Dtb to dts linux

Dtb to dts linux

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Linux device tree file (dtb)

Linux introduced the concept of device tree after kernel 3.x. Instead of adding device information in arch/arm/mach-s2440.c like the 2.6 era. (Recommended Song Baohua《Detailed Linux device driver deve.

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Как скомпилировать исходные файлы дерева устройств DTS Linux в dtb?

У меня есть файл дерево устройств (.dts), и я хочу скомпилировать файл для моей платы на основе powerpc.

Как я могу это сделать на своей машине, которая не основана на powerpc?? Могу ли я сделать это с помощью DTC, установленного на моей системе Ubuntu? Или это будет больше похоже на использование отдельного компилятора и передачу информации ARCH (например, с помощью цепочки инструментов)?

3 ответов

деревья устройств не нужно компилировать с помощью инструментов, «учитывающих архитектуру». Компилятор dtc на вашей машине ubuntu, вероятно, достаточно актуален для компиляции дерева устройств. Или вы можете загрузить последний источник и скомпилировать его самостоятельно. Компилятор dtc можно найти здесь:

в этом пакете есть несколько хороших документов, которые помогут вам лучше понять деревья устройств в генеральный.

довольно легко скомпилировать (и разобрать) деревья устройств. Например

чтобы получить дерево устройств в тексте из blob дерева устройств, сделайте следующее:

надеюсь, что это помогает!

make dtbs из дерева ядра-еще один распространенный способ их компиляции, так как стандартное место для размещения dts находится под деревом ядра в каталогах вида ./arch//boot/dts .

это заканчивается вызовом dtc , но могли бы работать лучше, потому что потенциал включает будет в нужном месте.

dtbs размещаются в том же каталоге, что и dts.

dtc может быть установлен этой командой в linux:

sudo apt-get install device-tree-compiler

вы можете compile dts или dtsi файлы по этой команде:

dtc -I dts -O dtb -o devicetree_file_name.dtb devicetree_file_name.dts

вы можете преобразование dts to dtb по этого команда:

dtc -I dts -O dtb -f devicetree_file_name.dts -o devicetree_file_name.dtb

вы можете преобразование dtb to dts С помощью этой команды:

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How to compile dts to dtb from Linux kernel and manually

Lets say, you have been trying to compile Linux kernel source code for Raspberry Pi following steps from “Cross Compilation and Booting of Linux kernel for Raspberry Pi3 – Manual Compilation” although most of the steps remains same in general for other ARM architectures as well , so just replace Raspberry Pi name with your own platform if any.

As we know all recent kernels use device tree formats for defining the devices information in Linux kernel which has been written in “device tree syntax” DTS files, generally kept at arch/arm/boot/dts directory and the file which normally gets flashed on device is “device tree blog” DTB which is compiled using “device tree compiler” DTC.

Compile the dtb from Linux kernel source code as,

Install the dtb using following command,

NOTE: you can create out folder in current directory if not present, just to save output binary files.

and you will see, dtbs directory created in out folder.

out/dtbs/4.9.45-v7+/bcm2708-rpi-b.dtb: Device Tree Blob version 17, size=15197, boot CPU=0, string block size=1393, DT structure block size=13732

If you check the kernel source code, the make file arch/arm/boot/dts/Makefile defines which target selects which dts file and also mentions about the compilation targets.

You can also create a single dtb using below command,

where you can replace bcm2708-rpi-b with any name of dts you need from arch/arm/boot/dts/

While you can create a dtb from dtc command manually using below command,

If you try to create dts already written in Linux kernel, chances are that you will get an error as,

syntax error
FATAL ERROR: Unable to parse input tree

This is because, dts files in kernel use #include whereas standard dts uses include in between two / like “/include/”
so if you replace line like below,
#include “bcm2708.dtsi”

The above error may go, which is because the newer kernels run a C preprocessor on dts files like below,

where you will find that bcm2708-rpi-b.dts.tmp has /include/ instead of #include.

But this also might fail to add #include of standard C headers which some dts files use, so best approach is to use “make dtbs” from kernel if you are writing a complicated dts file.

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Device Tree Reference

Contents

Introduction

Device Tree Usage

If Device Tree is new to you, start with Device Tree Usage page. That page describes what Device Tree source looks like. It walks through building the source for a new machine. It describes the basic concepts, shows specific examples, and covers some advanced features.

Device Tree Usage page was previously located at devicetree.org.

What Is Device Tree

The primary purpose of Device Tree in Linux is to provide a way to describe non-discoverable hardware. This information was previously hard coded in source code.

Some more background on what Device Tree is, advantages, and competing solutions, see this page. Most of the contents of this page was previously located at Device_Tree, which now redirects to Device_Tree_Reference.

