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.