1# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
2# Copyright 2018 Linaro Ltd.
3%YAML 1.2
4---
5# All the top-level keys are standard json-schema keywords except for
6# 'maintainers' and 'select'
7
8# $id is a unique identifier based on the filename. There may or may not be a
9# file present at the URL.
10$id: http://devicetree.org/schemas/example-schema.yaml#
11# $schema is the meta-schema this schema should be validated with.
12$schema: http://devicetree.org/meta-schemas/core.yaml#
13
14title: An example schema annotated with jsonschema details
15
16maintainers:
17  - Rob Herring <robh@kernel.org>
18
19description: |
20  A more detailed multi-line description of the binding.
21
22  Details about the hardware device and any links to datasheets can go here.
23
24  Literal blocks are marked with the '|' at the beginning. The end is marked by
25  indentation less than the first line of the literal block. Lines also cannot
26  begin with a tab character.
27
28select: false
29  # 'select' is a schema applied to a DT node to determine if this binding
30  # schema should be applied to the node. It is optional and by default the
31  # possible compatible strings are extracted and used to match.
32
33  # In this case, a 'false' schema will never match.
34
35properties:
36  # A dictionary of DT properties for this binding schema
37  compatible:
38    # More complicated schema can use oneOf (XOR), anyOf (OR), or allOf (AND)
39    # to handle different conditions.
40    # In this case, it's needed to handle a variable number of values as there
41    # isn't another way to express a constraint of the last string value.
42    # The boolean schema must be a list of schemas.
43    oneOf:
44      - items:
45          # items is a list of possible values for the property. The number of
46          # values is determined by the number of elements in the list.
47          # Order in lists is significant, order in dicts is not
48          # Must be one of the 1st enums followed by the 2nd enum
49          #
50          # Each element in items should be 'enum' or 'const'
51          - enum:
52              - vendor,soc4-ip
53              - vendor,soc3-ip
54              - vendor,soc2-ip
55          - enum:
56              - vendor,soc1-ip
57        # additionalItems being false is implied
58        # minItems/maxItems equal to 2 is implied
59      - items:
60          # 'const' is just a special case of an enum with a single possible value
61          - const: vendor,soc1-ip
62
63  reg:
64    # The core schema already checks that reg values are numbers, so device
65    # specific schema don't need to do those checks.
66    # The description of each element defines the order and implicitly defines
67    # the number of reg entries.
68    items:
69      - description: core registers
70      - description: aux registers
71    # minItems/maxItems equal to 2 is implied
72
73  reg-names:
74    # The core schema enforces this (*-names) is a string array
75    items:
76      - const: core
77      - const: aux
78
79  clocks:
80    # Cases that have only a single entry just need to express that with maxItems
81    maxItems: 1
82    description: bus clock. A description is only needed for a single item if
83      there's something unique to add.
84
85  clock-names:
86    items:
87      - const: bus
88
89  interrupts:
90    # Either 1 or 2 interrupts can be present
91    minItems: 1
92    maxItems: 2
93    items:
94      - description: tx or combined interrupt
95      - description: rx interrupt
96    description:
97      A variable number of interrupts warrants a description of what conditions
98      affect the number of interrupts. Otherwise, descriptions on standard
99      properties are not necessary.
100
101  interrupt-names:
102    # minItems must be specified here because the default would be 2
103    minItems: 1
104    maxItems: 2
105    items:
106      - const: tx irq
107      - const: rx irq
108
109  # Property names starting with '#' must be quoted
110  '#interrupt-cells':
111    # A simple case where the value must always be '2'.
112    # The core schema handles that this must be a single integer.
113    const: 2
114
115  interrupt-controller: true
116    # The core checks this is a boolean, so just have to list it here to be
117    # valid for this binding.
118
119  clock-frequency:
120    # The type is set in the core schema. Per device schema only need to set
121    # constraints on the possible values.
122    minimum: 100
123    maximum: 400000
124    # The value that should be used if the property is not present
125    default: 200
126
127  foo-gpios:
128    maxItems: 1
129    description: A connection of the 'foo' gpio line.
130
131  # *-supply is always a single phandle, so nothing more to define.
132  foo-supply: true
133
134  # Vendor specific properties
135  #
136  # Vendor specific properties have slightly different schema requirements than
137  # common properties. They must have at least a type definition and
138  # 'description'.
139  vendor,int-property:
140    description: Vendor specific properties must have a description
141    $ref: /schemas/types.yaml#/definitions/uint32
142    enum: [2, 4, 6, 8, 10]
143
144  vendor,bool-property:
145    description: Vendor specific properties must have a description. Boolean
146      properties are one case where the json-schema 'type' keyword can be used
147      directly.
148    type: boolean
149
150  vendor,string-array-property:
151    description: Vendor specific properties should reference a type in the
152      core schema.
153    $ref: /schemas/types.yaml#/definitions/string-array
154    items:
155      - enum: [foo, bar]
156      - enum: [baz, boo]
157
158  vendor,property-in-standard-units-microvolt:
159    description: Vendor specific properties having a standard unit suffix
160      don't need a type.
161    enum: [ 100, 200, 300 ]
162
163  child-node:
164    description: Child nodes are just another property from a json-schema
165      perspective.
166    type: object  # DT nodes are json objects
167    properties:
168      vendor,a-child-node-property:
169        description: Child node properties have all the same schema
170          requirements.
171        type: boolean
172
173    required:
174      - vendor,a-child-node-property
175
176# Describe the relationship between different properties
177dependencies:
178  # 'vendor,bool-property' is only allowed when 'vendor,string-array-property'
179  # is present
180  vendor,bool-property: [ vendor,string-array-property ]
181  # Expressing 2 properties in both orders means all of the set of properties
182  # must be present or none of them.
183  vendor,string-array-property: [ vendor,bool-property ]
184
185required:
186  - compatible
187  - reg
188  - interrupts
189  - interrupt-controller
190
191# if/then schema can be used to handle conditions on a property affecting
192# another property. A typical case is a specific 'compatible' value changes the
193# constraints on other properties.
194#
195# For multiple 'if' schema, group them under an 'allOf'.
196#
197# If the conditionals become too unweldy, then it may be better to just split
198# the binding into separate schema documents.
199if:
200  properties:
201    compatible:
202      contains:
203        const: vendor,soc2-ip
204then:
205  required:
206    - foo-supply
207
208# Ideally, the schema should have this line otherwise any other properties
209# present are allowed. There's a few common properties such as 'status' and
210# 'pinctrl-*' which are added automatically by the tooling.
211#
212# This can't be used in cases where another schema is referenced
213# (i.e. allOf: [{$ref: ...}]).
214additionalProperties: false
215
216examples:
217  # Examples are now compiled with dtc and validated against the schemas
218  #
219  # Examples have a default #address-cells and #size-cells value of 1. This can
220  # be overridden or an appropriate parent bus node should be shown (such as on
221  # i2c buses).
222  #
223  # Any includes used have to be explicitly included.
224  - |
225    node@1000 {
226          compatible = "vendor,soc4-ip", "vendor,soc1-ip";
227          reg = <0x1000 0x80>,
228                <0x3000 0x80>;
229          reg-names = "core", "aux";
230          interrupts = <10>;
231          interrupt-controller;
232    };
233