362 lines
12 KiB
YAML
362 lines
12 KiB
YAML
description: |
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Free-form description of the device/node. Can have multiple
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lines/paragraphs.
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See https://yaml-multiline.info/ for formatting help.
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# Used to map nodes to bindings
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compatible: "manufacturer,device"
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# The 'compatible' above would match this node:
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#
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# device {
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# compatible = "manufacturer,device";
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# ...
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# };
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#
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# Assuming no binding has 'compatible: "manufacturer,device-v2"', it would also
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# match this node:
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#
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# device {
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# compatible = "manufacturer,device-v2", "manufacturer,device";
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# ...
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# };
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#
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# Strings in 'compatible' properties on nodes are tried from left to right, and
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# the first binding found is used.
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#
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# If more than one binding for a compatible is found, an error is raised.
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# Bindings can include other files, which can be used to share common
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# definitions between bindings.
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#
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# Included files are merged into bindings with a simple recursive dictionary
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# merge. It is up to the binding author to make sure that the final merged
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# binding is well-formed, though it is checked by the code as well.
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#
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# It is an error if a key appears with a different value in a binding and in a
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# file it includes, with one exception: A binding can have 'required: true' for
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# some property for which the included file has 'required: false' (see the
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# description of 'properties' below). The 'required: true' from the binding
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# takes precedence, allowing bindings to strengthen requirements from included
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# files.
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#
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# Note that weakening requirements by having 'required: false' where the
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# included file has 'required: true' is an error. This is meant to keep the
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# organization clean.
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#
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# The file base.yaml contains definitions for many common properties. When
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# writing a new binding, it is a good idea to check if base.yaml already
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# defines some of the needed properties, and including it in that case. Note
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# that you can make a property defined in base.yaml obligatory like this
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# (taking 'reg' as an example):
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#
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# reg:
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# required: true
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#
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# This relies on the dictionary merge to fill in the other keys for 'reg', like
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# 'type'.
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#
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# When including multiple files, any overlapping 'required' keys on properties
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# in the included files are ORed together. This makes sure that a
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# 'required: true' is always respected.
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include: other.yaml # or [other1.yaml, other2.yaml]
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# If the node describes a bus, then the bus type should be given, like below
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bus: <string describing bus type, e.g. "i2c">
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# If the node appears on a bus, then the bus type should be given, like below.
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#
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# When looking for a binding for a node, the code checks if the binding for the
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# parent node contains 'bus: <bus type>'. If it does, then only bindings with a
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# matching 'on-bus: <bus type>' are considered. This allows the same type of
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# device to have different bindings depending on what bus it appears on.
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on-bus: <string describing bus type, e.g. "i2c">
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# 'properties' describes properties on the node, e.g.
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#
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# reg = <1 2>;
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# current-speed = <115200>;
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# label = "foo";
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#
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# This is used to check that required properties appear, and to
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# control the format of output generated for them. Except for some
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# special-cased properties like 'reg', only properties listed here will
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# generate output.
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#
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# A typical property entry looks like this:
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#
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# <property name>:
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# required: <true | false>
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# type: <string | int | boolean | array | uint8-array | string-array |
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# phandle | phandles | phandle-array | path | compound>
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# description: <description of the property>
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# enum:
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# - <item1>
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# - <item2>
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# ...
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# - <itemN>
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# const: <string | int>
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# default: <default>
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#
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# These types are available:
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#
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# - 'type: string' is for properties that are assigned a single string, like
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#
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# ident = "foo";
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#
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# - 'type: int' is for properties that are assigned a single 32-bit value,
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# like
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#
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# frequency = <100>;
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#
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# - 'type: boolean' is for properties used as flags that don't take a value,
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# like
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#
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# hw-flow-control;
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#
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# The macro generated for the property gets set to 1 if the property exists
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# on the node, and to 0 otherwise. When combined with 'required: true',
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# this type just forces the flag to appear on the node. The output will
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# always be 1 in that case.
