Day 8 - Linux Device Model & Device Tree

Summary

Today I learned how Linux manages hardware using a structured model.

Instead of directly accessing hardware, Linux uses:

Bus <-> Device <-> Driver

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Key Concepts

Device Model

• Devices and drivers are separated
• Matching happens through bus
• probe() is called after matching

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Platform Driver

• Used for fixed hardware in embedded systems
• Created from Device Tree

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Device Tree

• Describes hardware layout
• Not part of driver logic
• Enables driver reuse

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sysfs vs dev

• /dev → user interface
• /sys → kernel device structure
• /proc/device-tree → hardware description

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Hands-on Observations

• Found many buses in /sys/bus
• Explored platform devices and drivers
• Confirmed test-device@0 exists in:
• /proc/device-tree
• /sys/bus/platform/devices

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Important Insight

Even without a driver:

Device Tree → platform device (exists)
Driver → not yet attached

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Issues & Notes

• dtc shows many warnings when dumping live DT
• warning about test-device@0 due to missing reg
• naming should be improved

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Conclusion

• Linux driver is not standalone
• Device Tree plays a critical role
• sysfs is essential for debugging

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Next Step

Convert test-device into a platform driver and trigger probe()