/** @file
  The EFI Legacy BIOS Protocol is used to abstract legacy Option ROM usage
  under EFI and Legacy OS boot.  This file also includes all the related
  COMPATIBILIY16 structures and defintions.

  Note: The names for EFI_IA32_REGISTER_SET elements were picked to follow
  well known naming conventions.

  Thunk is the code that switches from 32-bit protected environment into the 16-bit real-mode
  environment. Reverse thunk is the code that does the opposite.

Copyright (c) 2007 - 2018, Intel Corporation. All rights reserved.<BR>
SPDX-License-Identifier: BSD-2-Clause-Patent

  @par Revision Reference:
  This protocol is defined in Framework for EFI Compatibility Support Module spec
  Version 0.98.

**/

#ifndef _EFI_LEGACY_BIOS_H_
#define _EFI_LEGACY_BIOS_H_

///
///
///
#pragma pack(1)

typedef UINT8                       SERIAL_MODE;
typedef UINT8                       PARALLEL_MODE;

#define EFI_COMPATIBILITY16_TABLE_SIGNATURE SIGNATURE_32 ('I', 'F', 'E', '$')

///
/// There is a table located within the traditional BIOS in either the 0xF000:xxxx or 0xE000:xxxx
/// physical address range. It is located on a 16-byte boundary and provides the physical address of the
/// entry point for the Compatibility16 functions. These functions provide the platform-specific
/// information that is required by the generic EfiCompatibility code. The functions are invoked via
/// thunking by using EFI_LEGACY_BIOS_PROTOCOL.FarCall86() with the 32-bit physical
/// entry point.
///
typedef struct {
  ///
  /// The string "$EFI" denotes the start of the EfiCompatibility table. Byte 0 is "I," byte
  /// 1 is "F," byte 2 is "E," and byte 3 is "$" and is normally accessed as a DWORD or UINT32.
  ///
  UINT32                            Signature;

  ///
  /// The value required such that byte checksum of TableLength equals zero.
  ///
  UINT8                             TableChecksum;

  ///
  /// The length of this table.
  ///
  UINT8                             TableLength;

  ///
  /// The major EFI revision for which this table was generated.
  ///
  UINT8                             EfiMajorRevision;

  ///
  /// The minor EFI revision for which this table was generated.
  ///
  UINT8                             EfiMinorRevision;

  ///
  /// The major revision of this table.
  ///
  UINT8                             TableMajorRevision;

  ///
  /// The minor revision of this table.
  ///
  UINT8                             TableMinorRevision;

  ///
  /// Reserved for future usage.
  ///
  UINT16                            Reserved;

  ///
  /// The segment of the entry point within the traditional BIOS for Compatibility16 functions.
  ///
  UINT16                            Compatibility16CallSegment;

  ///
  /// The offset of the entry point within the traditional BIOS for Compatibility16 functions.
  ///
  UINT16                            Compatibility16CallOffset;

  ///
  /// The segment of the entry point within the traditional BIOS for EfiCompatibility
  /// to invoke the PnP installation check.
  ///
  UINT16                            PnPInstallationCheckSegment;

  ///
  /// The Offset of the entry point within the traditional BIOS for EfiCompatibility
  /// to invoke the PnP installation check.
  ///
  UINT16                            PnPInstallationCheckOffset;

  ///
  /// EFI system resources table. Type EFI_SYSTEM_TABLE is defined in the IntelPlatform
  ///Innovation Framework for EFI Driver Execution Environment Core Interface Specification (DXE CIS).
  ///
  UINT32                            EfiSystemTable;

  ///
  /// The address of an OEM-provided identifier string. The string is null terminated.
  ///
  UINT32                            OemIdStringPointer;

  ///
  /// The 32-bit physical address where ACPI RSD PTR is stored within the traditional
  /// BIOS. The remained of the ACPI tables are located at their EFI addresses. The size
  /// reserved is the maximum for ACPI 2.0. The EfiCompatibility will fill in the ACPI
  /// RSD PTR with either the ACPI 1.0b or 2.0 values.
  ///
  UINT32                            AcpiRsdPtrPointer;

