OS X and iOS Kernel Programming

Mac OS X Serial Port Architecture Overview

On Mac OS X, serial ports have an interesting architecture. In the kernel, a serial driver is implemented using the object-oriented I/O Kit framework, but in user space it is accessed through the BSD layer, and the serial port is presented as a traditional UNIX device file. For each serial driver that is loaded in the kernel, the I/O Kit's serial family creates a corresponding device object in the /dev directory of the file system. To interact with a serial port, applications open the device file and read and write to it as if it were an ordinary file. This is an alternative to communicating with a driver through a user client; in fact, serial drivers don't have a user client. The advantage of this architecture ...