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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 The items should have a fixed order, so pattern matching names are
85 discouraged.
86
87 clock-names:
88 items:
89 - const: bus
90
91 interrupts:
92 # Either 1 or 2 interrupts can be present
93 minItems: 1
94 maxItems: 2
95 items:
96 - description: tx or combined interrupt
97 - description: rx interrupt
98 description:
99 A variable number of interrupts warrants a description of what conditions
100 affect the number of interrupts. Otherwise, descriptions on standard
101 properties are not necessary.
102 The items should have a fixed order, so pattern matching names are
103 discouraged.
104
105 interrupt-names:
106 # minItems must be specified here because the default would be 2
107 minItems: 1
108 maxItems: 2
109 items:
110 - const: tx irq
111 - const: rx irq
112
113 # Property names starting with '#' must be quoted
114 '#interrupt-cells':
115 # A simple case where the value must always be '2'.
116 # The core schema handles that this must be a single integer.
117 const: 2
118
119 interrupt-controller: true
120 # The core checks this is a boolean, so just have to list it here to be
121 # valid for this binding.
122
123 clock-frequency:
124 # The type is set in the core schema. Per device schema only need to set
125 # constraints on the possible values.
126 minimum: 100
127 maximum: 400000
128 # The value that should be used if the property is not present
129 default: 200
130
131 foo-gpios:
132 maxItems: 1
133 description: A connection of the 'foo' gpio line.
134
135 # *-supply is always a single phandle, so nothing more to define.
136 foo-supply: true
137
138 # Vendor specific properties
139 #
140 # Vendor specific properties have slightly different schema requirements than
141 # common properties. They must have at least a type definition and
142 # 'description'.
143 vendor,int-property:
144 description: Vendor specific properties must have a description
145 $ref: /schemas/types.yaml#/definitions/uint32
146 enum: [2, 4, 6, 8, 10]
147
148 vendor,bool-property:
149 description: Vendor specific properties must have a description. Boolean
150 properties are one case where the json-schema 'type' keyword can be used
151 directly.
152 type: boolean
153
154 vendor,string-array-property:
155 description: Vendor specific properties should reference a type in the
156 core schema.
157 $ref: /schemas/types.yaml#/definitions/string-array
158 items:
159 - enum: [foo, bar]
160 - enum: [baz, boo]
161
162 vendor,property-in-standard-units-microvolt:
163 description: Vendor specific properties having a standard unit suffix
164 don't need a type.
165 enum: [ 100, 200, 300 ]
166
167 child-node:
168 description: Child nodes are just another property from a json-schema
169 perspective.
170 type: object # DT nodes are json objects
171 properties:
172 vendor,a-child-node-property:
173 description: Child node properties have all the same schema
174 requirements.
175 type: boolean
176
177 required:
178 - vendor,a-child-node-property
179
180# Describe the relationship between different properties
181dependencies:
182 # 'vendor,bool-property' is only allowed when 'vendor,string-array-property'
183 # is present
184 vendor,bool-property: [ 'vendor,string-array-property' ]
185 # Expressing 2 properties in both orders means all of the set of properties
186 # must be present or none of them.
187 vendor,string-array-property: [ 'vendor,bool-property' ]
188
189required:
190 - compatible
191 - reg
192 - interrupts
193 - interrupt-controller
194
195# if/then schema can be used to handle conditions on a property affecting
196# another property. A typical case is a specific 'compatible' value changes the
197# constraints on other properties.
198#
199# For multiple 'if' schema, group them under an 'allOf'.
200#
201# If the conditionals become too unweldy, then it may be better to just split
202# the binding into separate schema documents.
203allOf:
204 - if:
205 properties:
206 compatible:
207 contains:
208 const: vendor,soc2-ip
209 then:
210 required:
211 - foo-supply
212 # Altering schema depending on presence of properties is usually done by
213 # dependencies (see above), however some adjustments might require if:
214 - if:
215 required:
216 - vendor,bool-property
217 then:
218 properties:
219 vendor,int-property:
220 enum: [2, 4, 6]
221
222# Ideally, the schema should have this line otherwise any other properties
223# present are allowed. There's a few common properties such as 'status' and
224# 'pinctrl-*' which are added automatically by the tooling.
225#
226# This can't be used in cases where another schema is referenced
227# (i.e. allOf: [{$ref: ...}]).
228# If and only if another schema is referenced and arbitrary children nodes can
229# appear, "unevaluatedProperties: false" could be used. A typical example is
230# an I2C controller where no name pattern matching for children can be added.
231additionalProperties: false
232
233examples:
234 # Examples are now compiled with dtc and validated against the schemas
235 #
236 # Examples have a default #address-cells and #size-cells value of 1. This can
237 # be overridden or an appropriate parent bus node should be shown (such as on
238 # i2c buses).
239 #
240 # Any includes used have to be explicitly included.
241 - |
242 node@1000 {
243 compatible = "vendor,soc4-ip", "vendor,soc1-ip";
244 reg = <0x1000 0x80>,
245 <0x3000 0x80>;
246 reg-names = "core", "aux";
247 interrupts = <10>;
248 interrupt-controller;
249 };