Connecting to a Parallel Device
A client uses the IOCTL_INTERNAL_PARCLASS_CONNECT request to obtain a PARCLASS_INFORMATION structure that contains:
I/O resources allocated to the parallel port
Hardware capabilities of the parallel port
Pointers to callback routines that a kernel-mode driver can use to set the IEEE 1284 operating modes for a parallel device - see Setting and Clearing a Communication Mode for a Parallel Device
Pointers to callback routines that a kernel-mode driver can use to read and write a parallel device - see Reading and Writing a Parallel Device.
The callback routines provide functionality that a typical function driver needs. Using the callback routines is more efficient than using equivalent device control requests.
A client disconnects from a device by using a IOCTL_INTERNAL_PARCLASS_DISCONNECT request.