linux-kernel - Re: [RFC PATCH 1/2] dt-bindings: mtd: partitions: Document new dynamic-partitions node

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Date:   Mon, 24 Jan 2022 23:02:24 +0100
From:   Rafał Miłecki <zajec5@...il.com>
To:     Ansuel Smith <ansuelsmth@...il.com>,
        Miquel Raynal <miquel.raynal@...tlin.com>,
        Richard Weinberger <richard@....at>,
        Vignesh Raghavendra <vigneshr@...com>,
        Rob Herring <robh+dt@...nel.org>,
        linux-mtd@...ts.infradead.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH 1/2] dt-bindings: mtd: partitions: Document new
 dynamic-partitions node

On 20.01.2022 21:26, Ansuel Smith wrote:
> Document new dynamic-partitions node used to provide an of node for
> partition registred at runtime by parsers. This is required for nvmem
> system to declare and detect nvmem-cells.
> 
> Signed-off-by: Ansuel Smith <ansuelsmth@...il.com>
> ---
>   .../mtd/partitions/dynamic-partitions.yaml    | 59 +++++++++++++++++++
>   1 file changed, 59 insertions(+)
>   create mode 100644 Documentation/devicetree/bindings/mtd/partitions/dynamic-partitions.yaml
> 
> diff --git a/Documentation/devicetree/bindings/mtd/partitions/dynamic-partitions.yaml b/Documentation/devicetree/bindings/mtd/partitions/dynamic-partitions.yaml
> new file mode 100644
> index 000000000000..7528e49f2d7e
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/mtd/partitions/dynamic-partitions.yaml
> @@ -0,0 +1,59 @@
> +# SPDX-License-Identifier: GPL-2.0-only OR BSD-2-Clause
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/mtd/partitions/dynamic-partitions.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: Dynamic partitions
> +
> +description: |
> +  This binding can be used on platforms which have partitions registered at
> +  runtime by parsers or partition table present on the flash. Example are
> +  partitions declared from smem parser or cmdlinepart. This will create an
> +  of node for these dynamic partition where systems like Nvmem can get a
> +  reference to register nvmem-cells.
> +
> +  The partition table should be a node named "dynamic-partitions".
> +  Partitions are then defined as subnodes. Only the label is required
> +  as any other data will be taken from the parser.
> +
> +maintainers:
> +  - Ansuel Smith <ansuelsmth@...il.com>
> +
> +properties:
> +  compatible:
> +    const: dynamic-partitions
> +
> +patternProperties:
> +  "@[0-9a-f]+$":
> +    $ref: "partition.yaml#"
> +
> +additionalProperties: true
> +
> +examples:
> +  - |
> +    partitions {
> +        compatible = "qcom,smem";
> +        #address-cells = <1>;
> +        #size-cells = <1>;
> +    };
> +
> +    dynamic-partitions {
> +      compatible = "dynamic-partitions";
> +
> +      art: art {
> +        label = "0:art";
> +        read-only;
> +        compatible = "nvmem-cells";
> +        #address-cells = <1>;
> +        #size-cells = <1>;
> +
> +        macaddr_art_0: macaddr@0 {
> +          reg = <0x0 0x6>;
> +        };
> +
> +        macaddr_art_6: macaddr@6 {
> +          reg = <0x6 0x6>;
> +        };
> +      };
> +    };

First of all: I fully support such a feature. I need it for Broadom
platforms that use "brcm,bcm947xx-cfe-partitions" dynamic partitions.
In my case bootloader partition is created dynamically (it doesn't have
const offset and size). It contains NVMEM data however that needs to be
described in DT.

This binding however looks loose and confusing to me.

First of all did you really mean to use "qcom,smem"? My first guess is
you meant "qcom,smem-part".

Secondly can't we have partitions defined just as subnodes of the
partitions { ... }; node?


I think sth like below would make more sense:

partitions {
     compatible = "qcom,smem-part";

     art {
         label = "0:art";
         read-only;
         compatible = "nvmem-cells";
         #address-cells = <1>;
         #size-cells = <1>;

         macaddr_art_0: macaddr@0 {
             reg = <0x0 0x6>;
         };

         macaddr_art_6: macaddr@6 {
             reg = <0x6 0x6>;
         };
     };
};


Then I could also reuse that for something like:

partitions {
     compatible = "brcm,bcm947xx-cfe-partitions";

     partition-0 {
         compatible = "nvmem-cells";
         label = "boot";

         #address-cells = <1>;
         #size-cells = <1>;

         mac: macaddr@0 {
             reg = <0x100 0x6>;
         };
     }
};