Flattened Devicetree Format: Java parsing library

Also referred to as Devicetree Blob (DTB). It is a flat binary encoding of data (primarily devicetree data, although other data is possible as well). The data is internally stored as a tree of named nodes and properties. Nodes contain properties and child nodes, while properties are name–value pairs.

The Devicetree Blobs (.dtb files) are compiled from the Devicetree Source files (.dts) through the Devicetree compiler (DTC).

On Linux systems that support this, the blobs can be accessed in /sys/firmware/fdt:

The encoding of strings used in the strings_block and structure_block is actually a subset of ASCII:

https://devicetree-specification.readthedocs.io/en/v0.3/devicetree-basics.html#node-names

Example files:

Application

["Linux", "Das U-Boot"]

File extension

dtb

KS implementation details

License: CC0-1.0
Minimal Kaitai Struct required: 0.9

References

This page hosts a formal specification of Flattened Devicetree Format using Kaitai Struct. This specification can be automatically translated into a variety of programming languages to get a parsing library.

Usage

Runtime library

All parsing code for Java generated by Kaitai Struct depends on the Java runtime library. You have to install it before you can parse data.

The Java runtime library is published in the Maven Central Repository. Refer to the artifact page for instructions how to add it into your project with the build tool that you use.

Code

Parse a local file and get structure in memory:

Dtb data = Dtb.fromFile("path/to/local/file.dtb");

Or parse structure from a byte array:

byte[] someArray = new byte[] { ... };
Dtb data = new Dtb(new ByteBufferKaitaiStream(someArray));

After that, one can get various attributes from the structure by invoking getter methods like:

data.magic() // => get magic

Java source code to parse Flattened Devicetree Format

Dtb.java

// This is a generated file! Please edit source .ksy file and use kaitai-struct-compiler to rebuild

import io.kaitai.struct.ByteBufferKaitaiStream;
import io.kaitai.struct.KaitaiStruct;
import io.kaitai.struct.KaitaiStream;
import java.io.IOException;
import java.util.Map;
import java.util.HashMap;
import java.util.Arrays;
import java.util.ArrayList;
import java.nio.charset.Charset;


/**
 * Also referred to as Devicetree Blob (DTB). It is a flat binary encoding
 * of data (primarily devicetree data, although other data is possible as well).
 * The data is internally stored as a tree of named nodes and properties. Nodes
 * contain properties and child nodes, while properties are name–value pairs.
 * 
 * The Devicetree Blobs (`.dtb` files) are compiled from the Devicetree Source
 * files (`.dts`) through the Devicetree compiler (DTC).
 * 
 * On Linux systems that support this, the blobs can be accessed in
 * `/sys/firmware/fdt`:
 * 
 * * <https://www.kernel.org/doc/Documentation/ABI/testing/sysfs-firmware-ofw>
 * 
 * The encoding of strings used in the `strings_block` and `structure_block` is
 * actually a subset of ASCII:
 * 
 * <https://devicetree-specification.readthedocs.io/en/v0.3/devicetree-basics.html#node-names>
 * 
 * Example files:
 * 
 * * <https://github.com/qemu/qemu/tree/master/pc-bios>
 * @see <a href="https://devicetree-specification.readthedocs.io/en/v0.3/flattened-format.html">Source</a>
 * @see <a href="https://elinux.org/images/f/f4/Elc2013_Fernandes.pdf">Source</a>
 */
public class Dtb extends KaitaiStruct {
    public static Dtb fromFile(String fileName) throws IOException {
        return new Dtb(new ByteBufferKaitaiStream(fileName));
    }

    public enum Fdt {
        BEGIN_NODE(1),
        END_NODE(2),
        PROP(3),
        NOP(4),
        END(9);

        private final long id;
        Fdt(long id) { this.id = id; }
        public long id() { return id; }
        private static final Map<Long, Fdt> byId = new HashMap<Long, Fdt>(5);
        static {
            for (Fdt e : Fdt.values())
                byId.put(e.id(), e);
        }
        public static Fdt byId(long id) { return byId.get(id); }
    }

    public Dtb(KaitaiStream _io) {
        this(_io, null, null);
    }

    public Dtb(KaitaiStream _io, KaitaiStruct _parent) {
        this(_io, _parent, null);
    }

