Re: [PATCH V2] dt-bindings: nvmem: fixed-cell: add compatible for MAC cells

[Rob Herring <robh@kernel.org>]

On Mon, Jun 26, 2023 at 01:37:16PM +0200, Rafał Miłecki wrote:
> From: Rafał Miłecki <rafal@milecki.pl>
> 
> A lot of home routers have NVMEM fixed cells containing MAC address that
> need some further processing. In ~99% cases MAC needs to be:
> 1. Optionally parsed from ASCII format
> 2. Increased by a vendor-picked value
> 
> There was already an attempt to design a binding for that at NVMEM
> device level in the past. It wasn't accepted though as it didn't really
> fit NVMEM device layer.
> 
> The introduction of NVMEM fixed-cells layout seems to be an opportunity
> to provide a relevant binding in a clean way.
> 
> This commit adds a *generic* compatible string: "mac-base". As always it
> needs to be carefully reviewed.
> 
> OpenWrt project currently supports ~300 home routers that have NVMEM
> cell with binary-stored base MAC.T hose devices are manufactured by
> multiple vendors. There are TP-Link devices (76 of them), Netgear (19),
> D-Link (11), OpenMesh (9), EnGenius (8), GL.iNet (8), ZTE (7),
> Xiaomi (5), Ubiquiti (6) and more. Those devices don't share an
> architecture or SoC.
> 
> Another 200 devices have base MAC stored in an ASCII format (not all
> those devices have been converted to DT though).
> 
> It would be impractical to provide unique "compatible" strings for NVMEM
> layouts of all those devices. It seems like a valid case for allowing a
> generic binding instead. Even if this binding will not be sufficient for
> some further devices it seems to be useful enough as it is.
> 
> Signed-off-by: Rafał Miłecki <rafal@milecki.pl>
> ---
> V2: Drop "mac-ascii" as length can be checked instead
>     Fix "allOf" by adding required: [ compatible ]
> ---
>  .../bindings/nvmem/layouts/fixed-cell.yaml    | 26 +++++++++++++++++++
>  .../bindings/nvmem/layouts/fixed-layout.yaml  | 12 +++++++++
>  .../devicetree/bindings/nvmem/nvmem.yaml      |  5 +++-
>  3 files changed, 42 insertions(+), 1 deletion(-)
> 
> diff --git a/Documentation/devicetree/bindings/nvmem/layouts/fixed-cell.yaml b/Documentation/devicetree/bindings/nvmem/layouts/fixed-cell.yaml
> index e698098450e1..036a9ed88893 100644
> --- a/Documentation/devicetree/bindings/nvmem/layouts/fixed-cell.yaml
> +++ b/Documentation/devicetree/bindings/nvmem/layouts/fixed-cell.yaml
> @@ -11,6 +11,15 @@ maintainers:
>    - Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
>  
>  properties:
> +  compatible:
> +    oneOf:
> +      - const: mac-base
> +        description: >
> +          Cell with base MAC address to be used for calculating extra relative
> +          addresses.
> +          It can be stored in a plain binary format (cell length 12) or as an

Don't you mean a length of 6?

> +          ASCII text like "00:11:22:33:44:55" (cell length 17).
> +
>    reg:
>      maxItems: 1
>  
> @@ -25,6 +34,23 @@ properties:
>          description:
>            Size in bit within the address range specified by reg.
>  
> +allOf:
> +  - if:
> +      required: [ compatible ]
> +    then:
> +      if:
> +        properties:
> +          compatible:
> +            contains:
> +              const: mac-base
> +      then:
> +        properties:
> +          "#nvmem-cell-cells":
> +            description: The first argument is a MAC address offset.
> +            const: 1
> +        required:
> +          - "#nvmem-cell-cells"
> +
>  required:
>    - reg
>  
> diff --git a/Documentation/devicetree/bindings/nvmem/layouts/fixed-layout.yaml b/Documentation/devicetree/bindings/nvmem/layouts/fixed-layout.yaml
> index c271537d0714..b3a09e8864f1 100644
> --- a/Documentation/devicetree/bindings/nvmem/layouts/fixed-layout.yaml
> +++ b/Documentation/devicetree/bindings/nvmem/layouts/fixed-layout.yaml
> @@ -44,6 +44,18 @@ examples:
>          #address-cells = <1>;
>          #size-cells = <1>;
>  
> +        mac@100 {
> +            compatible = "mac-base";
> +            reg = <0x100 0xc>;
> +            #nvmem-cell-cells = <1>;
> +        };
> +
> +        mac@110 {
> +            compatible = "mac-base";
> +            reg = <0x110 0x11>;
> +            #nvmem-cell-cells = <1>;
> +        };
> +
>          calibration@4000 {
>              reg = <0x4000 0x100>;
>          };
> diff --git a/Documentation/devicetree/bindings/nvmem/nvmem.yaml b/Documentation/devicetree/bindings/nvmem/nvmem.yaml
> index 980244100690..9f921d940142 100644
> --- a/Documentation/devicetree/bindings/nvmem/nvmem.yaml
> +++ b/Documentation/devicetree/bindings/nvmem/nvmem.yaml
> @@ -49,7 +49,10 @@ properties:
>  patternProperties:
>    "@[0-9a-f]+(,[0-7])?$":
>      type: object
> -    $ref: layouts/fixed-cell.yaml
> +    allOf:
> +      - $ref: layouts/fixed-cell.yaml
> +      - properties:
> +          compatible: false
>      deprecated: true
>  
>  additionalProperties: true
> -- 
> 2.35.3
>