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#
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# Warning: Since a macro is always generated for 'type: boolean'
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# properties, don't use #ifdef in tests. Do this instead:
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#
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# #if DT_SOME_BOOLEAN_PROP == 1
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#
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# - 'type: array' is for properties that are assigned zero or more 32-bit
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# values, like
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#
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# pin-config = <1 2 3>;
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#
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# - 'type: uint8-array' is for properties that are assigned zero or more
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# bytes with the [] syntax, like
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#
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# lookup-table = [89 AB CD EF];
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#
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# Each byte is given in hex.
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#
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# This type is called 'bytestring' in the Devicetree specification.
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#
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# - 'type: string-array' if for properties that are assigned zero or more
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# strings, like
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#
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# idents = "foo", "bar", "baz";
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#
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# - 'type: phandle' is for properties that are assigned a single phandle,
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# like
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#
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# foo = <&label>;
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#
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# - 'type: phandles' is for properties that are assigned zero or more
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# phandles, like
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#
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# foo = <&label1 &label2 ...>;
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#
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# - 'type: phandle-array' is for properties that take a list of phandles and
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# (possibly) 32-bit numbers, like
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#
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# pwms = <&ctrl-1 1 2 &ctrl-2 3 4>;
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#
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# This type requires that the property works in the standard way that
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# devicetree properties like pwms, clocks, *-gpios, and io-channels work.
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# Taking 'pwms' as an example, the final -s is stripped from the property
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# name, and #pwm-cells is looked up in the node for the controller
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# (&ctrl-1/&ctrl-2) to determine the number of data values after the
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# phandle. The binding for each controller must also have a *-cells key
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# (e.g. pwm-cells), giving names to data values. See below for an
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# explanation of *-cells.
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#
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# A *-names (e.g. pwm-names) property can appear on the node as well,
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# giving a name to each entry (the 'pwms' example above has two entries,
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# <&ctrl-1 1 2> and <&ctrl-2 3 4>).
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#
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# Because other property names are derived from the name of the property by
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# removing the final -s, the property name must end in -s. An error is
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# raised if it doesn't.
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#
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# *-gpios properties are special-cased so that e.g. foo-gpios resolves to
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# #gpio-cells rather than #foo-gpio-cells.
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#
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# All phandle-array properties support mapping through *-map properties,
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# e.g. gpio-map. See the devicetree spec.
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#
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# - 'type: path' is for properties that are assigned a path. Usually, this
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# would be done with a path reference:
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#
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# foo = &label;
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#
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# Plain strings are accepted too, and are verified to be a path to an
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# existing node:
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#
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# foo = "/path/to/some/node";
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#
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# - 'type: compound' is a catch-all for more complex types, e.g.
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#
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# foo = <&label>, [01 02];
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#
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# 'type: array' and the other array types also allow splitting the value into
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# several <> blocks, e.g. like this:
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#
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# foo = <1 2>, <3 4>; // Okay for 'type: array'
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# foo = <&label1 &label2>, <&label3 &label4>; // Okay for 'type: phandles'
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# foo = <&label1 1 2>, <&label2 3 4>; // Okay for 'type: phandle-array'
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# etc.
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#
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# The optional 'default:' setting gives a value that will be used if the
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# property is missing from the device tree node. If 'default: <default>' is
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# given for a property <prop> and <prop> is missing, then the output will be as
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# if '<prop> = <default>' had appeared (except YAML data types are used for the
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# default value).
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#
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# Note that it only makes sense to combine 'default:' with 'required: false'.
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# Combining it with 'required: true' will raise an error.
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#
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# See below for examples of 'default:'. Putting 'default:' on any property type
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# besides those used in the examples will raise an error.
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properties:
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# Describes a property like 'current-speed = <115200>;'. We pretend that
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# it's obligatory for the example node and set 'required: true'.
