From 9e80202352dd49bdd9e67b8b906d86f058431505 Mon Sep 17 00:00:00 2001 From: Timothy Pearson Date: Sat, 11 May 2019 15:12:49 -0500 Subject: Initial import of abandoned HQEMU version 2.5.2 --- src/dtc/Documentation/dts-format.txt | 122 +++++++++++++++++++++++++++++++++++ 1 file changed, 122 insertions(+) create mode 100644 src/dtc/Documentation/dts-format.txt (limited to 'src/dtc/Documentation/dts-format.txt') diff --git a/src/dtc/Documentation/dts-format.txt b/src/dtc/Documentation/dts-format.txt new file mode 100644 index 0000000..41741df --- /dev/null +++ b/src/dtc/Documentation/dts-format.txt @@ -0,0 +1,122 @@ +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 -- cgit v1.1