Re: [PATCH v3 1/3] dt-bindings: Convert graph bindings to json-schema

Sameer Pujar
2020-11-11T09:52:09Z

Hi Rob,

> From: Sameer Pujar <spujar@nvidia.com>
>
> Convert device tree bindings of graph to YAML format. Currently graph.txt
> doc is referenced in multiple files and all of these need to use schema
> references. For now graph.txt is updated to refer to graph.yaml.
>
> For users of the graph binding, they should reference to the graph
> schema from either 'ports' or 'port' property:
>
> properties:
> ports:
> type: object
> $ref: graph.yaml#/properties/ports
>
> properties:
> port@0:
> description: What data this port has
>
> ...
>
> Or:
>
> properties:
> port:
> description: What data this port has
> type: object
> $ref: graph.yaml#/properties/port
>
> Signed-off-by: Sameer Pujar <spujar@nvidia.com>
> Acked-by: Philipp Zabel <p.zabel@pengutronix.de>
> Signed-off-by: Rob Herring <robh@kernel.org>
> ---
> v3:
> - Move port 'reg' to port@* and make required
> - Make remote-endpoint required
> - Add 'additionalProperties: true' now required
> - Fix yamllint warnings
>
> Documentation/devicetree/bindings/graph.txt | 129 +-----------
> Documentation/devicetree/bindings/graph.yaml | 199 +++++++++++++++++++
> 2 files changed, 200 insertions(+), 128 deletions(-)
> create mode 100644 Documentation/devicetree/bindings/graph.yaml
>
...
> diff --git a/Documentation/devicetree/bindings/graph.yaml b/Documentation/devicetree/bindings/graph.yaml
> new file mode 100644
> index 000000000000..b56720c5a13e
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/graph.yaml
> @@ -0,0 +1,199 @@
> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/graph.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: Common bindings for device graphs
> +
> +description: |
> + The hierarchical organisation of the device tree is well suited to describe
> + control flow to devices, but there can be more complex connections between
> + devices that work together to form a logical compound device, following an
> + arbitrarily complex graph.
> + There already is a simple directed graph between devices tree nodes using
> + phandle properties pointing to other nodes to describe connections that
> + can not be inferred from device tree parent-child relationships. The device
> + tree graph bindings described herein abstract more complex devices that can
> + have multiple specifiable ports, each of which can be linked to one or more
> + ports of other devices.
> +
> + These common bindings do not contain any information about the direction or
> + type of the connections, they just map their existence. Specific properties
> + may be described by specialized bindings depending on the type of connection.
> +
> + To see how this binding applies to video pipelines, for example, see
> + Documentation/devicetree/bindings/media/video-interfaces.txt.
> + Here the ports describe data interfaces, and the links between them are
> + the connecting data buses. A single port with multiple connections can
> + correspond to multiple devices being connected to the same physical bus.
> +
> +maintainers:
> + - Philipp Zabel <p.zabel@pengutronix.de>
> +
> +select: false
> +
> +properties:
> + port:
> + type: object
> + description:
> + If there is more than one endpoint node or 'reg' property present in
> + endpoint nodes then '#address-cells' and '#size-cells' properties are
> + required.
> +
> + properties:
> + "#address-cells":
> + const: 1
> +
> + "#size-cells":
> + const: 0
> +
> + patternProperties:
> + "^endpoint(@[0-9a-f]+)?$":
> + type: object
> + properties:
> + reg:
> + maxItems: 1
> +
> + remote-endpoint:
> + description: |
> + phandle to an 'endpoint' subnode of a remote device node.
> + $ref: /schemas/types.yaml#/definitions/phandle
> +
> + required:
> + - remote-endpoint

Does 'remote-endpoint' have to be a required property?
In case of pluggable modules, the remote-endpoint may not be available
unless the module is plugged in. In other words, device-2 in below
example may not always be available, but still device-1 endpoint
configuration and usage may be required?

...

> + # 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>;
> + };
> + };
> + };
> +
> +...
> --
> 2.25.1