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

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Date:   Thu, 10 Nov 2022 18:38:55 +0100
From:   Miquel Raynal <miquel.raynal@...tlin.com>
To:     Rob Herring <robh@...nel.org>
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

Hi Rob,

robh@...nel.org wrote on Thu, 10 Nov 2022 07:49:18 -0600:

> 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.

Oh right, I knew about the "select: false" thing, but I forgot it in
the two layouts.

> 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.

Oh that's right, actually I solved it in the mtd dt-binding series with:

partitions.yaml:

	oneOf:
	  - $ref: <parser>.yaml

	generic-property:
	  $ref: something
	  min/max...: foo

<parser>.yaml:
	generic-property: true

But in this case, are the constraints provided by partitions.yaml on
"generic-property" actually still enforced?

Thanks,
Miquèl