## Virtual Device Driver Reference for OS/2

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### VDHDevIOCtl - Parameters

DevHandle (HFILE) Device handle returned by VDHOpen or VDHPhysicalDisk.

Category (ULONG) Category of function performed.

Function (ULONG) Function within category performed.

ParmList (PVOID) Pointer to the command-specific input parameter area.

ParmLengthMax (ULONG) Maximum size of the application input parameter area, in bytes. ParmLengthInOut can be longer than this on input, but not on output.

ParmLengthInOut (PULONG) Pointer to the length (in bytes) of the parameters passed by the caller in ParmList.

DataArea (PVOID) Pointer to the data area.

DataLengthMax (ULONG) Maximum size of the application data area, in bytes.

DataLengthInOut (PULONG) Pointer to the length (in bytes) of the parameters passed by the caller in ParmList. ParmLengthInOut can be longer than this on input, but not on output.

rc (HFILE) - returns

Success If the function is successful, it returns a nonzero value.

Failure If the function fails, it returns 0. VDHGetError should be called to determine the nature of the problem. VDHGetError can return the following errors:

ERROR_INVALID_HANDLE
ERROR_INVALID_FUNCTION
ERROR_INVALID_CATEGORY
ERROR_INVALID_DRIVE
ERROR_INVALID_PARAMETER.

If the function is called when not at DOS session-task time, a system halt occurs.