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Linux/Device_Driver/1 LDD Introduction/README.md

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+# Linux Device Driver – Part 1: Introduction
+- This repository contains notes and example code for learning the basics of Linux device drivers, focusing on how drivers integrate with the Linux kernel and user space.
+
+## What is a Device Driver?
+- A device driver is a piece of software that lets the operating system communicate with hardware devices.  
+- In Linux, many drivers are built into the kernel or loaded as kernel modules, allowing hardware to be
+  controlled via standard interfaces.
+
+## Types of Linux Device Drivers
+
+Common categories of Linux device drivers include:
+
+- **Character drivers** – Accessed as streams of bytes (for example `/dev/ttyS0` for serial ports)  
+- **Block drivers** – Handle data in blocks and are used for storage devices  
+- **Network drivers** – Interface network hardware with the kernel’s networking stack
+
+This introduction usually starts with character drivers because they are simpler conceptually.
+
+## Kernel Space vs User Space
+
+Linux clearly separates:
+
+- **User space** – Where normal applications run, with restricted access
+- **Kernel space** – Where the kernel and drivers run, with full access to hardware and system resources
+
+A device driver typically runs in kernel space and exposes an interface (often via `/dev` files or sysfs) that user-space programs can use.
+
+## Loadable Kernel Modules (LKM)
+
+Instead of compiling every driver into the kernel, Linux supports **loadable kernel modules**:
+
+- Drivers can be compiled as modules
+- Modules can be inserted (`insmod`/`modprobe`) and removed (`rmmod`) at runtime
+- `dmesg` and `/var/log` can be used to inspect kernel messages from drivers
+
+This introduction often walks through how to build a simple module, load it, and see messages using `dmesg`.
+
+## Basic Steps to Write a Simple Driver Module
+
+Typical steps you will follow in this series:
+
+1. Write a minimal C file that defines `init` and `exit` functions for the module  
+2. Use `module_init()` and `module_exit()` macros to register these functions  
+3. Add a `Makefile` that uses the kernel build system to compile the module  
+4. Build the module against your current kernel headers  
+5. Load the module and verify its messages in the kernel log  
+6. Unload the module cleanly
+
+## Prerequisites
+
+Before following along:
+
+- Basic knowledge of C programming  
+- A Linux environment (for example, Ubuntu) with kernel headers installed  
+- Ability to use the terminal and run basic compilation commands
+
+REFER: 
+- https://github.com/darshankharbikar/raspberry-pi-4b
+- https://embetronicx.com/tutorials/linux/device-drivers/setup-ubuntu-and-raspberry-pi-linux-device-driver-tutorial/