ioctl Device Example

Description

Character device demonstrating ioctl (input/output control) commands for device configuration.

Features

• Reset device to default state
• Get/set single values
• Get/set complex configuration structures
• Input validation
• Shared header between kernel and userspace

Build

make  # Builds both kernel module and test program

Test

# Load module
sudo insmod ioctl_device.ko

# Run test program
./test_ioctl

# Expected output shows all tests passing

# Unload module
sudo rmmod ioctl_device

Manual Testing

# You can also test manually using the test program
./test_ioctl

# Or use ioctl from other programs
# See test_ioctl.c for example usage

ioctl Commands

Command	Type	Description
IOCTL_RESET	_IO	Reset device to defaults
IOCTL_GET_VALUE	_IOR	Read current value
IOCTL_SET_VALUE	_IOW	Write new value (0-1000)
IOCTL_GET_CONFIG	_IOR	Read full configuration
IOCTL_SET_CONFIG	_IOW	Write full configuration

Configuration Structure

struct ioctl_config {
    int value;      // Device value (0-1000)
    int speed;      // Speed setting
    char name[32];  // Device name
    bool enabled;   // Enable flag
};

Learning Points

• ioctl command encoding (_IO, _IOR, _IOW)
• Magic numbers for command validation
• Copying data to/from userspace
• Input validation
• Shared header files