    public Dtb(KaitaiStream _io, KaitaiStruct _parent, Dtb _root) {
        super(_io);
        this._parent = _parent;
        this._root = _root == null ? this : _root;
        _read();
    }
    private void _read() {
        this.magic = this._io.readBytes(4);
        if (!(Arrays.equals(magic(), new byte[] { -48, 13, -2, -19 }))) {
            throw new KaitaiStream.ValidationNotEqualError(new byte[] { -48, 13, -2, -19 }, magic(), _io(), "/seq/0");
        }
        this.totalSize = this._io.readU4be();
        this.ofsStructureBlock = this._io.readU4be();
        this.ofsStringsBlock = this._io.readU4be();
        this.ofsMemoryReservationBlock = this._io.readU4be();
        this.version = this._io.readU4be();
        this.minCompatibleVersion = this._io.readU4be();
        if (!(minCompatibleVersion() <= version())) {
            throw new KaitaiStream.ValidationGreaterThanError(version(), minCompatibleVersion(), _io(), "/seq/6");
        }
        this.bootCpuidPhys = this._io.readU4be();
        this.lenStringsBlock = this._io.readU4be();
        this.lenStructureBlock = this._io.readU4be();
    }
    public static class MemoryBlock extends KaitaiStruct {
        public static MemoryBlock fromFile(String fileName) throws IOException {
            return new MemoryBlock(new ByteBufferKaitaiStream(fileName));
        }

        public MemoryBlock(KaitaiStream _io) {
            this(_io, null, null);
        }

        public MemoryBlock(KaitaiStream _io, Dtb _parent) {
            this(_io, _parent, null);
        }

        public MemoryBlock(KaitaiStream _io, Dtb _parent, Dtb _root) {
            super(_io);
            this._parent = _parent;
            this._root = _root;
            _read();
        }
        private void _read() {
            this.entries = new ArrayList<MemoryBlockEntry>();
            {
                int i = 0;
                while (!this._io.isEof()) {
                    this.entries.add(new MemoryBlockEntry(this._io, this, _root));
                    i++;
                }
            }
        }
        private ArrayList<MemoryBlockEntry> entries;
        private Dtb _root;
        private Dtb _parent;
        public ArrayList<MemoryBlockEntry> entries() { return entries; }
        public Dtb _root() { return _root; }
        public Dtb _parent() { return _parent; }
    }
    public static class FdtBlock extends KaitaiStruct {
        public static FdtBlock fromFile(String fileName) throws IOException {
            return new FdtBlock(new ByteBufferKaitaiStream(fileName));
        }

        public FdtBlock(KaitaiStream _io) {
            this(_io, null, null);
        }

        public FdtBlock(KaitaiStream _io, Dtb _parent) {
            this(_io, _parent, null);
        }

        public FdtBlock(KaitaiStream _io, Dtb _parent, Dtb _root) {
            super(_io);
            this._parent = _parent;
            this._root = _root;
            _read();
        }
        private void _read() {
            this.nodes = new ArrayList<FdtNode>();
            {
                FdtNode _it;
                int i = 0;
                do {
                    _it = new FdtNode(this._io, this, _root);
                    this.nodes.add(_it);
                    i++;
                } while (!(_it.type() == Dtb.Fdt.END));
            }
        }
        private ArrayList<FdtNode> nodes;
        private Dtb _root;
        private Dtb _parent;
        public ArrayList<FdtNode> nodes() { return nodes; }
        public Dtb _root() { return _root; }
        public Dtb _parent() { return _parent; }
    }
    public static class MemoryBlockEntry extends KaitaiStruct {
        public static MemoryBlockEntry fromFile(String fileName) throws IOException {
            return new MemoryBlockEntry(new ByteBufferKaitaiStream(fileName));
        }

        public MemoryBlockEntry(KaitaiStream _io) {
            this(_io, null, null);
        }

        public MemoryBlockEntry(KaitaiStream _io, Dtb.MemoryBlock _parent) {
            this(_io, _parent, null);
        }

        public MemoryBlockEntry(KaitaiStream _io, Dtb.MemoryBlock _parent, Dtb _root) {
            super(_io);
            this._parent = _parent;
            this._root = _root;
            _read();
        }
        private void _read() {
            this.address = this._io.readU8be();
            this.size = this._io.readU8be();
        }
        private long address;
        private long size;
        private Dtb _root;
        private Dtb.MemoryBlock _parent;

        /**
         * physical address of a reserved memory region
         */
        public long address() { return address; }

