audk/IntelFrameworkPkg/Include/Ppi/ReadOnlyVariable.h

/** @file
  This file declares Read-only Variable Service PPI
  These services provide a lightweight, read-only variant of the full EFI variable services. The
  reason that these services are read-only is to reduce the complexity of flash management. Also,
  some implementation of the PEI may use the same physical flash part for variable and PEIM
  storage; as such, a write command to certain technologies would alter the contents of the entire part,
  thus making the in situ PEIM execution not follow the required flow.

  Copyright (c) 2006, Intel Corporation
  All rights reserved. This program and the accompanying materials
  are licensed and made available under the terms and conditions of the BSD License
  which accompanies this distribution.  The full text of the license may be found at
  http://opensource.org/licenses/bsd-license.php

  THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
  WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.

  Module Name:  ReadOnlyVariable.h

  @par Revision Reference:
  This PPI is defined in PEI CIS
  Version 0.91.

**/

#ifndef __PEI_READ_ONLY_VARIABLE_PPI_H__
#define __PEI_READ_ONLY_VARIABLE_PPI_H__

#include <PiPei.h>

#define EFI_PEI_READ_ONLY_VARIABLE_ACCESS_PPI_GUID \
  { \
    0x3cdc90c6, 0x13fb, 0x4a75, {0x9e, 0x79, 0x59, 0xe9, 0xdd, 0x78, 0xb9, 0xfa } \
  }

typedef struct _EFI_PEI_READ_ONLY_VARIABLE_PPI  EFI_PEI_READ_ONLY_VARIABLE_PPI;

//
// Variable attributes
//
#define EFI_VARIABLE_NON_VOLATILE       0x00000001
#define EFI_VARIABLE_BOOTSERVICE_ACCESS 0x00000002
#define EFI_VARIABLE_RUNTIME_ACCESS     0x00000004
#define EFI_VARIABLE_READ_ONLY          0x00000008

/**
  Get Variable value by Name and GUID pair

  @param  PeiServices    An indirect pointer to the PEI Services Table published by the PEI Foundation.
  @param  VariableName   A NULL-terminated Unicode string that is the name of the vendor's variable.
  @param  VendorGuid     A unique identifier for the vendor.
  @param  Attributes     If not NULL, a pointer to the memory location to return
                         the attributes bitmask for the variable.
  @param  DataSize       On input, the size in bytes of the return Data buffer.
                         On output, the size of data returned in Data.
  @param  Data           The buffer to return the contents of the variable.

  @retval EFI_SUCCESS           The function completed successfully.
  @retval EFI_NOT_FOUND         The variable was not found.
  @retval EFI_BUFFER_TOO_SMALL  The BufferSize is too small for the result.
  @retval EFI_INVALID_PARAMETER One of the parameters has an invalid value.
  @retval EFI_DEVICE_ERROR      The variable could not be retrieved due to a hardware error.

**/
typedef
EFI_STATUS
(EFIAPI *EFI_PEI_GET_VARIABLE)(
  IN EFI_PEI_SERVICES             **PeiServices,
  IN CHAR16                       *VariableName,
  IN EFI_GUID                     *VendorGuid,
  OUT UINT32                      *Attributes OPTIONAL,
  IN OUT UINTN                    *DataSize,
  OUT VOID                        *Data
  );

/**
  This function can be called multiple times to retrieve the VariableName
  and VendorGuid of all variables currently available in the system. On each call
  to GetNextVariableName() the previous results are passed into the interface,
  and on output the interface returns the next variable name data.  When the
  entire variable list has been returned, the error EFI_NOT_FOUND is returned.

  @param  PeiServices      An indirect pointer to the PEI Services Table published by the PEI Foundation.
  @param  VariableNameSize The size of the VariableName buffer.
  @param  VariableName     On input, supplies the last VariableName that was
                           returned by GetNextVariableName(). On output, returns the Null-terminated
                           Unicode string of the current variable.
  @param  VendorGuid       On input, supplies the last VendorGuid that was
                           returned by GetNextVariableName(). On output, returns the VendorGuid
                           of the current variable.

  @retval EFI_SUCCESS           The function completed successfully.
  @retval EFI_NOT_FOUND         The next variable was not found.
  @retval EFI_BUFFER_TOO_SMALL  The VariableNameSize is too small for the result.
  @retval EFI_INVALID_PARAMETER One of the parameters has an invalid value.
  @retval EFI_DEVICE_ERROR      The variable name could not be retrieved due to a hardware error.

**/
typedef
EFI_STATUS
(EFIAPI *EFI_PEI_GET_NEXT_VARIABLE_NAME)(
  IN EFI_PEI_SERVICES             **PeiServices,
  IN OUT UINTN                    *VariableNameSize,
  IN OUT CHAR16                   *VariableName,
  IN OUT EFI_GUID                 *VendorGuid
  );

/**
  @par Ppi Description:
  This PPI provides a lightweight, read-only variant of the full EFI
  variable services.

  @param GetVariable
  A service to ascertain a given variable name.

  @param GetNextVariableName
  A service to ascertain a variable based upon a given, known variable

**/
struct _EFI_PEI_READ_ONLY_VARIABLE_PPI {
  EFI_PEI_GET_VARIABLE            PeiGetVariable;
  EFI_PEI_GET_NEXT_VARIABLE_NAME  PeiGetNextVariableName;
};

extern EFI_GUID gEfiPeiReadOnlyVariablePpiGuid;

#endif