REF: https://bugzilla.tianocore.org/show_bug.cgi?id=2298

UefiDevicePathLibOptionalDevicePathProtocol's implementation isn't
fit its description. It should be implement as blow:
Try to find the DevicePathProtocol, if found then use it to implement
the interface. Else, use the local interface. It should not have the
depex and ASSERT of gEfiDevicePathUtilitiesProtocolGuid when not find
the DevicePathProtocol.

Add a mandatory one to force using the DevicePathUtilities,
DevicePathToText and DevicePathFromText protocol.

Cc: Michael D Kinney <michael.d.kin...@intel.com>
Cc: Liming Gao <liming....@intel.com>
Cc: Vitaly Cheptsov <vit9...@protonmail.com>
Signed-off-by: Zhichao Gao <zhichao....@intel.com>
---

V2:
Optional one should always return EFI_SUCCESS in its constructor.
Change the description of optional one's uni file.
Fix the copyright date of mandatory one's uni file.

 ...DevicePathLibMandatoryDevicePathProtocol.c | 469 ++++++++++++++++++
 ...vicePathLibMandatoryDevicePathProtocol.inf |  86 ++++
 ...vicePathLibMandatoryDevicePathProtocol.uni |  18 +
 ...iDevicePathLibOptionalDevicePathProtocol.c |   9 +-
 ...evicePathLibOptionalDevicePathProtocol.inf |   5 +-
 ...evicePathLibOptionalDevicePathProtocol.uni |   6 +-
 6 files changed, 580 insertions(+), 13 deletions(-)
 create mode 100644 
MdePkg/Library/UefiDevicePathLib/UefiDevicePathLibMandatoryDevicePathProtocol.c
 create mode 100644 
MdePkg/Library/UefiDevicePathLib/UefiDevicePathLibMandatoryDevicePathProtocol.inf
 create mode 100644 
MdePkg/Library/UefiDevicePathLib/UefiDevicePathLibMandatoryDevicePathProtocol.uni

diff --git 
a/MdePkg/Library/UefiDevicePathLib/UefiDevicePathLibMandatoryDevicePathProtocol.c
 
