## Virtual Device Driver Reference for OS/2

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### VDHOpenPDD - Parameters

DeviceName (PSZ) Pointer to the device name of the physical device driver to open.

VDDEntryPoint (FPFNVDD) Virtual device driver entry point for use by the physical device driver. Since physical device drivers are 16:16 modules, this is a 16:32 entry point.

The interface for the VDDEntryPoint:

     USHORT VDDENTRY VDDEntryPoint (ulFunc, ul1, ul2)

     ENTRY

         ULONG ulFunc - function code

               All function codes are private to a physical device driver/

               virtual device driver pair.

         ULONG ul1 - function/specific;

               If a pointer, it is 16:16, and will generally be an input packet

         ULONG ul2 - function/specific;

               If a pointer, it is 16:16, and will generally be an output packet

     EXIT-SUCCESS  Returns !0

     EXIT-FAILURE  Returns 0

rc (FPFNPDD) - returns

Success If the function is successful, it returns a pointer to the physical device driver Inter-Device-Driver Communication (IDC) function. See " RegisterPDD" in the OS/2 Physical Device Driver Reference for a description of the physical device driver's IDC function.

Failure If the function fails, it returns 0 (zero). VDHGetError should be called to determine the nature of the problem.