linux-kernel - Re: [PATCH v3 4/6] dt-bindings: nvmem: add YAML schema for the sl28 vpd layout

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Message-ID: <20221110134918.GB3436769-robh@kernel.org>
Date:   Thu, 10 Nov 2022 07:49:18 -0600
From:   Rob Herring <robh@...nel.org>
To:     Miquel Raynal <miquel.raynal@...tlin.com>
Cc:     Krzysztof Kozlowski <krzk+dt@...nel.org>,
        devicetree@...r.kernel.org,
        Srinivas Kandagatla <srinivas.kandagatla@...aro.org>,
        linux-kernel@...r.kernel.org,
        Robert Marko <robert.marko@...tura.hr>,
        Luka Perkov <luka.perkov@...tura.hr>,
        Thomas Petazzoni <thomas.petazzoni@...tlin.com>,
        Michael Walle <michael@...le.cc>,
        linux-arm-kernel@...ts.infradead.org,
        Bartosz Golaszewski <brgl@...ev.pl>,
        Christian Eggers <ceggers@...i.de>,
        Cory Tusar <cory.tusar@...1solutions.com>
Subject: Re: [PATCH v3 4/6] dt-bindings: nvmem: add YAML schema for the sl28
 vpd layout

On Fri, Nov 04, 2022 at 05:38:31PM +0100, Miquel Raynal wrote:
> From: Michael Walle <michael@...le.cc>
> 
> Add a schema for the NVMEM layout on Kontron's sl28 boards.
> 
> Signed-off-by: Michael Walle <michael@...le.cc>
> Signed-off-by: Miquel Raynal <miquel.raynal@...tlin.com>
> ---
>  .../nvmem/layouts/kontron,sl28-vpd.yaml       | 60 +++++++++++++++++++
>  .../bindings/nvmem/layouts/nvmem-layout.yaml  |  3 +
>  2 files changed, 63 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/nvmem/layouts/kontron,sl28-vpd.yaml
> 
> diff --git a/Documentation/devicetree/bindings/nvmem/layouts/kontron,sl28-vpd.yaml b/Documentation/devicetree/bindings/nvmem/layouts/kontron,sl28-vpd.yaml
> new file mode 100644
> index 000000000000..44088c8b4153
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/nvmem/layouts/kontron,sl28-vpd.yaml
> @@ -0,0 +1,60 @@
> +# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/nvmem/layouts/kontron,sl28-vpd.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: NVMEM layout of the Kontron SMARC-sAL28 vital product data
> +
> +maintainers:
> +  - Michael Walle <michael@...le.cc>
> +
> +description:
> +  The vital product data (VPD) of the sl28 boards contains a serial
> +  number and a base MAC address. The actual MAC addresses for the
> +  on-board ethernet devices are derived from this base MAC address by
> +  adding an offset.
> +
> +properties:
> +  compatible:
> +    const: kontron,sl28-vpd
> +
> +  serial-number:
> +    type: object
> +    description: The board's serial number
> +
> +  base-mac-address:
> +    type: object
> +    description:
> +      Base MAC address for all on-module network interfaces. The first
> +      argument of the phandle will be treated as an offset.
> +
> +    properties:
> +      "#nvmem-cell-cells":
> +        const: 1
> +
> +    additionalProperties: false
> +
> +required:
> +  - compatible
> +
> +additionalProperties: false
> +
> +examples:
> +  - |
> +      otp-1 {
> +          compatible = "user-otp";
> +
> +          nvmem-layout {
> +              compatible = "kontron,sl28-vpd";
> +
> +              serial_number: serial-number {
> +              };
> +
> +              base_mac_address: base-mac-address {
> +                  #nvmem-cell-cells = <1>;
> +              };
> +          };
> +      };
> +
> +...
> diff --git a/Documentation/devicetree/bindings/nvmem/layouts/nvmem-layout.yaml b/Documentation/devicetree/bindings/nvmem/layouts/nvmem-layout.yaml
> index ecc7c37cbc1f..f64ea2fa362d 100644
> --- a/Documentation/devicetree/bindings/nvmem/layouts/nvmem-layout.yaml
> +++ b/Documentation/devicetree/bindings/nvmem/layouts/nvmem-layout.yaml
> @@ -17,6 +17,9 @@ description: |
>    define and might require dynamic reading of the NVMEM device in order to
>    perform their parsing. The nvmem-layout container is here to describe these.
>  
> +oneOf:
> +  - $ref: kontron,sl28-vpd.yaml

This is the other way around from how we normally structure things. 
Normally, the specific schema would reference the common/base schema. 
This works, though you will be applying the schema twice. Once here and 
then by matching on compatible string. Not a big deal as that happens 
fairly often, but a 'select: false' in kontron,sl28-vpd.yaml would 
prevent that. This way does more to enforce the overall structure of 
nodes.

The one downside I see with it this way is nvmem-layout can't ever have 
common properties defined without listing them in each layout schema.

In the end, I'm okay with either way.

Rob