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diff --git a/Documentation/devicetree/writing-schema.md b/Documentation/devicetree/writing-schema.md deleted file mode 100644 index dc032db36262..000000000000 --- a/Documentation/devicetree/writing-schema.md +++ /dev/null @@ -1,130 +0,0 @@ -# Writing DeviceTree Bindings in json-schema - -Devicetree bindings are written using json-schema vocabulary. Schema files are -written in a JSON compatible subset of YAML. YAML is used instead of JSON as it -considered more human readable and has some advantages such as allowing -comments (Prefixed with '#'). - -## Schema Contents - -Each schema doc is a structured json-schema which is defined by a set of -top-level properties. Generally, there is one binding defined per file. The -top-level json-schema properties used are: - -- __$id__ - A json-schema unique identifier string. The string must be a valid -URI typically containing the binding's filename and path. For DT schema, it must -begin with "http://devicetree.org/schemas/". The URL is used in constructing -references to other files specified in schema "$ref" properties. A $ref values -with a leading '/' will have the hostname prepended. A $ref value a relative -path or filename only will be prepended with the hostname and path components -of the current schema file's '$id' value. A URL is used even for local files, -but there may not actually be files present at those locations. - -- __$schema__ - Indicates the meta-schema the schema file adheres to. - -- __title__ - A one line description on the contents of the binding schema. - -- __maintainers__ - A DT specific property. Contains a list of email address(es) -for maintainers of this binding. - -- __description__ - Optional. A multi-line text block containing any detailed -information about this binding. It should contain things such as what the block -or device does, standards the device conforms to, and links to datasheets for -more information. - -- __select__ - Optional. A json-schema used to match nodes for applying the -schema. By default without 'select', nodes are matched against their possible -compatible string values or node name. Most bindings should not need select. - -- __allOf__ - Optional. A list of other schemas to include. This is used to -include other schemas the binding conforms to. This may be schemas for a -particular class of devices such as I2C or SPI controllers. - -- __properties__ - A set of sub-schema defining all the DT properties for the -binding. The exact schema syntax depends on whether properties are known, -common properties (e.g. 'interrupts') or are binding/vendor specific properties. - - A property can also define a child DT node with child properties defined -under it. - - For more details on properties sections, see 'Property Schema' section. - -- __patternProperties__ - Optional. Similar to 'properties', but names are regex. - -- __required__ - A list of DT properties from the 'properties' section that -must always be present. - -- __examples__ - Optional. A list of one or more DTS hunks implementing the -binding. Note: YAML doesn't allow leading tabs, so spaces must be used instead. - -Unless noted otherwise, all properties are required. - -## Property Schema - -The 'properties' section of the schema contains all the DT properties for a -binding. Each property contains a set of constraints using json-schema -vocabulary for that property. The properties schemas are what is used for -validation of DT files. - -For common properties, only additional constraints not covered by the common -binding schema need to be defined such as how many values are valid or what -possible values are valid. - -Vendor specific properties will typically need more detailed schema. With the -exception of boolean properties, they should have a reference to a type in -schemas/types.yaml. A "description" property is always required. - -The Devicetree schemas don't exactly match the YAML encoded DT data produced by -dtc. They are simplified to make them more compact and avoid a bunch of -boilerplate. The tools process the schema files to produce the final schema for -validation. There are currently 2 transformations the tools perform. - -The default for arrays in json-schema is they are variable sized and allow more -entries than explicitly defined. This can be restricted by defining 'minItems', -'maxItems', and 'additionalItems'. However, for DeviceTree Schemas, a fixed -size is desired in most cases, so these properties are added based on the -number of entries in an 'items' list. - -The YAML Devicetree format also makes all string values an array and scalar -values a matrix (in order to define groupings) even when only a single value -is present. Single entries in schemas are fixed up to match this encoding. - -## Testing - -### Dependencies - -The DT schema project must be installed in order to validate the DT schema -binding documents and validate DTS files using the DT schema. The DT schema -project can be installed with pip: - -`pip3 install git+https://github.com/devicetree-org/dt-schema.git@master` - -dtc must also be built with YAML output support enabled. This requires that -libyaml and its headers be installed on the host system. - -### Running checks - -The DT schema binding documents must be validated using the meta-schema (the -schema for the schema) to ensure they are both valid json-schema and valid -binding schema. All of the DT binding documents can be validated using the -`dt_binding_check` target: - -`make dt_binding_check` - -In order to perform validation of DT source files, use the `dtbs_check` target: - -`make dtbs_check` - -This will first run the `dt_binding_check` which generates the processed schema. - -It is also possible to run checks with a single schema file by setting the -'DT_SCHEMA_FILES' variable to a specific schema file. - -`make dtbs_check DT_SCHEMA_FILES=Documentation/devicetree/bindings/trivial-devices.yaml` - - -## json-schema Resources - -[JSON-Schema Specifications](http://json-schema.org/) - -[Using JSON Schema Book](http://usingjsonschema.com/) |