In computing, a device tree is a data structure describing the hardware components of a particular computer so that the operating system's kernel can use and manage those components, including the CPU or CPUs, the memory, the buses and the peripherals. The device tree was derived from SPARC-based workstations and servers via the Open Firmware project. The current Devicetree specification is targeted at smaller systems, but is still used with some server-class systems. Personal computers with the x86 architecture generally do not use device trees, relying instead on various auto configuration protocols to discover hardware. Systems which use device trees usually pass a static device tree to the operating system, but can also generate a device tree in the early stages of booting. As an example, Das U-Boot and kexec can pass a device tree when launching a new operating system. On systems with a boot loader that does not support device trees, a static device tree may be installed along with the operating system; the Linux kernel supports this approach. The Devicetree specification is currently managed by a community named devicetree.org, which is associated with, among others, Linaro and Arm.
Given the correct device tree, the same compiled kernel can support different hardware configurations within a wider architecture family. The Linux kernel for the ARC, ARM, C6x, H8/300, MicroBlaze, MIPS, NDS32, Nios II, OpenRISC, PowerPC, RISC-V, SuperH, and Xtensa architectures reads device tree information; on ARM, device trees have been mandatory for all new SoCs since 2012. This can be seen as a remedy to the vast number of forks that have historically been created to support different ARM boards. The purpose is to move a significant part of the hardware description out of the kernel binary, and into the compiled device tree blob, which is handed to the kernel by the boot loader, replacing a range of board-specific Csource files and compile-time options in the kernel. It has been customary for ARM-based Linux distributions to include a boot loader, that necessarily was customised for specific boards, for example Raspberry Pi or Hackberry A10. This has created problems for the creators of Linux distributions as some part of the operating system must be compiled specifically for every board variant, or updated to support new boards. However, some modern SoCs have a vendor-provided boot loader with device tree on a separate chip from the operating system. A proprietary configuration file format used for similar purposes, the FEX file format, is a de facto standard among Allwinner SoCs.
Usage in Windows
In Windows, a device tree is maintained by the Plug-and-Play manager to evaluate things like whether devices can be safely ejected.
