Summary

In this chapter, we covered an important aspect of device driver authors – how exactly you can interface between user and kernel  (driver) space. We walked you through several interfacing methods; we began with an older one, which is interfacing via the venerable proc filesystem (and then mentioned why it's not the preferred method for driver authors). We then moved on to interfacing via the newer 2.6-based sysfs. This turns out to be the preferred interface for the user space, at least for a device driver. Sysfs has limitations, though (recall the one-value-per-sysfs-file rule). Thus, using the completely free-format debugfs interfacing technique makes writing debug (and other) interfaces very simple and powerful indeed. The netlink socket is a powerful interfacing technology and is used by the network subsystem, udev, and a few drivers; it does require some knowledge on socket programming and the kernel socket buffer, though. To perform generic command...