Flattened Devicetree Format: Perl 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.

Perl source code to parse Flattened Devicetree Format

Dtb.pm

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

use strict;
use warnings;
use IO::KaitaiStruct 0.009_000;
use Encode;

########################################################################
package Dtb;

our @ISA = 'IO::KaitaiStruct::Struct';

sub from_file {
    my ($class, $filename) = @_;
    my $fd;

    open($fd, '<', $filename) or return undef;
    binmode($fd);
    return new($class, IO::KaitaiStruct::Stream->new($fd));
}

our $FDT_BEGIN_NODE = 1;
our $FDT_END_NODE = 2;
our $FDT_PROP = 3;
our $FDT_NOP = 4;
our $FDT_END = 9;

sub new {
    my ($class, $_io, $_parent, $_root) = @_;
    my $self = IO::KaitaiStruct::Struct->new($_io);

    bless $self, $class;
    $self->{_parent} = $_parent;
    $self->{_root} = $_root || $self;;

    $self->_read();

    return $self;
}

sub _read {
    my ($self) = @_;

    $self->{magic} = $self->{_io}->read_bytes(4);
    $self->{total_size} = $self->{_io}->read_u4be();
    $self->{ofs_structure_block} = $self->{_io}->read_u4be();
    $self->{ofs_strings_block} = $self->{_io}->read_u4be();
    $self->{ofs_memory_reservation_block} = $self->{_io}->read_u4be();
    $self->{version} = $self->{_io}->read_u4be();
    $self->{min_compatible_version} = $self->{_io}->read_u4be();
    $self->{boot_cpuid_phys} = $self->{_io}->read_u4be();
    $self->{len_strings_block} = $self->{_io}->read_u4be();
    $self->{len_structure_block} = $self->{_io}->read_u4be();
}

sub memory_reservation_block {
    my ($self) = @_;
    return $self->{memory_reservation_block} if ($self->{memory_reservation_block});
    my $_pos = $self->{_io}->pos();
    $self->{_io}->seek($self->ofs_memory_reservation_block());
    $self->{_raw_memory_reservation_block} = $self->{_io}->read_bytes(($self->ofs_structure_block() - $self->ofs_memory_reservation_block()));
    my $io__raw_memory_reservation_block = IO::KaitaiStruct::Stream->new($self->{_raw_memory_reservation_block});
    $self->{memory_reservation_block} = Dtb::MemoryBlock->new($io__raw_memory_reservation_block, $self, $self->{_root});
    $self->{_io}->seek($_pos);
    return $self->{memory_reservation_block};
}

sub structure_block {
    my ($self) = @_;
    return $self->{structure_block} if ($self->{structure_block});
    my $_pos = $self->{_io}->pos();
    $self->{_io}->seek($self->ofs_structure_block());
    $self->{_raw_structure_block} = $self->{_io}->read_bytes($self->len_structure_block());
    my $io__raw_structure_block = IO::KaitaiStruct::Stream->new($self->{_raw_structure_block});
    $self->{structure_block} = Dtb::FdtBlock->new($io__raw_structure_block, $self, $self->{_root});
    $self->{_io}->seek($_pos);
    return $self->{structure_block};
}

sub strings_block {
    my ($self) = @_;
    return $self->{strings_block} if ($self->{strings_block});
    my $_pos = $self->{_io}->pos();
    $self->{_io}->seek($self->ofs_strings_block());
    $self->{_raw_strings_block} = $self->{_io}->read_bytes($self->len_strings_block());
    my $io__raw_strings_block = IO::KaitaiStruct::Stream->new($self->{_raw_strings_block});
    $self->{strings_block} = Dtb::Strings->new($io__raw_strings_block, $self, $self->{_root});
    $self->{_io}->seek($_pos);
    return $self->{strings_block};
}

sub magic {
    my ($self) = @_;
    return $self->{magic};
}

sub total_size {
    my ($self) = @_;
    return $self->{total_size};
}

sub ofs_structure_block {
    my ($self) = @_;
    return $self->{ofs_structure_block};
}

sub ofs_strings_block {
    my ($self) = @_;
    return $self->{ofs_strings_block};
}

sub ofs_memory_reservation_block {
    my ($self) = @_;
    return $self->{ofs_memory_reservation_block};
}

