266 lines
8.9 KiB
YAML
266 lines
8.9 KiB
YAML
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# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
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# Copyright 2018 Linaro Ltd.
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%YAML 1.2
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---
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# All the top-level keys are standard json-schema keywords except for
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# 'maintainers' and 'select'
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# $id is a unique identifier based on the filename. There may or may not be a
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# file present at the URL.
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$id: http://devicetree.org/schemas/example-schema.yaml#
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# $schema is the meta-schema this schema should be validated with.
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$schema: http://devicetree.org/meta-schemas/core.yaml#
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title: An Example Device
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maintainers:
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- Rob Herring <robh@kernel.org>
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description: |
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A more detailed multi-line description of the binding.
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Details about the hardware device and any links to datasheets can go here.
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Literal blocks are marked with the '|' at the beginning. The end is marked by
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indentation less than the first line of the literal block. Lines also cannot
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begin with a tab character.
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select: false
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# 'select' is a schema applied to a DT node to determine if this binding
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# schema should be applied to the node. It is optional and by default the
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# possible compatible strings are extracted and used to match.
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# In this case, a 'false' schema will never match.
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properties:
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# A dictionary of DT properties for this binding schema
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compatible:
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# More complicated schema can use oneOf (XOR), anyOf (OR), or allOf (AND)
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# to handle different conditions.
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# In this case, it's needed to handle a variable number of values as there
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# isn't another way to express a constraint of the last string value.
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# The boolean schema must be a list of schemas.
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oneOf:
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- items:
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# items is a list of possible values for the property. The number of
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# values is determined by the number of elements in the list.
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# Order in lists is significant, order in dicts is not
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# Must be one of the 1st enums followed by the 2nd enum
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#
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# Each element in items should be 'enum' or 'const'
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- enum:
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- vendor,soc4-ip
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- vendor,soc3-ip
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- vendor,soc2-ip
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- const: vendor,soc1-ip
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# additionalItems being false is implied
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# minItems/maxItems equal to 2 is implied
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- items:
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# 'const' is just a special case of an enum with a single possible value
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- const: vendor,soc1-ip
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reg:
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# The core schema already checks that reg values are numbers, so device
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# specific schema don't need to do those checks.
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# The description of each element defines the order and implicitly defines
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# the number of reg entries.
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items:
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- description: core registers
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- description: aux registers
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# minItems/maxItems equal to 2 is implied
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reg-names:
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# The core schema enforces this (*-names) is a string array
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items:
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- const: core
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- const: aux
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clocks:
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# Cases that have only a single entry just need to express that with maxItems
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maxItems: 1
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description: bus clock. A description is only needed for a single item if
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there's something unique to add.
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The items should have a fixed order, so pattern matching names are
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discouraged.
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clock-names:
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# For single-entry lists in clocks, resets etc., the xxx-names often do not
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# bring any value, especially if they copy the IP block name. In such case
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# just skip the xxx-names.
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items:
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- const: bus
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interrupts:
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# Either 1 or 2 interrupts can be present
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minItems: 1
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items:
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- description: tx or combined interrupt
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- description: rx interrupt
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description:
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A variable number of interrupts warrants a description of what conditions
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affect the number of interrupts. Otherwise, descriptions on standard
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properties are not necessary.
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The items should have a fixed order, so pattern matching names are
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discouraged.
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interrupt-names:
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# minItems must be specified here because the default would be 2
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minItems: 1
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items:
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- const: tx irq
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- const: rx irq
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# Property names starting with '#' must be quoted
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'#interrupt-cells':
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# A simple case where the value must always be '2'.
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# The core schema handles that this must be a single integer.
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const: 2
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interrupt-controller: true
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# The core checks this is a boolean, so just have to list it here to be
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# valid for this binding.
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clock-frequency:
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# The type is set in the core schema. Per-device schema only need to set
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# constraints on the possible values.
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minimum: 100
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maximum: 400000
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# The value that should be used if the property is not present
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default: 200
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foo-gpios:
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maxItems: 1
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description: A connection of the 'foo' gpio line.
