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linux/Documentation/devicetree/bindings/example-schema.yaml

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