sub version {
    my ($self) = @_;
    return $self->{version};
}

sub min_compatible_version {
    my ($self) = @_;
    return $self->{min_compatible_version};
}

sub boot_cpuid_phys {
    my ($self) = @_;
    return $self->{boot_cpuid_phys};
}

sub len_strings_block {
    my ($self) = @_;
    return $self->{len_strings_block};
}

sub len_structure_block {
    my ($self) = @_;
    return $self->{len_structure_block};
}

sub _raw_memory_reservation_block {
    my ($self) = @_;
    return $self->{_raw_memory_reservation_block};
}

sub _raw_structure_block {
    my ($self) = @_;
    return $self->{_raw_structure_block};
}

sub _raw_strings_block {
    my ($self) = @_;
    return $self->{_raw_strings_block};
}

########################################################################
package Dtb::MemoryBlock;

our @ISA = 'IO::KaitaiStruct::Struct';

sub from_file {
    my ($class, $filename) = @_;
    my $fd;

    open($fd, '<', $filename) or return undef;
    binmode($fd);
    return new($class, IO::KaitaiStruct::Stream->new($fd));
}

sub new {
    my ($class, $_io, $_parent, $_root) = @_;
    my $self = IO::KaitaiStruct::Struct->new($_io);

    bless $self, $class;
    $self->{_parent} = $_parent;
    $self->{_root} = $_root || $self;;

    $self->_read();

    return $self;
}

sub _read {
    my ($self) = @_;

    $self->{entries} = ();
    while (!$self->{_io}->is_eof()) {
        push @{$self->{entries}}, Dtb::MemoryBlockEntry->new($self->{_io}, $self, $self->{_root});
    }
}

sub entries {
    my ($self) = @_;
    return $self->{entries};
}

########################################################################
package Dtb::FdtBlock;

our @ISA = 'IO::KaitaiStruct::Struct';

sub from_file {
    my ($class, $filename) = @_;
    my $fd;

    open($fd, '<', $filename) or return undef;
    binmode($fd);
    return new($class, IO::KaitaiStruct::Stream->new($fd));
}

sub new {
    my ($class, $_io, $_parent, $_root) = @_;
    my $self = IO::KaitaiStruct::Struct->new($_io);

    bless $self, $class;
    $self->{_parent} = $_parent;
    $self->{_root} = $_root || $self;;

    $self->_read();

    return $self;
}

sub _read {
    my ($self) = @_;

    $self->{nodes} = ();
    do {
        $_ = Dtb::FdtNode->new($self->{_io}, $self, $self->{_root});
        push @{$self->{nodes}}, $_;
    } until ($_->type() == $Dtb::FDT_END);
}

sub nodes {
    my ($self) = @_;
    return $self->{nodes};
}

########################################################################
package Dtb::MemoryBlockEntry;

our @ISA = 'IO::KaitaiStruct::Struct';

sub from_file {
    my ($class, $filename) = @_;
    my $fd;

    open($fd, '<', $filename) or return undef;
    binmode($fd);
    return new($class, IO::KaitaiStruct::Stream->new($fd));
}

sub new {
    my ($class, $_io, $_parent, $_root) = @_;
    my $self = IO::KaitaiStruct::Struct->new($_io);

    bless $self, $class;
    $self->{_parent} = $_parent;
    $self->{_root} = $_root || $self;;

    $self->_read();

    return $self;
}

sub _read {
    my ($self) = @_;

    $self->{address} = $self->{_io}->read_u8be();
    $self->{size} = $self->{_io}->read_u8be();
}

sub address {
    my ($self) = @_;
    return $self->{address};
}

sub size {
    my ($self) = @_;
    return $self->{size};
}

########################################################################
package Dtb::Strings;

our @ISA = 'IO::KaitaiStruct::Struct';

sub from_file {
    my ($class, $filename) = @_;
    my $fd;

    open($fd, '<', $filename) or return undef;
    binmode($fd);
    return new($class, IO::KaitaiStruct::Stream->new($fd));
}

sub new {
    my ($class, $_io, $_parent, $_root) = @_;
    my $self = IO::KaitaiStruct::Struct->new($_io);

    bless $self, $class;
    $self->{_parent} = $_parent;
    $self->{_root} = $_root || $self;;

    $self->_read();

    return $self;
}

sub _read {
    my ($self) = @_;