b/MdePkg/Library/UefiDevicePathLib/UefiDevicePathLibMandatoryDevicePathProtocol.c
new file mode 100644
index 0000000000..fa27110fd4
--- /dev/null
+++ 
b/MdePkg/Library/UefiDevicePathLib/UefiDevicePathLibMandatoryDevicePathProtocol.c
@@ -0,0 +1,469 @@
+/** @file
+  Device Path services. The thing to remember is device paths are built out of
+  nodes. The device path is terminated by an end node that is length
+  sizeof(EFI_DEVICE_PATH_PROTOCOL). That would be why there is 
sizeof(EFI_DEVICE_PATH_PROTOCOL)
+  all over this file.
+
+  The only place where multi-instance device paths are supported is in
+  environment varibles. Multi-instance device paths should never be placed
+  on a Handle.
+
+  Copyright (c) 2019, Intel Corporation. All rights reserved.<BR>
+  SPDX-License-Identifier: BSD-2-Clause-Patent
+
+**/
+
+
+#include "UefiDevicePathLib.h"
+
+GLOBAL_REMOVE_IF_UNREFERENCED EFI_DEVICE_PATH_UTILITIES_PROTOCOL 
*mDevicePathLibDevicePathUtilities = NULL;
+GLOBAL_REMOVE_IF_UNREFERENCED EFI_DEVICE_PATH_TO_TEXT_PROTOCOL   
*mDevicePathLibDevicePathToText    = NULL;
+GLOBAL_REMOVE_IF_UNREFERENCED EFI_DEVICE_PATH_FROM_TEXT_PROTOCOL 
*mDevicePathLibDevicePathFromText  = NULL;
+
+/**
+  The constructor function caches the pointer to DevicePathUtilites protocol,
+  DevicePathToText protocol and DevicePathFromText protocol.
+
+  The constructor function locates these three protocols from protocol 
database.
+  It will caches the pointer to local protocol instance if that operation fails
+  and it will always return EFI_SUCCESS.
+
+  @param  ImageHandle   The firmware allocated handle for the EFI image.
+  @param  SystemTable   A pointer to the EFI System Table.
+
+  @retval EFI_SUCCESS   The constructor always returns EFI_SUCCESS.
+
+**/
+EFI_STATUS
+EFIAPI
+UefiDevicePathLibMandatoryDevicePathProtocolConstructor (
+  IN      EFI_HANDLE                ImageHandle,
+  IN      EFI_SYSTEM_TABLE          *SystemTable
+  )
+{
+  EFI_STATUS                        Status;
+
+  Status = gBS->LocateProtocol (
+                  &gEfiDevicePathUtilitiesProtocolGuid,
+                  NULL,
+                  (VOID**) &mDevicePathLibDevicePathUtilities
+                  );
+  ASSERT_EFI_ERROR (Status);
+  ASSERT (mDevicePathLibDevicePathUtilities != NULL);
+
+  Status = gBS->LocateProtocol (
+                  &gEfiDevicePathToTextProtocolGuid,
+                  NULL,
+                  (VOID**) &mDevicePathLibDevicePathToText
+                  );
+  ASSERT_EFI_ERROR (Status);
+  ASSERT (mDevicePathLibDevicePathToText != NULL);
+
+  Status = gBS->LocateProtocol (
+                  &gEfiDevicePathFromTextProtocolGuid,
+                  NULL,
+                  (VOID**) &mDevicePathLibDevicePathFromText
+                  );
+  ASSERT_EFI_ERROR (Status);
+  ASSERT (mDevicePathLibDevicePathFromText != NULL);
+
+  return Status;
+}
+
+/**
+  Returns the size of a device path in bytes.
+
+  This function returns the size, in bytes, of the device path data structure
+  specified by DevicePath including the end of device path node.
+  If DevicePath is NULL or invalid, then 0 is returned.
+
+  @param  DevicePath  A pointer to a device path data structure.
+
+  @retval 0           If DevicePath is NULL or invalid.
+  @retval Others      The size of a device path in bytes.
+
+**/
+UINTN
+EFIAPI
+GetDevicePathSize (
+  IN CONST EFI_DEVICE_PATH_PROTOCOL  *DevicePath
+  )
+{
+  if (mDevicePathLibDevicePathUtilities != NULL) {
+    return mDevicePathLibDevicePathUtilities->GetDevicePathSize (DevicePath);
+  }
+
+  ASSERT (FALSE);
+  return 0;
+}
+
+/**
+  Creates a new copy of an existing device path.
+
+  This function allocates space for a new copy of the device path specified by 
DevicePath.
+  If DevicePath is NULL, then NULL is returned.  If the memory is successfully
+  allocated, then the contents of DevicePath are copied to the newly allocated
+  buffer, and a pointer to that buffer is returned.  Otherwise, NULL is 
returned.
+  The memory for the new device path is allocated from EFI boot services 
memory.
+  It is the responsibility of the caller to free the memory allocated.
+
+  @param  DevicePath    A pointer to a device path data structure.
+
+  @retval NULL          DevicePath is NULL or invalid.
+  @retval Others        A pointer to the duplicated device path.
+
+**/
+EFI_DEVICE_PATH_PROTOCOL *
+EFIAPI
+DuplicateDevicePath (
+  IN CONST EFI_DEVICE_PATH_PROTOCOL  *DevicePath
+  )
+{
