[mirror_edk2.git] / MdePkg / Library / UefiDevicePathLibDevicePathProtocol / UefiDevicePathLib.c

/** @file\r
  Library instance that implement UEFI Device Path Library class based on protocol\r
  gEfiDevicePathUtilitiesProtocolGuid.\r
\r
  Copyright (c) 2006 - 2012, Intel Corporation. All rights reserved.<BR>\r
  This program and the accompanying materials\r
  are licensed and made available under the terms and conditions of the BSD License\r
  which accompanies this distribution.  The full text of the license may be found at\r
  http://opensource.org/licenses/bsd-license.php.\r
\r
  THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,\r
  WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.\r
\r
**/\r
\r
\r
#include <Uefi.h>\r
\r
#include <Protocol/DevicePathUtilities.h>\r
\r
#include <Library/DevicePathLib.h>\r
#include <Library/DebugLib.h>\r
#include <Library/BaseLib.h>\r
#include <Library/MemoryAllocationLib.h>\r
#include <Library/BaseMemoryLib.h>\r
#include <Library/UefiBootServicesTableLib.h>\r
#include <Library/PcdLib.h>\r
\r
EFI_DEVICE_PATH_UTILITIES_PROTOCOL          *mDevicePathUtilities = NULL;\r
\r
//\r
// Template for an end-of-device path node.\r
//\r
GLOBAL_REMOVE_IF_UNREFERENCED CONST EFI_DEVICE_PATH_PROTOCOL  mUefiDevicePathLibEndDevicePath = {\r
  END_DEVICE_PATH_TYPE,\r
  END_ENTIRE_DEVICE_PATH_SUBTYPE,\r
  {\r
    END_DEVICE_PATH_LENGTH,\r
    0\r
  }\r
};\r
\r
/**\r
  The constructor function caches the pointer to DevicePathUtilites protocol.\r
  \r
  The constructor function locates DevicePathUtilities protocol from protocol database.\r
  It will ASSERT() if that operation fails and it will always return EFI_SUCCESS. \r
\r
  @param  ImageHandle   The firmware allocated handle for the EFI image.\r
  @param  SystemTable   A pointer to the EFI System Table.\r
  \r
  @retval EFI_SUCCESS   The constructor always returns EFI_SUCCESS.\r
\r
**/\r
EFI_STATUS\r
EFIAPI\r
DevicePathLibConstructor (\r
  IN      EFI_HANDLE                ImageHandle,\r
  IN      EFI_SYSTEM_TABLE          *SystemTable\r
  )\r
{\r
  EFI_STATUS                        Status;\r
\r
  Status = gBS->LocateProtocol (\r
                  &gEfiDevicePathUtilitiesProtocolGuid,\r
                  NULL,\r
                  (VOID**) &mDevicePathUtilities\r
                  );\r
  ASSERT_EFI_ERROR (Status);\r
  ASSERT (mDevicePathUtilities != NULL);\r
\r
  return Status;\r
}\r
\r
/**\r
  Determine whether a given device path is valid.\r
  If DevicePath is NULL, then ASSERT().\r
\r
  @param  DevicePath  A pointer to a device path data structure.\r
  @param  MaxSize     The maximum size of the device path data structure.\r
\r
  @retval TRUE        DevicePath is valid.\r
  @retval FALSE       The length of any node node in the DevicePath is less\r
                      than sizeof (EFI_DEVICE_PATH_PROTOCOL).\r
  @retval FALSE       If MaxSize is not zero, the size of the DevicePath\r
                      exceeds MaxSize.\r
  @retval FALSE       If PcdMaximumDevicePathNodeCount is not zero, the node\r
                      count of the DevicePath exceeds PcdMaximumDevicePathNodeCount.\r
**/\r
BOOLEAN\r
EFIAPI\r
IsDevicePathValid (\r
  IN CONST EFI_DEVICE_PATH_PROTOCOL *DevicePath,\r
  IN       UINTN                    MaxSize\r
  )\r
{\r
  UINTN Count;\r
  UINTN Size;\r
  UINTN NodeLength;\r
\r
  ASSERT (DevicePath != NULL);\r
\r
  for (Count = 0, Size = 0; !IsDevicePathEnd (DevicePath); DevicePath = NextDevicePathNode (DevicePath)) {\r
    NodeLength = DevicePathNodeLength (DevicePath);\r
