Re: [PATCH 1/2] MdePkg/UefiDevicePathLib: Separate the device path lib

["Liming Gao" <liming.gao@intel.com>]

Zhichao:
  The change is good. New library instance is benefit for image size. 

  But, please make sure library constructor always return success. Otherwise, error status will assert in autogen code. 

Thanks
Liming
>-----Original Message-----
>From: Gao, Zhichao
>Sent: Thursday, November 28, 2019 10:15 AM
>To: devel@edk2.groups.io
>Cc: Kinney, Michael D <michael.d.kinney@intel.com>; Gao, Liming
><liming.gao@intel.com>; Vitaly Cheptsov <vit9696@protonmail.com>
>Subject: [PATCH 1/2] MdePkg/UefiDevicePathLib: Separate the device path lib
>
>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.kinney@intel.com>
>Cc: Liming Gao <liming.gao@intel.com>
>Cc: Vitaly Cheptsov <vit9696@protonmail.com>
>Signed-off-by: Zhichao Gao <zhichao.gao@intel.com>
>---
> ...DevicePathLibMandatoryDevicePathProtocol.c | 469
>++++++++++++++++++
> ...vicePathLibMandatoryDevicePathProtocol.inf |  86 ++++
> ...vicePathLibMandatoryDevicePathProtocol.uni |  18 +
> ...iDevicePathLibOptionalDevicePathProtocol.c |   7 +-
> ...evicePathLibOptionalDevicePathProtocol.inf |   5 +-
> 5 files changed, 576 insertions(+), 9 deletions(-)
> create mode 100644
>MdePkg/Library/UefiDevicePathLib/UefiDevicePathLibMandatoryDevicePath
>Protocol.c
> create mode 100644
>MdePkg/Library/UefiDevicePathLib/UefiDevicePathLibMandatoryDevicePath
>Protocol.inf
> create mode 100644
>MdePkg/Library/UefiDevicePathLib/UefiDevicePathLibMandatoryDevicePath
>Protocol.uni
>
>diff --git
>a/MdePkg/Library/UefiDevicePathLib/UefiDevicePathLibMandatoryDevicePat
>hProtocol.c
>b/MdePkg/Library/UefiDevicePathLib/UefiDevicePathLibMandatoryDevicePa
>thProtocol.c
>new file mode 100644
>index 0000000000..fa27110fd4
>--- /dev/null
>+++
>b/MdePkg/Library/UefiDevicePathLib/UefiDevicePathLibMandatoryDevicePa
>thProtocol.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/UefiDevicePathLibMandatoryDevicePat
>hProtocol.inf
>b/MdePkg/Library/UefiDevicePathLib/UefiDevicePathLibMandatoryDevicePa
>thProtocol.inf
>new file mode 100644
>index 0000000000..eb545d4601
>--- /dev/null
>+++
>b/MdePkg/Library/UefiDevicePathLib/UefiDevicePathLibMandatoryDevicePa
>thProtocol.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/UefiDevicePathLibMandatoryDevicePat
>hProtocol.uni
>b/MdePkg/Library/UefiDevicePathLib/UefiDevicePathLibMandatoryDevicePa
>thProtocol.uni
>new file mode 100644
>index 0000000000..070f0add9f
>--- /dev/null
>+++
>b/MdePkg/Library/UefiDevicePathLib/UefiDevicePathLibMandatoryDevicePa
>thProtocol.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) 2013 - 2014, 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/UefiDevicePathLibOptionalDevicePathP
>rotocol.c
>b/MdePkg/Library/UefiDevicePathLib/UefiDevicePathLibOptionalDevicePath
>Protocol.c
>index 106ff245cc..68b4abfa2d 100644
>---
>a/MdePkg/Library/UefiDevicePathLib/UefiDevicePathLibOptionalDevicePathP
>rotocol.c
>+++
>b/MdePkg/Library/UefiDevicePathLib/UefiDevicePathLibOptionalDevicePath
>Protocol.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
>@@ -48,8 +47,6 @@
>UefiDevicePathLibOptionalDevicePathProtocolConstructor (
>                   NULL,
>                   (VOID**) &mDevicePathLibDevicePathUtilities
>                   );
>-  ASSERT_EFI_ERROR (Status);
>-  ASSERT (mDevicePathLibDevicePathUtilities != NULL);
>   return Status;
> }
>
>diff --git
>a/MdePkg/Library/UefiDevicePathLib/UefiDevicePathLibOptionalDevicePathP
>rotocol.inf
>b/MdePkg/Library/UefiDevicePathLib/UefiDevicePathLibOptionalDevicePath
>Protocol.inf
>index e812e3e1d4..d194300bde 100644
>---
>a/MdePkg/Library/UefiDevicePathLib/UefiDevicePathLibOptionalDevicePathP
>rotocol.inf
>+++
>b/MdePkg/Library/UefiDevicePathLib/UefiDevicePathLibOptionalDevicePath
>Protocol.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
>-
>--
>2.21.0.windows.1