I/O Control:-


A user program can send commands to a device via ioctl () calls. When an application opens a serial device, it can usually issue three classes of ioctls to it:

1. Commands supported by the serial device driver, such as TIOCMSET that sets modem information.

2. Commands supported by the tty driver, such as TIOCSETD that changes the attached line discipline.

3. Commands supported by the attached line discipline, such as a command to reset the touch controller in the case of N_TCH.

The ioctl () implementation for N_TCH is largely standard. Supported commands depend on the protocol described in the touch controller's data sheet.