/** @file
  This file declares the Variable Storage PPI
  This PPI abstracts read-only access to the UEFI variable store on a
  NVM (Non-Volatile Memory) device during the PEI phase.

  Copyright (c) 2016, 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
  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.

**/

#ifndef _PEI_VARIABLE_STORAGE_PPI_H_
#define _PEI_VARIABLE_STORAGE_PPI_H_

extern EFI_GUID gVariableStoragePpiGuid;

///
/// Revision
///
#define PEI_VARIABLE_STORAGE_PPI_REVISION  1

typedef struct _VARIABLE_STORAGE_PPI  VARIABLE_STORAGE_PPI;

/**
  Retrieves a PPI instance-specific GUID.
  Returns a unique GUID per VARIABLE_STORAGE_PPI instance.

  @param[out]      VariableGuid           A pointer to an EFI_GUID that is this PPI instance's GUID.

  @retval          EFI_SUCCESS            The data was returned successfully.
  @retval          EFI_INVALID_PARAMETER  A required parameter is NULL.

**/
typedef
EFI_STATUS
(EFIAPI *PEI_VARIABLE_STORAGE_GET_ID)(
  OUT       EFI_GUID                        *InstanceGuid
  );

/**
  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[in]       This                   A pointer to this instance of the VARIABLE_STORAGE_PPI.
  @param[in]       VariableName           A pointer to a null-terminated string that is the variable's name.
  @param[in]       VariableGuid           A pointer to an EFI_GUID that is the variable's GUID. The combination of
                                          VariableGuid and VariableName must be unique.
  @param[out]      Attributes             If non-NULL, on return, points to the variable's attributes.
  @param[in, out]  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[out]      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 *PEI_VARIABLE_STORAGE_GET_VARIABLE)(
  IN CONST  VARIABLE_STORAGE_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[in]      This                   A pointer to this instance of the VARIABLE_STORAGE_PPI.

  @param[in, out] VariableNameSize       On entry, points to the size of the buffer pointed to by
                                         VariableName. On return, the size of the variable name buffer.
  @param[in, out] 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[in, out] 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.
  @param[out]     VariableAttributes     A pointer to the variable attributes.

  @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 *PEI_VARIABLE_STORAGE_GET_NEXT_VARIABLE_NAME)(
  IN CONST  VARIABLE_STORAGE_PPI            *This,
  IN OUT    UINTN                           *VariableNameSize,
  IN OUT    CHAR16                          *VariableName,
  IN OUT    EFI_GUID                        *VariableGuid,
  OUT       UINT32                          *VariableAttributes
  );

///
/// Variable Storage PPI
/// Interface functions for variable NVM storage access in PEI phase.
///
struct _VARIABLE_STORAGE_PPI {
  PEI_VARIABLE_STORAGE_GET_ID                   GetId;                 ///< Retrieves a PPI instance-specific GUID
  PEI_VARIABLE_STORAGE_GET_VARIABLE             GetVariable;           ///< Retrieves a variable's value given its name and GUID
  PEI_VARIABLE_STORAGE_GET_NEXT_VARIABLE_NAME   GetNextVariableName;   ///< Return the next variable name and GUID
};

#endif