    $self->{strings} = ();
    while (!$self->{_io}->is_eof()) {
        push @{$self->{strings}}, Encode::decode("ASCII", $self->{_io}->read_bytes_term(0, 0, 1, 1));
    }
}

sub strings {
    my ($self) = @_;
    return $self->{strings};
}

########################################################################
package Dtb::FdtProp;

our @ISA = 'IO::KaitaiStruct::Struct';

sub from_file {
    my ($class, $filename) = @_;
    my $fd;

    open($fd, '<', $filename) or return undef;
    binmode($fd);
    return new($class, IO::KaitaiStruct::Stream->new($fd));
}

sub new {
    my ($class, $_io, $_parent, $_root) = @_;
    my $self = IO::KaitaiStruct::Struct->new($_io);

    bless $self, $class;
    $self->{_parent} = $_parent;
    $self->{_root} = $_root || $self;;

    $self->_read();

    return $self;
}

sub _read {
    my ($self) = @_;

    $self->{len_property} = $self->{_io}->read_u4be();
    $self->{ofs_name} = $self->{_io}->read_u4be();
    $self->{property} = $self->{_io}->read_bytes($self->len_property());
    $self->{padding} = $self->{_io}->read_bytes((-($self->_io()->pos()) % 4));
}

sub name {
    my ($self) = @_;
    return $self->{name} if ($self->{name});
    my $io = $self->_root()->strings_block()->_io();
    my $_pos = $io->pos();
    $io->seek($self->ofs_name());
    $self->{name} = Encode::decode("ASCII", $io->read_bytes_term(0, 0, 1, 1));
    $io->seek($_pos);
    return $self->{name};
}

sub len_property {
    my ($self) = @_;
    return $self->{len_property};
}

sub ofs_name {
    my ($self) = @_;
    return $self->{ofs_name};
}

sub property {
    my ($self) = @_;
    return $self->{property};
}

sub padding {
    my ($self) = @_;
    return $self->{padding};
}

########################################################################
package Dtb::FdtNode;

our @ISA = 'IO::KaitaiStruct::Struct';

sub from_file {
    my ($class, $filename) = @_;
    my $fd;

    open($fd, '<', $filename) or return undef;
    binmode($fd);
    return new($class, IO::KaitaiStruct::Stream->new($fd));
}

sub new {
    my ($class, $_io, $_parent, $_root) = @_;
    my $self = IO::KaitaiStruct::Struct->new($_io);

    bless $self, $class;
    $self->{_parent} = $_parent;
    $self->{_root} = $_root || $self;;

    $self->_read();

    return $self;
}

sub _read {
    my ($self) = @_;

    $self->{type} = $self->{_io}->read_u4be();
    my $_on = $self->type();
    if ($_on == $Dtb::FDT_BEGIN_NODE) {
        $self->{body} = Dtb::FdtBeginNode->new($self->{_io}, $self, $self->{_root});
    }
    elsif ($_on == $Dtb::FDT_PROP) {
        $self->{body} = Dtb::FdtProp->new($self->{_io}, $self, $self->{_root});
    }
}

sub type {
    my ($self) = @_;
    return $self->{type};
}

sub body {
    my ($self) = @_;
    return $self->{body};
}

########################################################################
package Dtb::FdtBeginNode;

our @ISA = 'IO::KaitaiStruct::Struct';

sub from_file {
    my ($class, $filename) = @_;
    my $fd;

    open($fd, '<', $filename) or return undef;
    binmode($fd);
    return new($class, IO::KaitaiStruct::Stream->new($fd));
}

sub new {
    my ($class, $_io, $_parent, $_root) = @_;
    my $self = IO::KaitaiStruct::Struct->new($_io);

    bless $self, $class;
    $self->{_parent} = $_parent;
    $self->{_root} = $_root || $self;;

    $self->_read();

    return $self;
}

sub _read {
    my ($self) = @_;

    $self->{name} = Encode::decode("ASCII", $self->{_io}->read_bytes_term(0, 0, 1, 1));
    $self->{padding} = $self->{_io}->read_bytes((-($self->_io()->pos()) % 4));
}

sub name {
    my ($self) = @_;
    return $self->{name};
}

sub padding {
    my ($self) = @_;
    return $self->{padding};
}

1;