  ///
  /// The OEM revision number. Usage is undefined but provided for OEM module usage.
  ///
  UINT16                            OemRevision;

  ///
  /// The 32-bit physical address where INT15 E820 data is stored within the traditional
  /// BIOS. The EfiCompatibility code will fill in the E820Pointer value and copy the
  /// data to the indicated area.
  ///
  UINT32                            E820Pointer;

  ///
  /// The length of the E820 data and is filled in by the EfiCompatibility code.
  ///
  UINT32                            E820Length;

  ///
  /// The 32-bit physical address where the $PIR table is stored in the traditional BIOS.
  /// The EfiCompatibility code will fill in the IrqRoutingTablePointer value and
  /// copy the data to the indicated area.
  ///
  UINT32                            IrqRoutingTablePointer;

  ///
  /// The length of the $PIR table and is filled in by the EfiCompatibility code.
  ///
  UINT32                            IrqRoutingTableLength;

  ///
  /// The 32-bit physical address where the MP table is stored in the traditional BIOS.
  /// The EfiCompatibility code will fill in the MpTablePtr value and copy the data
  /// to the indicated area.
  ///
  UINT32                            MpTablePtr;

  ///
  /// The length of the MP table and is filled in by the EfiCompatibility code.
  ///
  UINT32                            MpTableLength;

  ///
  /// The segment of the OEM-specific INT table/code.
  ///
  UINT16                            OemIntSegment;

  ///
  /// The offset of the OEM-specific INT table/code.
  ///
  UINT16                            OemIntOffset;

  ///
  /// The segment of the OEM-specific 32-bit table/code.
  ///
  UINT16                            Oem32Segment;

  ///
  /// The offset of the OEM-specific 32-bit table/code.
  ///
  UINT16                            Oem32Offset;

  ///
  /// The segment of the OEM-specific 16-bit table/code.
  ///
  UINT16                            Oem16Segment;

  ///
  /// The offset of the OEM-specific 16-bit table/code.
  ///
  UINT16                            Oem16Offset;

  ///
  /// The segment of the TPM binary passed to 16-bit CSM.
  ///
  UINT16                            TpmSegment;

  ///
  /// The offset of the TPM binary passed to 16-bit CSM.
  ///
  UINT16                            TpmOffset;

  ///
  /// A pointer to a string identifying the independent BIOS vendor.
  ///
  UINT32                            IbvPointer;

  ///
  /// This field is NULL for all systems not supporting PCI Express. This field is the base
  /// value of the start of the PCI Express memory-mapped configuration registers and
  /// must be filled in prior to EfiCompatibility code issuing the Compatibility16 function
  /// Compatibility16InitializeYourself().
  /// Compatibility16InitializeYourself() is defined in Compatability16
  /// Functions.
  ///
  UINT32                            PciExpressBase;

  ///
  /// Maximum PCI bus number assigned.
  ///
  UINT8                             LastPciBus;

  ///
  /// Start Address of Upper Memory Area (UMA) to be set as Read/Write. If
  /// UmaAddress is a valid address in the shadow RAM, it also indicates that the region
  /// from 0xC0000 to (UmaAddress - 1) can be used for Option ROM.
  ///
  UINT32                            UmaAddress;

  ///
  /// Upper Memory Area size in bytes to be set as Read/Write. If zero, no UMA region
  /// will be set as Read/Write (i.e. all Shadow RAM is set as Read-Only).
  ///
  UINT32                            UmaSize;

  ///
  /// Start Address of high memory that can be used for permanent allocation. If zero,
  /// high memory is not available for permanent allocation.
  ///
  UINT32                            HiPermanentMemoryAddress;

  ///
  /// Size of high memory that can be used for permanent allocation in bytes. If zero,
  /// high memory is not available for permanent allocation.
  ///
  UINT32                            HiPermanentMemorySize;
} EFI_COMPATIBILITY16_TABLE;