+  if (mDevicePathLibDevicePathUtilities != NULL) {
+    return mDevicePathLibDevicePathUtilities->DuplicateDevicePath (DevicePath);
+  }
+
+  ASSERT (FALSE);
+  return NULL;
+}
+
+/**
+  Creates a new device path by appending a second device path to a first 
device path.
+
+  This function creates a new device path by appending a copy of 
SecondDevicePath
+  to a copy of FirstDevicePath in a newly allocated buffer.  Only the 
end-of-device-path
+  device node from SecondDevicePath is retained. The newly created device path 
is
+  returned. If FirstDevicePath is NULL, then it is ignored, and a duplicate of
+  SecondDevicePath is returned.  If SecondDevicePath is NULL, then it is 
ignored,
+  and a duplicate of FirstDevicePath is returned. If both FirstDevicePath and
+  SecondDevicePath are NULL, then a copy of an end-of-device-path is returned.
+
+  If there is not enough memory for the newly allocated buffer, then NULL is 
returned.
+  The memory for the new device path is allocated from EFI boot services 
memory.
+  It is the responsibility of the caller to free the memory allocated.
+
+  @param  FirstDevicePath            A pointer to a device path data structure.
+  @param  SecondDevicePath           A pointer to a device path data structure.
+
+  @retval NULL      If there is not enough memory for the newly allocated 
buffer.
+  @retval NULL      If FirstDevicePath or SecondDevicePath is invalid.
+  @retval Others    A pointer to the new device path if success.
+                    Or a copy an end-of-device-path if both FirstDevicePath 
and SecondDevicePath are NULL.
+
+**/
+EFI_DEVICE_PATH_PROTOCOL *
+EFIAPI
+AppendDevicePath (
+  IN CONST EFI_DEVICE_PATH_PROTOCOL  *FirstDevicePath,  OPTIONAL
+  IN CONST EFI_DEVICE_PATH_PROTOCOL  *SecondDevicePath  OPTIONAL
+  )
+{
+  if (mDevicePathLibDevicePathUtilities != NULL) {
+    return mDevicePathLibDevicePathUtilities->AppendDevicePath 
(FirstDevicePath, SecondDevicePath);
+  }
+
+  ASSERT (FALSE);
+  return NULL;
+}
+
+/**
+  Creates a new path by appending the device node to the device path.
+
+  This function creates a new device path by appending a copy of the device 
node
+  specified by DevicePathNode to a copy of the device path specified by 
DevicePath
+  in an allocated buffer. The end-of-device-path device node is moved after the
+  end of the appended device node.
+  If DevicePathNode is NULL then a copy of DevicePath is returned.
+  If DevicePath is NULL then a copy of DevicePathNode, followed by an 
end-of-device
+  path device node is returned.
+  If both DevicePathNode and DevicePath are NULL then a copy of an 
end-of-device-path
+  device node is returned.
+  If there is not enough memory to allocate space for the new device path, then
+  NULL is returned.
+  The memory is allocated from EFI boot services memory. It is the 
responsibility
+  of the caller to free the memory allocated.
+
+  @param  DevicePath                 A pointer to a device path data structure.
+  @param  DevicePathNode             A pointer to a single device path node.
+
+  @retval NULL      If there is not enough memory for the new device path.
+  @retval Others    A pointer to the new device path if success.
+                    A copy of DevicePathNode followed by an end-of-device-path 
node
+                    if both FirstDevicePath and SecondDevicePath are NULL.
+                    A copy of an end-of-device-path node if both 
FirstDevicePath
+                    and SecondDevicePath are NULL.
+
+**/
+EFI_DEVICE_PATH_PROTOCOL *
+EFIAPI
+AppendDevicePathNode (
+  IN CONST EFI_DEVICE_PATH_PROTOCOL  *DevicePath,     OPTIONAL
+  IN CONST EFI_DEVICE_PATH_PROTOCOL  *DevicePathNode  OPTIONAL
+  )
+{
+  if (mDevicePathLibDevicePathUtilities != NULL) {
+    return mDevicePathLibDevicePathUtilities->AppendDeviceNode (DevicePath, 
DevicePathNode);
+  }
+
+  ASSERT (FALSE);
+  return NULL;
+}
+
+/**
+  Creates a new device path by appending the specified device path instance to 
the specified device
+  path.
+
+  This function creates a new device path by appending a copy of the device 
path
+  instance specified by DevicePathInstance to a copy of the device path 
specified
+  by DevicePath in a allocated buffer.
+  The end-of-device-path device node is moved after the end of the appended 
device
+  path instance and a new end-of-device-path-instance node is inserted between.
+  If DevicePath is NULL, then a copy if DevicePathInstance is returned.
+  If DevicePathInstance is NULL, then NULL is returned.
