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Diffstat (limited to 'dts/Bindings/writing-schema.rst')
| -rw-r--r-- | dts/Bindings/writing-schema.rst | 66 |
1 files changed, 36 insertions, 30 deletions
diff --git a/dts/Bindings/writing-schema.rst b/dts/Bindings/writing-schema.rst index 23d6579aea..0a6cf19a14 100644 --- a/dts/Bindings/writing-schema.rst +++ b/dts/Bindings/writing-schema.rst @@ -4,7 +4,7 @@ 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 +written in a JSON-compatible subset of YAML. YAML is used instead of JSON as it is considered more human readable and has some advantages such as allowing comments (Prefixed with '#'). @@ -22,16 +22,16 @@ $id URI typically containing the binding's filename and path. For DT schema, it must begin with "http://devicetree.org/schemas/". The URL is used in constructing references to other files specified in schema "$ref" properties. A $ref value - 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. + with a leading '/' will have the hostname prepended. A $ref value with only a + relative path or filename will be prepended with the hostname and path + components of the current schema file's '$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. + A one-line description on the contents of the binding schema. maintainers A DT specific property. Contains a list of email address(es) @@ -45,8 +45,8 @@ description 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. + 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 @@ -56,7 +56,8 @@ allOf 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. + 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. @@ -81,23 +82,23 @@ 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 +vocabulary for that property. The properties schemas are what are used for validation of DT files. -For common properties, only additional constraints not covered by the common +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 +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 +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 +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 @@ -107,6 +108,12 @@ 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. +Coding style +------------ + +Use YAML coding style (two-space indentation). For DTS examples in the schema, +preferred is four-space indentation. + Testing ------- @@ -117,22 +124,17 @@ 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 - -Several executables (dt-doc-validate, dt-mk-schema, dt-validate) will be -installed. Ensure they are in your PATH (~/.local/bin by default). - -dtc must also be built with YAML output support enabled. This requires that -libyaml and its headers be installed on the host system. For some distributions -that involves installing the development package, such as: + pip3 install dtschema -Debian:: +Note that 'dtschema' installation requires 'swig' and Python development files +installed first. On Debian/Ubuntu systems:: - apt-get install libyaml-dev + apt install swig python3-dev -Fedora:: +Several executables (dt-doc-validate, dt-mk-schema, dt-validate) will be +installed. Ensure they are in your PATH (~/.local/bin by default). - dnf -y install libyaml-devel +Recommended is also to install yamllint (used by dtschema when present). Running checks ~~~~~~~~~~~~~~ @@ -156,13 +158,17 @@ It is possible to run both in a single command:: make dt_binding_check dtbs_check -It is also possible to run checks with a single schema file by setting the -``DT_SCHEMA_FILES`` variable to a specific schema file. +It is also possible to run checks with a subset of matching schema files by +setting the ``DT_SCHEMA_FILES`` variable to 1 or more specific schema files or +patterns (partial match of a fixed string). Each file or pattern should be +separated by ':'. :: - make dt_binding_check DT_SCHEMA_FILES=Documentation/devicetree/bindings/trivial-devices.yaml - make dtbs_check DT_SCHEMA_FILES=Documentation/devicetree/bindings/trivial-devices.yaml + make dt_binding_check DT_SCHEMA_FILES=trivial-devices.yaml + make dt_binding_check DT_SCHEMA_FILES=trivial-devices.yaml:rtc.yaml + make dt_binding_check DT_SCHEMA_FILES=/gpio/ + make dtbs_check DT_SCHEMA_FILES=trivial-devices.yaml json-schema Resources |