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 8, 16, 32, or 64-bit integer elements, as NUL-terminated strings, as bytestrings or a combination of these. * Arrays are represented by angle brackets surrounding a space separated list of C-style integers or character literals. Array elements default to 32-bits in size. An array of 32-bit elements is also known as a cell list or a list of cells. A cell being an unsigned 32-bit integer. e.g. interrupts = <17 0xc>; * A 64-bit value can be represented with two 32-bit elements. e.g. clock-frequency = <0x00000001 0x00000000>; * The storage size of an element can be changed using the /bits/ prefix. The /bits/ prefix allows for the creation of 8, 16, 32, and 64-bit elements. The resulting array will not be padded to a multiple of the default 32-bit element size. e.g. interrupts = /bits/ 8 <17 0xc>; e.g. clock-frequency = /bits/ 64 <0x0000000100000000>; * 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 an 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} >; References are only permitted in arrays that have an element size of 32-bits. * Outside an 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 elements of an 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/
; Where
and 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 -- Yoder Stuart -- Anton Staaf