+  If DevicePath or DevicePathInstance is invalid, then NULL is returned.
+  If there is not enough memory to allocate space for the new device path, then
+  NULL is returned.
+  The memory is allocated from EFI boot services memory. It is the 
responsibility
+  of the caller to free the memory allocated.
+
+  @param  DevicePath                 A pointer to a device path data structure.
+  @param  DevicePathInstance         A pointer to a device path instance.
+
+  @return A pointer to the new device path.
+
+**/
+EFI_DEVICE_PATH_PROTOCOL *
+EFIAPI
+AppendDevicePathInstance (
+  IN CONST EFI_DEVICE_PATH_PROTOCOL  *DevicePath,        OPTIONAL
+  IN CONST EFI_DEVICE_PATH_PROTOCOL  *DevicePathInstance OPTIONAL
+  )
+{
+  if (mDevicePathLibDevicePathUtilities != NULL) {
+    return mDevicePathLibDevicePathUtilities->AppendDevicePathInstance 
(DevicePath, DevicePathInstance);
+  }
+
+  ASSERT (FALSE);
+  return NULL;
+}
+
+/**
+  Creates a copy of the current device path instance and returns a pointer to 
the next device path
+  instance.
+
+  This function creates a copy of the current device path instance. It also 
updates
+  DevicePath to point to the next device path instance in the device path (or 
NULL
+  if no more) and updates Size to hold the size of the device path instance 
copy.
+  If DevicePath is NULL, then NULL is returned.
+  If DevicePath points to a invalid device path, then NULL is returned.
+  If there is not enough memory to allocate space for the new device path, then
+  NULL is returned.
+  The memory is allocated from EFI boot services memory. It is the 
responsibility
+  of the caller to free the memory allocated.
+  If Size is NULL, then ASSERT().
+
+  @param  DevicePath                 On input, this holds the pointer to the 
current
+                                     device path instance. On output, this 
holds
+                                     the pointer to the next device path 
instance
+                                     or NULL if there are no more device path
+                                     instances in the device path pointer to a
+                                     device path data structure.
+  @param  Size                       On output, this holds the size of the 
device
+                                     path instance, in bytes or zero, if 
DevicePath
+                                     is NULL.
+
+  @return A pointer to the current device path instance.
+
+**/
+EFI_DEVICE_PATH_PROTOCOL *
+EFIAPI
+GetNextDevicePathInstance (
+  IN OUT EFI_DEVICE_PATH_PROTOCOL    **DevicePath,
+  OUT UINTN                          *Size
+  )
+{
+  if (mDevicePathLibDevicePathUtilities != NULL) {
+    return mDevicePathLibDevicePathUtilities->GetNextDevicePathInstance 
(DevicePath, Size);
+  }
+
+  ASSERT (FALSE);
+  return NULL;
+}
+
+/**
+  Creates a device node.
+
+  This function creates a new device node in a newly allocated buffer of size
+  NodeLength and initializes the device path node header with NodeType and 
NodeSubType.
+  The new device path node is returned.
+  If NodeLength is smaller than a device path header, then NULL is returned.
+  If there is not enough memory to allocate space for the new device path, then
+  NULL is returned.
+  The memory is allocated from EFI boot services memory. It is the 
responsibility
+  of the caller to free the memory allocated.
+
+  @param  NodeType                   The device node type for the new device 
node.
+  @param  NodeSubType                The device node sub-type for the new 
device node.
+  @param  NodeLength                 The length of the new device node.
+
+  @return The new device path.
+
+**/
+EFI_DEVICE_PATH_PROTOCOL *
+EFIAPI
+CreateDeviceNode (
+  IN UINT8                           NodeType,
+  IN UINT8                           NodeSubType,
+  IN UINT16                          NodeLength
+  )
+{
+  if (mDevicePathLibDevicePathUtilities != NULL) {
+    return mDevicePathLibDevicePathUtilities->CreateDeviceNode (NodeType, 
NodeSubType, NodeLength);
+  }
+
+  ASSERT (FALSE);
+  return NULL;
+}
+
+/**
+  Determines if a device path is single or multi-instance.
+
+  This function returns TRUE if the device path specified by DevicePath is
+  multi-instance.
+  Otherwise, FALSE is returned.
+  If DevicePath is NULL or invalid, then FALSE is returned.
+
+  @param  DevicePath                 A pointer to a device path data structure.
+
+  @retval  TRUE                      DevicePath is multi-instance.
