number of cells specified in its parent node (GPIO controller
>  	      node).
> @@ -175,9 +187,6 @@ configuration.
>  - output-high A property specifying to set the GPIO direction as output with
>  	      the value high.
>  
> -Optional properties:
> -- line-name:  The GPIO label name. If not present the node name is used.
> -
>  Example of two SOC GPIO banks defined as gpio-controller nodes:
>  
>  	qe_pio_a: gpio-controller@1400 {
> @@ -192,6 +201,11 @@ Example of two SOC GPIO banks defined as gpio-controller nodes:
>  			output-low;
>  			line-name = "foo-bar-gpio";
>  		};
> +
> +		line_c {
> +			gpios = <7 0>;
> +			line-name = "SCHEMATIC_LINE_NAME";
> +		};
>  	};
>  
>  	qe_pio_e: gpio-controller@1460 {
> -- 
> 2.7.0
> 
> --
> To unsubscribe from this list: send the line "unsubscribe devicetree" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html