MdePkg/Include/Protocol/MmAccess.h

/** @file
  EFI MM Access Protocol as defined in the PI 1.5 specification.

  This protocol is used to control the visibility of the MMRAM on the platform.
  It abstracts the location and characteristics of MMRAM.  The expectation is
  that the north bridge or memory controller would publish this protocol.

  The principal functionality found in the memory controller includes the following:
  - Exposing the MMRAM to all non-MM agents, or the "open" state
  - Shrouding the MMRAM to all but the MM agents, or the "closed" state
  - Preserving the system integrity, or "locking" the MMRAM, such that the settings cannot be
    perturbed by either boot service or runtime agents

  Copyright (c) 2017, Intel Corporation. All rights reserved.<BR>
  SPDX-License-Identifier: BSD-2-Clause-Patent

**/

#ifndef _MM_ACCESS_H_
#define _MM_ACCESS_H_

#define EFI_MM_ACCESS_PROTOCOL_GUID \
  { \
     0xc2702b74, 0x800c, 0x4131, {0x87, 0x46, 0x8f, 0xb5, 0xb8, 0x9c, 0xe4, 0xac } \
  }

typedef struct _EFI_MM_ACCESS_PROTOCOL EFI_MM_ACCESS_PROTOCOL;

/**
  Opens the MMRAM area to be accessible by a boot-service driver.

  This function "opens" MMRAM so that it is visible while not inside of MM. The function should
  return EFI_UNSUPPORTED if the hardware does not support hiding of MMRAM. The function
  should return EFI_DEVICE_ERROR if the MMRAM configuration is locked.

  @param[in] This           The EFI_MM_ACCESS_PROTOCOL instance.

  @retval EFI_SUCCESS       The operation was successful.
  @retval EFI_UNSUPPORTED   The system does not support opening and closing of MMRAM.
  @retval EFI_DEVICE_ERROR  MMRAM cannot be opened, perhaps because it is locked.
**/
typedef
EFI_STATUS
(EFIAPI *EFI_MM_OPEN)(
  IN EFI_MM_ACCESS_PROTOCOL  *This
  );

/**
  Inhibits access to the MMRAM.

  This function "closes" MMRAM so that it is not visible while outside of MM. The function should
  return EFI_UNSUPPORTED if the hardware does not support hiding of MMRAM.

  @param[in] This           The EFI_MM_ACCESS_PROTOCOL instance.

  @retval EFI_SUCCESS       The operation was successful.
  @retval EFI_UNSUPPORTED   The system does not support opening and closing of MMRAM.
  @retval EFI_DEVICE_ERROR  MMRAM cannot be closed.
**/
typedef
EFI_STATUS
(EFIAPI *EFI_MM_CLOSE)(
  IN EFI_MM_ACCESS_PROTOCOL  *This
  );

/**
  Inhibits access to the MMRAM.

  This function prohibits access to the MMRAM region.  This function is usually implemented such
  that it is a write-once operation.

  @param[in] This          The EFI_MM_ACCESS_PROTOCOL instance.

  @retval EFI_SUCCESS      The device was successfully locked.
  @retval EFI_UNSUPPORTED  The system does not support locking of MMRAM.
**/
typedef
EFI_STATUS
(EFIAPI *EFI_MM_LOCK)(
  IN EFI_MM_ACCESS_PROTOCOL  *This
  );

/**
  Queries the memory controller for the possible regions that will support MMRAM.

  @param[in]     This           The EFI_MM_ACCESS_PROTOCOL instance.
  @param[in,out] MmramMapSize   A pointer to the size, in bytes, of the MmramMemoryMap buffer.
  @param[in,out] MmramMap       A pointer to the buffer in which firmware places the current memory map.

  @retval EFI_SUCCESS           The chipset supported the given resource.
  @retval EFI_BUFFER_TOO_SMALL  The MmramMap parameter was too small.  The current buffer size
                                needed to hold the memory map is returned in MmramMapSize.
**/
typedef
EFI_STATUS
(EFIAPI *EFI_MM_CAPABILITIES)(
  IN CONST EFI_MM_ACCESS_PROTOCOL    *This,
  IN OUT UINTN                       *MmramMapSize,
  IN OUT EFI_MMRAM_DESCRIPTOR        *MmramMap
  );

///
///  EFI MM Access Protocol is used to control the visibility of the MMRAM on the platform.
///  It abstracts the location and characteristics of MMRAM. The platform should report all
///  MMRAM via EFI_MM_ACCESS_PROTOCOL. The expectation is that the north bridge or memory
///  controller would publish this protocol.
///
struct _EFI_MM_ACCESS_PROTOCOL {
  EFI_MM_OPEN            Open;
  EFI_MM_CLOSE           Close;
  EFI_MM_LOCK            Lock;
  EFI_MM_CAPABILITIES    GetCapabilities;
  ///
  /// Indicates the current state of the MMRAM. Set to TRUE if MMRAM is locked.
  ///
  BOOLEAN                LockState;
  ///
  /// Indicates the current state of the MMRAM. Set to TRUE if MMRAM is open.
  ///
  BOOLEAN                OpenState;
};

extern EFI_GUID  gEfiMmAccessProtocolGuid;

#endif