While here, fix a typo and bump the date.
Obtained from: https://github.com/davidchisnall/dtc/pull/71
Fixes: 6979e8cb6e
448 lines
14 KiB
Groff
448 lines
14 KiB
Groff
.\"-
|
|
.\" Copyright (c) 2013 David Chisnall
|
|
.\" All rights reserved.
|
|
.\"
|
|
.\" This software was developed by SRI International and the University of
|
|
.\" Cambridge Computer Laboratory under DARPA/AFRL contract (FA8750-10-C-0237)
|
|
.\" ("CTSRD"), as part of the DARPA CRASH research programme.
|
|
.\"
|
|
.\" This software was developed by SRI International and the University of
|
|
.\" Redistribution and use in source and binary forms, with or without
|
|
.\" modification, are permitted provided that the following conditions
|
|
.\" are met:
|
|
.\" 1. Redistributions of source code must retain the above copyright
|
|
.\" notice, this list of conditions and the following disclaimer.
|
|
.\" 2. Redistributions in binary form must reproduce the above copyright
|
|
.\" notice, this list of conditions and the following disclaimer in the
|
|
.\" documentation and/or other materials provided with the distribution.
|
|
.\"
|
|
.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
|
|
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
|
|
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
|
|
.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
|
|
.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
|
|
.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
|
|
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
|
|
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
|
|
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
|
|
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
|
|
.\" SUCH DAMAGE.
|
|
.\"
|
|
.\" $FreeBSD$
|
|
.\"/
|
|
.Dd February 26, 2022
|
|
.Dt DTC 1
|
|
.Os
|
|
.Sh NAME
|
|
.Nm dtc
|
|
.Nd device tree compiler
|
|
.Sh SYNOPSIS
|
|
.Nm
|
|
.Op Fl @fhsv
|
|
.Op Fl b Ar boot_cpu_id
|
|
.Op Fl d Ar dependency_file
|
|
.Op Fl i Ar include_path
|
|
.Op Fl E Ar [no-]checker_name
|
|
.Op Fl H Ar phandle_format
|
|
.Op Fl I Ar input_format
|
|
.Op Fl O Ar output_format
|
|
.Op Fl o Ar output_file
|
|
.Op Fl R Ar entries
|
|
.Op Fl S Ar bytes
|
|
.Op Fl p Ar bytes
|
|
.Op Fl V Ar blob_version
|
|
.Op Fl W Ar [no-]checker_name
|
|
.Op Fl P Ar predefined_properties
|
|
.Ar input_file
|
|
.Sh DESCRIPTION
|
|
The
|
|
.Nm
|
|
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.
|
|
.Pp
|
|
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
|
|
.Sx "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.
|
|
.Pp
|
|
The options are as follows:
|
|
.Bl -tag -width indent
|
|
.It Fl d Ar 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.
|
|
.It Fl i Ar include_path
|
|
Adds a path to search for include files.
|
|
.It Fl E Ar [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
|
|
.Sx CHECKERS .
|
|
.It Fl @
|
|
Emit a __symbols__ node to allow plugins to be loaded.
|
|
.It Fl f
|
|
Force the tool to attempt to generate the output, even if the input had errors.
|
|
.It Fl h
|
|
Display the help text and exit.
|
|
.It Fl H Ar phandle_format
|
|
Specifies the type of phandle nodes to generate in the output.
|
|
Valid values are:
|
|
.Pp
|
|
.Bl -tag -width indent -compact
|
|
.It Ar linux
|
|
Generate the legacy linux,phandle nodes expected by older systems.
|
|
.It Ar epapr
|
|
Generate the phandle nodes, as described in the ePAPR specification.
|
|
This is the most sensible option for device trees being used with
|
|
.Fx .
|
|
.It Ar both
|
|
Generate both, for maximum compatibility.
|
|
.El
|
|
.It Fl I Ar input_format
|
|
Specifies the input format.
|
|
Valid values are:
|
|
.Pp
|
|
.Bl -tag -width indent -compact
|
|
.It Ar dtb
|
|
Device tree blob.
|
|
The binary representation of the FDT.
|
|
.It Ar dts
|
|
Device tree source.
|
|
The ASCII representation of the FDT.
|
|
This is the default if the input format is not explicitly stated.
|
|
.El
|
|
.It Fl O Ar output_format
|
|
Specifies the output format.
|
|
Valid values are:
|
|
.Pp
|
|
.Bl -tag -width indent -compact
|
|
.It Ar asm
|
|
Assembler source for generating a device tree blob, as described in
|
|
.Sx "ASM FORMAT" .
|
|
.It Ar dtb
|
|
Device tree blob.
|
|
The binary representation of the FDT.
|
|
This is the default if the output format is not explicitly stated.
|
|
.It Ar dts
|
|
Device tree source.
