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Repair Windows errors before they cause bigger problemsFix Now →Scan for outdated or missing drivers - takes under a minuteDriver Scan →A Linux device tree describes the hardware in a particular system so the kernel can identify and configure it. You usually write the description in Device Tree Source (DTS), compile it into a Device Tree Blob (DTB), and have a bootloader pass that binary to the kernel. Bindings define how hardware and its connections must be represented; overlays let supported systems add or change parts of a base tree.
“Device Tree for Dummies” is the title of an introductory presentation by Thomas Petazzoni, rather than a verified commercial For Dummies book. Its subject remains useful for anyone learning how Linux represents hardware.
What is a device tree in Linux?
A device tree is structured data describing a computer’s hardware and how its components connect. Linux uses that description to learn about a platform without requiring every board-specific hardware detail to be built into machine-specific kernel code. This helps one kernel support multiple hardware configurations.
It is a description of the hardware, not a general-purpose file for choosing runtime preferences. Petazzoni characterizes it as “a hardware description language” that should describe “the hardware layout, and how it works.” Those words come from his presentation, not a current standard. Read the presentation. For a technical overview, see Toradex’s Device Tree Technical Overview.
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How DTS, DTB, the bootloader, and the kernel fit together
Device Tree Source (DTS) is the human-readable source format developers edit. A compiler turns it into a Device Tree Blob (DTB), the binary form commonly supplied to the Linux kernel by the bootloader. The kernel then uses the description while bringing up the platform and its devices.
The exact source files, build command, bootloader settings, and file locations depend on the board and its software. There is no safe universal command sequence: follow the current documentation for your board, firmware, and kernel rather than assuming an example for another platform applies.
What are device-tree bindings?
A binding defines how a type of hardware must be represented in the tree: which properties are expected and how connections such as buses, interrupts, and GPIO lines are described. Bindings help keep the device description consistent with what the relevant Linux driver expects.
When adding a component, look for an existing binding and use its property names and permitted values. A syntactically valid tree can still fail to describe a device correctly if its properties do not match the binding or the driver’s expectations.
What is a device-tree overlay?
An overlay is a partial device-tree fragment that extends or modifies a base tree. Rather than describing an entire platform, it can add information about a particular add-on or change selected nodes. Raspberry Pi’s HAT guide illustrates a boot-time approach: firmware reads an overlay and merges it into the system tree passed to Linux. Its examples include I2C, SPI, I2S, LEDs, and buttons. See the Raspberry Pi HAT Device Tree Blob guide.
That guide describes a Raspberry Pi workflow, not a universal overlay specification. An overlay can describe hardware connections, but it cannot provide a missing driver. The target firmware, kernel, and driver must support the hardware for it to work.
How to approach a first device-tree change
- Identify the target platform. Confirm the exact board, firmware or bootloader, operating system, and kernel version, then consult that platform’s current instructions.
- Find the existing description and binding. Check how similar hardware is represented and whether the relevant driver supports the component and its connections.
- Choose the right scope. Update the platform’s base tree when changing its hardware description; use an overlay only when the platform’s firmware and software support that mechanism.
- Compile and validate using the platform’s documented workflow. DTS-to-DTB steps and validation options vary; use the commands and locations specified for the target rather than copying a board-specific recipe blindly.
- Test on the target system. Confirm that the boot process supplies the intended tree and that Linux recognizes the device. If it does not, check the binding properties, connections, firmware support, and driver availability.
What the “Device Tree for Dummies” presentation covers
Thomas Petazzoni’s introductory presentation, delivered under the Free Electrons name, sets out three goals: boot a system with a device tree, understand basic syntax, and learn bindings and their rules. Its event description also identifies compilation and the interaction between bootloader and kernel as topics. The slides are an introduction, not a substitute for current board-specific documentation.
The presentation is available as a PDF: Device Tree for Dummies by Thomas Petazzoni. The event schedule describes it as a newcomer-focused talk covering what a device tree is, how it is written and compiled, bootloader/kernel interaction, and binding documentation: Embedded Linux Conference Europe 2013 schedule.
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