Device Tree Source Format (version 1)

=====================================

The Device Tree Source (DTS) format is a textual representation of a

device tree in a form that can be processed by dtc into a binary

device tree in the form expected by the kernel.  The description below

is not a formal syntax definition of DTS, but describes the basic

constructs used to represent device trees.

Node and property definitions

-----------------------------

Device tree nodes are defined with a node name and unit address with

braces marking the start and end of the node definition.  They may be

preceded by a label.

	[label:] node-name[@unit-address] {

		[properties definitions]

		[child nodes]

	}

Nodes may contain property definitions and/or child node

definitions. If both are present, properties must come before child

nodes.

Property definitions are name value pairs in the form:

	[label:] property-name = value;

except for properties with empty (zero length) value which have the

form:

	[label:] property-name;

Property values may be defined as an array of 32-bit integer cells, as

NUL-terminated strings, as bytestrings or a combination of these.

* Arrays of cells are represented by angle brackets surrounding a

  space separated list of C-style integers

	e.g. interrupts = <17 0xc>;

* A 64-bit value is represented with two 32-bit cells.

	e.g. clock-frequency = <0x00000001 0x00000000>;

* A NUL-terminated string value is represented using double quotes

  (the property value is considered to include the terminating NUL

  character).

	e.g. compatible = "simple-bus";

* A bytestring is enclosed in square brackets [] with each byte

  represented by two hexadecimal digits.  Spaces between each byte are

  optional.

	e.g. local-mac-address = [00 00 12 34 56 78]; or equivalently

	     local-mac-address = [000012345678];

* Values may have several comma-separated components, which are

  concatenated together.

	e.g. compatible = "ns16550", "ns8250";

	     example = <0xf00f0000 19>, "a strange property format";

* In a cell array a reference to another node will be expanded to that

  node's phandle.  References may by '&' followed by a node's label:

	e.g. interrupt-parent = < &mpic >;

  or they may be '&' followed by a node's full path in braces:

	e.g. interrupt-parent = < &{/soc/interrupt-controller@40000} >;

* Outside a cell array, a reference to another node will be expanded

  to that node's full path.

	e.g. ethernet0 = &EMAC0;

* Labels may also appear before or after any component of a property

  value, or between cells of a cell array, or between bytes of a

  bytestring.

	e.g. reg = reglabel: <0 sizelabel: 0x1000000>;

	e.g. prop = [ab cd ef byte4: 00 ff fe];

	e.g. str = start: "string value" end: ;

File layout

-----------

Version 1 DTS files have the overall layout:

	/dts-v1/;

	[memory reservations]

	/ {

		[property definitions]

		[child nodes]

	};

* The "/dts-v1/;" must be present to identify the file as a version 1

  DTS (dts files without this tag will be treated by dtc as being in

  the obsolete "version 0", which uses a different format for integers

  amongst other small but incompatible changes).

* Memory reservations define an entry for the device tree blob's

  memory reservation table.  They have the form:

	e.g. /memreserve/ <address> <length>;

  Where <address> and <length> are 64-bit C-style integers.

* The / { ... }; section defines the root node of the device tree.

* C style (/* ... */) and C++ style (// ...) comments are supported.

	-- David Gibson <david@gibson.dropbear.id.au>

	-- Yoder Stuart <stuart.yoder@freescale.com>