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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 Device
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 items:
95 - description: tx or combined interrupt
96 - description: rx interrupt
97 description:
98 A variable number of interrupts warrants a description of what conditions
99 affect the number of interrupts. Otherwise, descriptions on standard
100 properties are not necessary.
101 The items should have a fixed order, so pattern matching names are
102 discouraged.
103
104 interrupt-names:
105 # minItems must be specified here because the default would be 2
106 minItems: 1
107 items:
108 - const: tx irq
109 - const: rx irq
110
111 # Property names starting with '#' must be quoted
112 '#interrupt-cells':
113 # A simple case where the value must always be '2'.
114 # The core schema handles that this must be a single integer.
115 const: 2
116
117 interrupt-controller: true
118 # The core checks this is a boolean, so just have to list it here to be
119 # valid for this binding.
120
121 clock-frequency:
122 # The type is set in the core schema. Per-device schema only need to set
123 # constraints on the possible values.
124 minimum: 100
125 maximum: 400000
126 # The value that should be used if the property is not present
127 default: 200
128
129 foo-gpios:
130 maxItems: 1
131 description: A connection of the 'foo' gpio line.
132
133 # *-supply is always a single phandle, so nothing more to define.
134 foo-supply: true
135
136 # Vendor-specific properties
137 #
138 # Vendor-specific properties have slightly different schema requirements than
139 # common properties. They must have at least a type definition and
140 # 'description'.
141 vendor,int-property:
142 description: Vendor-specific properties must have a description
143 $ref: /schemas/types.yaml#/definitions/uint32
144 enum: [2, 4, 6, 8, 10]
145
146 vendor,bool-property:
147 description: Vendor-specific properties must have a description. Boolean
148 properties are one case where the json-schema 'type' keyword can be used
149 directly.
150 type: boolean
151
152 vendor,string-array-property:
153 description: Vendor-specific properties should reference a type in the
154 core schema.
155 $ref: /schemas/types.yaml#/definitions/string-array
156 items:
157 - enum: [foo, bar]
158 - enum: [baz, boo]
159
160 vendor,property-in-standard-units-microvolt:
161 description: Vendor-specific properties having a standard unit suffix
162 don't need a type.
163 enum: [ 100, 200, 300 ]
164
165 vendor,int-array-variable-length-and-constrained-values:
166 description: Array might define what type of elements might be used (e.g.
167 their range).
168 $ref: /schemas/types.yaml#/definitions/uint32-array
169 minItems: 2
170 maxItems: 3
171 items:
172 minimum: 0
173 maximum: 8
174
175 child-node:
176 description: Child nodes are just another property from a json-schema
177 perspective.
178 type: object # DT nodes are json objects
179 # Child nodes also need additionalProperties or unevaluatedProperties
180 additionalProperties: false
181 properties:
182 vendor,a-child-node-property:
183 description: Child node properties have all the same schema
184 requirements.
185 type: boolean
186
187 required:
188 - vendor,a-child-node-property
189
190# Describe the relationship between different properties
191dependencies:
192 # 'vendor,bool-property' is only allowed when 'vendor,string-array-property'
193 # is present
194 vendor,bool-property: [ 'vendor,string-array-property' ]
195 # Expressing 2 properties in both orders means all of the set of properties
196 # must be present or none of them.
197 vendor,string-array-property: [ 'vendor,bool-property' ]
198
199required:
200 - compatible
201 - reg
202 - interrupts
203 - interrupt-controller
204
205# if/then schema can be used to handle conditions on a property affecting
206# another property. A typical case is a specific 'compatible' value changes the
207# constraints on other properties.
208#
209# For multiple 'if' schema, group them under an 'allOf'.
210#
211# If the conditionals become too unweldy, then it may be better to just split
212# the binding into separate schema documents.
213allOf:
214 - if:
215 properties:
216 compatible:
217 contains:
218 const: vendor,soc2-ip
219 then:
220 required:
221 - foo-supply
222 else:
223 # If otherwise the property is not allowed:
224 properties:
225 foo-supply: false
226 # Altering schema depending on presence of properties is usually done by
227 # dependencies (see above), however some adjustments might require if:
228 - if:
229 required:
230 - vendor,bool-property
231 then:
232 properties:
233 vendor,int-property:
234 enum: [2, 4, 6]
235
236# Ideally, the schema should have this line otherwise any other properties
237# present are allowed. There's a few common properties such as 'status' and
238# 'pinctrl-*' which are added automatically by the tooling.
239#
240# This can't be used in cases where another schema is referenced
241# (i.e. allOf: [{$ref: ...}]).
242# If and only if another schema is referenced and arbitrary children nodes can
243# appear, "unevaluatedProperties: false" could be used. A typical example is
244# an I2C controller where no name pattern matching for children can be added.
245additionalProperties: false
246
247examples:
248 # Examples are now compiled with dtc and validated against the schemas
249 #
250 # Examples have a default #address-cells and #size-cells value of 1. This can
251 # be overridden or an appropriate parent bus node should be shown (such as on
252 # i2c buses).
253 #
254 # Any includes used have to be explicitly included. Use 4-space indentation.
255 - |
256 node@1000 {
257 compatible = "vendor,soc4-ip", "vendor,soc1-ip";
258 reg = <0x1000 0x80>,
259 <0x3000 0x80>;
260 reg-names = "core", "aux";
261 interrupts = <10>;
262 interrupt-controller;
263 };