The preferred method is to buy the OS/2 device driver kit (DDK) from IBM. It contains samples for display, printer, SCSI, and other drivers. You can develop kernel and PM drivers. NOTE: The kernel debugger comes with the IBM Toolkit, sold separately.
There's a book called Writing OS/2 2.0 Device Drivers in C from Van Nostrand-Reinhold and also IBM's flood of printed material.
As reference to SCSI programming, check SCSI Programming FAQ, available
at ftp.regent.e-technik.tu-muenchen.de
RelatedInformation :
What are good reference books
for programming in OS/2 and PM?