This is a sample OS/2 audio PDD.  It works fine for straight OS/2 support (made esp. for DART full-duplex).  Chipsets supported are CS4231, 4232, 4236, 4236B, 4237B, 4238B, Yamaha OPL3-SA3 (YMF715), and other compatibles. It works in mode 2.  The chipset dependency is restricted to just a module or two, and can be extended if you have any idea on what's going on.  This source is to be used only as a guide for making OS/2 audio drivers.