***
5.7 MM Communication Protocol

EFI_MM_COMMUNICATION_PROTOCOL

Summary
This protocol provides a means of communicating between drivers outside of
MM and MMI handlers inside of MM.

GUID
#define EFI_MM_COMMUNICATION_PROTOCOL_GUID \
{ 0xc68ed8e2, 0x9dc6, 0x4cbd, 0x9d, 0x94, 0xdb, 0x65, 0xac, 0xc5, 0xc3, 0x32 }

Prototype
typedef struct _EFI_MM_COMMUNICATION_PROTOCOL {
EFI_MM_COMMUNICATE Communicate;
} EFI_MM_COMMUNICATION_PROTOCOL;

Members
Communicate - Sends/receives a message for a registered handler. See the
Communicate() function description.

Description
This protocol provides runtime services for communicating between DXE drivers
and a registered MMI handler.

EFI_MM_COMMUNICATION_PROTOCOL.Communicate()

Summary
Communicates with a registered handler.

Prototype
typedef
EFI_STATUS
(EFIAPI *EFI_MM_COMMUNICATE) (
IN CONST EFI_MM_COMMUNICATION_PROTOCOL *This,
IN OUT VOID *CommBuffer,
IN OUT UINTN *CommSize OPTIONAL
);

Parameters
This - The EFI_MM_COMMUNICATION_PROTOCOL instance.
CommBuffer - Pointer to the buffer to convey into MMRAM.
CommSize - The size of the data buffer being passed in. On exit, the size of
data being returned. Zero if the handler does not wish to reply with any data.
This parameter is optional and may be NULL.

Description
This function provides a service to send and receive messages from a registered
UEFI service. The EFI_MM_COMMUNICATION_PROTOCOL driver is responsible for
doing any of the copies such that the data lives in boot-service-accessible RAM.
A given implementation of the EFI_MM_COMMUNICATION_PROTOCOL may choose
to use the EFI_MM_CONTROL_PROTOCOL for effecting the mode transition, or it may
use some other method.
The agent invoking the communication interface at runtime may be
virtually mapped.
The MM infrastructure code and handlers, on the other hand, execute
in physical mode.
As a result, the non-MM agent, which may be executing in the virtual-mode
OS context (as a result of an OS invocation of the UEFI
SetVirtualAddressMap() service), should use a contiguous
memory buffer with a physical address before invoking this service.
If the virtual address of the buffer is used, the MM Driver may
not know how to do the appropriate virtual-to-physical conversion.
To avoid confusion in interpreting frames, the CommunicateBuffer
parameter should always begin with EFI_MM_COMMUNICATE_HEADER,
which is defined in Related Definitions below.
The header data is mandatory for messages sent into the MM agent.
If the CommSize parameter is omitted the MessageLength field in the
EFI_MM_COMMUNICATE_HEADER, in conjunction with the size of the header itself,
can be used to ascertain the total size of the communication payload.
If the MessageLength is zero, or too large for the MM implementation to manage,
the MM implementation must update the MessageLength to reflect the size of the
Data buffer that it can tolerate.
If the CommSize parameter is passed into the call, but the integer it points to,
has a value of 0, then this must be updated to reflect the maximum size of the
CommBuffer that the implementation can tolerate.
Once inside of MM, the MM infrastructure will call all registered handlers with
the same HandlerType as the GUID specified by HeaderGuid and the
CommBuffer pointing to Data.
This function is not reentrant.
The standard header is used at the beginning of the
EFI_MM_INITIALIATION_HEADER structure during
MM initialization.
See "Related Definitions" below for more information.

Related Definitions
typedef struct {
EFI_GUID HeaderGuid;
UINTN MessageLength;
UINT8 Data[ANYSIZE_ARRAY];
} EFI_MM_COMMUNICATE_HEADER;

HeaderGuid - Allows for disambiguation of the message format. Type EFI_GUID is
defined in InstallProtocolInterface() in the UEFI Specification.
MessageLength - Describes the size of Data (in bytes) and does not include
the size of the header.
Data - Designates an array of bytes that is MessageLength in size.

typedef struct {
EFI_MM_COMMUNICATE_HEADER Header;
EFI_SYSTEM_TABLE *SystemTable;
} EFI_MM_INITIALIZATION_HEADER;

#define EFI_MM_INITIALIZATION_GUID \
{0x99be0d8f, 0x3548, 0x48aa, {0xb5, 0x77, 0xfc, 0xfb, 0xa5, 0x6a, 0x67, 0xf7}}

Header - A standard MM communication buffer header, where
HeaderGuid is set to EFI_MM_INITIALIZATION_GUID.
SystemTable - A pointer to the UEFI System Table. As with DXE driver
initialization, there is no guarantee that the entries in this structure
which rely on architectural protocols are implemented at the time
when this event is generated.

Status Codes Returned
EFI_SUCCESS - The message was successfully posted
EFI_INVALID_PARAMETER - The buffer was NULL.
EFI_BAD_BUFFER_SIZE - The buffer is too large for the MM implementation.
If this error is returned, the MessageLength field in the CommBuffer header or
the integer pointed by CommSize, are updated to reflect the maximum payload
size the implementation can accommodate.
See the function description above for more details.
EFI_ACCESS_DENIED - The CommunicateBuffer parameter or CommSize parameter,
if not omitted, are in address range that cannot be accessed by the MM environment.
***

Supreeth Venkatesh (2):
  MdePkg: Initial Version of MM Communication Protocol.
  MdePkg: Maintain backwards compatibility between MM/SMM.

 MdePkg/Include/Protocol/MmCommunication.h  | 75 ++++++++++++++++++++++++++++++
 MdePkg/Include/Protocol/SmmCommunication.h | 52 +++++----------------
 MdePkg/Include/Uefi/UefiAcpiDataTable.h    |  4 +-
 MdePkg/MdePkg.dec                          |  3 ++
 4 files changed, 93 insertions(+), 41 deletions(-)
 create mode 100644 MdePkg/Include/Protocol/MmCommunication.h

--
2.7.4

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