///
/// Functions provided by the CSM binary which communicate between the EfiCompatibility
/// and Compatability16 code.
///
/// Inconsistent with the specification here:
/// The member's name started with "Compatibility16" [defined in Intel Framework
/// Compatibility Support Module Specification / 0.97 version]
/// has been changed to "Legacy16" since keeping backward compatible.
///
typedef enum {
  ///
  /// Causes the Compatibility16 code to do any internal initialization required.
  /// Input:
  ///   AX = Compatibility16InitializeYourself
  ///   ES:BX = Pointer to EFI_TO_COMPATIBILITY16_INIT_TABLE
  /// Return:
  ///   AX = Return Status codes
  ///
  Legacy16InitializeYourself    = 0x0000,

  ///
  /// Causes the Compatibility16 BIOS to perform any drive number translations to match the boot sequence.
  /// Input:
  ///   AX = Compatibility16UpdateBbs
  ///   ES:BX = Pointer to EFI_TO_COMPATIBILITY16_BOOT_TABLE
  /// Return:
  ///   AX = Returned status codes
  ///
  Legacy16UpdateBbs             = 0x0001,

  ///
  /// Allows the Compatibility16 code to perform any final actions before booting. The Compatibility16
  /// code is read/write.
  /// Input:
  ///   AX = Compatibility16PrepareToBoot
  ///   ES:BX = Pointer to EFI_TO_COMPATIBILITY16_BOOT_TABLE structure
  /// Return:
  ///   AX = Returned status codes
  ///
  Legacy16PrepareToBoot         = 0x0002,

  ///
  /// Causes the Compatibility16 BIOS to boot. The Compatibility16 code is Read/Only.
  /// Input:
  ///   AX = Compatibility16Boot
  /// Output:
  ///   AX = Returned status codes
  ///
  Legacy16Boot                  = 0x0003,

  ///
  /// Allows the Compatibility16 code to get the last device from which a boot was attempted. This is
  /// stored in CMOS and is the priority number of the last attempted boot device.
  /// Input:
  ///   AX = Compatibility16RetrieveLastBootDevice
  /// Output:
  ///   AX = Returned status codes
  ///   BX = Priority number of the boot device.
  ///
  Legacy16RetrieveLastBootDevice = 0x0004,

  ///
  /// Allows the Compatibility16 code rehook INT13, INT18, and/or INT19 after dispatching a legacy OpROM.
  /// Input:
  ///   AX = Compatibility16DispatchOprom
  ///   ES:BX = Pointer to EFI_DISPATCH_OPROM_TABLE
  /// Output:
  ///   AX = Returned status codes
  ///   BX = Number of non-BBS-compliant devices found. Equals 0 if BBS compliant.
  ///
  Legacy16DispatchOprom         = 0x0005,

  ///
  /// Finds a free area in the 0xFxxxx or 0xExxxx region of the specified length and returns the address
  /// of that region.
  /// Input:
  ///   AX = Compatibility16GetTableAddress
  ///   BX = Allocation region
  ///       00 = Allocate from either 0xE0000 or 0xF0000 64 KB blocks.
  ///       Bit 0 = 1 Allocate from 0xF0000 64 KB block
  ///       Bit 1 = 1 Allocate from 0xE0000 64 KB block
  ///   CX = Requested length in bytes.
  ///   DX = Required address alignment. Bit mapped. First non-zero bit from the right is the alignment.
  /// Output:
  ///   AX = Returned status codes
  ///   DS:BX = Address of the region
  ///
  Legacy16GetTableAddress       = 0x0006,

  ///
  /// Enables the EfiCompatibility module to do any nonstandard processing of keyboard LEDs or state.
  /// Input:
  ///   AX = Compatibility16SetKeyboardLeds
  ///   CL = LED status.
  ///     Bit 0  Scroll Lock 0 = Off
  ///     Bit 1  NumLock
  ///     Bit 2  Caps Lock
  /// Output:
  ///     AX = Returned status codes
  ///
  Legacy16SetKeyboardLeds       = 0x0007,