Request for Documentation Suggestions

If you have any comments or suggestions about the Device Tree documentation on elinux.org, please send them to frowand (dot) list (at) gmail (dot) com

I am currently trying to make the information more organized, more comprehensive, and a more complete index of information available elsewhere. I am looking for comments on what is incorrect, incomplete, or missing. I would appreciate pointers to good documentation, tutorials, etc that I can link to.

History

Future

• How device tree is changing and where it is headed
  • Includes Linux Plumbers conference, Kernel Summit, etc
• Frank’s thoughts on what is needed to complete basic overlay support

Device Tree Related Communications

Device-Tree irc

The Device Tree IRC channel is #devicetree on libera.chat.

You can also connect over the Matrix network with #devicetree:libera.chat

You are likely to find many people connected to the channel, but many of them are not actively monitoring traffic. There may be a delay of several days or weeks before a question or comment is acknowledged.

Device-tree Mailing List

This list contained all devicetree related discussion until February 2014. At that time, the devicetree.spec and devicetree.compiler lists were created to provide lower volume lists for those specific topic areas.

Additional archive added in 2019:

After July 2013:

Up through July 2013:

Core devicetree binding / Devicetree Specification Mailing List

Created February 2014.

The devicetree.spec list is for «core» binding discussions; anything that affects entire subsystems or the kinds of things that would make sense to be added to the ePAPR Devicetree Specification.

Individual device bindings continue to be posted to devicetree@vger.kernel.org, but anything affecting subsystems or generic patterns should be posted to this list.

After April 28, 2016:

The creation and updating of the Devicetree Specification is also discussed on this list.

Device-tree Compiler and Tools Mailing List

Created February 2014.

The devicetree.compiler list is for discussion related to dtc and other tools.

It is specifically for discussing dt tooling topics (parsing, schema validation, data format, etc).

Presentations, Papers, and Articles

The Device Tree presentations, papers, and articles page is organized by topic area and by date.

Device Tree Mysteries

If you can not find a specific piece of information elsewhere, it might be on the Device_Tree_Mysteries page.

Linux Specific

Standards

Devicetree Specification Release 0.2, located on the devicetree.org web site has superseded the ePAPR for the Linux kernel. The specification is meant to be OS independent. The Linux kernel devicetree maintainers are actively involved in the specification process.

Device Tree Source Format

• Devicetree Specification Release 0.2
  • chapter 2 «The Devicetree»
  • chapter 6 «Devicetree Source Format (version 1)»

• Power.org Standard for Embedded Power Architecture Platform Requirements (ePAPR) v1.1
  • superseded by the Devicetree Specification
  • chapter 2 «The Device Tree»
  • Appendix A «Device Tree Source Format (Version 1)»

• dtc compiler repository documentation
  • Documentation/dts-format.txt Device Tree Source Format

• differences between ePAPR and the Linux dtc compiler

• presentations
  • «Device Tree for Dummies», ELC 2014 by Thomas Petazzoni
    • PDF
    • YouTube video

• Undocumented
  • Device_Tree_Source_Undocumented contains some information not documented elsewhere

Bindings

Bindings are documented in

Bindings Documentation in Linux Kernel Source Tree

Documentation files about device tree is available in the Linux kernel source at Documentation/devicetree

Specific bindings specifications are located in the Linux kernel source at: Documentation/devicetree/bindings

Before submitting a binding patch, read these:

Some especially useful files (in alphabetic order) are:

• ABI/testing/sysfs-firmware-ofw
  • description of /sys/firmware/devicetree/* on the target system

• devicetree/bindings
  • the bindings directory has details about the syntax and expected elements for each device type representable in the dts and used by kernel frameworks and drivers

• devicetree/bindings/property-units.txt
  • how to name properties which have a unit of measure

• devicetree/bindings/resource-names
  • *-name properties containing an ordered list of names corresponding to another property’

• devicetree/bindings/vendor-prefixes.txt
  • vendor prefix registry

Some subsystems have overview bindings descriptions under devicetree/bindings/:

Other Documentation in Linux Kernel Source Tree

• devicetree/booting-without-of.txt
  • original powerpc document on booting without Open Firmware

• devicetree/changesets.txt
  • Description of changesets. Apply changes such that full set of changes is applied successfully or none are.

• devicetree/dynamic-resolution-notes.txt
  • Implementation of resolver, used when applying overlays.

