Understanding DTS Files: Device Tree Source in Embedded Systems

Dts Files, or Device Tree Source files, are fundamental components in embedded Linux systems, specifically for describing hardware configurations. These human-readable text files provide a structured way to represent the hardware components connected to a system’s processor, allowing the Linux kernel to understand and interact with the hardware without requiring hard-coded device information.

What is a DTS File? A Deep Dive into Device Tree Source

A DTS file essentially acts as a hardware map for the Linux kernel. It defines various aspects of the hardware, including:

• Processors: Type, number of cores, clock speed.
• Memory: RAM size, location, and configuration.
• Peripherals: UART, I2C, SPI, GPIO, and other interfaces, along with their addresses and interrupt settings.
• Buses and Interconnections: How different components are connected.

This structured description enables a single Linux kernel image to boot and function correctly on different hardware platforms without modification. The kernel parses the DTS file during boot time to determine the hardware present and configure itself accordingly.

Types of DTS Files: DTS vs. DTSI

There are two primary types of DTS files:

• .dts (Device Tree Source): This file describes the hardware configuration of a specific platform or board. It contains a complete description of all the hardware components on that particular system.
• .dtsi (Device Tree Source Include): This file contains hardware descriptions that are common to multiple platforms. It allows for code reuse and simplifies the maintenance of DTS files by centralizing common configurations. .dts files can then #include these .dtsi files to inherit their common settings.

Think of .dtsi files as templates or building blocks for hardware descriptions, while .dts files represent the final, specific configuration for a particular board.

DTS Files in Practice: The ConnectCore 6 Plus Example

Let’s examine a real-world example with the ConnectCore 6 Plus system-on-module (SOM) and its associated single-board computer (SBC).

The ConnectCore 6 Plus SOM integrates various components like the NXP i.MX 6QuadPlus processor, memory, and communication interfaces. Since it’s a module designed to be used on different carrier boards, its hardware is described in .dtsi files to accommodate variations:

• imx6qp-ccimx6.dtsi: Defines the common hardware for ConnectCore 6 Plus variants with different CPUs.
• imx6qp-ccimx6-wb.dtsi: Describes the variant with wireless and Bluetooth capabilities.

The ConnectCore 6 Plus SBC, a carrier board for the SOM, has its own .dts file. This file includes the relevant ConnectCore 6 Plus .dtsi file based on the specific SOM variant used, and adds descriptions for the SBC’s unique hardware like HDMI, Ethernet, and audio. This hierarchical structure allows for efficient management of hardware configurations.

Conclusion: The Importance of DTS Files in Embedded Systems

DTS files play a critical role in the development and deployment of embedded Linux systems. They provide a flexible and maintainable way to describe hardware configurations, enabling a single kernel image to support a wide range of platforms. Understanding the structure and purpose of DTS files is essential for anyone working with embedded Linux development. Their hierarchical nature, utilizing both .dts and .dtsi files, promotes code reuse and simplifies the process of adapting to different hardware revisions or custom designs.