IntelFrameworkPkg/Include/Ppi/ReadOnlyVariable.h

   1 /** @file
   2   This file declares Read-only Variable Service PPI
   3   These services provide a lightweight, read-only variant of the full EFI variable services. The
   4   reason that these services are read-only is to reduce the complexity of flash management. Also,
   5   some implementation of the PEI may use the same physical flash part for variable and PEIM
   6   storage; as such, a write command to certain technologies would alter the contents of the entire part,
   7   thus making the in situ PEIM execution not follow the required flow.
   8
   9   Copyright (c) 2006 - 2009, Intel Corporation
  10   All rights reserved. This program and the accompanying materials
  11   are licensed and made available under the terms and conditions of the BSD License
  12   which accompanies this distribution.  The full text of the license may be found at
  13   http://opensource.org/licenses/bsd-license.php
  14
  15   THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
  16   WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
  17
  18   Module Name:  ReadOnlyVariable.h
  19
  20   @par Revision Reference:
  21   This PPI is defined in PEI CIS
  22   Version 0.91.
  23
  24 **/
  25
  26 #ifndef __PEI_READ_ONLY_VARIABLE_PPI_H__
  27 #define __PEI_READ_ONLY_VARIABLE_PPI_H__
  28
  29 #include <PiPei.h>
  30
  31 #define EFI_PEI_READ_ONLY_VARIABLE_ACCESS_PPI_GUID \
  32   { \
  33     0x3cdc90c6, 0x13fb, 0x4a75, {0x9e, 0x79, 0x59, 0xe9, 0xdd, 0x78, 0xb9, 0xfa } \
  34   }
  35
  36 typedef struct _EFI_PEI_READ_ONLY_VARIABLE_PPI  EFI_PEI_READ_ONLY_VARIABLE_PPI;
  37
  38 //
  39 // Variable attributes
  40 //
  41 #define EFI_VARIABLE_NON_VOLATILE       0x00000001
  42 #define EFI_VARIABLE_BOOTSERVICE_ACCESS 0x00000002
  43 #define EFI_VARIABLE_RUNTIME_ACCESS     0x00000004
  44 #define EFI_VARIABLE_READ_ONLY          0x00000008
  45
  46 /**
  47   Get Variable value by Name and GUID pair
  48
  49   @param  PeiServices    An indirect pointer to the PEI Services Table published by the PEI Foundation.
  50   @param  VariableName   A NULL-terminated Unicode string that is the name of the vendor's variable.
  51   @param  VendorGuid     A unique identifier for the vendor.
  52   @param  Attributes     If not NULL, a pointer to the memory location to return
  53                          the attributes bitmask for the variable.
  54   @param  DataSize       On input, the size in bytes of the return Data buffer.
  55                          On output, the size of data returned in Data.
  56   @param  Data           The buffer to return the contents of the variable.
  57
  58   @retval EFI_SUCCESS           The function completed successfully.
  59   @retval EFI_NOT_FOUND         The variable was not found.
  60   @retval EFI_BUFFER_TOO_SMALL  The BufferSize is too small for the result.
  61   @retval EFI_INVALID_PARAMETER One of the parameters has an invalid value.
  62   @retval EFI_DEVICE_ERROR      The variable could not be retrieved due to a hardware error.
  63
  64 **/
  65 typedef
  66 EFI_STATUS
  67 (EFIAPI *EFI_PEI_GET_VARIABLE)(
  68   IN EFI_PEI_SERVICES             **PeiServices,
  69   IN CHAR16                       *VariableName,
  70   IN EFI_GUID                     *VendorGuid,
  71   OUT UINT32                      *Attributes OPTIONAL,
  72   IN OUT UINTN                    *DataSize,
  73   OUT VOID                        *Data
  74   );
  75
  76 /**
  77   This function can be called multiple times to retrieve the VariableName
  78   and VendorGuid of all variables currently available in the system. On each call
  79   to GetNextVariableName() the previous results are passed into the interface,
  80   and on output the interface returns the next variable name data.  When the
  81   entire variable list has been returned, the error EFI_NOT_FOUND is returned.
  82
  83   @param  PeiServices      An indirect pointer to the PEI Services Table published by the PEI Foundation.
  84   @param  VariableNameSize The size of the VariableName buffer.
  85   @param  VariableName     On input, supplies the last VariableName that was
  86                            returned by GetNextVariableName(). On output, returns the Null-terminated
  87                            Unicode string of the current variable.
  88   @param  VendorGuid       On input, supplies the last VendorGuid that was
  89                            returned by GetNextVariableName(). On output, returns the VendorGuid
  90                            of the current variable.
  91
  92   @retval EFI_SUCCESS           The function completed successfully.
  93   @retval EFI_NOT_FOUND         The next variable was not found.
  94   @retval EFI_BUFFER_TOO_SMALL  The VariableNameSize is too small for the result.
  95   @retval EFI_INVALID_PARAMETER One of the parameters has an invalid value.
  96   @retval EFI_DEVICE_ERROR      The variable name could not be retrieved due to a hardware error.
  97
  98 **/
  99 typedef
 100 EFI_STATUS
 101 (EFIAPI *EFI_PEI_GET_NEXT_VARIABLE_NAME)(
 102   IN EFI_PEI_SERVICES             **PeiServices,
 103   IN OUT UINTN                    *VariableNameSize,
 104   IN OUT CHAR16                   *VariableName,
 105   IN OUT EFI_GUID                 *VendorGuid
 106   );
 107
 108 /**
 109   This PPI provides a lightweight, read-only variant of the full EFI
 110   variable services.
 111 **/
 112 struct _EFI_PEI_READ_ONLY_VARIABLE_PPI {
 113   EFI_PEI_GET_VARIABLE            PeiGetVariable;         ///< A service to ascertain a given variable name.
 114   EFI_PEI_GET_NEXT_VARIABLE_NAME  PeiGetNextVariableName; ///< A service to ascertain a variable based upon a given, known variable
 115 };
 116
 117 extern EFI_GUID gEfiPeiReadOnlyVariablePpiGuid;
 118
 119 #endif