+  @retval  FALSE                     DevicePath is not multi-instance, or 
DevicePath
+                                     is NULL or invalid.
+
+**/
+BOOLEAN
+EFIAPI
+IsDevicePathMultiInstance (
+  IN CONST EFI_DEVICE_PATH_PROTOCOL  *DevicePath
+  )
+{
+  if (mDevicePathLibDevicePathUtilities != NULL) {
+    return mDevicePathLibDevicePathUtilities->IsDevicePathMultiInstance 
(DevicePath);
+  }
+
+  ASSERT (FALSE);
+  return FALSE;
+}
+
+/**
+  Converts a device node to its string representation.
+
+  @param DeviceNode        A Pointer to the device node to be converted.
+  @param DisplayOnly       If DisplayOnly is TRUE, then the shorter text 
representation
+                           of the display node is used, where applicable. If 
DisplayOnly
+                           is FALSE, then the longer text representation of 
the display node
+                           is used.
+  @param AllowShortcuts    If AllowShortcuts is TRUE, then the shortcut forms 
of text
+                           representation for a device node can be used, where 
applicable.
+
+  @return A pointer to the allocated text representation of the device node or 
NULL if DeviceNode
+          is NULL or there was insufficient memory.
+
+**/
+CHAR16 *
+EFIAPI
+ConvertDeviceNodeToText (
+  IN CONST EFI_DEVICE_PATH_PROTOCOL  *DeviceNode,
+  IN BOOLEAN                         DisplayOnly,
+  IN BOOLEAN                         AllowShortcuts
+  )
+{
+  if (mDevicePathLibDevicePathToText != NULL) {
+    return mDevicePathLibDevicePathToText->ConvertDeviceNodeToText 
(DeviceNode, DisplayOnly, AllowShortcuts);
+  }
+
+  ASSERT (FALSE);
+  return NULL;
+}
+
+/**
+  Converts a device path to its text representation.
+
+  @param DevicePath      A Pointer to the device to be converted.
+  @param DisplayOnly     If DisplayOnly is TRUE, then the shorter text 
representation
+                         of the display node is used, where applicable. If 
DisplayOnly
+                         is FALSE, then the longer text representation of the 
display node
+                         is used.
+  @param AllowShortcuts  If AllowShortcuts is TRUE, then the shortcut forms of 
text
+                         representation for a device node can be used, where 
applicable.
+
+  @return A pointer to the allocated text representation of the device path or
+          NULL if DeviceNode is NULL or there was insufficient memory.
+
+**/
+CHAR16 *
+EFIAPI
+ConvertDevicePathToText (
+  IN CONST EFI_DEVICE_PATH_PROTOCOL   *DevicePath,
+  IN BOOLEAN                          DisplayOnly,
+  IN BOOLEAN                          AllowShortcuts
+  )
+{
+  if (mDevicePathLibDevicePathToText != NULL) {
+    return mDevicePathLibDevicePathToText->ConvertDevicePathToText 
(DevicePath, DisplayOnly, AllowShortcuts);
+  }
+
+  ASSERT (FALSE);
+  return NULL;
+}
+
+/**
+  Convert text to the binary representation of a device node.
+
+  @param TextDeviceNode  TextDeviceNode points to the text representation of a 
device
+                         node. Conversion starts with the first character and 
continues
+                         until the first non-device node character.
+
+  @return A pointer to the EFI device node or NULL if TextDeviceNode is NULL 
or there was
+          insufficient memory or text unsupported.
+
+**/
+EFI_DEVICE_PATH_PROTOCOL *
+EFIAPI
+ConvertTextToDeviceNode (
+  IN CONST CHAR16 *TextDeviceNode
+  )
+{
+  if (mDevicePathLibDevicePathFromText != NULL) {
+    return mDevicePathLibDevicePathFromText->ConvertTextToDeviceNode 
(TextDeviceNode);
+  }
+
+  ASSERT (FALSE);
+  return NULL;
+}
+
+/**
+  Convert text to the binary representation of a device path.
+
+
+  @param TextDevicePath  TextDevicePath points to the text representation of a 
device
+                         path. Conversion starts with the first character and 
continues
+                         until the first non-device node character.
+
+  @return A pointer to the allocated device path or NULL if TextDeviceNode is 
NULL or
+          there was insufficient memory.
+
+**/
+EFI_DEVICE_PATH_PROTOCOL *
+EFIAPI
+ConvertTextToDevicePath (
+  IN CONST CHAR16 *TextDevicePath
+  )
+{
+  if (mDevicePathLibDevicePathFromText != NULL) {
+    return mDevicePathLibDevicePathFromText->ConvertTextToDevicePath 
(TextDevicePath);
+  }
+
+  ASSERT (FALSE);
+  return NULL;
+}
+
diff --git 
a/MdePkg/Library/UefiDevicePathLib/UefiDevicePathLibMandatoryDevicePathProtocol.inf
 