  ///
  /// Enables the EfiCompatibility module to install an interrupt handler for PCI mass media devices that
  /// do not have an OpROM associated with them. An example is SATA.
  /// Input:
  ///   AX = Compatibility16InstallPciHandler
  ///   ES:BX = Pointer to EFI_LEGACY_INSTALL_PCI_HANDLER structure
  /// Output:
  ///   AX = Returned status codes
  ///
  Legacy16InstallPciHandler     = 0x0008
} EFI_COMPATIBILITY_FUNCTIONS;


///
/// EFI_DISPATCH_OPROM_TABLE
///
typedef struct {
  UINT16  PnPInstallationCheckSegment;  ///< A pointer to the PnpInstallationCheck data structure.
  UINT16  PnPInstallationCheckOffset;   ///< A pointer to the PnpInstallationCheck data structure.
  UINT16  OpromSegment;                 ///< The segment where the OpROM was placed. Offset is assumed to be 3.
  UINT8   PciBus;                       ///< The PCI bus.
  UINT8   PciDeviceFunction;            ///< The PCI device * 0x08 | PCI function.
  UINT8   NumberBbsEntries;             ///< The number of valid BBS table entries upon entry and exit. The IBV code may
                                        ///< increase this number, if BBS-compliant devices also hook INTs in order to force the
                                        ///< OpROM BIOS Setup to be executed.
  UINT32  BbsTablePointer;              ///< A pointer to the BBS table.
  UINT16  RuntimeSegment;               ///< The segment where the OpROM can be relocated to. If this value is 0x0000, this
                                        ///< means that the relocation of this run time code is not supported.
                                        ///< Inconsistent with specification here:
                                        ///< The member's name "OpromDestinationSegment" [defined in Intel Framework Compatibility Support Module Specification / 0.97 version]
                                        ///< has been changed to "RuntimeSegment" since keeping backward compatible.

} EFI_DISPATCH_OPROM_TABLE;

///
/// EFI_TO_COMPATIBILITY16_INIT_TABLE
///
typedef struct {
  ///
  /// Starting address of memory under 1 MB. The ending address is assumed to be 640 KB or 0x9FFFF.
  ///
  UINT32                            BiosLessThan1MB;

  ///
  /// The starting address of the high memory block.
  ///
  UINT32                            HiPmmMemory;

  ///
  /// The length of high memory block.
  ///
  UINT32                            HiPmmMemorySizeInBytes;

  ///
  /// The segment of the reverse thunk call code.
  ///
  UINT16                            ReverseThunkCallSegment;

  ///
  /// The offset of the reverse thunk call code.
  ///
  UINT16                            ReverseThunkCallOffset;

  ///
  /// The number of E820 entries copied to the Compatibility16 BIOS.
  ///
  UINT32                            NumberE820Entries;

  ///
  /// The amount of usable memory above 1 MB, e.g., E820 type 1 memory.
  ///
  UINT32                            OsMemoryAbove1Mb;

  ///
  /// The start of thunk code in main memory. Memory cannot be used by BIOS or PMM.
  ///
  UINT32                            ThunkStart;

  ///
  /// The size of the thunk code.
  ///
  UINT32                            ThunkSizeInBytes;

  ///
  /// Starting address of memory under 1 MB.
  ///
  UINT32                            LowPmmMemory;

  ///
  /// The length of low Memory block.
  ///
  UINT32                            LowPmmMemorySizeInBytes;
} EFI_TO_COMPATIBILITY16_INIT_TABLE;

///
/// DEVICE_PRODUCER_SERIAL.
///
typedef struct {
  UINT16                            Address;    ///< I/O address assigned to the serial port.
  UINT8                             Irq;        ///< IRQ assigned to the serial port.
  SERIAL_MODE                       Mode;       ///< Mode of serial port. Values are defined below.
} DEVICE_PRODUCER_SERIAL;

///
/// DEVICE_PRODUCER_SERIAL's modes.
///@{
#define DEVICE_SERIAL_MODE_NORMAL               0x00
#define DEVICE_SERIAL_MODE_IRDA                 0x01
#define DEVICE_SERIAL_MODE_ASK_IR               0x02
#define DEVICE_SERIAL_MODE_DUPLEX_HALF          0x00
#define DEVICE_SERIAL_MODE_DUPLEX_FULL          0x10
///@)

