Appendix B: Kernel Interfaces

Choosing the right interface for exposing driver functionality.

Decision Guide

flowchart TB
    Q["Need to expose something?"]
    Q --> Q1{"For users or debugging?"}
    Q1 -->|Users| Q2{"Device config or generic?"}
    Q1 -->|Debugging| DEBUGFS["debugfs"]
    Q2 -->|Device config| SYSFS["sysfs<br/>(DEVICE_ATTR)"]
    Q2 -->|System-wide| PROCFS["procfs<br/>(if legacy)"]
    Q2 -->|User-configurable| CONFIGFS["configfs"]

    style SYSFS fill:#7a8f73,stroke:#2e7d32
    style DEBUGFS fill:#738f99,stroke:#0277bd

Quick Comparison

Interface	Use For	Stable ABI?	Example
sysfs	Device attributes	Yes	/sys/class/leds/*/brightness
debugfs	Debug info, testing	No	/sys/kernel/debug/my_driver/
procfs	System/process info	Yes (legacy)	/proc/cpuinfo
configfs	User-defined objects	Yes	/sys/kernel/config/usb_gadget/

Recommendations

Scenario	Use
Device-specific attribute	sysfs (DEVICE_ATTR)
Hardware register dump	debugfs
Debug statistics	debugfs
New system info	sysfs (avoid procfs for new code)
User creates objects	configfs

Chapters

Chapter	What You’ll Learn
sysfs	DEVICE_ATTR, attribute groups
debugfs	Debug interfaces

Example

• sysfs Demo - Driver with custom attributes

Further Reading

• sysfs
• debugfs
• configfs

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Table of contents

• B.1 sysfs
• B.2 debugfs