    if (NodeLength < sizeof (EFI_DEVICE_PATH_PROTOCOL)) {\r
      return FALSE;\r
    }\r
\r
    if (MaxSize > 0) {\r
      Size += NodeLength;\r
      if (Size + END_DEVICE_PATH_LENGTH > MaxSize) {\r
        return FALSE;\r
      }\r
    }\r
\r
    if (PcdGet32 (PcdMaximumDevicePathNodeCount) > 0) {\r
      Count++;\r
      if (Count >= PcdGet32 (PcdMaximumDevicePathNodeCount)) {\r
        return FALSE;\r
      }\r
    }\r
  }\r
\r
  //\r
  // Only return TRUE when the End Device Path node is valid.\r
  //\r
  return (BOOLEAN) (DevicePathNodeLength (DevicePath) == END_DEVICE_PATH_LENGTH);\r
}\r
\r
/**\r
  Returns the Type field of a device path node.\r
\r
  Returns the Type field of the device path node specified by Node.\r
\r
  If Node is NULL, then ASSERT().\r
\r
  @param  Node      A pointer to a device path node data structure.\r
\r
  @return The Type field of the device path node specified by Node.\r
\r
**/\r
UINT8\r
EFIAPI\r
DevicePathType (\r
  IN CONST VOID  *Node\r
  )\r
{\r
  ASSERT (Node != NULL);\r
  return ((EFI_DEVICE_PATH_PROTOCOL *)(Node))->Type;\r
}\r
\r
/**\r
  Returns the SubType field of a device path node.\r
\r
  Returns the SubType field of the device path node specified by Node.\r
\r
  If Node is NULL, then ASSERT().\r
\r
  @param  Node      A pointer to a device path node data structure.\r
\r
  @return The SubType field of the device path node specified by Node.\r
\r
**/\r
UINT8\r
EFIAPI\r
DevicePathSubType (\r
  IN CONST VOID  *Node\r
  )\r
{\r
  ASSERT (Node != NULL);\r
  return ((EFI_DEVICE_PATH_PROTOCOL *)(Node))->SubType;\r
}\r
\r
/**\r
  Returns the 16-bit Length field of a device path node.\r
\r
  Returns the 16-bit Length field of the device path node specified by Node.  \r
  Node is not required to be aligned on a 16-bit boundary, so it is recommended\r
  that a function such as ReadUnaligned16() be used to extract the contents of \r
  the Length field.\r
\r
  If Node is NULL, then ASSERT().\r
\r
  @param  Node      A pointer to a device path node data structure.\r
\r
  @return The 16-bit Length field of the device path node specified by Node.\r
\r
**/\r
UINTN\r
EFIAPI\r
DevicePathNodeLength (\r
  IN CONST VOID  *Node\r
  )\r
{\r
  UINTN Length;\r
\r
  ASSERT (Node != NULL);\r
  Length = ReadUnaligned16 ((UINT16 *)&((EFI_DEVICE_PATH_PROTOCOL *)(Node))->Length[0]);\r
  ASSERT (Length >= sizeof (EFI_DEVICE_PATH_PROTOCOL));\r
  return Length;\r
}\r
\r
/**\r
  Returns a pointer to the next node in a device path.\r
\r
  Returns a pointer to the device path node that follows the device path node \r
  specified by Node.\r
\r
  If Node is NULL, then ASSERT().\r
\r
  @param  Node      A pointer to a device path node data structure.\r
\r
  @return a pointer to the device path node that follows the device path node \r
  specified by Node.\r
\r
**/\r
EFI_DEVICE_PATH_PROTOCOL *\r
EFIAPI\r
NextDevicePathNode (\r
  IN CONST VOID  *Node\r
  )\r
{\r
  ASSERT (Node != NULL);\r
  return (EFI_DEVICE_PATH_PROTOCOL *)((UINT8 *)(Node) + DevicePathNodeLength(Node));\r
}\r
\r
/**\r
  Determines if a device path node is an end node of a device path.\r
  This includes nodes that are the end of a device path instance and nodes that \r
  are the end of an entire device path.\r
\r
  Determines if the device path node specified by Node is an end node of a device path.  \r
  This includes nodes that are the end of a device path instance and nodes that are the \r
  end of an entire device path.  If Node represents an end node of a device path, \r
  then TRUE is returned.  Otherwise, FALSE is returned.\r
\r
  If Node is NULL, then ASSERT().\r
