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:
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.
-- This is a generated file! Please edit source .ksy file and use kaitai-struct-compiler to rebuild
--
-- This file is compatible with Lua 5.3
local class = require("class")
require("kaitaistruct")
local enum = require("enum")
local stringstream = require("string_stream")
local str_decode = require("string_decode")
--
-- 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 also: Source (https://devicetree-specification.readthedocs.io/en/v0.3/flattened-format.html)
-- See also: Source (https://elinux.org/images/f/f4/Elc2013_Fernandes.pdf)
Dtb = class.class(KaitaiStruct)
Dtb.Fdt = enum.Enum {
begin_node = 1,
end_node = 2,
prop = 3,
nop = 4,
end = 9,
}
function Dtb:_init(io, parent, root)
KaitaiStruct._init(self, io)
self._parent = parent
self._root = root or self
self:_read()
end
function Dtb:_read()
self.magic = self._io:read_bytes(4)
if not(self.magic == "\208\013\254\237") then
error("not equal, expected " .. "\208\013\254\237" .. ", but got " .. self.magic)
end
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()
if not(self.min_compatible_version <= self.version) then
error("ValidationGreaterThanError")
end
self.boot_cpuid_phys = self._io:read_u4be()
self.len_strings_block = self._io:read_u4be()
self.len_structure_block = self._io:read_u4be()
end
Dtb.property.memory_reservation_block = {}
function Dtb.property.memory_reservation_block:get()
if self._m_memory_reservation_block ~= nil then
return self._m_memory_reservation_block
end
local _pos = self._io:pos()
self._io:seek(self.ofs_memory_reservation_block)
self._raw__m_memory_reservation_block = self._io:read_bytes(self.ofs_structure_block - self.ofs_memory_reservation_block)
local _io = KaitaiStream(stringstream(self._raw__m_memory_reservation_block))
self._m_memory_reservation_block = Dtb.MemoryBlock(_io, self, self._root)
self._io:seek(_pos)
return self._m_memory_reservation_block
end
Dtb.property.strings_block = {}
function Dtb.property.strings_block:get()
if self._m_strings_block ~= nil then
return self._m_strings_block
end
local _pos = self._io:pos()
self._io:seek(self.ofs_strings_block)
self._raw__m_strings_block = self._io:read_bytes(self.len_strings_block)
local _io = KaitaiStream(stringstream(self._raw__m_strings_block))
self._m_strings_block = Dtb.Strings(_io, self, self._root)
self._io:seek(_pos)
return self._m_strings_block
end
Dtb.property.structure_block = {}
function Dtb.property.structure_block:get()
if self._m_structure_block ~= nil then
return self._m_structure_block
end
local _pos = self._io:pos()
self._io:seek(self.ofs_structure_block)
self._raw__m_structure_block = self._io:read_bytes(self.len_structure_block)
local _io = KaitaiStream(stringstream(self._raw__m_structure_block))
self._m_structure_block = Dtb.FdtBlock(_io, self, self._root)
self._io:seek(_pos)
return self._m_structure_block
end
Dtb.FdtBeginNode = class.class(KaitaiStruct)
function Dtb.FdtBeginNode:_init(io, parent, root)
KaitaiStruct._init(self, io)
self._parent = parent
self._root = root
self:_read()
end
function Dtb.FdtBeginNode:_read()
self.name = str_decode.decode(self._io:read_bytes_term(0, false, true, true), "ASCII")
self.padding = self._io:read_bytes(-(self._io:pos()) % 4)
end
Dtb.FdtBlock = class.class(KaitaiStruct)
function Dtb.FdtBlock:_init(io, parent, root)
KaitaiStruct._init(self, io)
self._parent = parent
self._root = root
self:_read()
end
function Dtb.FdtBlock:_read()
self.nodes = {}
local i = 0
while true do
local _ = Dtb.FdtNode(self._io, self, self._root)
self.nodes[i + 1] = _
if _.type == Dtb.Fdt.end then
break
end
i = i + 1
end
end
Dtb.FdtNode = class.class(KaitaiStruct)
function Dtb.FdtNode:_init(io, parent, root)
KaitaiStruct._init(self, io)
self._parent = parent
self._root = root
self:_read()
end
function Dtb.FdtNode:_read()
self.type = Dtb.Fdt(self._io:read_u4be())
local _on = self.type
if _on == Dtb.Fdt.begin_node then
self.body = Dtb.FdtBeginNode(self._io, self, self._root)
elseif _on == Dtb.Fdt.prop then
self.body = Dtb.FdtProp(self._io, self, self._root)
end
end
Dtb.FdtProp = class.class(KaitaiStruct)
function Dtb.FdtProp:_init(io, parent, root)
KaitaiStruct._init(self, io)
self._parent = parent
self._root = root
self:_read()
end
function Dtb.FdtProp:_read()
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)
end
Dtb.FdtProp.property.name = {}
function Dtb.FdtProp.property.name:get()
if self._m_name ~= nil then
return self._m_name
end
local _io = self._root.strings_block._io
local _pos = _io:pos()
_io:seek(self.ofs_name)
self._m_name = str_decode.decode(_io:read_bytes_term(0, false, true, true), "ASCII")
_io:seek(_pos)
return self._m_name
end
Dtb.MemoryBlock = class.class(KaitaiStruct)
function Dtb.MemoryBlock:_init(io, parent, root)
KaitaiStruct._init(self, io)
self._parent = parent
self._root = root
self:_read()
end
function Dtb.MemoryBlock:_read()
self.entries = {}
local i = 0
while not self._io:is_eof() do
self.entries[i + 1] = Dtb.MemoryBlockEntry(self._io, self, self._root)
i = i + 1
end
end
Dtb.MemoryBlockEntry = class.class(KaitaiStruct)
function Dtb.MemoryBlockEntry:_init(io, parent, root)
KaitaiStruct._init(self, io)
self._parent = parent
self._root = root
self:_read()
end
function Dtb.MemoryBlockEntry:_read()
self.address = self._io:read_u8be()
self.size = self._io:read_u8be()
end
--
-- physical address of a reserved memory region.
--
-- size of a reserved memory region.
Dtb.Strings = class.class(KaitaiStruct)
function Dtb.Strings:_init(io, parent, root)
KaitaiStruct._init(self, io)
self._parent = parent
self._root = root
self:_read()
end
function Dtb.Strings:_read()
self.strings = {}
local i = 0
while not self._io:is_eof() do
self.strings[i + 1] = str_decode.decode(self._io:read_bytes_term(0, false, true, true), "ASCII")
i = i + 1
end
end