linux-kernel - Re: [RFCv2 PATCH 1/4] dt-bindings: bus: add Wiegand bus dt documentation

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Date:   Thu, 6 Oct 2022 10:25:03 +0200
From:   Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
To:     Martin Zaťovič <m.zatovic1@...il.com>,
        robh+dt@...nel.org, krzysztof.kozlowski+dt@...aro.org,
        linus.walleij@...aro.org, brgl@...ev.pl,
        gregkh@...uxfoundation.org, jeffrey.l.hugo@...il.com,
        andersson@...nel.org, Michael.Srba@...nam.cz, saravanak@...gle.com,
        mani@...nel.org, hemantk@...eaurora.org,
        linux-kernel@...r.kernel.org, devicetree@...r.kernel.org,
        linux-gpio@...r.kernel.org
Subject: Re: [RFCv2 PATCH 1/4] dt-bindings: bus: add Wiegand bus dt
 documentation

On 05/10/2022 16:57, Martin Zaťovič wrote:
> This patch documents the devicetree entry for enabling Wiegand
> bus driver. The drivers that will use Wiegand bus driver shall
> create a sub-node of the documented node.
> 
> Signed-off-by: Martin Zaťovič <m.zatovic1@...il.com>
> ---
> Hello again,
> 
> this is the second round of RFC patches in an attempt to add Wiegand
> driver to linux kernel. Thank you for all the issues you have pointed
> out in the first round. I have tried to fix all of them and I have
> also implemented a Wiegand bus driver, that is now used by the GPIO
> driver itself - as suggested by Linus.
> 
> Any advice you have for me regarding the patches will be appreciated!
> 
> With regards,
> Martin Zaťovič
> ---
>  .../devicetree/bindings/bus/wiegand.yaml      | 50 +++++++++++++++++++
>  1 file changed, 50 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/bus/wiegand.yaml
> 
> diff --git a/Documentation/devicetree/bindings/bus/wiegand.yaml b/Documentation/devicetree/bindings/bus/wiegand.yaml
> new file mode 100644
> index 000000000000..1ed863ab925c
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/bus/wiegand.yaml
> @@ -0,0 +1,50 @@
> +# SPDX-License-Identifier: GPL-2.0
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/bus/wiegand.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: Wiegand Bus
> +
> +maintainers:
> +  - Martin Zaťovič <m.zatovic1@...il.com>
> +
> +description: |
> +  Wiegand interface is a wiring standard popularized in the 1980s. To this day
> +  many card readers, fingerprint readers, sensors, etc. use Wiegand interface
> +  particularly for access control applications. It utilizes two wires to
> +  transmit the data - D0 and D1.
> +
> +  Both data lines are initially pulled up. To send a bit of value 1, the D1
> +  line is set low. Similarly to send a bit of value 0, the D0 line is set low.
> +
> +properties:
> +  $nodename:
> +    pattern: "^wiegand(@[0-9a-f]+)?$"
> +
> +  compatible:
> +    contains:
> +      const: wiegand
> +

If the bus uses two wires, shouldn't you describe them here? Otherwise
what wires are you using?

> +required:
> +  - compatible
> +
> +additionalProperties: false
> +
> +examples:
> +  - |
> +    #include <dt-bindings/gpio/gpio.h>
> +
> +    wiegand {
> +        compatible = "wiegand";
> +
> +        wiegand-gpio {
> +            compatible = "wiegand,wiegand-gpio";
> +            pinctrl-names = "default";
> +            pinctrl-0 = <&pinctrl_uart2_wiegand>;
> +            data-hi-gpios = <&gpio 7 (GPIO_ACTIVE_HIGH|GPIO_OPEN_DRAIN)>;
> +            data-lo-gpios = <&gpio 6 (GPIO_ACTIVE_HIGH|GPIO_OPEN_DRAIN)>;
> +        };
> +    };
> +
> +...

Best regards,
Krzysztof