Re: [PATCH v4 08/15] Documentation: of: Convert graph bindings to json-schema

[Rob Herring <robh@kernel.org>]

On Fri, Oct 16, 2020 at 08:12:55PM +0530, Sameer Pujar wrote:
> Convert device tree bindings of graph to YAML format.

Thanks for doing this.

> Signed-off-by: Sameer Pujar <spujar@nvidia.com>
> Cc: Philipp Zabel <p.zabel@pengutronix.de>
> ---
>  Documentation/devicetree/bindings/graph.txt  | 128 --------------------
>  Documentation/devicetree/bindings/graph.yaml | 170 +++++++++++++++++++++++++++
>  2 files changed, 170 insertions(+), 128 deletions(-)
>  delete mode 100644 Documentation/devicetree/bindings/graph.txt
>  create mode 100644 Documentation/devicetree/bindings/graph.yaml

I'd like to move this to the dtschema repository instead.

> diff --git a/Documentation/devicetree/bindings/graph.yaml b/Documentation/devicetree/bindings/graph.yaml
> new file mode 100644
> index 0000000..67804c1
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/graph.yaml
> @@ -0,0 +1,170 @@
> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)

As the original text defaulted to GPL2, this needs Philipp's permission 
to re-license.

> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/graph.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: Common bindings for device graphs
> +
> +description: |
> +  The hierarchical organisation of the device tree is well suited to describe
> +  control flow to devices, but there can be more complex connections between
> +  devices that work together to form a logical compound device, following an
> +  arbitrarily complex graph.
> +  There already is a simple directed graph between devices tree nodes using
> +  phandle properties pointing to other nodes to describe connections that
> +  can not be inferred from device tree parent-child relationships. The device
> +  tree graph bindings described herein abstract more complex devices that can
> +  have multiple specifiable ports, each of which can be linked to one or more
> +  ports of other devices.
> +
> +  These common bindings do not contain any information about the direction or
> +  type of the connections, they just map their existence. Specific properties
> +  may be described by specialized bindings depending on the type of connection.
> +
> +  To see how this binding applies to video pipelines, for example, see
> +  Documentation/devicetree/bindings/media/video-interfaces.txt.
> +  Here the ports describe data interfaces, and the links between them are
> +  the connecting data buses. A single port with multiple connections can
> +  correspond to multiple devices being connected to the same physical bus.
> +
> +maintainers:
> +  - Philipp Zabel <p.zabel@pengutronix.de>
> +
> +definitions:
> +
> +  port:
> +    type: object
> +    description: |
> +      If there is more than one 'port' or more than one 'endpoint' node
> +      or 'reg' property present in the port and/or endpoint nodes then
> +      '#address-cells' and '#size-cells' properties are required in relevant
> +      parent node.

reg property.

> +
> +    patternProperties:
> +      "^endpoint(@[0-9a-f]+)?$":
> +        type: object
> +        properties:

reg?

> +          remote-endpoint:
> +            description: |
> +              phandle to an 'endpoint' subnode of a remote device node.
> +            $ref: /schemas/types.yaml#/definitions/phandle
> +
> +  ports:
> +    type: object
> +    patternProperties:
> +      "^port(@[0-9a-f]+)?$":
> +        $ref: "#/definitions/port"

No reason for this to be under 'definitions'. Just move down.

> +
> +properties:
> +  ports:
> +    $ref: "#/definitions/ports"
> +
> +patternProperties:
> +  "^port(@[0-9a-f]+)?$":
> +    $ref: "#/definitions/port"
> +
> +additionalProperties: false

This needs to be true here. But you need this within 'ports' and 'port'. 
(I think... I think we only have extra properties within endpoint 
nodes.) 

> +
> +examples:
> +  # Organisation of ports and endpoints:
> +  #
> +  # Ports are described by child 'port' nodes contained in the device node.
> +  # Each port node contains an 'endpoint' subnode for each remote device port
> +  # connected to this port. If a single port is connected to more than one
> +  # remote device, an 'endpoint' child node must be provided for each link.
> +  # If more than one port is present in a device node or there is more than
> +  # one endpoint at a port, or a port node needs to be associated with a
> +  # selected hardware interface, a common scheme using '#address-cells',
> +  # '#size-cells' and 'reg' properties is used to number the nodes.
> +  - |
> +    device {
> +        #address-cells = <1>;
> +        #size-cells = <0>;
> +
> +        port@0 {
> +            #address-cells = <1>;
> +            #size-cells = <0>;
> +            reg = <0>;
> +
> +            endpoint@0 {
> +                reg = <0>;
> +                // ...
> +            };
> +            endpoint@1 {
> +                reg = <1>;
> +                // ...
> +            };
> +        };
> +
> +        port@1 {
> +            reg = <1>;
> +
> +            endpoint {
> +                // ...
> +            };
> +        };
> +    };
> +
> +  # All 'port' nodes can be grouped under an optional 'ports' node, which
> +  # allows to specify #address-cells, #size-cells properties for the 'port'
> +  # nodes independently from any other child device nodes a device might
> +  # have.
> +  - |
> +    device {
> +        // ...
> +        ports {
> +            #address-cells = <1>;
> +            #size-cells = <0>;
> +
> +            port@0 {
> +                #address-cells = <1>;
> +                #size-cells = <0>;
> +                reg = <0>;
> +                // ...
> +
> +                endpoint@0 {
> +                    reg = <0>;
> +                    // ...
> +                };
> +                endpoint@1 {
> +                    reg = <1>;
> +                    // ...
> +                };
> +            };
> +
> +            port@1 {
> +                #address-cells = <1>;
> +                #size-cells = <0>;
> +                reg = <1>;
> +                // ...
> +            };
> +        };
> +    };
> +
> +  # Links between endpoints:
> +  #
> +  # Each endpoint should contain a 'remote-endpoint' phandle property that
> +  # points to the corresponding endpoint in the port of the remote device.
> +  # In turn, the remote endpoint should contain a 'remote-endpoint' property.
> +  # If it has one, it must not point to anything other than the local endpoint.
> +  # Two endpoints with their 'remote-endpoint' phandles pointing at each other
> +  # form a link between the containing ports.
> +  - |
> +    device-1 {
> +        port {
> +            device_1_output: endpoint {
> +                remote-endpoint = <&device_2_input>;
> +            };
> +        };
> +    };
> +
> +    device-2 {
> +        port {
> +            device_2_input: endpoint {
> +                remote-endpoint = <&device_1_output>;
> +            };
> +        };
> +    };
> +
> +...
> -- 
> 2.7.4
>