{}
{   This request is used by the Device Manager to perform disk I/O.
{}
{       IOP$MASS_STORAGE_IO (PVA, LENGTH, IO_FUNCTION, DEVICE_ADDRESS,
{         STATUS);
{}
{ PVA: (input) This parameter specifies the pva of the buffer which
{       contains the data to be transferred.
{}
{ LENGTH: (input) This parameter specifies the number of bytes to
{       transfer.
{}
{ IO_FUNCTION: (input) This parameter specifies the type of I/O
{       function to be performed.
{}
{ DEVICE_ADDRESS: (input) This parameter specifies the logical
{       address on the device in which to start data transfer.
{}
{ STATUS: (output) This parameter specifies the request status.
{}
