# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause) # Copyright 2018 Linaro Ltd. %YAML 1.2 --- # All the top-level keys are standard json-schema keywords except for # 'maintainers' and 'select' # $id is a unique identifier based on the filename. There may or may not be a # file present at the URL. $id: http://devicetree.org/schemas/example-schema.yaml# # $schema is the meta-schema this schema should be validated with. $schema: http://devicetree.org/meta-schemas/core.yaml# title: An Example Device maintainers: - Rob Herring description: | A more detailed multi-line description of the binding. Details about the hardware device and any links to datasheets can go here. Literal blocks are marked with the '|' at the beginning. The end is marked by indentation less than the first line of the literal block. Lines also cannot begin with a tab character. select: false # 'select' is a schema applied to a DT node to determine if this binding # schema should be applied to the node. It is optional and by default the # possible compatible strings are extracted and used to match. # In this case, a 'false' schema will never match. properties: # A dictionary of DT properties for this binding schema compatible: # More complicated schema can use oneOf (XOR), anyOf (OR), or allOf (AND) # to handle different conditions. # In this case, it's needed to handle a variable number of values as there # isn't another way to express a constraint of the last string value. # The boolean schema must be a list of schemas. oneOf: - items: # items is a list of possible values for the property. The number of # values is determined by the number of elements in the list. # Order in lists is significant, order in dicts is not # Must be one of the 1st enums followed by the 2nd enum # # Each element in items should be 'enum' or 'const' - enum: - vendor,soc4-ip - vendor,soc3-ip - vendor,soc2-ip - const: vendor,soc1-ip # additionalItems being false is implied # minItems/maxItems equal to 2 is implied - items: # 'const' is just a special case of an enum with a single possible value - const: vendor,soc1-ip reg: # The core schema already checks that reg values are numbers, so device # specific schema don't need to do those checks. # The description of each element defines the order and implicitly defines # the number of reg entries. items: - description: core registers - description: aux registers # minItems/maxItems equal to 2 is implied reg-names: # The core schema enforces this (*-names) is a string array items: - const: core - const: aux clocks: # Cases that have only a single entry just need to express that with maxItems maxItems: 1 description: bus clock. A description is only needed for a single item if there's something unique to add. The items should have a fixed order, so pattern matching names are discouraged. clock-names: # For single-entry lists in clocks, resets etc., the xxx-names often do not # bring any value, especially if they copy the IP block name. In such case # just skip the xxx-names. items: - const: bus interrupts: # Either 1 or 2 interrupts can be present minItems: 1 items: - description: tx or combined interrupt - description: rx interrupt description: A variable number of interrupts warrants a description of what conditions affect the number of interrupts. Otherwise, descriptions on standard properties are not necessary. The items should have a fixed order, so pattern matching names are discouraged. interrupt-names: # minItems must be specified here because the default would be 2 minItems: 1 items: - const: tx irq - const: rx irq # Property names starting with '#' must be quoted '#interrupt-cells': # A simple case where the value must always be '2'. # The core schema handles that this must be a single integer. const: 2 interrupt-controller: true # The core checks this is a boolean, so just have to list it here to be # valid for this binding. clock-frequency: # The type is set in the core schema. Per-device schema only need to set # constraints on the possible values. minimum: 100 maximum: 400000 # The value that should be used if the property is not present default: 200 foo-gpios: maxItems: 1 description: A connection of the 'foo' gpio line. # *-supply is always a single phandle, so nothing more to define. foo-supply: true # Vendor-specific properties # # Vendor-specific properties have slightly different schema requirements than # common properties. They must have at least a type definition and # 'description'. vendor,int-property: description: Vendor-specific properties must have a description $ref: /schemas/types.yaml#/definitions/uint32 enum: [2, 4, 6, 8, 10] vendor,bool-property: description: Vendor-specific properties must have a description. Boolean properties are one case where the json-schema 'type' keyword can be used directly. type: boolean vendor,string-array-property: description: Vendor-specific properties should reference a type in the core schema. $ref: /schemas/types.yaml#/definitions/string-array items: - enum: [foo, bar] - enum: [baz, boo] vendor,property-in-standard-units-microvolt: description: Vendor-specific properties having a standard unit suffix don't need a type. enum: [ 100, 200, 300 ] vendor,int-array-variable-length-and-constrained-values: description: Array might define what type of elements might be used (e.g. their range). $ref: /schemas/types.yaml#/definitions/uint32-array minItems: 2 maxItems: 3 items: minimum: 0 maximum: 8 child-node: description: Child nodes are just another property from a json-schema perspective. type: object # DT nodes are json objects # Child nodes also need additionalProperties or unevaluatedProperties additionalProperties: false properties: vendor,a-child-node-property: description: Child node properties have all the same schema requirements. type: boolean required: - vendor,a-child-node-property # Describe the relationship between different properties dependencies: # 'vendor,bool-property' is only allowed when 'vendor,string-array-property' # is present vendor,bool-property: [ 'vendor,string-array-property' ] # Expressing 2 properties in both orders means all of the set of properties # must be present or none of them. vendor,string-array-property: [ 'vendor,bool-property' ] required: - compatible - reg - interrupts - interrupt-controller # if/then schema can be used to handle conditions on a property affecting # another property. A typical case is a specific 'compatible' value changes the # constraints on other properties. # # For multiple 'if' schema, group them under an 'allOf'. # # If the conditionals become too unweldy, then it may be better to just split # the binding into separate schema documents. allOf: - if: properties: compatible: contains: const: vendor,soc2-ip then: required: - foo-supply else: # If otherwise the property is not allowed: properties: foo-supply: false # Altering schema depending on presence of properties is usually done by # dependencies (see above), however some adjustments might require if: - if: required: - vendor,bool-property then: properties: vendor,int-property: enum: [2, 4, 6] # Ideally, the schema should have this line otherwise any other properties # present are allowed. There's a few common properties such as 'status' and # 'pinctrl-*' which are added automatically by the tooling. # # This can't be used in cases where another schema is referenced # (i.e. allOf: [{$ref: ...}]). # If and only if another schema is referenced and arbitrary children nodes can # appear, "unevaluatedProperties: false" could be used. A typical example is # an I2C controller where no name pattern matching for children can be added. additionalProperties: false examples: # Examples are now compiled with dtc and validated against the schemas # # Examples have a default #address-cells and #size-cells value of 1. This can # be overridden or an appropriate parent bus node should be shown (such as on # i2c buses). # # Any includes used have to be explicitly included. Use 4-space indentation. - | node@1000 { compatible = "vendor,soc4-ip", "vendor,soc1-ip"; reg = <0x1000 0x80>, <0x3000 0x80>; reg-names = "core", "aux"; interrupts = <10>; interrupt-controller; #interrupt-cells = <2>; };