Manual Pages  — DTC

dtc – device tree compiler

SYNOPSIS DESCRIPTION ASM FORMAT CHECKERS OVERLAYS NODE OMISSION EXAMPLES COMPATIBILITY SEE ALSO STANDARDS HISTORY AUTHORS BUGS

dtc [-@fhsv] [-b boot_cpu_id] [-d dependency_file] [-i include_path] [-E [no-]checker_name] [-H phandle_format] [-I input_format] [-O output_format] [-o output_file] [-R entries] [-S bytes] [-p bytes] [-V blob_version] [-W [no-]checker_name] [-P predefined_properties] input_file

The dtc utility converts between flattened device tree (FDT) representations. It is most commonly used to generate device tree blobs (DTB), the binary representation of an FDT, from device tree sources (DTS), the ASCII text source representation.

The binary can be written in two formats, binary and assembly. The binary is identical to the in-memory representation and can be used directly by firmware, loaders, and so on. The assembly format, documented in ASM FORMAT, will produce the same binary format when assembled, but also includes some global variables that refer to parts of the table. This format is most commonly used to produce a kernel specific to a device, with the device tree blob compiled in.

The options are as follows:

-d dependency_file
	Writes a dependency file understandable by make to the specified file. This file can be included in a Makefile and will ensure that the output file depends on the input file and any files that it includes. This argument is only useful when the input is DTS, as only the source format has a notion of inclusions.
-i include_path
	Adds a path to search for include files.
-E [no-]checker_name
	Enable or disable a specified checker. The argument is the name of the checker. The full list of checkers is given in CHECKERS.
-@
	Emit a __symbols__ node to allow plugins to be loaded.
-f
	Force the tool to attempt to generate the output, even if the input had errors.
-h
	Display the help text and exit.
-H phandle_format
	Specifies the type of phandle nodes to generate in the output. Valid values are:
linux	Generate the legacy linux,phandle nodes expected by older systems.
epapr	Generate the phandle nodes, as described in the ePAPR specification. This is the most sensible option for device trees being used with FreeBSD .
both	Generate both, for maximum compatibility.

-I input_format
	Specifies the input format. Valid values are:
dtb	Device tree blob. The binary representation of the FDT.
dts	Device tree source. The ASCII representation of the FDT. This is the default if the input format is not explicitly stated.

-O output_format
	Specifies the output format. Valid values are:
asm	Assembler source for generating a device tree blob, as described in ASM FORMAT.
dtb	Device tree blob. The binary representation of the FDT. This is the default if the output format is not explicitly stated.
dts	Device tree source. The ASCII representation of the FDT.

-o output_file
	The file to which to write the output.
-P predefined_macro
	Defines a macro, in the form name=value or name to be used for device tree source files that contain conditional components. This tool supports two extensions to the standard to support conditional compilation of device trees. The first is an /include/if [property]/ file.dts directive that is allowed at the start of a file and which will only include the specified file if it the specified property is passed with this flag. The second is the $NAME format for property values. These allow property value to be specified on the command line.
-R entries
	The number of empty reservation table entries to pad the table with. This is useful if you are generating a device tree blob for bootloader or similar that needs to reserve some memory before passing control to the operating system.
-S bytes
	The minimum size in bytes of the blob. The blob will be padded after the strings table to ensure that it is the correct size. This is useful for environments where the device tree blob must be modified in place.
-p bytes
	The number of bytes of padding to add to the blob. The blob will be padded after the strings table to ensure that it is the correct size. This is useful for environments where the device tree blob must be modified in place.
-W [no-]checker_name
	Enable or disable a specified checker. This is an alias for -E.
-s
	Sorts the properties and nodes in the tree. This is mainly useful when using tools like diff(1) to compare two device tree sources.
-V output_version
	The version of the format to output. This is only relevant for binary outputs, and only a value of 17 is currently supported.
-v
	Display the tool version and exit.
input_file
	The source file.

The assembly format defines several globals that can be referred to from other compilation units, in addition to any labels specified in the source. These are:

dt_blob_start	start of the device tree blob.
dt_header	start of the header, usually identical to the start of the blob.
dt_reserve_map	start of the reservation map.
dt_struct_start	start of the structure table.
dt_struct_end	end of the structure table.
dt_strings_start
	start of the strings table.
dt_strings_end	end of the strings table.
dt_blob_end	end of the device tree blob.

The utility provides a number of semantic checks on the correctness of the tree. These can be disabled with the -W flag. For example, -W no-type-phandle will disable the phandle type check. The supported checks are:

type-compatible
	Checks the type of the compatible property.
type-model	Checks the type of the model property.
type-compatible
	Checks the type of the compatible property.
cells-attributes
	Checks that all nodes with children have both #address-cells and #size-cells properties.
deleted-nodes	Checks that all /delete-node/ statements refer to nodes that are merged.

This utility supports the /omit-if-no-ref/ statement to mark nodes for omission if they are ultimately not referenced elsewhere in the device tree. This may be used in more space-constrained environments to remove nodes that may not be applicable to the specific device the tree is being compiled for.

When the -@ flag is used to write symbols, nodes with labels will be considered referenced and will not be removed from the tree.

The command:

    dtc -o blob.S -O asm device.dts

will generate a blob.S file from the device tree source device.dts and print errors if any occur during parsing or property checking. The resulting file can be assembled and linked into a binary.

The command:

    dtc -o - -O dts -I dtb device.dtb

will write the device tree source for the device tree blob device.dtb to the standard output. This is useful when debugging device trees.

The command:

    dtc -@ -O dtb -I dts -o device.dtb device.dts

will generate a device.dtb file from the device tree source device.dts with a __symbols__ node included so that overlays may be applied to it.

The command:

    dtc -@ -O dtb -I dts -o device_overlay.dtbo device_overlay.dts

will generate a device_overlay.dtbo file, using the standard extension for a device tree overlay, from the device tree source device_overlay.dts. A __symbols__ node will be included so that overlays may be applied to it. The presence of a /plugin/; directive in device_overlay.dts will indicate to the utility that it should also generate the underlying metadata required in overlays.

The device tree formats understood by this tool conform to the Power.org Standard for Embedded Power Architecture Platform Requirements (ePAPR), except as noted in the BUGS section and with the following exceptions for compatibility with the elinux.org tool:

• The target of cross references is defined to be a node name in the specification, but is in fact a label.

The /include/ directive is not part of the standard, however it is implemented with the semantics compatible with the elinux.org tool. It must appear in the top level of a file, and imports a new root definition. If a file, plus all of its inclusions, contains multiple roots then they are merged. All nodes that are present in the second but not the first are imported. Any that appear in both are recursively merged, with properties from the second replacing those from the first and properties child nodes being recursively merged.

A dtc tool first appeared in FreeBSD 9.0 . This version of the tool first appeared in FreeBSD 10.0 .

dtc was written by David T. Chisnall. Some features were added later by Kyle Evans.

Note: The fact that the tool and the author share the same initials is entirely coincidental.

The device tree compiler does not yet support the following features:

• Labels in the middle of property values. This is only useful in the assembly output, and only vaguely useful there, so is unlikely to be added soon.
• Full paths, rather than labels, as the targets for phandles. This is not very hard to add, but will probably not be added until something actually needs it.

The current version performs a very limited set of semantic checks on the tree. This will be improved in future versions.