|
|
The ASCII representation of the FDT.
|
|
.El
|
|
.It Fl o Ar output_file
|
|
The file to which to write the output.
|
|
.It Fl P Ar predefined_macro
|
|
Defines a macro, in the form
|
|
.Ar name=value
|
|
or
|
|
.Ar 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
|
|
.Ar /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
|
|
.Ar $NAME
|
|
format for property values.
|
|
These allow property value to be specified on the command line.
|
|
.It Fl R Ar 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.
|
|
.It Fl S Ar 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.
|
|
.It Fl p Ar 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.
|
|
.It Fl W Ar [no-]checker_name
|
|
Enable or disable a specified checker.
|
|
This is an alias for
|
|
.Fl E .
|
|
.It Fl s
|
|
Sorts the properties and nodes in the tree.
|
|
This is mainly useful when using tools like
|
|
.Xr diff 1
|
|
to compare two device tree sources.
|
|
.It Fl V Ar 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.
|
|
.It Fl v
|
|
Display the tool version and exit.
|
|
.It Ar input_file
|
|
The source file.
|
|
.El
|
|
.Sh "ASM FORMAT"
|
|
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:
|
|
.Pp
|
|
.Bl -tag -width "dt_strings_start" -compact -offset indent
|
|
.It dt_blob_start
|
|
start of the device tree blob.
|
|
.It dt_header
|
|
start of the header, usually identical to the start of the blob.
|
|
.It dt_reserve_map
|
|
start of the reservation map.
|
|
.It dt_struct_start
|
|
start of the structure table.
|
|
.It dt_struct_end
|
|
end of the structure table.
|
|
.It dt_strings_start
|
|
start of the strings table.
|
|
.It dt_strings_end
|
|
end of the strings table.
|
|
.It dt_blob_end
|
|
end of the device tree blob.
|
|
.El
|
|
.Sh CHECKERS
|
|
The utility provides a number of semantic checks on the correctness of the
|
|
tree.
|
|
These can be disabled with the
|
|
.Fl W
|
|
flag.
|
|
For example,
|
|
.Fl W Ar no-type-phandle
|
|
will disable the phandle type check.
|
|
The supported checks are:
|
|
.Pp
|
|
.Bl -tag -width "no-type-phandle" -compact -offset indent
|
|
.It type-compatible
|
|
Checks the type of the
|
|
.Va compatible
|
|
property.
|
|
.It type-model
|
|
Checks the type of the
|
|
.Va model
|
|
property.
|
|
.It type-compatible
|
|
Checks the type of the
|
|
.Va compatible
|
|
property.
|
|
.It cells-attributes
|
|
Checks that all nodes with children have both
|
|
.Va #address-cells
|
|
and
|
|
.Va #size-cells
|
|
properties.
|
|
.It deleted-nodes
|
|
Checks that all
|
|
.Va /delete-node/
|
|
statements refer to nodes that are merged.
|
|
.El
|
|
.Sh OVERLAYS
|
|
The utility provides support for generating overlays, also known as plugins.
|
|
Overlays are a method of patching a base device tree that has been compiled with
|
|
the
|
|
.Fl @
|
|
flag, with some limited support for patching device trees that were not compiled
|
|
with the
|
|
.Fl @
|
|
flag.
|
|
.Pp
|
|
To denote that a DTS is intended to be used as an overlay,
|
|
.Va /plugin/\&;
|
|
should be included in the header, following any applicable
|
|
.Va /dts-v1/\&;
|
|
tag.
|
|
.Pp
|
|
Conventional overlays are crafted by creating
|
|
.Va fragment
|
|
nodes in a root.
|
|
Each fragment node must have either a
|
|
.Va target
|
|
property set to a label reference, or a
|
|
.Va target-path
|
|
string property set to a path.
|
|
It must then have an
|
|
.Va __overlay__
|
|
child node, whose properties and child nodes are merged into the base device
|
|
tree when the overlay is applied.
|
|
.Pp
|
|
Much simpler syntactic sugar was later invented to simplify generating overlays.
|
|
Instead of creating targeted fragments manually, one can instead create a root
|
|
node that targets a label in the base FDT using the
|
|
.Va &label
|
|
syntax supported in conventional DTS.
|
|
This will indicate that a fragment should be generated for the node, with the
|
|
given
|
|
.Va label
|
|
being the target, and the properties and child nodes will be used as the
|
|
__overlay__.
|
|
.Pp
|
|
Additionally, a path-based version of this syntactic sugar is supported.
|
|
A root node may target a path in the base FDT using a name of the form
|
|
.Va &{/path} .
|
|
A fragment will be generated for the node as it is in the
|
|
.Va &label
|
|
case, except the
|
|
.Va target-path
|
|
property will be set to
|
|
.Va /path
|
|
and no
|
|
.Va target
|
|
will be set.