\r
  @param  Node      A pointer to a device path node data structure.\r
\r
  @retval TRUE      The device path node specified by Node is an end node of a device path.\r
  @retval FALSE     The device path node specified by Node is not an end node of \r
                    a device path.\r
  \r
**/\r
BOOLEAN\r
EFIAPI\r
IsDevicePathEndType (\r
  IN CONST VOID  *Node\r
  )\r
{\r
  ASSERT (Node != NULL);\r
  return (BOOLEAN) (DevicePathType (Node) == END_DEVICE_PATH_TYPE);\r
}\r
\r
/**\r
  Determines if a device path node is an end node of an entire device path.\r
\r
  Determines if a device path node specified by Node is an end node of an entire \r
  device path.\r
  If Node represents the end of an entire device path, then TRUE is returned.  \r
  Otherwise, FALSE is returned.\r
\r
  If Node is NULL, then ASSERT().\r
\r
  @param  Node      A pointer to a device path node data structure.\r
\r
  @retval TRUE      The device path node specified by Node is the end of an entire device path.\r
  @retval FALSE     The device path node specified by Node is not the end of an entire device path.\r
\r
**/\r
BOOLEAN\r
EFIAPI\r
IsDevicePathEnd (\r
  IN CONST VOID  *Node\r
  )\r
{\r
  ASSERT (Node != NULL);\r
  return (BOOLEAN) (IsDevicePathEndType (Node) && DevicePathSubType(Node) == END_ENTIRE_DEVICE_PATH_SUBTYPE);\r
}\r
\r
/**\r
  Determines if a device path node is an end node of a device path instance.\r
\r
  Determines if a device path node specified by Node is an end node of a device \r
  path instance.\r
  If Node represents the end of a device path instance, then TRUE is returned.  \r
  Otherwise, FALSE is returned.\r
\r
  If Node is NULL, then ASSERT().\r
\r
  @param  Node      A pointer to a device path node data structure.\r
\r
  @retval TRUE      The device path node specified by Node is the end of a device \r
  path instance.\r
  @retval FALSE     The device path node specified by Node is not the end of a \r
  device path instance.\r
\r
**/\r
BOOLEAN\r
EFIAPI\r
IsDevicePathEndInstance (\r
  IN CONST VOID  *Node\r
  )\r
{\r
  ASSERT (Node != NULL);\r
  return (BOOLEAN) (IsDevicePathEndType (Node) && DevicePathSubType(Node) == END_INSTANCE_DEVICE_PATH_SUBTYPE);\r
}\r
\r
/**\r
  Sets the length, in bytes, of a device path node.\r
\r
  Sets the length of the device path node specified by Node to the value specified \r
  by NodeLength.  NodeLength is returned.  Node is not required to be aligned on \r
  a 16-bit boundary, so it is recommended that a function such as WriteUnaligned16()\r
  be used to set the contents of the Length field.\r
\r
  If Node is NULL, then ASSERT().\r
  If NodeLength >= SIZE_64KB, then ASSERT().\r
  If NodeLength < sizeof (EFI_DEVICE_PATH_PROTOCOL), then ASSERT().\r
\r
  @param  Node      A pointer to a device path node data structure.\r
  @param  Length    The length, in bytes, of the device path node.\r
\r
  @return Length\r
\r
**/\r
UINT16\r
EFIAPI\r
SetDevicePathNodeLength (\r
  IN OUT VOID  *Node,\r
  IN UINTN     Length\r
  )\r
{\r
  ASSERT (Node != NULL);\r
  ASSERT ((Length >= sizeof (EFI_DEVICE_PATH_PROTOCOL)) && (Length < SIZE_64KB));\r
  return WriteUnaligned16 ((UINT16 *)&((EFI_DEVICE_PATH_PROTOCOL *)(Node))->Length[0], (UINT16)(Length));\r
}\r
\r
/**\r
  Fills in all the fields of a device path node that is the end of an entire device path.\r
\r
  Fills in all the fields of a device path node specified by Node so Node represents \r
  the end of an entire device path.  The Type field of Node is set to \r
  END_DEVICE_PATH_TYPE, the SubType field of Node is set to \r
