BOOL DeviceIoControl(
  HANDLE hDevice,              // handle to device of =
interest
  DWORD dwIoControlCode,       // control code of =
operation to perform
  LPVOID lpInBuffer,           // pointer to buffer =
to supply input data
  DWORD nInBufferSize,         // size, in bytes, =
of input buffer
  LPVOID lpOutBuffer,          // pointer to buffer =
to receive output data
  DWORD nOutBufferSize,        // size, in bytes, =
of output buffer
  LPDWORD lpBytesReturned,     // pointer to =
variable to receive byte count
  LPOVERLAPPED lpOverlapped    // pointer to structure for =
asynchronous operation
);

Parameters

hDevice=20

Handle to the device that is to perform the operation. Call the = CreateFile=20 function to obtain a device handle.=20

dwIoControlCode=20

Specifies the control code for the operation. This value = identifies the=20 specific operation to be performed and the type of device on which = the=20 operation is to be performed. The following values are defined:=20

Value	Meaning
FSCTL_ALLOW_EXTENDED_DASD_IO	Signals the file system driver not to = perform any=20 I/O boundary checks on partition read or write calls. = Instead,=20 boundary checks are performed by the device driver. =
FSCTL_DELETE_REPARSE_POINT	Deletes a reparse point for a file or = directory.
FSCTL_DISMOUNT_VOLUME	Dismounts a volume.
FSCTL_ENABLE_UPGRADE=20	Enables or disables upgrading an NTFS volume = to=20 NTFS version 5.
FSCTL_GET_COMPRESSION	Obtains the compression state of a file or=20 directory
FSCTL_GET_HFS_INFORMATION	Returns Macintosh Finder information about = the=20 file associated with the input handle.
FSCTL_GET_REPARSE_POINT	Returns reparse point data for a file or=20 directory.
FSCTL_LOCK_VOLUME	Locks a volume.
FSCTL_QUERY_ALLOCATED_RANGES	Scans a file for ranges of the file for = which disk=20 space is allocated.
FSCTL_QUERY_FAT_BPB	Returns the first 36 bytes of a FAT16 or = FAT12=20 volume.
FSCTL_READ_COMPRESSION	Reserved for future use.
FSCTL_SET_COMPRESSION	Sets the compression state of a file or=20 directory.
FSCTL_SET_REPARSE_POINT	Sets a reparse point on a file or = directory.
FSCTL_SET_SPARSE	Marks a file as a sparse file.
FSCTL_SET_ZERO_DATA	Sets a range of a files bytes to = zeroes.
FSCTL_UNLOCK_VOLUME	Unlocks a volume.
FSCTL_WRITE_COMPRESSION	Reserved for future use.
IOCTL_DISK_CHECK_VERIFY	Obsolete. Use = IOCTL_STORAGE_CHECK_VERIFY
IOCTL_DISK_EJECT_MEDIA	Obsolete. Use = IOCTL_STORAGE_EJECT_MEDIA
IOCTL_DISK_FORMAT_TRACKS	Formats a contiguous set of disk = tracks.
IOCTL_DISK_GET_DRIVE_GEOMETRY	Obtains information on the physical disk's=20 geometry.
IOCTL_DISK_GET_DRIVE_LAYOUT	Provides information about each partition on = a=20 disk.
IOCTL_DISK_GET_MEDIA_TYPES	Obsolete. Use = IOCTL_STORAGE_GET_MEDIA_TYPES
IOCTL_DISK_GET_PARTITION_INFO	Obtains disk partition = information.
IOCTL_DISK_LOAD_MEDIA	Obsolete. Use = IOCTL_STORAGE_LOAD_MEDIA
IOCTL_DISK_MEDIA_REMOVAL	Obsolete. Use = IOCTL_STORAGE_MEDIA_REMOVAL
IOCTL_DISK_PERFORMANCE	Provides disk performance = information.
IOCTL_DISK_REASSIGN_BLOCKS	Maps disk blocks to spare-block = pool.
IOCTL_DISK_SET_DRIVE_LAYOUT	Partitions a disk.
IOCTL_DISK_SET_PARTITION_INFO	Sets the disk partition type.
IOCTL_DISK_VERIFY	Performs logical format of a disk = extent.
IOCTL_SERIAL_LSRMST_INSERT	Enables or disables placement of a line and = modem=20 status data into the data stream.
IOCTL_STORAGE_CHECK_VERIFY	Checks for change in a removable-media = device.
IOCTL_STORAGE_EJECT_MEDIA	Ejects media from a SCSI device.
IOCTL_STORAGE_GET_MEDIA_TYPES	Obtains information about media = support.
IOCTL_STORAGE_LOAD_MEDIA	Loads media into a device.
IOCTL_STORAGE_MEDIA_REMOVAL	Enables or disables the media eject=20 mechanism.

