Device Tree Reference

Reference Manual

Device Tree Usage

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

It walks through how to write a device tree for a new machine.

It is intended to provide an overview of device tree concepts and how they are used to describe a machine.

Device Tree Source

• Power.org Standard for Embedded Power Architecture Platform Requirements (ePAPR) v1.1
  • 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
• xxx differences between ePAPR and the Linux dtc compiler

• presentations

Subsystem specific

• gpio / pinctrl

• interrupts

• timers

• etc

Compiling .dtb (FDT binary blob)

• via kernel make system
  • all configured .dtb
    • make dtbs
  • specific .dtb
    • make arch/arm/boot/dts/qcom-apq8074-dragonboard.dtb

• via generated script in build directory
  • arch/arm/boot/dts/.*.dtb.cmd
  • arch/${ARCH}/boot/dts/.*.dtb.cmd

• Documentation/manual.txt Device Tree Compiler Manual

install

• make dtbs_install
  • installs in /boot/dtbs/<kernel version> ???? -- is this useful ???

• many other ways to install ....

debugging

• tutorials
  • "Solving Device Tree Issues" (updated), LinuxCon North America August 2015 by Frank Rowand
    • PDF slides
    • Supporting Resources (patches, etc)

• diffing .dts, .dtb, /proc/devicetree/

• locating source location for properties

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

Glossary

• .dtb
• .dts
• Binary Blob
• EDT Expanded Device Tree
• FDT Flattened Device Tree