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
14 title: An Example Device
15
16 maintainers:
17 - Rob Herring <robh@kernel.org>
18
19 description: |
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
28 select: 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
35 properties:
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 - const: vendor,soc1-ip
56 # additionalItems being false is implied
57 # minItems/maxItems equal to 2 is implied
58 - items:
59 # 'const' is just a special case of an enum with a single possible value
60 - const: vendor,soc1-ip
61
62 reg:
63 # The core schema already checks that reg values are numbers, so device
64 # specific schema don't need to do those checks.
65 # The description of each element defines the order and implicitly defines
66 # the number of reg entries.
67 items:
68 - description: core registers
69 - description: aux registers
70 # minItems/maxItems equal to 2 is implied
71
72 reg-names:
73 # The core schema enforces this (*-names) is a string array
74 items:
75 - const: core
76 - const: aux
77
78 clocks:
79 # Cases that have only a single entry just need to express that with maxItems
80 maxItems: 1
81 description: bus clock. A description is only needed for a single item if
82 there's something unique to add.
83 The items should have a fixed order, so pattern matching names are
84 discouraged.
85
86 clock-names:
87 # For single-entry lists in clocks, resets etc., the xxx-names often do not
88 # bring any value, especially if they copy the IP block name. In such case
89 # just skip the xxx-names.
90 items:
91 - const: bus
92
93 interrupts:
94 # Either 1 or 2 interrupts can be present
95 minItems: 1
96 items:
97 - description: tx or combined interrupt
98 - description: rx interrupt
99 description:
100 A variable number of interrupts warrants a description of what conditions
101 affect the number of interrupts. Otherwise, descriptions on standard
102 properties are not necessary.
103 The items should have a fixed order, so pattern matching names are
104 discouraged.
105
106 interrupt-names:
107 # minItems must be specified here because the default would be 2
108 minItems: 1
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 vendor,int-array-variable-length-and-constrained-values:
168 description: Array might define what type of elements might be used (e.g.
169 their range).
170 $ref: /schemas/types.yaml#/definitions/uint32-array
171 minItems: 2
172 maxItems: 3
173 items:
174 minimum: 0
175 maximum: 8
176
177 child-node:
178 description: Child nodes are just another property from a json-schema
179 perspective.
180 type: object # DT nodes are json objects
181 # Child nodes also need additionalProperties or unevaluatedProperties
182 additionalProperties: false
183 properties:
184 vendor,a-child-node-property:
185 description: Child node properties have all the same schema
186 requirements.
187 type: boolean
188
189 required:
190 - vendor,a-child-node-property
191
192 # Describe the relationship between different properties
193 dependencies:
194 # 'vendor,bool-property' is only allowed when 'vendor,string-array-property'
195 # is present
196 vendor,bool-property: [ 'vendor,string-array-property' ]
197 # Expressing 2 properties in both orders means all of the set of properties
198 # must be present or none of them.
199 vendor,string-array-property: [ 'vendor,bool-property' ]
200
201 required:
202 - compatible
203 - reg
204 - interrupts
205 - interrupt-controller
206
207 # if/then schema can be used to handle conditions on a property affecting
208 # another property. A typical case is a specific 'compatible' value changes the
209 # constraints on other properties.
210 #
211 # For multiple 'if' schema, group them under an 'allOf'.
212 #
213 # If the conditionals become too unweldy, then it may be better to just split
214 # the binding into separate schema documents.
215 allOf:
216 - if:
217 properties:
218 compatible:
219 contains:
220 const: vendor,soc2-ip
221 then:
222 required:
223 - foo-supply
224 else:
225 # If otherwise the property is not allowed:
226 properties:
227 foo-supply: false
228 # Altering schema depending on presence of properties is usually done by
229 # dependencies (see above), however some adjustments might require if:
230 - if:
231 required:
232 - vendor,bool-property
233 then:
234 properties:
235 vendor,int-property:
236 enum: [2, 4, 6]
237
238 # Ideally, the schema should have this line otherwise any other properties
239 # present are allowed. There's a few common properties such as 'status' and
240 # 'pinctrl-*' which are added automatically by the tooling.
241 #
242 # This can't be used in cases where another schema is referenced
243 # (i.e. allOf: [{$ref: ...}]).
244 # If and only if another schema is referenced and arbitrary children nodes can
245 # appear, "unevaluatedProperties: false" could be used. A typical example is
246 # an I2C controller where no name pattern matching for children can be added.
247 additionalProperties: false
248
249 examples:
250 # Examples are now compiled with dtc and validated against the schemas
251 #
252 # Examples have a default #address-cells and #size-cells value of 1. This can
253 # be overridden or an appropriate parent bus node should be shown (such as on
254 # i2c buses).
255 #
256 # Any includes used have to be explicitly included. Use 4-space indentation.
257 - |
258 node@1000 {
259 compatible = "vendor,soc4-ip", "vendor,soc1-ip";
260 reg = <0x1000 0x80>,
261 <0x3000 0x80>;
262 reg-names = "core", "aux";
263 interrupts = <10>;
264 interrupt-controller;
265 };
Linux® is a registered trademark of Linus Torvalds in the United States and other countries.
TOMOYO® is a registered trademark of NTT DATA CORPORATION.