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# *-supply is always a single phandle, so nothing more to define.
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foo-supply: true
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# Vendor-specific properties
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#
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# Vendor-specific properties have slightly different schema requirements than
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# common properties. They must have at least a type definition and
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# 'description'.
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vendor,int-property:
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description: Vendor-specific properties must have a description
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$ref: /schemas/types.yaml#/definitions/uint32
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enum: [2, 4, 6, 8, 10]
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vendor,bool-property:
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description: Vendor-specific properties must have a description. Boolean
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properties are one case where the json-schema 'type' keyword can be used
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directly.
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type: boolean
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vendor,string-array-property:
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description: Vendor-specific properties should reference a type in the
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core schema.
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$ref: /schemas/types.yaml#/definitions/string-array
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items:
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- enum: [foo, bar]
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- enum: [baz, boo]
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vendor,property-in-standard-units-microvolt:
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description: Vendor-specific properties having a standard unit suffix
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don't need a type.
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enum: [ 100, 200, 300 ]
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vendor,int-array-variable-length-and-constrained-values:
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description: Array might define what type of elements might be used (e.g.
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their range).
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$ref: /schemas/types.yaml#/definitions/uint32-array
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minItems: 2
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maxItems: 3
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items:
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minimum: 0
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maximum: 8
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child-node:
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description: Child nodes are just another property from a json-schema
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perspective.
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type: object # DT nodes are json objects
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# Child nodes also need additionalProperties or unevaluatedProperties
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additionalProperties: false
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properties:
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vendor,a-child-node-property:
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description: Child node properties have all the same schema
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requirements.
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type: boolean
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required:
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- vendor,a-child-node-property
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# Describe the relationship between different properties
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dependencies:
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# 'vendor,bool-property' is only allowed when 'vendor,string-array-property'
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# is present
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vendor,bool-property: [ 'vendor,string-array-property' ]
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# Expressing 2 properties in both orders means all of the set of properties
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# must be present or none of them.
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vendor,string-array-property: [ 'vendor,bool-property' ]
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required:
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- compatible
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- reg
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- interrupts
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- interrupt-controller
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# if/then schema can be used to handle conditions on a property affecting
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# another property. A typical case is a specific 'compatible' value changes the
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# constraints on other properties.
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#
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# For multiple 'if' schema, group them under an 'allOf'.
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#
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# If the conditionals become too unweldy, then it may be better to just split
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# the binding into separate schema documents.
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allOf:
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- if:
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properties:
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compatible:
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contains:
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const: vendor,soc2-ip
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then:
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required:
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- foo-supply
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else:
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# If otherwise the property is not allowed:
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properties:
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foo-supply: false
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# Altering schema depending on presence of properties is usually done by
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# dependencies (see above), however some adjustments might require if:
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- if:
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required:
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- vendor,bool-property
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then:
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properties:
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vendor,int-property:
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enum: [2, 4, 6]
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# Ideally, the schema should have this line otherwise any other properties
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# present are allowed. There's a few common properties such as 'status' and
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# 'pinctrl-*' which are added automatically by the tooling.
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#
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# This can't be used in cases where another schema is referenced
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# (i.e. allOf: [{$ref: ...}]).
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# If and only if another schema is referenced and arbitrary children nodes can
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# appear, "unevaluatedProperties: false" could be used. A typical example is
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# an I2C controller where no name pattern matching for children can be added.
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additionalProperties: false
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examples:
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# Examples are now compiled with dtc and validated against the schemas
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#
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# Examples have a default #address-cells and #size-cells value of 1. This can
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# be overridden or an appropriate parent bus node should be shown (such as on
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# i2c buses).
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#
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# Any includes used have to be explicitly included. Use 4-space indentation.
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- |
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node@1000 {
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compatible = "vendor,soc4-ip", "vendor,soc1-ip";
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reg = <0x1000 0x80>,
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<0x3000 0x80>;
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reg-names = "core", "aux";
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interrupts = <10>;
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interrupt-controller;
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};
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