Day 21 - Cache Mechanism for hwmon Driver

Summary

Implemented a cache layer in the I2C hwmon driver to reduce unnecessary hardware access.

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What I Did

• Added cache fields:
• temp_mc_cached
• last_update
• cache_interval_ms
• Implemented update_if_needed()
• Modified read path to use cached data
• Added sysfs control: cache_interval

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Key Insight

Previously:

read → always I2C

Now:

read → cache → (optional I2C)

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Verification

Tested with different cache intervals:

• 0 ms → always update
• 200 ms → update every ~2 reads
• 1000 ms → almost no updates

Observed expected behavior.

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Reflection

This change is small in code, but significant in design.

It introduces:

• time-based logic
• state management
• performance optimization

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Conclusion

Driver evolved from:

• functional → optimized
• passive → decision-making

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