1 Device Tree Source Format (version 1)
2 =====================================
4 The Device Tree Source (DTS) format is a textual representation of a
5 device tree in a form that can be processed by dtc into a binary
6 device tree in the form expected by the kernel. The description below
7 is not a formal syntax definition of DTS, but describes the basic
8 constructs used to represent device trees.
10 Node and property definitions
11 -----------------------------
13 Device tree nodes are defined with a node name and unit address with
14 braces marking the start and end of the node definition. They may be
17 [label:] node-name[@unit-address] {
18 [properties definitions]
22 Nodes may contain property definitions and/or child node
23 definitions. If both are present, properties must come before child
26 Property definitions are name value pairs in the form:
27 [label:] property-name = value;
28 except for properties with empty (zero length) value which have the
30 [label:] property-name;
32 Property values may be defined as an array of 8, 16, 32, or 64-bit integer
33 elements, as NUL-terminated strings, as bytestrings or a combination of these.
35 * Arrays are represented by angle brackets surrounding a space separated list
36 of C-style integers or character literals. Array elements default to 32-bits
37 in size. An array of 32-bit elements is also known as a cell list or a list
38 of cells. A cell being an unsigned 32-bit integer.
40 e.g. interrupts = <17 0xc>;
42 * A 64-bit value can be represented with two 32-bit elements.
44 e.g. clock-frequency = <0x00000001 0x00000000>;
46 * The storage size of an element can be changed using the /bits/ prefix. The
47 /bits/ prefix allows for the creation of 8, 16, 32, and 64-bit elements.
48 The resulting array will not be padded to a multiple of the default 32-bit
51 e.g. interrupts = /bits/ 8 <17 0xc>;
52 e.g. clock-frequency = /bits/ 64 <0x0000000100000000>;
54 * A NUL-terminated string value is represented using double quotes
55 (the property value is considered to include the terminating NUL
58 e.g. compatible = "simple-bus";
60 * A bytestring is enclosed in square brackets [] with each byte
61 represented by two hexadecimal digits. Spaces between each byte are
64 e.g. local-mac-address = [00 00 12 34 56 78]; or equivalently
65 local-mac-address = [000012345678];
67 * Values may have several comma-separated components, which are
68 concatenated together.
69 e.g. compatible = "ns16550", "ns8250";
70 example = <0xf00f0000 19>, "a strange property format";
72 * In an array a reference to another node will be expanded to that node's
73 phandle. References may by '&' followed by a node's label:
74 e.g. interrupt-parent = < &mpic >;
75 or they may be '&' followed by a node's full path in braces:
76 e.g. interrupt-parent = < &{/soc/interrupt-controller@40000} >;
77 References are only permitted in arrays that have an element size of
80 * Outside an array, a reference to another node will be expanded to that
82 e.g. ethernet0 = &EMAC0;
84 * Labels may also appear before or after any component of a property
85 value, or between elements of an array, or between bytes of a bytestring.
86 e.g. reg = reglabel: <0 sizelabel: 0x1000000>;
87 e.g. prop = [ab cd ef byte4: 00 ff fe];
88 e.g. str = start: "string value" end: ;
94 Version 1 DTS files have the overall layout:
100 [property definitions]
104 * The "/dts-v1/;" must be present to identify the file as a version 1
105 DTS (dts files without this tag will be treated by dtc as being in
106 the obsolete "version 0", which uses a different format for integers
107 amongst other small but incompatible changes).
109 * Memory reservations define an entry for the device tree blob's
110 memory reservation table. They have the form:
111 e.g. /memreserve/ <address> <length>;
112 Where <address> and <length> are 64-bit C-style integers.
114 * The / { ... }; section defines the root node of the device tree.
116 * C style (/* ... */) and C++ style (// ...) comments are supported.
120 -- David Gibson <david@gibson.dropbear.id.au>
121 -- Yoder Stuart <stuart.yoder@freescale.com>
122 -- Anton Staaf <robotboy@chromium.org>