audk/MdePkg/Include/Ppi/ReadOnlyVariable2.h

/** @file
  This file declares Read-only Variable Service2 PPI.
  This ppi permits read-only access to the UEFI variable store during the PEI phase.

Copyright (c) 2006 - 2010, Intel Corporation. All rights reserved.<BR>
This program and the accompanying materials are licensed and made available under 
the terms and conditions of the BSD License that 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.             

  @par Revision Reference:
  This PPI is introduced in PI Version 1.0.

**/

#ifndef __PEI_READ_ONLY_VARIABLE2_PPI_H__
#define __PEI_READ_ONLY_VARIABLE2_PPI_H__

#define EFI_PEI_READ_ONLY_VARIABLE2_PPI_GUID \
  { 0x2ab86ef5, 0xecb5, 0x4134, { 0xb5, 0x56, 0x38, 0x54, 0xca, 0x1f, 0xe1, 0xb4 } }


typedef struct _EFI_PEI_READ_ONLY_VARIABLE2_PPI  EFI_PEI_READ_ONLY_VARIABLE2_PPI;

/**
  This service retrieves a variable's value using its name and GUID.

  Read the specified variable from the UEFI variable store. If the Data 
  buffer is too small to hold the contents of the variable, 
  the error EFI_BUFFER_TOO_SMALL is returned and DataSize is set to the
  required buffer size to obtain the data.

  @param  This                  A pointer to this instance of the EFI_PEI_READ_ONLY_VARIABLE2_PPI.
  @param  VariableName          A pointer to a null-terminated string that is the variable's name.
  @param  VariableGuid          A pointer to an EFI_GUID that is the variable's GUID. The combination of
                                VariableGuid and VariableName must be unique.
  @param  Attributes            If non-NULL, on return, points to the variable's attributes.
  @param  DataSize              On entry, points to the size in bytes of the Data buffer.
                                On return, points to the size of the data returned in Data.
  @param  Data                  Points to the buffer which will hold the returned variable value.

  @retval EFI_SUCCESS           The variable was read successfully.
  @retval EFI_NOT_FOUND         The variable could not be found.
  @retval EFI_BUFFER_TOO_SMALL  The DataSize is too small for the resulting data. 
                                DataSize is updated with the size required for 
                                the specified variable.
  @retval EFI_INVALID_PARAMETER VariableName, VariableGuid, DataSize or Data is NULL.
  @retval EFI_DEVICE_ERROR      The variable could not be retrieved because of a device error.

**/
typedef
EFI_STATUS
(EFIAPI *EFI_PEI_GET_VARIABLE2)(
  IN CONST  EFI_PEI_READ_ONLY_VARIABLE2_PPI *This,
  IN CONST  CHAR16                          *VariableName,
  IN CONST  EFI_GUID                        *VariableGuid,
  OUT       UINT32                          *Attributes,
  IN OUT    UINTN                           *DataSize,
  OUT       VOID                            *Data
  );


/**
  Return the next variable name and GUID.

  This function is called multiple times to retrieve the VariableName 
  and VariableGuid of all variables currently available in the system. 
  On each call, the previous results are passed into the interface, 
  and, on return, the interface returns the data for the next 
  interface. When the entire variable list has been returned, 
  EFI_NOT_FOUND is returned.

  @param  This              A pointer to this instance of the EFI_PEI_READ_ONLY_VARIABLE2_PPI.

  @param  VariableNameSize  On entry, points to the size of the buffer pointed to by VariableName.
                            On return, the size of the variable name buffer.
  @param  VariableName      On entry, a pointer to a null-terminated string that is the variable's name.
                            On return, points to the next variable's null-terminated name string.

  @param  VariableGuid      On entry, a pointer to an EFI_GUID that is the variable's GUID. 
                            On return, a pointer to the next variable's GUID.

  @retval EFI_SUCCESS           The variable was read successfully.
  @retval EFI_NOT_FOUND         The variable could not be found.
  @retval EFI_BUFFER_TOO_SMALL  The VariableNameSize is too small for the resulting
                                data. VariableNameSize is updated with the size
                                required for the specified variable.
  @retval EFI_INVALID_PARAMETER VariableName, VariableGuid or
                                VariableNameSize is NULL.
  @retval EFI_DEVICE_ERROR      The variable could not be retrieved because of a device error.

**/
typedef
EFI_STATUS
(EFIAPI *EFI_PEI_GET_NEXT_VARIABLE_NAME2)(
  IN CONST  EFI_PEI_READ_ONLY_VARIABLE2_PPI *This,
  IN OUT    UINTN                           *VariableNameSize,
  IN OUT    CHAR16                          *VariableName,
  IN OUT    EFI_GUID                        *VariableGuid
  );

///
/// This PPI provides a lightweight, read-only variant of the full EFI 
/// variable services. 
///
struct _EFI_PEI_READ_ONLY_VARIABLE2_PPI {
  EFI_PEI_GET_VARIABLE2           GetVariable;
  EFI_PEI_GET_NEXT_VARIABLE_NAME2 NextVariableName;
};

extern EFI_GUID gEfiPeiReadOnlyVariable2PpiGuid;

#endif