        /**
         * size of a reserved memory region
         */
        public long size() { return size; }
        public Dtb _root() { return _root; }
        public Dtb.MemoryBlock _parent() { return _parent; }
    }
    public static class Strings extends KaitaiStruct {
        public static Strings fromFile(String fileName) throws IOException {
            return new Strings(new ByteBufferKaitaiStream(fileName));
        }

        public Strings(KaitaiStream _io) {
            this(_io, null, null);
        }

        public Strings(KaitaiStream _io, Dtb _parent) {
            this(_io, _parent, null);
        }

        public Strings(KaitaiStream _io, Dtb _parent, Dtb _root) {
            super(_io);
            this._parent = _parent;
            this._root = _root;
            _read();
        }
        private void _read() {
            this.strings = new ArrayList<String>();
            {
                int i = 0;
                while (!this._io.isEof()) {
                    this.strings.add(new String(this._io.readBytesTerm(0, false, true, true), Charset.forName("ASCII")));
                    i++;
                }
            }
        }
        private ArrayList<String> strings;
        private Dtb _root;
        private Dtb _parent;
        public ArrayList<String> strings() { return strings; }
        public Dtb _root() { return _root; }
        public Dtb _parent() { return _parent; }
    }
    public static class FdtProp extends KaitaiStruct {
        public static FdtProp fromFile(String fileName) throws IOException {
            return new FdtProp(new ByteBufferKaitaiStream(fileName));
        }

        public FdtProp(KaitaiStream _io) {
            this(_io, null, null);
        }

        public FdtProp(KaitaiStream _io, Dtb.FdtNode _parent) {
            this(_io, _parent, null);
        }

        public FdtProp(KaitaiStream _io, Dtb.FdtNode _parent, Dtb _root) {
            super(_io);
            this._parent = _parent;
            this._root = _root;
            _read();
        }
        private void _read() {
            this.lenProperty = this._io.readU4be();
            this.ofsName = this._io.readU4be();
            this.property = this._io.readBytes(lenProperty());
            this.padding = this._io.readBytes(KaitaiStream.mod(-(_io().pos()), 4));
        }
        private String name;
        public String name() {
            if (this.name != null)
                return this.name;
            KaitaiStream io = _root.stringsBlock()._io();
            long _pos = io.pos();
            io.seek(ofsName());
            this.name = new String(io.readBytesTerm(0, false, true, true), Charset.forName("ASCII"));
            io.seek(_pos);
            return this.name;
        }
        private long lenProperty;
        private long ofsName;
        private byte[] property;
        private byte[] padding;
        private Dtb _root;
        private Dtb.FdtNode _parent;
        public long lenProperty() { return lenProperty; }
        public long ofsName() { return ofsName; }
        public byte[] property() { return property; }
        public byte[] padding() { return padding; }
        public Dtb _root() { return _root; }
        public Dtb.FdtNode _parent() { return _parent; }
    }
    public static class FdtNode extends KaitaiStruct {
        public static FdtNode fromFile(String fileName) throws IOException {
            return new FdtNode(new ByteBufferKaitaiStream(fileName));
        }

        public FdtNode(KaitaiStream _io) {
            this(_io, null, null);
        }

        public FdtNode(KaitaiStream _io, Dtb.FdtBlock _parent) {
            this(_io, _parent, null);
        }

        public FdtNode(KaitaiStream _io, Dtb.FdtBlock _parent, Dtb _root) {
            super(_io);
            this._parent = _parent;
            this._root = _root;
            _read();
        }
        private void _read() {
            this.type = Dtb.Fdt.byId(this._io.readU4be());
            {
                Fdt on = type();
                if (on != null) {
                    switch (type()) {
                    case BEGIN_NODE: {
                        this.body = new FdtBeginNode(this._io, this, _root);
                        break;
                    }
                    case PROP: {
                        this.body = new FdtProp(this._io, this, _root);
                        break;
                    }
                    }
                }
            }
        }
        private Fdt type;
        private KaitaiStruct body;
        private Dtb _root;
        private Dtb.FdtBlock _parent;
        public Fdt type() { return type; }
        public KaitaiStruct body() { return body; }
        public Dtb _root() { return _root; }
        public Dtb.FdtBlock _parent() { return _parent; }
    }
    public static class FdtBeginNode extends KaitaiStruct {
        public static FdtBeginNode fromFile(String fileName) throws IOException {
            return new FdtBeginNode(new ByteBufferKaitaiStream(fileName));
        }