  END_ENTIRE_DEVICE_PATH_SUBTYPE, and the Length field of Node is set to \r
  END_DEVICE_PATH_LENGTH.  Node is not required to be aligned on a 16-bit boundary, \r
  so it is recommended that a function such as WriteUnaligned16() be used to set \r
  the contents of the Length field. \r
\r
  If Node is NULL, then ASSERT(). \r
\r
  @param  Node      A pointer to a device path node data structure.\r
\r
**/\r
VOID\r
EFIAPI\r
SetDevicePathEndNode (\r
  OUT VOID  *Node\r
  )\r
{\r
  ASSERT (Node != NULL);\r
  CopyMem (Node, &mUefiDevicePathLibEndDevicePath, sizeof (mUefiDevicePathLibEndDevicePath));\r
}\r
\r
/**\r
  Returns the size of a device path in bytes.\r
\r
  This function returns the size, in bytes, of the device path data structure \r
  specified by DevicePath including the end of device path node.\r
  If DevicePath is NULL or invalid, then 0 is returned.\r
\r
  @param  DevicePath  A pointer to a device path data structure.\r
\r
  @retval 0           If DevicePath is NULL or invalid.\r
  @retval Others      The size of a device path in bytes.\r
\r
**/\r
UINTN\r
EFIAPI\r
GetDevicePathSize (\r
  IN CONST EFI_DEVICE_PATH_PROTOCOL  *DevicePath\r
  )\r
{\r
  return mDevicePathUtilities->GetDevicePathSize (DevicePath);\r
}\r
\r
/**\r
  Creates a new copy of an existing device path.\r
\r
  This function allocates space for a new copy of the device path specified by \r
  DevicePath.  If DevicePath is NULL, then NULL is returned.  \r
  If the memory is successfully allocated, then the\r
  contents of DevicePath are copied to the newly allocated buffer, and a pointer to that buffer\r
  is returned.  Otherwise, NULL is returned.  \r
  The memory for the new device path is allocated from EFI boot services memory. \r
  It is the responsibility of the caller to free the memory allocated. \r
  \r
  @param  DevicePath                 A pointer to a device path data structure.\r
\r
  @retval NULL    If DevicePath is NULL or invalid.\r
  @retval Others  A pointer to the duplicated device path.\r
  \r
**/\r
EFI_DEVICE_PATH_PROTOCOL *\r
EFIAPI\r
DuplicateDevicePath (\r
  IN CONST EFI_DEVICE_PATH_PROTOCOL  *DevicePath\r
  )\r
{\r
  return mDevicePathUtilities->DuplicateDevicePath (DevicePath);\r
}\r
\r
/**\r
  Creates a new device path by appending a second device path to a first device path.\r
\r
  This function creates a new device path by appending a copy of SecondDevicePath to a copy of\r
  FirstDevicePath in a newly allocated buffer.  Only the end-of-device-path device node from\r
  SecondDevicePath is retained. The newly created device path is returned.  \r
  If FirstDevicePath is NULL, then it is ignored, and a duplicate of SecondDevicePath is returned.  \r
  If SecondDevicePath is NULL, then it is ignored, and a duplicate of FirstDevicePath is returned.  \r
  If both FirstDevicePath and SecondDevicePath are NULL, then a copy of an end-of-device-path is\r
  returned.  \r
  If there is not enough memory for the newly allocated buffer, then NULL is returned.\r
  The memory for the new device path is allocated from EFI boot services memory. It is the\r
  responsibility of the caller to free the memory allocated.\r
\r
  @param  FirstDevicePath            A pointer to a device path data structure.\r
  @param  SecondDevicePath           A pointer to a device path data structure.\r
  \r
  @retval NULL      If there is not enough memory for the newly allocated buffer.\r
  @retval NULL      If FirstDevicePath or SecondDevicePath is invalid.\r
  @retval Others    A pointer to the new device path if success.\r