For more detailed information on each control code, see its = topic. In=20 particular, each topic provides details on the usage of the=20 lpInBuffer, nInBufferSize, lpOutBuffer,=20 nOutBufferSize, and lpBytesReturned parameters.

lpInBuffer=20

Pointer to a buffer that contains the data required to perform = the=20 operation.=20

This parameter can be NULL if the dwIoControlCode = parameter=20 specifies an operation that does not require input data.

nInBufferSize=20

Size, in bytes, of the buffer pointed to by lpInBuffer.=20

lpOutBuffer=20

Pointer to a buffer that receives the operation's output data.=20

This parameter can be NULL if the dwIoControlCode = parameter=20 specifies an operation that does not produce output data.

nOutBufferSize=20

Size, in bytes, of the buffer pointed to by lpOutBuffer.=20

lpBytesReturned=20

Pointer to a variable that receives the size, in bytes, of the = data=20 stored into the buffer pointed to by lpOutBuffer.=20

If lpOverlapped is NULL, lpBytesReturned cannot be = NULL.=20 Even when an operation produces no output data, and = lpOutBuffer can=20 be NULL, the DeviceIoControl function makes use of the = variable=20 pointed to by lpBytesReturned. After such an operation, the = value of=20 the variable is without meaning.=20

If lpOverlapped is not NULL, lpBytesReturned can be = NULL.=20 If this is an overlapped operation, you can get the number of bytes = returned=20 by calling GetOverlappedResult.=20 If hDevice is associated with an I/O completion port, you can = get the=20 number of bytes returned by calling GetQueuedCompletionStatus.=20

lpOverlapped=20

Pointer to an OVERLAPPED=20 structure.=20

If hDevice was opened with the FILE_FLAG_OVERLAPPED flag, = this=20 parameter must point to a valid OVERLAPPED structure. In this = case,=20 DeviceIoControl is performed as an overlapped (asynchronous)=20 operation. If the device was opened with FILE_FLAG_OVERLAPPED and=20 lpOverlapped is NULL, the function fails in unpredictable = ways.=20

If hDevice was opened without specifying the = FILE_FLAG_OVERLAPPED=20 flag, this parameter is ignored and the DeviceIoControl = function does=20 not return until the operation has been completed, or an error = occurs.=20

Return Values

If the function succeeds, the return value is nonzero.

If the function fails, the return value is zero. To get extended = error=20 information, call GetLastError.=20

Remarks

If hDevice was opened with FILE_FLAG_OVERLAPPED and the=20 lpOverlapped parameter points to an OVERLAPPED structure,=20 DeviceIoControl is performed as an overlapped (asynchronous) = operation.=20 In this case, the OVERLAPPED structure must contain a handle to a = manual-reset event object created by a call to the CreateEvent = function.=20 For more information on manual-reset event objects, see Synchronization.=20

Windows CE: No specific values are defined for the = dwIoControlCode=20 parameter. However, the writer of a custom device driver can define=20 IOCTL_XXXX control codes, per the CTL_CODE macro. These control = codes can=20 then be advertised, and an application can use these control codes with=20 DeviceIoControl to perform the driver-specific functions.

The lpOverlapped parameter is ignored and should be NULL.

QuickInfo

Windows NT: Requires version 3.1 or later.
= Windows: Requires Windows 95 or later.
Windows CE: = Requires=20 version 1.0 or later.
Header: Declared in=20 winbase.h.
Import Library: Use kernel32.lib.

hope this will be of some help to u

Regards

Nirmal Prasad R.