Technology Sharing: Linux DTS Application and Practice Guide

Technical Sharing: Linux DTS Application and Practice Guide

With the widespread application of Linux in embedded systems, Device Tree (Device Tree) serves as a description Tools for hardware device information and resource allocation are becoming increasingly important. In the Linux kernel, Device Tree source files are usually called DTS (Device Tree Source) files. This article will delve into the application and practice guide of Linux DTS, and help readers better understand and use Device Tree through specific code examples.

1. What is Device Tree?

Device Tree is a data structure format used in the Linux kernel to describe hardware platform information. It separates the description information of hardware devices and resources from the kernel source code and exists in the form of a text file similar to a tree structure. When Linux starts, the Bootloader loads the Device Tree file into memory and passes it to the Linux kernel. The kernel initializes the device and allocates resources based on the contents of the Device Tree file at startup.

2. Composition of Device Tree

1. Node: Device Tree organizes information about hardware devices in units of nodes. In Device Tree, each device corresponds to a node. . Each node describes the type, address, interrupt and other information of the device through keywords and attributes.
2. Node properties (Property): Node properties can include specific information about the device, such as device address, interrupts, register addresses, etc. Attributes exist in the form of key-value pairs and describe various characteristics of the device through nodes.
3. include directive: You can use the include directive in a Device Tree file to reference other Device Tree files to facilitate organization and reuse of device description information.

3. How to write a Device Tree file

Next we use a simple example to show how to write a simple Device Tree file to describe an LED device. Assuming the LED is connected to the GPIO1_1 pin, the physical address of GPIO1_1 is 0x44.

First, create a new Device Tree file led.dts with the following content:

/dts-v1/;

/ {
    compatible = "my_led";
    led {
        compatible = "gpio-led";
        status = "okay";

        gpios = <0x1 0x1 0>;
        label = "led_1";
    };
};

In this Device Tree file, we define an LED node, which includes some basic functions of LED. Information, such as the GPIO pin to which the LED is connected, the label of the LED, etc.

4. How to compile and use Device Tree files

In the source code directory of the Linux kernel, there is usually an arch/arm/boot/dts/ directory. We can put the written Device Copy the Tree file led.dts to this directory.

Next, execute the following command in the root directory of the Linux kernel source code to compile the Device Tree file:

make dtbs

After the compilation is completed, a led.dtb file will be generated. This file is the compiled Binary Device Tree file.

During the boot process, the Bootloader needs to load this led.dtb file and pass it to the kernel so that the kernel can initialize the LED device based on the hardware information described in the file.

5. Practice Guide

1. Understand device tree specifications: When writing Device Tree files, you need to follow the device tree specifications and understand the meanings of various attributes and keywords of nodes in order to Make sure the description is accurate.
2. Debugging and verification: After writing the Device Tree file, you can use the device tree interpreter (dtc) tool to verify whether the syntax of the file is correct. You can use this tool to view the contents of the Device Tree file through disassembly.
3. Flexible configuration: Device Tree files can be flexibly configured and modified according to changes in specific hardware platforms to adapt to the needs of different hardware devices.

Through the above practical guide and specific code examples, I hope readers can better understand and use Linux DTS, flexibly configure and manage hardware devices, and improve the stability and maintainability of embedded systems.

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