b/MdePkg/Library/UefiDevicePathLib/UefiDevicePathLibMandatoryDevicePathProtocol.inf
new file mode 100644
index 0000000000..eb545d4601
--- /dev/null
+++ 
b/MdePkg/Library/UefiDevicePathLib/UefiDevicePathLibMandatoryDevicePathProtocol.inf
@@ -0,0 +1,86 @@
+## @file
+# Instance of Device Path Library based on Device Path Protocol.
+#
+#  Device Path Library that layers on top of the UEFI 2.0 Device Path Protocol.
+#  If the DevicePathFromText/DevicePathToText protocol doesn't exist, the 
library
+#  uses its internal conversion logic.
+#
+# Copyright (c) 2019, Intel Corporation. All rights reserved.<BR>
+#
+#  SPDX-License-Identifier: BSD-2-Clause-Patent
+#
+#
+##
+
+[Defines]
+  INF_VERSION                    = 0x00010005
+  BASE_NAME                      = UefiDevicePathLibMandatoryDevicePathProtocol
+  MODULE_UNI_FILE                = 
UefiDevicePathLibMandatoryDevicePathProtocol.uni
+  FILE_GUID                      = 5A8389AF-DAE4-407E-8FD5-D026948BC579
+  MODULE_TYPE                    = UEFI_DRIVER
+  VERSION_STRING                 = 1.0
+  LIBRARY_CLASS                  = DevicePathLib|DXE_DRIVER DXE_RUNTIME_DRIVER 
DXE_SMM_DRIVER UEFI_APPLICATION UEFI_DRIVER SMM_CORE
+
+  CONSTRUCTOR                    = 
UefiDevicePathLibMandatoryDevicePathProtocolConstructor
+
+#
+#  VALID_ARCHITECTURES           = IA32 X64 EBC
+#
+
+[Sources]
+  DevicePathUtilities.c
+  DevicePathToText.c
+  DevicePathFromText.c
+  UefiDevicePathLibMandatoryDevicePathProtocol.c
+  UefiDevicePathLib.h
+
+[Packages]
+  MdePkg/MdePkg.dec
+
+
+[LibraryClasses]
+  BaseLib
+  UefiBootServicesTableLib
+  MemoryAllocationLib
+  DebugLib
+  BaseMemoryLib
+  PcdLib
+  PrintLib
+
+[Guids]
+  ## SOMETIMES_CONSUMES  ## GUID
+  gEfiVTUTF8Guid
+  ## SOMETIMES_CONSUMES  ## GUID
+  gEfiVT100Guid
+  ## SOMETIMES_CONSUMES  ## GUID
+  gEfiVT100PlusGuid
+  ## SOMETIMES_CONSUMES  ## GUID
+  gEfiPcAnsiGuid
+  ## SOMETIMES_CONSUMES  ## GUID
+  gEfiUartDevicePathGuid
+  ## SOMETIMES_CONSUMES  ## GUID
+  gEfiSasDevicePathGuid
+  ## SOMETIMES_CONSUMES  ## GUID
+  gEfiVirtualDiskGuid
+  ## SOMETIMES_CONSUMES  ## GUID
+  gEfiVirtualCdGuid
+  ## SOMETIMES_CONSUMES  ## GUID
+  gEfiPersistentVirtualDiskGuid
+  ## SOMETIMES_CONSUMES  ## GUID
+  gEfiPersistentVirtualCdGuid
+
+[Protocols]
+  gEfiDevicePathProtocolGuid                    ## SOMETIMES_CONSUMES
+  gEfiDevicePathUtilitiesProtocolGuid           ## CONSUMES
+  gEfiDevicePathToTextProtocolGuid              ## SOMETIMES_CONSUMES
+  gEfiDevicePathFromTextProtocolGuid            ## SOMETIMES_CONSUMES
+  gEfiDebugPortProtocolGuid                     ## UNDEFINED
+
+[Pcd]
+  gEfiMdePkgTokenSpaceGuid.PcdMaximumDevicePathNodeCount ## SOMETIMES_CONSUMES
+
+[Depex.common.DXE_DRIVER, Depex.common.DXE_RUNTIME_DRIVER, 
Depex.common.DXE_SAL_DRIVER, Depex.common.DXE_SMM_DRIVER]
+  gEfiDevicePathUtilitiesProtocolGuid AND
+  gEfiDevicePathToTextProtocolGuid AND
+  gEfiDevicePathFromTextProtocolGuid
+
diff --git 
a/MdePkg/Library/UefiDevicePathLib/UefiDevicePathLibMandatoryDevicePathProtocol.uni
 