        public FdtBeginNode(KaitaiStream _io) {
            this(_io, null, null);
        }

        public FdtBeginNode(KaitaiStream _io, Dtb.FdtNode _parent) {
            this(_io, _parent, null);
        }

        public FdtBeginNode(KaitaiStream _io, Dtb.FdtNode _parent, Dtb _root) {
            super(_io);
            this._parent = _parent;
            this._root = _root;
            _read();
        }
        private void _read() {
            this.name = new String(this._io.readBytesTerm(0, false, true, true), Charset.forName("ASCII"));
            this.padding = this._io.readBytes(KaitaiStream.mod(-(_io().pos()), 4));
        }
        private String name;
        private byte[] padding;
        private Dtb _root;
        private Dtb.FdtNode _parent;
        public String name() { return name; }
        public byte[] padding() { return padding; }
        public Dtb _root() { return _root; }
        public Dtb.FdtNode _parent() { return _parent; }
    }
    private MemoryBlock memoryReservationBlock;
    public MemoryBlock memoryReservationBlock() {
        if (this.memoryReservationBlock != null)
            return this.memoryReservationBlock;
        long _pos = this._io.pos();
        this._io.seek(ofsMemoryReservationBlock());
        this._raw_memoryReservationBlock = this._io.readBytes((ofsStructureBlock() - ofsMemoryReservationBlock()));
        KaitaiStream _io__raw_memoryReservationBlock = new ByteBufferKaitaiStream(_raw_memoryReservationBlock);
        this.memoryReservationBlock = new MemoryBlock(_io__raw_memoryReservationBlock, this, _root);
        this._io.seek(_pos);
        return this.memoryReservationBlock;
    }
    private FdtBlock structureBlock;
    public FdtBlock structureBlock() {
        if (this.structureBlock != null)
            return this.structureBlock;
        long _pos = this._io.pos();
        this._io.seek(ofsStructureBlock());
        this._raw_structureBlock = this._io.readBytes(lenStructureBlock());
        KaitaiStream _io__raw_structureBlock = new ByteBufferKaitaiStream(_raw_structureBlock);
        this.structureBlock = new FdtBlock(_io__raw_structureBlock, this, _root);
        this._io.seek(_pos);
        return this.structureBlock;
    }
    private Strings stringsBlock;
    public Strings stringsBlock() {
        if (this.stringsBlock != null)
            return this.stringsBlock;
        long _pos = this._io.pos();
        this._io.seek(ofsStringsBlock());
        this._raw_stringsBlock = this._io.readBytes(lenStringsBlock());
        KaitaiStream _io__raw_stringsBlock = new ByteBufferKaitaiStream(_raw_stringsBlock);
        this.stringsBlock = new Strings(_io__raw_stringsBlock, this, _root);
        this._io.seek(_pos);
        return this.stringsBlock;
    }
    private byte[] magic;
    private long totalSize;
    private long ofsStructureBlock;
    private long ofsStringsBlock;
    private long ofsMemoryReservationBlock;
    private long version;
    private long minCompatibleVersion;
    private long bootCpuidPhys;
    private long lenStringsBlock;
    private long lenStructureBlock;
    private Dtb _root;
    private KaitaiStruct _parent;
    private byte[] _raw_memoryReservationBlock;
    private byte[] _raw_structureBlock;
    private byte[] _raw_stringsBlock;
    public byte[] magic() { return magic; }
    public long totalSize() { return totalSize; }
    public long ofsStructureBlock() { return ofsStructureBlock; }
    public long ofsStringsBlock() { return ofsStringsBlock; }
    public long ofsMemoryReservationBlock() { return ofsMemoryReservationBlock; }
    public long version() { return version; }
    public long minCompatibleVersion() { return minCompatibleVersion; }
    public long bootCpuidPhys() { return bootCpuidPhys; }
    public long lenStringsBlock() { return lenStringsBlock; }
    public long lenStructureBlock() { return lenStructureBlock; }
    public Dtb _root() { return _root; }
    public KaitaiStruct _parent() { return _parent; }
    public byte[] _raw_memoryReservationBlock() { return _raw_memoryReservationBlock; }
    public byte[] _raw_structureBlock() { return _raw_structureBlock; }
    public byte[] _raw_stringsBlock() { return _raw_stringsBlock; }
}