Chapter 6. Case Study: Virtual Null Modem
This chapter is the first of several case studies that’ll guide you through a real-world device driver. The purpose of these case studies is to expose you to genuine driver code—warts and all—and to consolidate the information presented in earlier chapters.
In this chapter, we’ll go through nmdm(4), the virtual null modem terminal driver. This driver creates two tty(4) devices that are connected by a virtual null modem cable. In other words, the output of one tty(4) device is the input for the other tty(4) device, and vice versa. I chose to profile nmdm(4) because it uses event handlers, callouts, and taskqueues, ...
Get FreeBSD Device Drivers now with the O’Reilly learning platform.
O’Reilly members experience books, live events, courses curated by job role, and more from O’Reilly and nearly 200 top publishers.
