2 .\" Copyright (c) 2013 David Chisnall
3 .\" All rights reserved.
5 .\" This software was developed by SRI International and the University of
6 .\" Cambridge Computer Laboratory under DARPA/AFRL contract (FA8750-10-C-0237)
7 .\" ("CTSRD"), as part of the DARPA CRASH research programme.
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38 .Nd device tree compiler
42 .Op Fl b Ar boot_cpu_id
43 .Op Fl d Ar dependency_file
44 .Op Fl E Ar [no-]checker_name
45 .Op Fl H Ar phandle_format
46 .Op Fl I Ar input_format
47 .Op Fl O Ar output_format
48 .Op Fl o Ar output_file
52 .Op Fl V Ar blob_version
53 .Op Fl W Ar [no-]checker_name
54 .Op Fl P Ar predefined_properties
59 utility converts flattened device tree (FDT) representations.
60 It is most commonly used to generate device tree blobs (DTB), the binary
61 representation of an FDT, from device tree sources (DTS), the ASCII text source
64 The binary can be written in two formats, binary and assembly.
65 The binary is identical to the in-memory representation and can be used
66 directly by firmware, loaders, and so on.
67 The assembly format, documented in
69 will produce the same binary format when assembled, but also includes some
70 global variables that refer to parts of the table.
71 This format is most commonly used to produce a kernel specific to a device,
72 with the device tree blob compiled in.
74 The options are as follows:
75 .Bl -tag -width indent
76 .It Fl d Ar dependency_file
77 Writes a dependency file understandable by make to the specified file.
78 This file can be included in a Makefile and will ensure that the output file
79 depends on the input file and any files that it includes.
80 This argument is only useful when the input is DTS, as only the source format
81 has a notion of inclusions.
82 .It Fl E Ar [no-]checker_name
83 Enable or disable a specified checker.
84 The argument is the name of the checker.
85 The full list of checkers is given in
88 Force the tool to attempt to generate the output, even if the input had errors.
90 Display the help text and exit.
91 .It Fl H Ar phandle_format
92 Specifies the type of phandle nodes to generate in the output.
95 .Bl -tag -width indent -compact
97 Generate the legacy linux,phandle nodes expected by older systems.
99 Generate the phandle nodes, as described in the ePAPR specification.
100 This is the most sensible option for device trees being used with
103 Generate both, for maximum compatibility.
105 .It Fl I Ar input_format
106 Specifies the input format.
109 .Bl -tag -width indent -compact
112 The binary representation of the FDT.
115 The ASCII representation of the FDT.
116 This is the default if the input format is not explicitly stated.
118 .It Fl O Ar output_format
119 Specifies the output format.
122 .Bl -tag -width indent -compact
124 Assembler source for generating a device tree blob, as described in
128 The binary representation of the FDT.
129 This is the default if the output format is not explicitly stated.
132 The ASCII representation of the FDT.
134 .It Fl o Ar output_file
135 The file to which to write the output.
136 .It Fl P Ar predefined_macro
137 Defines a macro, in the form
141 to be used for device tree source files that contain conditional components.
142 This tool supports two extensions to the standard to support conditional
143 compilation of device trees.
145 .Ar /include/if [property]/ "file.dts"
146 directive that is allowed at the start of a file and which will only include
147 the specified file if it the specified property is passed with this flag.
150 format for property values.
151 These allow property value to be specified on the command line.
153 The number of empty reservation table entries to pad the table with.
155 useful if you are generating a device tree blob for bootloader or similar that
156 needs to reserve some memory before passing control to the operating system.
158 The minimum size in bytes of the blob.
159 The blob will be padded after the strings table to ensure that it is the
161 This is useful for environments where the device tree blob must be modified in
164 The number of bytes of padding to add to the blob.
165 The blob will be padded after the strings table to ensure that it is the
167 This is useful for environments where the device tree blob must be modified in
169 .It Fl W Ar [no-]checker_name
170 Enable or disable a specified checker.
174 Sorts the properties and nodes in the tree.
175 This is mainly useful when using tools like
177 to compare two device tree sources.
178 .It Fl V Ar output_version
179 The version of the format to output.
180 This is only relevant for binary outputs, and only a value of 17 is currently
183 Display the tool version and exit.
188 The assembly format defines several globals that can be referred to from other
189 compilation units, in addition to any labels specified in the source.
192 .Bl -tag -width "dt_strings_start" -compact -offset indent
194 start of the device tree blob.
196 start of the header, usually identical to the start of the blob.
198 start of the reservation map.
200 start of the structure table.
202 end of the structure table.
204 start of the strings table.
206 end of the strings table.
208 end of the device tree blob.
211 The utility provides a number of semantic checks on the correctness of the
213 These can be disabled with the
217 .Fl W Ar no-type-phandle
218 will disable the phandle type check.
219 The supported checks are:
221 .Bl -tag -width "no-type-phandle" -compact -offset indent
223 Checks the type of the
227 Checks the type of the
231 Checks the type of the
235 Checks that all nodes with children have both
243 statements refer to nodes that are merged.
248 .Dl "dtc -o blob.S -O asm device.dts"
252 file from the device tree source
254 and print errors if any occur during parsing or property checking.
256 resulting file can be assembled and linked into a binary.
260 .Dl "dtc -o - -O dts -I dtb device.dtb"
262 will write the device tree source for the device tree blob
264 to the standard output.
265 This is useful when debugging device trees.
267 This utility is intended to be compatible with the device tree compiler
268 provided by elinux.org.
269 Currently, it implements the subset of features
270 required to build FreeBSD and others that have been requested by FreeBSD
275 input format is not supported.
276 This builds a tree from a Linux
277 .Pa /proc/device-tree ,
278 a file system hierarchy not found in FreeBSD, which instead exposes the DTB
279 directly via a sysctl.
281 The warnings and errors supported by the elinux.org tool are not documented.
282 This tool supports the warnings described in the
288 The device tree formats understood by this tool conform to the Power.org
289 Standard for Embedded Power Architecture Platform Requirements
291 except as noted in the
293 section and with the following exceptions for compatibility with the elinux.org
298 The target of cross references is defined to be a node name in the
299 specification, but is in fact a label.
302 The /include/ directive is not part of the standard, however it is implemented
303 with the semantics compatible with the elinux.org tool.
304 It must appear in the top level of a file, and imports a new root definition.
305 If a file, plus all of its inclusions, contains multiple roots then they are
307 All nodes that are present in the second but not the first are imported.
308 Any that appear in both are recursively merged, with properties from the second
309 replacing those from the first and properties child nodes being recursively
312 A dtc tool first appeared in
314 This version of the tool first appeared in
317 .An David T. Chisnall
319 Note: The fact that the tool and the author share the same initials is entirely
322 The device tree compiler does not yet support the following features:
326 Labels in the middle of property values.
327 This is only useful in the assembly output, and only vaguely useful there, so
328 is unlikely to be added soon.
330 Full paths, rather than labels, as the targets for phandles.
331 This is not very hard to add, but will probably not be added until something
335 The current version performs a very limited set of semantic checks on the tree.
336 This will be improved in future versions.