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, Appendix O — 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.