This chapter is the second case study in this book. In this chapter, we’ll go through
lpt(4), the parallel port printer driver.
lpt(4), by default, is configured to be interrupt-driven, which gives us an opportunity to go through a nontrivial interrupt handler. Aside from this, I chose to profile
lpt(4) because it uses almost every topic described in the previous chapters. It’s also relatively short.
To improve readability, some of the variables and functions presented in this chapter have been renamed and restructured from their counterparts in the FreeBSD source.
Example 9-1 provides ...