                    Or a copy an end-of-device-path if both FirstDevicePath and \r
                    SecondDevicePath are NULL.\r
\r
**/\r
EFI_DEVICE_PATH_PROTOCOL *\r
EFIAPI\r
AppendDevicePath (\r
  IN CONST EFI_DEVICE_PATH_PROTOCOL  *FirstDevicePath,  OPTIONAL\r
  IN CONST EFI_DEVICE_PATH_PROTOCOL  *SecondDevicePath  OPTIONAL\r
  )\r
{\r
  return mDevicePathUtilities->AppendDevicePath (FirstDevicePath, SecondDevicePath);\r
}\r
\r
/**\r
  Creates a new path by appending the device node to the device path.\r
\r
  This function creates a new device path by appending a copy of the device node \r
  specified by DevicePathNode to a copy of the device path specified by DevicePath \r
  in an allocated buffer.\r
  The end-of-device-path device node is moved after the end of the appended device node.\r
  If DevicePathNode is NULL then a copy of DevicePath is returned.\r
  If DevicePath is NULL then a copy of DevicePathNode, followed by an end-of-device \r
  path device node is returned.\r
  If both DevicePathNode and DevicePath are NULL then a copy of an end-of-device-path \r
  device node is returned.\r
  If there is not enough memory to allocate space for the new device path, then \r
  NULL is returned.  \r
  The memory is allocated from EFI boot services memory. It is the responsibility \r
  of the caller to free the memory allocated.\r
\r
  @param  DevicePath                 A pointer to a device path data structure.\r
  @param  DevicePathNode             A pointer to a single device path node.\r
\r
  @retval NULL      If there is not enough memory for the new device path.\r
  @retval Others    A pointer to the new device path if success.\r
                    A copy of DevicePathNode followed by an end-of-device-path node \r
                    if both FirstDevicePath and SecondDevicePath are NULL.\r
                    A copy of an end-of-device-path node if both FirstDevicePath \r
                    and SecondDevicePath are NULL.\r
\r
**/\r
EFI_DEVICE_PATH_PROTOCOL *\r
EFIAPI\r
AppendDevicePathNode (\r
  IN CONST EFI_DEVICE_PATH_PROTOCOL  *DevicePath,     OPTIONAL\r
  IN CONST EFI_DEVICE_PATH_PROTOCOL  *DevicePathNode  OPTIONAL\r
  )\r
{\r
  return mDevicePathUtilities->AppendDeviceNode (DevicePath, DevicePathNode);\r
}\r
\r
/**\r
  Creates a new device path by appending the specified device path instance to \r
  the specified device path.\r
 \r
  This function creates a new device path by appending a copy of the device path \r
  instance specified by DevicePathInstance to a copy of the device path specified \r
  by DevicePath in a allocated buffer.\r
  The end-of-device-path device node is moved after the end of the appended device \r
  path instance and a new end-of-device-path-instance node is inserted between. \r
  If DevicePath is NULL, then a copy if DevicePathInstance is returned.\r
  If DevicePathInstance is NULL, then NULL is returned.\r
  If DevicePath or DevicePathInstance is invalid, then NULL is returned.\r
  If there is not enough memory to allocate space for the new device path, then \r
  NULL is returned.   \r
  The memory is allocated from EFI boot services memory. It is the responsibility \r
  of the caller to free the memory allocated.\r
  \r
  @param  DevicePath                 A pointer to a device path data structure.\r
  @param  DevicePathInstance         A pointer to a device path instance.\r
\r
  @return A pointer to the new device path.\r
\r
**/\r
EFI_DEVICE_PATH_PROTOCOL *\r
EFIAPI\r
AppendDevicePathInstance (\r
  IN CONST EFI_DEVICE_PATH_PROTOCOL  *DevicePath,        OPTIONAL\r
