Documentation/devicetree/bindings/example-schema.yaml

   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 schema annotated with jsonschema details
  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           - 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
 177 dependencies:
 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
 185 required:
 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.
 199 if:
 200   properties:
 201     compatible:
 202       contains:
 203         const: vendor,soc2-ip
 204 then:
 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: ...}]).
 214 additionalProperties: false
 215
 216 examples:
 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     };