20. Protocols — ACPI Protocols¶

20.1. EFI_ACPI_TABLE_PROTOCOL¶

Summary

This protocol may be used to install or remove an ACPI table from a platform.

GUID

#define EFI_ACPI_TABLE_PROTOCOL_GUID \
  {0xffe06bdd, 0x6107, 0x46a6,\
    {0x7b, 0xb2, 0x5a, 0x9c, 0x7e, 0xc5, 0x27, 0x5c}}

Protocol Interface Structure

typedef struct _EFI_ACPI_TABLE_PROTOCOL {
  EFI_ACPI_TABLE_INSTALL_ACPI_TABLE       InstallAcpiTable;
  EFI_ACPI_TABLE_UNINSTALL_ACPI_TABLE     UninstallAcpiTable;
}  EFI_ACPI_TABLE_PROTOCOL;

Parameters

InstallAcpiTable: Installs an ACPI table into the system.
UninstallAcpiTable: Removes a previously installed ACPI table from the system.

Description

The EFI_ACPI_TABLE_PROTOCOL provides the ability for a component to install and uninstall ACPI tables from a platform.

20.2. EFI_ACPI_TABLE_PROTOCOL.InstallAcpiTable()¶

Summary

Installs an ACPI table into the RSDT/XSDT.

Prototype

typedef
EFI_STATUS
(EFIAPI *EFI_ACPI_TABLE_INSTALL_ACPI_TABLE) (
  IN EFI_ACPI_TABLE_PROTOCOL                   *This,
  IN VOID                                      *AcpiTableBuffer,
  IN UINTN                                     AcpiTableBufferSize,
  OUT UINTN                                    *TableKey,
  );

Parameters

This: A pointer to a EFI_ACPI_TABLE_PROTOCOL .
AcpiTableBuffer: A pointer to a buffer containing the ACPI table to be installed.
AcpiTableBufferSize: Specifies the size, in bytes, of the AcpiTableBuffer buffer.
TableKey: Returns a key to refer to the ACPI table.

Description

The InstallAcpiTable() function allows a caller to install an ACPI table. The ACPI table may either by a System Description Table or the FACS. For all tables except for the DSDT and FACS, a copy of the table will be linked by the RSDT/XSDT. For the FACS and DSDT, the pointer to a copy of the table will be updated in the FADT, if present.

To prevent namespace collision, ACPI tables may be created using UEFI ACPI table format, UEFI ACPI Data Table. If this protocol is used to install a table with a signature already present in the system, the new table will not replace the existing table. It is a platform implementation decision to add a new table with a signature matching an existing table or disallow duplicate table signatures and return EFI_ACCESS_DENIED.

On successful output, TableKey is initialized with a unique key. Its value may be used in a subsequent call to UninstallAcpiTable to remove an ACPI table.

On successful output, the EFI_ACPI_TABLE_PROTOCOL will ensure that the checksum field is correct for both the RSDT/XSDT table and the copy of the table being installed that is linked by the RSDT/XSDT.

On successful completion, this function reinstalls the relevant EFI_CONFIGURATION_TABLE pointer to the RSDT.

Status Codes Returned

EFI_SUCCESS	The table was successfully inserted
EFI_INVALID_PARAMETER	The AcpiTableBuffer is NULL , the TableKey is NULL ;the AcpiTableBufferSize , and the size field embedded in the ACPI table pointed to by AcpiTableBuffer are not in sync.
EFI_OUT_OF_RESOURCES	Insufficient resources exist to complete the request.
EFI_ACCESS_DENIED	The table signature matches a table already present in the system and platform policy does not allow duplicate tables of this type.

20.3. EFI_ACPI_TABLE_PROTOCOL.UninstallAcpiTable()¶

Summary

Removes an ACPI table from the RSDT/XSDT.

Prototype

typedef
EFI_STATUS
(EFIAPI *EFI_ACPI_TABLE_UNINSTALL_ACPI_TABLE) (
  IN EFI_ACPI_TABLE_PROTOCOL             *This,
  IN UINTN                               TableKey,
  );

Parameters

This: A pointer to a EFI_ACPI_TABLE_PROTOCOL .
TableKey: Specifies the table to uninstall. The key was returned from InstallAcpiTable().

Description

The UninstallAcpiTable() function allows a caller to remove an ACPI table. The routine will remove its reference from the RSDT/XSDT. A table is referenced by the TableKey parameter returned from a prior call to InstallAcpiTable().

On successful completion, this function reinstalls the relevant EFI_CONFIGURATION_TABLE pointer to the RSDT.

Status Codes Returned

EFI_SUCCESS	The table was successfully inserted
EFI_NOT_FOUND	TableKey does not refer to a valid key for a table entry.
EFI_OUT_OF_RESOURCES	Insufficient resources exist to complete the request.