b/MdePkg/Library/UefiDevicePathLib/UefiDevicePathLibMandatoryDevicePathProtocol.uni
new file mode 100644
index 0000000000..1b8a556698
--- /dev/null
+++ 
b/MdePkg/Library/UefiDevicePathLib/UefiDevicePathLibMandatoryDevicePathProtocol.uni
@@ -0,0 +1,18 @@
+// /** @file
+// Instance of Device Path Library based on Device Path Protocol.
+//
+// Device Path Library that layers on top of the UEFI 2.0 Device Path Protocol.
+// If the DevicePathFromText/DevicePathToText protocol doesn't exist, the 
library
+// uses its internal conversion logic.
+//
+// Copyright (c) 2019, Intel Corporation. All rights reserved.<BR>
+//
+// SPDX-License-Identifier: BSD-2-Clause-Patent
+//
+// **/
+
+
+#string STR_MODULE_ABSTRACT             #language en-US "Instance of Device 
Path Library based on Device Path Protocol."
+
+#string STR_MODULE_DESCRIPTION          #language en-US "Instance of Device 
Path Library based on Device Path Protocol."
+
diff --git 
a/MdePkg/Library/UefiDevicePathLib/UefiDevicePathLibOptionalDevicePathProtocol.c
 
b/MdePkg/Library/UefiDevicePathLib/UefiDevicePathLibOptionalDevicePathProtocol.c
index 106ff245cc..10614f0516 100644
--- 
a/MdePkg/Library/UefiDevicePathLib/UefiDevicePathLibOptionalDevicePathProtocol.c
+++ 
b/MdePkg/Library/UefiDevicePathLib/UefiDevicePathLibOptionalDevicePathProtocol.c
@@ -8,7 +8,7 @@
   environment varibles. Multi-instance device paths should never be placed
   on a Handle.
 
