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Introduction to Linux Device Drivers

May 21, 2025

Linux Device Drivers Tutorial | Linux Drivers and Kernel Modules

Introduction

  • Focus on character drivers and their implementation.
  • Provides easy and practical examples for understanding device drivers in Linux.

What is Linux?

  • A free, open-source operating system based on UNIX.
  • Created in 1991 by Linus Torvalds.
  • Supports various distributions for computers and other devices.

Linux Architecture

  • Divided into User Space and Kernel Space.
  • Kernel Space: where the core of the operating system executes and provides its services.
  • User Space: where user applications are executed.
  • Interaction through a System Call Interface.

Linux Kernel Modules

  • Pieces of code that can be loaded and unloaded into the kernel on demand.
  • Extends kernel functionality without rebooting.

Methods to Add Custom Codes

  1. Add code to the kernel source tree and recompile.
  2. Loadable Kernel Modules (LKMs): add code at runtime without recompiling the kernel.

Types of Loadable Kernel Modules

  1. Device drivers
  2. Filesystem drivers
  3. System calls

Advantages of LKMs

  • Avoids frequent kernel rebuilds when adding new devices.
  • Flexibility in loading/unloading modules.
  • Helps in saving memory and keeping the base kernel error-free.

Differences Between Kernel Modules and User Programs

  • Address Spaces: Kernel modules run in kernel space; user programs run in user space.
  • Execution Privileges: Kernel modules have higher privileges.
  • Execution Order: User programs execute sequentially; kernel modules do not.
  • Header Files: Use different header files than user programs.

Kernel Drivers vs. Kernel Modules

  • Kernel Module: Compiled code inserted at runtime (e.g., using insmod).
  • Driver: Code in the kernel to communicate with hardware.

Linux Device Drivers

  • Software enabling interaction with hardware devices.
  • OS-specific and hardware-dependent.
  • Acts as a translator between hardware devices and operating systems.

Types of Linux Device Drivers

  1. Character Device: Reads/writes data character by character (e.g., keyboard, mouse).
  2. Block Device: Reads/writes data in blocks (e.g., HDD, USB).
  3. Network Device: Sends/receives data packets (e.g., Ethernet card).

Key Questions

  • What is a Linux Device Driver?: Software component for OS and hardware interaction.
  • User Space vs. Kernel Space: User space for applications; kernel space for OS core functions and drivers.
  • Are Device Drivers OS-specific?: Yes, they are OS-specific.
  • Where to find more tutorials?: Available on various platforms including EmbeTronicX and video platforms like YouTube.