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current-speed:
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type: int
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required: true
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description: Initial baud rate for bar-device
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# Describes an optional property like 'keys = "foo", "bar";'
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keys:
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type: string-array
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required: false
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description: Keys for bar-device
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# Describes an optional property like 'maximum-speed = "full-speed";
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# the enum specifies known values that the string property may take
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maximum-speed:
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type: string
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required: false
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description: Configures USB controllers to work up to a specific speed.
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enum:
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- "low-speed"
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- "full-speed"
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- "high-speed"
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- "super-speed"
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# Describes a required property '#address-cells = <1>'; the const
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# specifies that the value for the property is expected to be the value 1
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"#address-cells":
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type: int
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required: true
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const: 1
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int-with-default:
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type: int
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required: false
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default: 123
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array-with-default:
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type: array
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required: false
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default: [1, 2, 3] # Same as 'array-with-default = <1 2 3>'
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string-with-default:
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type: string
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required: false
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default: "foo"
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string-array-with-default:
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type: string-array
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required: false
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default: ["foo", "bar"] # Same as 'string-array-with-default = "foo", "bar"'
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uint8-array-with-default:
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type: uint8-array
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required: false
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default: [0x12, 0x34] # Same as 'uint8-array-with-default = [12 34]'
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# 'child-binding' can be used when a node has children that all share the same
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# properties. Each child gets the contents of 'child-binding' as its binding
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# (though an explicit 'compatible = ...' on the child node takes precedence, if
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# a binding is found for it).
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#
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# The example below is for a binding for PWM LEDs, where the child nodes are
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# required to have a 'pwms' property. It corresponds to this .dts structure
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# (assuming the binding has 'compatible: "pwm-leds"'):
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#
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# pwmleds {
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# compatible = "pwm-leds";
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#
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# red_pwm_led {
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# pwms = <&pwm3 4 15625000>;
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# };
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# green_pwm_led {
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# pwms = <&pwm3 0 15625000>;
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# };
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# ...
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# };
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child-binding:
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description: LED that uses PWM
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properties:
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pwms:
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type: phandle-array
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required: true
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# 'child-binding' also works recursively. For example, the binding below would
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# provide a binding for the 'grandchild' node in this .dts (assuming
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# 'compatible: "foo"'):
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#
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# parent {
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# compatible = "foo";
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# child {
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# grandchild {
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# prop = <123>;
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# };
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# };
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# }
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child-binding:
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description: ...
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...
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child-binding:
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description: ...
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properties:
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prop:
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type: int
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required: true
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# If the binding describes an interrupt controller, GPIO controller, pinmux
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# device, or any other node referenced by other nodes via 'phandle-array'
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# properties, then *-cells should be given.
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#
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# To understand the purpose of *-cells, assume that some node has
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#
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# pwms = <&pwm-ctrl 1 2>;
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#
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# , where &pwm-ctrl refers to a node whose binding is this file.
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#
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# The <1 2> part of the property value is called a *specifier* (this
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# terminology is from the devicetree specification), and contains additional
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# data associated with the GPIO. Here, the specifier has two cells, and the
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# node pointed at by &gpio-ctrl is expected to have '#pwm-cells = <2>'.
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#
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# *-cells gives a name to each cell in the specifier. These names are used when
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# generating identifiers.
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#
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# In this example, assume that 1 refers to a pin and that 2 is a flag value.
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# This gives a *-cells assignment like below.
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pwm-cells:
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- channel # name of first cell
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- period # name of second cell
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# If the specifier is empty (e.g. '#clock-cells = <0>'), then *-cells can
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# either be omitted (recommended) or set to an empty array. Note that an empty
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# array is specified as e.g. 'clock-cells: []' in YAML.
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# As a special case, all *-gpio properties map to the key 'gpio-cells',
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# regardless of prefix
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gpio-cells:
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- pin
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- flags
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