• devicetree/of_unittest.txt
  • How data for device tree unit tests is added to the kernel

• devicetree/overlay-notes.txt
  • Kernel internal implementation notes on overlays

• devicetree/usage-model.txt
  • Overview of: Linux and the Device Tree

Subsystem specific

• gpio / pinctrl

• interrupts

• timers

• etc

Overlays

Mainline Linux Support

Run time overlay apply and run time overlay remove from user space are not supported in the mainline kernel. There are out of tree patches to implement this feature via an overlay manager. The overlay manager is used successfully by many users for specific overlays on specific boards with specific environments and use cases. However, there are many issues with the Linux kernel overlay implementation due to incomplete and incorrect code. The overlay manager has not been accepted in mainline due to these issues. Once these issues are resolved, it is expected that some method of run time overlay apply and overlay removal from user space will be supported by the Linux kernel.

There is a possibility that overlay apply and overlay remove support could be phased in slowly, feature by feature, as specific issues are resolved.

Boot Loader Support

An alternative to Linux kernel run time overlay apply is boot loader overlay apply. For example, U-Boot supports overlay apply. This method of overlay apply avoids the complications and issues of run time Linux kernel overlay apply. This method is likely to be more robust and less problematic than run time Linux kernel overlay apply and is thus the recommended technique.

Overlay Source Format

In early overlay days, much of the overlay metadata was hand coded in the overlay source file. The current dtc compiler in the Linux kernel source tree eliminates the need for this hand coding. It is expected that the Linux kernel overlay apply code will at some time in the future refuse to apply an overlay compiled from source with hand coded metadata. The metadata includes fragment nodes and nodes with names beginning with an underscore, such as __overlay__, __fixup__, __local_fixup__, and __symbols__.

For examples of transforming overlay source from the hand coded metadata form, see slides 29 — 34 of the ELCE 2018 Devicetree BoF [PDF].

Device Tree Source Validation

The most basic validation is warnings from the dtc compiler. Noisy checks are disabled by default. Enable the noisy checks by specifying ‘W=1’ on the make command line.

Compiling source into .dtb (FDT binary blob)

via Linux kernel make system

All configured .dtb

A specific .dtb

This is an example of compiling arch/arm/boot/dts/qcom-msm8960-cdp.dts

The make target is the name of the .dts file, with «.dts» changed to «.dtb».

Check that the config option that enables the dtb is set, for example:

Either specify the correct architecture in the make command (or export the ARCH)

via generated script in build directory

After a .dtb has been built by the Linux kernel make system, files containing the precise build commands will remain in the build directory:

FDT format

Other names for Flattened Device Tree (FDT) are «binary blob» and «.dtb».

The format of version 17 of the FDT is described in chapter 5, «Flat Devicetree Physical Structure» of the Devicetree Specification Release 0.2.

The format of version 17 of the FDT is described in chapter 8, «Flat Device Tree Physical Structure» of the ePAPR v1.1 (superseded by the Devicetree Specification).

Section «II — The DT block format» of booting-without-of is a more expansive description of the format of FDT:

Install

• make dtbs_install
  • installs in /boot/dtbs/

• many other ways to install .

Boot loaders

Booting

Debugging

• tutorials
  • «Solving Device Tree Issues» (updated), ELCE October 2015 by Frank Rowand
    • PDF slides
    • Supporting Resources (patches, etc)

• diffing .dts, .dtb, /proc/devicetree/
  • scripts/dtc/dtx_diff
    • in the Linux kernel source tree as of 4.6-rc1
    • use cases, advantages, and things to be aware of are described in «Solving Device Tree Issues» (updated), ELCE October 2015 by Frank Rowand (PDF). dtx_diff is referred to as «dtdiff» in this presentation.

• locating source file and line for nodes and properties
  • scripts/dtc/dtx_diff —annotate
    • in the Linux kernel source tree as of 5.0-rc1
    • useful for ‘dtx_diff DTx’
    • not useful for ‘dtx_diff DTx_1 DTx_2’

• boot time messages
  • device creation
  • driver registration
  • binding driver to device
  • deferred binding

Debugging — random hints

You can set CONFIG_PROC_DEVICETREE to be able to see the device tree information in /proc after booting. Build the kernel with this option set to ‘Y’, boot the kernel, then ‘cd /proc/device-tree’

For newer kernels where the CONFIG_PROC_DEVICETREE option does not exist, /proc/device-tree will be created if CONFIG_PROC_FS is set to ‘Y’.

You might also try CONFIG_DEBUG_DRIVER=Y.

Also, often, you can set the line: «#define DEBUG 1» to an individual C file, to produce add debug statements to the routines in that file. This will activate any pr_debug() lines in the source for that file.

