Custom Linux Kernel Drivers

This repository contains a collection of simple Linux kernel modules and character device drivers, primarily for educational purposes and targeted at the BeagleBone Black (ARM architecture). Each subfolder is a self-contained kernel module project with its own source and Makefile.

Contents

001-hello-world

A minimal kernel module that prints a message when loaded and unloaded. Useful as a first test of kernel module development and cross-compilation.

• Source: main.c
• Build:

  make

• Description:
  • Prints a greeting to the kernel log on insertion and a farewell on removal.
  • Demonstrates the basics of module_init/module_exit.

002-pseudo-char-driver

A simple pseudo character device driver that implements open, read, write, lseek, and release operations.

• Source: main.c
• Build:

  make

• Description:
  • Allocates a 512-byte buffer as device memory.
  • Registers a single character device with the kernel.
  • Supports basic file operations from userspace.
• Usage:
  • After inserting the module, a device node (e.g., /dev/pcd_devices) will be created.
  • You can read/write to the device using standard tools:

    echo "HELLO THERE" | sudo tee /dev/pcd_devices
    cat /dev/pcd_devices

003-pseudo-char-driver-multi-device

A more advanced pseudo character driver that supports multiple devices, each with its own buffer, permissions, and serial number.

• Source: pcd_n.c
• Build:

  make

• Description:
  • Creates 4 character devices (e.g., /dev/pcdev-1, /dev/pcdev-2, ...).
  • Each device has different buffer sizes and permissions (read-only, write-only, read-write).
  • Demonstrates handling multiple devices and device-specific data in a single driver.

Building the Drivers

All Makefiles are set up for cross-compiling for ARM (BeagleBone Black). You may need to adjust the KERN_DIR variable in the Makefiles to point to your kernel source tree.

• To build for ARM:

  make

• To build for the host (your current Linux machine):

  make host

• To clean build artifacts:

  make clean

Prerequisites

• Linux kernel headers/source for your target platform
• ARM cross-compiler (e.g., arm-linux-gnueabihf-gcc)
• Sufficient privileges to insert/remove kernel modules (usually sudo)

License

All code is licensed under the GPL. See individual source files for author information.

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Happy hacking with Linux device drivers!