|
|
.Pp
|
|
Both conventional overlays and the later-added syntactic sugar are supported.
|
|
.Pp
|
|
Overlay blobs can be applied at boot time by setting
|
|
.Va fdt_overlays
|
|
in
|
|
.Xr loader.conf 5 .
|
|
Multiple overlays may be specified, and they will be applied in the order given.
|
|
.Sh NODE OMISSION
|
|
This utility supports the
|
|
.Va /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.
|
|
.Pp
|
|
When the
|
|
.Fl @
|
|
flag is used to write symbols, nodes with labels will be considered referenced
|
|
and will not be removed from the tree.
|
|
.Sh EXAMPLES
|
|
The command:
|
|
.Pp
|
|
.Dl "dtc -o blob.S -O asm device.dts"
|
|
.Pp
|
|
will generate a
|
|
.Pa blob.S
|
|
file from the device tree source
|
|
.Pa device.dts
|
|
and print errors if any occur during parsing or property checking.
|
|
The resulting file can be assembled and linked into a binary.
|
|
.Pp
|
|
The command:
|
|
.Pp
|
|
.Dl "dtc -o - -O dts -I dtb device.dtb"
|
|
.Pp
|
|
will write the device tree source for the device tree blob
|
|
.Pa device.dtb
|
|
to the standard output.
|
|
This is useful when debugging device trees.
|
|
.Pp
|
|
The command:
|
|
.Pp
|
|
.Dl "dtc -@ -O dtb -I dts -o device.dtb device.dts"
|
|
.Pp
|
|
will generate a
|
|
.Pa device.dtb
|
|
file from the device tree source
|
|
.Pa device.dts
|
|
with a __symbols__ node included so that overlays may be applied to it.
|
|
.Pp
|
|
The command:
|
|
.Pp
|
|
.Dl "dtc -@ -O dtb -I dts -o device_overlay.dtbo device_overlay.dts"
|
|
.Pp
|
|
will generate a
|
|
.Pa device_overlay.dtbo
|
|
file, using the standard extension for a device tree overlay, from the device
|
|
tree source
|
|
.Pa device_overlay.dts .
|
|
A __symbols__ node will be included so that overlays may be applied to it.
|
|
The presence of a
|
|
.Va /plugin/\&;
|
|
directive in
|
|
.Pa device_overlay.dts
|
|
will indicate to the utility that it should also generate the underlying
|
|
metadata required in overlays.
|
|
.Sh COMPATIBILITY
|
|
This utility is intended to be compatible with the device tree compiler
|
|
provided by elinux.org.
|
|
Currently, it implements the subset of features
|
|
required to build
|
|
.Fx
|
|
and others that have been requested by
|
|
.Fx
|
|
developers.
|
|
.Pp
|
|
The
|
|
.Ar fs
|
|
input format is not supported.
|
|
This builds a tree from a Linux
|
|
.Pa /proc/device-tree ,
|
|
a file system hierarchy not found in
|
|
.Fx ,
|
|
which instead exposes the DTB directly via a sysctl.
|
|
.Pp
|
|
The warnings and errors supported by the elinux.org tool are not documented.
|
|
This tool supports the warnings described in the
|
|
.Sx CHECKERS
|
|
section.
|
|
.Sh SEE ALSO
|
|
.Xr fdt 4
|
|
.Sh STANDARDS
|
|
The device tree formats understood by this tool conform to the Power.org
|
|
Standard for Embedded Power Architecture Platform Requirements
|
|
.Pq Vt ePAPR ,
|
|
except as noted in the
|
|
.Sx BUGS
|
|
section and with the following exceptions for compatibility with the elinux.org
|
|
tool:
|
|
.Pp
|
|
.Bl -bullet -compact
|
|
.It
|
|
The target of cross references is defined to be a node name in the
|
|
specification, but is in fact a label.
|
|
.El
|
|
.Pp
|
|
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.
|
|
.Sh HISTORY
|
|
A dtc tool first appeared in
|
|
.Fx 9.0 .
|
|
This version of the tool first appeared in
|
|
.Fx 10.0 .
|
|
.Sh AUTHORS
|
|
.Nm
|
|
was written by
|
|
.An David T. Chisnall .
|
|
Some features were added later by
|
|
.An Kyle Evans .
|
|
.Pp
|
|
Note: The fact that the tool and the author share the same initials is entirely
|
|
coincidental.
|
|
.Sh BUGS
|
|
The device tree compiler does not yet support the following features:
|
|
.Pp
|
|
.Bl -bullet -compact
|
|
.It
|
|
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.
|
|
.It
|
|
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.
|
|
.El
|
|
.Pp
|
|
The current version performs a very limited set of semantic checks on the tree.
|
|
This will be improved in future versions.
|