Subject: Re: [PATCH v3 1/7] dt-bindings: Arm: Add Firmware Framework for Armv8-A (FF-A) binding

From: Rob Herring <[email-masked]>
Date: Mon, 14 Dec 2020 16:01:07 -0600

On Fri, Dec 04, 2020 at 12:11:31PM +0000, Sudeep Holla wrote:
> Since the FF-A v1.0 specification doesn't list the UUID of all the
> partitions in the discovery API, we need to specify the UUID of the
> partitions that need to be accessed by drivers within the kernel.
> 
> This binding to provide the list of partitions that kernel drivers
> may need to access.
> 
> Signed-off-by: Sudeep Holla <[email-masked]>
> ---
>  .../devicetree/bindings/arm/arm,ffa.yaml      | 58 +++++++++++++++++++
>  1 file changed, 58 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/arm/arm,ffa.yaml
> 
> diff --git a/Documentation/devicetree/bindings/arm/arm,ffa.yaml b/Documentation/devicetree/bindings/arm/arm,ffa.yaml
> new file mode 100644
> index 000000000000..a014a5801c34
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/arm/arm,ffa.yaml
> @@ -0,0 +1,58 @@
> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/arm/arm,ffa.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: Arm Firmware Framework for Arm v8-A (in-kernel users)
> +
> +maintainers:
> +  - Sudeep Holla <[email-masked]>
> +
> +description: |
> +  Firmware frameworks implementing partition according to the FF-A
> +  specification defined by ARM document number ARM DEN 0077A ("Arm Firmware
> +  Framework for Arm v8-A") [0], providing services to be used by other
> +  partitions.
> +
> +  [0] https://developer.arm.com/docs/den0077/latest
> +
> +properties:
> +  $nodename:
> +    const: ffa
> +
> +  compatible:
> +    oneOf:
> +      - const: arm,ffa-1.0
> +
> +patternProperties:
> +  "^ffa_partition[0-9]+$":
> +    type: object
> +    description: One or more child nodes, each describing an FFA partition.
> +    properties:
> +      $nodename:
> +        const: ffa_partition
> +
> +      compatible:
> +        oneOf:
> +          - const: arm,ffa-1.0-partition
> +
> +      uuid:
> +        $ref: '/schemas/types.yaml#definitions/string'
> +        description: |
> +          The 128-bit UUID [2] of the service implemented by this partition.
> +
> +          [2] https://tools.ietf.org/html/rfc4122

UUIDs are actually a known thing in json-schema with 'format: uuid'. 
The meta-schema will probably reject that, so we'll need to add support 
to dtschema. Maybe it should be a new definition to reference.

> +
> +additionalProperties: false
> +
> +examples:
> +  - |
> +    ffa {
> +      compatible = "arm,ffa-1.0";
> +
> +      ffa_partition0 {
> +        compatible = "arm,ffa-1.0-partition";
> +        uuid = "12345678-9abc-def0-1234-56789abcdef0";
> +      };
> +    };

This could all be simplified down to just a single property:

arm,ffa-partitions = "12345678-9abc-def0-1234-56789abcdef0", 
	"12345678-9abc-def0-1234-56789abcdef1"
	"12345678-9abc-def0-1234-56789abcdef2";

Obviously, that's not extensible, but do we need it to be?

Rob

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