-  Copyright (c) 2013 - 2018, Intel Corporation. All rights reserved.<BR>
+  Copyright (c) 2013 - 2019, Intel Corporation. All rights reserved.<BR>
   SPDX-License-Identifier: BSD-2-Clause-Patent
 
 **/
@@ -21,8 +21,7 @@ GLOBAL_REMOVE_IF_UNREFERENCED 
EFI_DEVICE_PATH_TO_TEXT_PROTOCOL   *mDevicePathLib
 GLOBAL_REMOVE_IF_UNREFERENCED EFI_DEVICE_PATH_FROM_TEXT_PROTOCOL 
*mDevicePathLibDevicePathFromText  = NULL;
 
 /**
-  The constructor function caches the pointer to DevicePathUtilites protocol,
-  DevicePathToText protocol and DevicePathFromText protocol.
+  The constructor function caches the pointer to DevicePathUtilites protocol.
 
   The constructor function locates these three protocols from protocol 
database.
   It will caches the pointer to local protocol instance if that operation fails
@@ -48,9 +47,7 @@ UefiDevicePathLibOptionalDevicePathProtocolConstructor (
                   NULL,
                   (VOID**) &mDevicePathLibDevicePathUtilities
                   );
-  ASSERT_EFI_ERROR (Status);
-  ASSERT (mDevicePathLibDevicePathUtilities != NULL);
-  return Status;
+  return EFI_SUCCESS;
 }
 
 /**
diff --git 
a/MdePkg/Library/UefiDevicePathLib/UefiDevicePathLibOptionalDevicePathProtocol.inf
 
b/MdePkg/Library/UefiDevicePathLib/UefiDevicePathLibOptionalDevicePathProtocol.inf
index e812e3e1d4..d194300bde 100644
--- 
a/MdePkg/Library/UefiDevicePathLib/UefiDevicePathLibOptionalDevicePathProtocol.inf
+++ 
b/MdePkg/Library/UefiDevicePathLib/UefiDevicePathLibOptionalDevicePathProtocol.inf
@@ -5,7 +5,7 @@
 #  If the DevicePathFromText/DevicePathToText protocol doesn't exist, the 
library
 #  uses its internal conversion logic.
 #
-# Copyright (c) 2013 - 2018, Intel Corporation. All rights reserved.<BR>
+# Copyright (c) 2013 - 2019, Intel Corporation. All rights reserved.<BR>
 #
 #  SPDX-License-Identifier: BSD-2-Clause-Patent
 #
@@ -79,6 +79,3 @@
 [Pcd]
   gEfiMdePkgTokenSpaceGuid.PcdMaximumDevicePathNodeCount ## SOMETIMES_CONSUMES
 
-[Depex.common.DXE_DRIVER, Depex.common.DXE_RUNTIME_DRIVER, 
Depex.common.DXE_SAL_DRIVER, Depex.common.DXE_SMM_DRIVER]
-  gEfiDevicePathUtilitiesProtocolGuid
-
diff --git 
a/MdePkg/Library/UefiDevicePathLib/UefiDevicePathLibOptionalDevicePathProtocol.uni
 
b/MdePkg/Library/UefiDevicePathLib/UefiDevicePathLibOptionalDevicePathProtocol.uni
index 070f0add9f..7a7ebaaf1e 100644
--- 
a/MdePkg/Library/UefiDevicePathLib/UefiDevicePathLibOptionalDevicePathProtocol.uni
+++ 
b/MdePkg/Library/UefiDevicePathLib/UefiDevicePathLibOptionalDevicePathProtocol.uni
@@ -5,14 +5,14 @@
 // If the DevicePathFromText/DevicePathToText protocol doesn't exist, the 
library
 // uses its internal conversion logic.
 //
-// Copyright (c) 2013 - 2014, Intel Corporation. All rights reserved.<BR>
+// Copyright (c) 2013 - 2019, Intel Corporation. All rights reserved.<BR>
 //
 // SPDX-License-Identifier: BSD-2-Clause-Patent
 //
 // **/
 
 
-#string STR_MODULE_ABSTRACT             #language en-US "Instance of Device 
Path Library based on Device Path Protocol."
+#string STR_MODULE_ABSTRACT             #language en-US "Instance of Device 
Path Library based on Device Path Protocol or Memory Allocation Library."
 
-#string STR_MODULE_DESCRIPTION          #language en-US "Instance of Device 
Path Library based on Device Path Protocol."
+#string STR_MODULE_DESCRIPTION          #language en-US "Instance of Device 
Path Library based on Device Path Protocol or Memory Allocation Library."
 
-- 
2.21.0.windows.1


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