Writing Character Drivers

Purpose

Guide agents through Linux character device implementation: struct file_operations, cdev registration, safe userspace copies, ioctl design, and basic mmap — focused depth beyond skills/kernel/device-drivers.

When to Use

• Exposing hardware to /dev/mydev
• Implementing read/write/poll from kernel
• Defining ioctl commands with type-safe macros
• Mapping device MMIO to userspace (carefully)

Workflow

1. Char device registration