{
{    The purpose of this request is to open a device file.
{
{       MMP$OPEN_DEVICE_FILE (sfid, asid, r1, r2, sequential_random_selection,
{            read_write_access_selection, file_kind, segment_number, status)
{
{ SFID: (input) This parameter specifies the SFID of the segment.
{
{ ASID: (input) This parameter specifies the ASID of the segment.
{
{ R1: (input) This parameter specifies the ring 1 value to be used in
{       creating the SDT entry for the new segment.
{
{ R2: (input) This parameter specifies the ring 2 value to be used in
{       creating the SDT entry for the new segment.
{
{ SEQUENTIAL_RANDOM_SELECTION: (input) This parameter specifies the access
{       selections for the segment. If a sequential access is specified,
{       read_transfer_unit and free_behind are added to the SDTX software
{       attribute selections for the segment.
{
{ READ_WRITE_ACCESS_SELECTION: (input) This parameter specifies the
{       read or write permissions in the SDT entry.
{
{ FILE_KIND: (input) This parameter specifies what type of file this segment
{       is to be.
{
{ SEGMENT_NUMBER: (output) This parameter returns the segment number of the segment
{       to the requestor. This segment number is only valid within the callers
{       address space.
{
{ STATUS: (output) This parameter returns the request status.
{