  IN CONST EFI_DEVICE_PATH_PROTOCOL  *DevicePathInstance OPTIONAL\r
  )\r
{\r
  return mDevicePathUtilities->AppendDevicePathInstance (DevicePath, DevicePathInstance);\r
}\r
\r
/**\r
  Creates a copy of the current device path instance and returns a pointer to the \r
  next device path instance.\r
\r
  This function creates a copy of the current device path instance. It also updates \r
  DevicePath to point to the next device path instance in the device path (or NULL \r
  if no more) and updates Size to hold the size of the device path instance copy.\r
  If DevicePath is NULL, then NULL is returned.\r
  If there is not enough memory to allocate space for the new device path, then \r
  NULL is returned.  \r
  The memory is allocated from EFI boot services memory. It is the responsibility \r
  of the caller to free the memory allocated.\r
  If Size is NULL, then ASSERT().\r
 \r
  @param  DevicePath                 On input, this holds the pointer to the current \r
                                     device path instance. On output, this holds \r
                                     the pointer to the next device path instance \r
                                     or NULL if there are no more device path\r
                                     instances in the device path pointer to a \r
                                     device path data structure.\r
  @param  Size                       On output, this holds the size of the device \r
                                     path instance, in bytes or zero, if DevicePath \r
                                     is NULL.\r
\r
  @return A pointer to the current device path instance.\r
\r
**/\r
EFI_DEVICE_PATH_PROTOCOL *\r
EFIAPI\r
GetNextDevicePathInstance (\r
  IN OUT EFI_DEVICE_PATH_PROTOCOL    **DevicePath,\r
  OUT UINTN                          *Size\r
  )\r
{\r
  ASSERT (Size != NULL);\r
  return mDevicePathUtilities->GetNextDevicePathInstance (DevicePath, Size);\r
}\r
\r
/**\r
  Creates a device node.\r
\r
  This function creates a new device node in a newly allocated buffer of size \r
  NodeLength and initializes the device path node header with NodeType and NodeSubType.  \r
  The new device path node is returned.\r
  If NodeLength is smaller than a device path header, then NULL is returned.  \r
  If there is not enough memory to allocate space for the new device path, then \r
  NULL is returned.  \r
  The memory is allocated from EFI boot services memory. It is the responsibility \r
  of the caller to\r
  free the memory allocated.\r
\r
  @param  NodeType                   The device node type for the new device node.\r
  @param  NodeSubType                The device node sub-type for the new device node.\r
  @param  NodeLength                 The length of the new device node.\r
\r
  @return The new device path.\r
\r
**/\r
EFI_DEVICE_PATH_PROTOCOL *\r
EFIAPI\r
CreateDeviceNode (\r
  IN UINT8                           NodeType,\r
  IN UINT8                           NodeSubType,\r
  IN UINT16                          NodeLength\r
  )\r
{\r
  return mDevicePathUtilities->CreateDeviceNode (NodeType, NodeSubType, NodeLength);\r
}\r
\r
/**\r
  Determines if a device path is single or multi-instance.\r
\r
  This function returns TRUE if the device path specified by DevicePath is\r
  multi-instance.\r
  Otherwise, FALSE is returned.\r
  If DevicePath is NULL or invalid, then FALSE is returned.\r
\r
  @param  DevicePath                 A pointer to a device path data structure.\r
\r
  @retval  TRUE                      DevicePath is multi-instance.\r
