Essential Linux Device Drivers

Appendix C. Seq Files

Monitoring and trending data points offered by procfs might help diagnose device driver problems when the cause of a symptom looks fuzzy. But sometimes, especially when the amount of data is large, the corresponding procfs read() implementations become complex. The seq file interface is a kernel helper mechanism designed to simplify such implementations. Seq files render procfs operations cleaner and easier.

Let’s gradually introduce complexities to a procfs read() routine and see how the seq file interface transforms the labored routine into a graceful one. We’ll also update one of the few remaining 2.6 drivers that does not yet leverage seq files.

The Seq File Advantage

Let’s discover the advantages offered by seq files ...