Alternatively, you can add the following to drivers/of/Makefile:

Tools in Linux kernel source tree

dtc (in kernel)

dtc (Device Tree Compiler) — converts between the human editable device tree source «dts» format and the compact device tree blob «dtb» representation usable by the kernel or assembler source. dtc is also a dtb decompiler.

• The linux version of dtc is located in scripts/dtc/ in the kernel source directory. New versions are periodically pulled from the upstream project.
  • dtc is built by the Linux kernel build process as a dependency when needed. If you want to explicitly build it in the Linux kernel source tree, use the command: make scripts
• Information about the upstream project is in a nearby section.
  • Documentation/manual.txt Device Tree Compiler Manual
  • Documentation/dts-format.txt Device Tree Source Format
• The Maintainers are listed in the file README

dtx_diff

dtx_diff has two modes of operation:

• compare two dtX files
• compile a single dtX file (using the normal Linux includes and .config) then decompiles that into a device tree source file.

A dtX file can be a device tree source file, a device tree compiled file (aka .dtb, FDT, or device tree blob), or a file system based subtree (either /proc/device-tree on the target system, or /proc/device-tree can be tarred on the target system and untarred on the system containing dtx_diff).

Examples of how to use dtx_diff can be found in «Solving Device Tree Issues» (updated), ELCE October 2015, Frank Rowand . Note that dtx_diff was named ‘dtdiff’ in the presentation.

dtx_diff was merged in 4.6-rc1

—annotate was merged in 5.0-rc1

dt_to_config

dt_to_config is a tool to provide information about the Linux kernel configuration options needed by a given device tree.

dt_to_config can also report on whether the kernel configuration options are set correctly.

Examples of how to use dt_to_config and some limitations to be aware of can be found in «Solving Device Tree Issues — part 2», LinuxCon Japan, July 2016, Frank Rowand .

dt_to_config was merged in 4.8-rc1.

Tools external to Linux kernel source tree

dtc (upstream project)

The dtc (Device Tree Compiler) upstream project is periodically pulled into the Linux kernel source tree. The upstream project is maintained in

Info on submitting patches is in section 1.1 of Documentation/manual.txt

How to build dtc, fdtdump, and other tools in the upstream project:

dts-mode

From the github README.mkd: a quick attempt at getting basic highlighting for Device Tree syntax in emacs.

From the announcement: Today I cobbled together a rudimentary devicetree major mode for emacs. At this point it’s pretty much limited to rather basic syntax highlighting but works fairly well all things considered. It can be found on Github[1]. Patches are of course quite welcome.

Project location on [github].

I am not an emacs user, so I would appreciate any feedback on how useful this tool is and additional information that could be added to this description (or if the tool is useless and should be removed from this page). Email me at frowand (dot) list (at) gmail (dot) com

• Xilinx EDK device-tree generator — Generates an FDT from Xilinx FPGA design files.
  • http://xilinx.wikidot.com/device-tree-generator

fdtdump

fdtdump is a tool to convert an FDT (flattened device tree, aka device tree blob) to source.

The dtc compiler is an alternate tool that also has an option to convert an FDT to source (-O dts).

fdtdump differs in some ways from «dtc -O dts»:

• fdtdump prints the FDT header as a source comment.
• The format of data differs in appearance (number of hex digits printed) but both formats result in the same FDT when compiled.
• The —scan option of fdtdump will search through a file that embeds an FDT, attempting to find the FDT. The embedded FDT will be converted to dts.

An unmaintained version of the source of fdtdump existed in the Linux kernel source tree. There is no makefile entry to build fdtdump in the Linux kernel source tree. fdtdump was removed from the Linux kernel source tree in 5.11.

fdtdump is located in the dtc project and can easily be built there.

fdtoverlay

fdtoverlay is a tool created to test libfdt. It applies one or more overlay .dtb files to a base .dtb file. It appears that some people are also using fdtoverlay to apply overlays pre-boot.

fdtoverlay is located in the dtc project and can easily be built there. It is queued up to be added to the Linux kernel source tree in Linux 5.11 or 5.12-rc1.

Validation

in kernel documentation

• Writing DeviceTree Bindings in json-schema
  • how to write the binding schemas that devicetree source is validated against
• Testing
  • Dependencies
    • how to install the validation tools
  • Running Checks
    • how to run the validation tools

validation tools project

presentations

Testing

linux kernel framework

The dtc tests are located in the upstream dtc project (see dtc (upstream project)).

Each test will report PASS or FAIL.

An example test result summary is:

Other projects using Device Tree

barebox

BSD operating system

U-Boot

Zephyr

Instead of loading a DTB and parsing it at run time, Zephyr generates source files from the devicetree .dts. The resulting devicetree data file is compiled as part of the Zephyr build.

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