237 lines
8.1 KiB
YAML
237 lines
8.1 KiB
YAML
title: Short description of the node
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description: >
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Longer free-form description of the node.
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Can go over multiple lines.
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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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# Many bindings have common fields. These are stored in files given in
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# 'include', which are merged into the binding (with a recursive dictionary
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# merge).
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#
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# If a key appears both in the binding and in a file it includes, then the
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# value in the binding takes precedence. This can be used to change a
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# 'required: false' from an inherited file to a 'required: true' (see the
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# 'properties' description below).
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#
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# An error is raised if this binding has 'required: false' for some property
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# for which the included file(s) have 'required: true'. Bindings can only
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# "strengthen" requirements from files they include. This is meant to keep the
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# organization clean.
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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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child:
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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 'child: bus: <bus type>'. If it does, then only bindings
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# with a matching 'parent: bus: <bus type>' are considered. This allows the
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# same type of device to have different bindings depending on what bus it
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# appears on.
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parent:
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bus: <string describing bus type, e.g. "i2c">
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# 'sub-node' is used to simplify cases where a node has children that can all
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# use the same binding. The contents of 'sub-node' becomes the binding for each
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# child node.
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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.
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sub-node:
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properties:
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pwms:
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type: compound
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required: true
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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 | 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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# 'type: boolean' is for properties used as flags that don't take a value, e.g.
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# 'hw-flow-control;'. The macro generated for the property gets set to 1 if the
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# property exists on the node, and to 0 otherwise. When combined with
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# 'required: true', this type just forces the flag to appear on the node,
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# though the output will always be the same in that case (1).
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#
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# 'type: uint8-array' is for what the device tree specification calls
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# 'bytestring'. Properties of type 'uint8-array' should be set like this:
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#
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# foo = [89 AB CD];
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#
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# Each value is a byte in hex.
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#
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# 'type: phandle' is for properties that are assigned a single phandle, like
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# this:
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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 a list of (just)
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# phandles, like this:
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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 are assigned a list of phandles
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# and (possibly) 32-bit numbers, like this:
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#
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# foo = <&label1 1 2 &label2 3 4 ...>;
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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 = <&label1>, [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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# If the binding describes an interrupt controller, GPIO controller, pinmux
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# device, or any other node referenced by other nodes, then #cells should be
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# 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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# foo-gpios = <&gpio-ctrl 1 2>;
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#
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# , where &gpio-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 '#gpio-cells = <2>'.
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#
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# #cells gives a name to each cell in the specifier. These names are used
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# when 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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"#cells":
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- pin # name of first cell
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- flag # name of second cell
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# If the specifier is empty (e.g. '#clock-cells = <0>'), then #cells can either
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# be omitted (recommended) or set to an empty array. Note that an empty array
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# is specified as '"#cells": []' in YAML.
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