  @retval  FALSE                     DevicePath is not multi-instance, or DevicePath \r
                                     is NULL or invalid.\r
\r
**/\r
BOOLEAN\r
EFIAPI\r
IsDevicePathMultiInstance (\r
  IN CONST EFI_DEVICE_PATH_PROTOCOL  *DevicePath\r
  )\r
{\r
  return mDevicePathUtilities->IsDevicePathMultiInstance (DevicePath);\r
}\r
\r
/**\r
  Retrieves the device path protocol from a handle.\r
\r
  This function returns the device path protocol from the handle specified by Handle.  \r
  If Handle is NULL or Handle does not contain a device path protocol, then NULL \r
  is returned.\r
 \r
  @param  Handle                     The handle from which to retrieve the device \r
                                     path protocol.\r
\r
  @return The device path protocol from the handle specified by Handle.\r
\r
**/\r
EFI_DEVICE_PATH_PROTOCOL *\r
EFIAPI\r
DevicePathFromHandle (\r
  IN EFI_HANDLE                      Handle\r
  )\r
{\r
  EFI_DEVICE_PATH_PROTOCOL  *DevicePath;\r
  EFI_STATUS                Status;\r
\r
  Status = gBS->HandleProtocol (\r
                  Handle,\r
                  &gEfiDevicePathProtocolGuid,\r
                  (VOID *) &DevicePath\r
                  );\r
  if (EFI_ERROR (Status)) {\r
    DevicePath = NULL;\r
  }\r
  return DevicePath;\r
}\r
\r
/**\r
  Allocates a device path for a file and appends it to an existing device path.\r
\r
  If Device is a valid device handle that contains a device path protocol, then \r
  a device path for the file specified by FileName  is allocated and appended to \r
  the device path associated with the handle Device.  The allocated device path \r
  is returned.  If Device is NULL or Device is a handle that does not support the \r
  device path protocol, then a device path containing a single device path node \r
  for the file specified by FileName is allocated and returned.\r
  The memory for the new device path is allocated from EFI boot services memory. \r
  It is the responsibility of the caller to free the memory allocated.\r
  \r
  If FileName is NULL, then ASSERT().\r
  If FileName is not aligned on a 16-bit boundary, then ASSERT().\r
\r
  @param  Device                     A pointer to a device handle.  This parameter \r
                                     is optional and may be NULL.\r
  @param  FileName                   A pointer to a Null-terminated Unicode string.\r
\r
  @return The allocated device path.\r
\r
**/\r
EFI_DEVICE_PATH_PROTOCOL *\r
EFIAPI\r
FileDevicePath (\r
  IN EFI_HANDLE                      Device,     OPTIONAL\r
  IN CONST CHAR16                    *FileName\r
  )\r
{\r
  UINTN                     Size;\r
  FILEPATH_DEVICE_PATH      *FilePath;\r
  EFI_DEVICE_PATH_PROTOCOL  *DevicePath;\r
  EFI_DEVICE_PATH_PROTOCOL  *FileDevicePath;\r
\r
  DevicePath = NULL;\r
\r
  Size = StrSize (FileName);\r
  FileDevicePath = AllocatePool (Size + SIZE_OF_FILEPATH_DEVICE_PATH + END_DEVICE_PATH_LENGTH);\r
  if (FileDevicePath != NULL) {\r
    FilePath = (FILEPATH_DEVICE_PATH *) FileDevicePath;\r
    FilePath->Header.Type    = MEDIA_DEVICE_PATH;\r
    FilePath->Header.SubType = MEDIA_FILEPATH_DP;\r
    CopyMem (&FilePath->PathName, FileName, Size);\r
    SetDevicePathNodeLength (&FilePath->Header, Size + SIZE_OF_FILEPATH_DEVICE_PATH);\r
    SetDevicePathEndNode (NextDevicePathNode (&FilePath->Header));\r
\r
    if (Device != NULL) {\r
      DevicePath = DevicePathFromHandle (Device);\r
    }\r
\r
    DevicePath = AppendDevicePath (DevicePath, FileDevicePath);\r
    FreePool (FileDevicePath);\r
  }\r
\r
  return DevicePath;\r
}\r