///
/// DEVICE_PRODUCER_PARALLEL.
///
typedef struct {
  UINT16                            Address;  ///< I/O address assigned to the parallel port.
  UINT8                             Irq;      ///< IRQ assigned to the parallel port.
  UINT8                             Dma;      ///< DMA assigned to the parallel port.
  PARALLEL_MODE                     Mode;     ///< Mode of the parallel port. Values are defined below.
} DEVICE_PRODUCER_PARALLEL;

///
/// DEVICE_PRODUCER_PARALLEL's modes.
///@{
#define DEVICE_PARALLEL_MODE_MODE_OUTPUT_ONLY   0x00
#define DEVICE_PARALLEL_MODE_MODE_BIDIRECTIONAL 0x01
#define DEVICE_PARALLEL_MODE_MODE_EPP           0x02
#define DEVICE_PARALLEL_MODE_MODE_ECP           0x03
///@}

///
/// DEVICE_PRODUCER_FLOPPY
///
typedef struct {
  UINT16                            Address;          ///< I/O address assigned to the floppy.
  UINT8                             Irq;              ///< IRQ assigned to the floppy.
  UINT8                             Dma;              ///< DMA assigned to the floppy.
  UINT8                             NumberOfFloppy;   ///< Number of floppies in the system.
} DEVICE_PRODUCER_FLOPPY;

///
/// LEGACY_DEVICE_FLAGS
///
typedef struct {
  UINT32                            A20Kybd : 1;      ///< A20 controller by keyboard controller.
  UINT32                            A20Port90 : 1;    ///< A20 controlled by port 0x92.
  UINT32                            Reserved : 30;    ///< Reserved for future usage.
} LEGACY_DEVICE_FLAGS;

///
/// DEVICE_PRODUCER_DATA_HEADER
///
typedef struct {
  DEVICE_PRODUCER_SERIAL            Serial[4];      ///< Data for serial port x. Type DEVICE_PRODUCER_SERIAL is defined below.
  DEVICE_PRODUCER_PARALLEL          Parallel[3];    ///< Data for parallel port x. Type DEVICE_PRODUCER_PARALLEL is defined below.
  DEVICE_PRODUCER_FLOPPY            Floppy;         ///< Data for floppy. Type DEVICE_PRODUCER_FLOPPY is defined below.
  UINT8                             MousePresent;   ///< Flag to indicate if mouse is present.
  LEGACY_DEVICE_FLAGS               Flags;          ///< Miscellaneous Boolean state information passed to CSM.
} DEVICE_PRODUCER_DATA_HEADER;

///
/// ATAPI_IDENTIFY
///
typedef struct {
  UINT16                            Raw[256];     ///< Raw data from the IDE IdentifyDrive command.
} ATAPI_IDENTIFY;

///
/// HDD_INFO
///
typedef struct {
  ///
  /// Status of IDE device. Values are defined below. There is one HDD_INFO structure
  /// per IDE controller. The IdentifyDrive is per drive. Index 0 is master and index
  /// 1 is slave.
  ///
  UINT16                            Status;

  ///
  /// PCI bus of IDE controller.
  ///
  UINT32                            Bus;

  ///
  /// PCI device of IDE controller.
  ///
  UINT32                            Device;

  ///
  /// PCI function of IDE controller.
  ///
  UINT32                            Function;

  ///
  /// Command ports base address.
  ///
  UINT16                            CommandBaseAddress;

  ///
  /// Control ports base address.
  ///
  UINT16                            ControlBaseAddress;

  ///
  /// Bus master address.
  ///
  UINT16                            BusMasterAddress;

  UINT8                             HddIrq;

  ///
  /// Data that identifies the drive data; one per possible attached drive.
  ///
  ATAPI_IDENTIFY                    IdentifyDrive[2];
} HDD_INFO;

///
/// HDD_INFO status bits
///
#define HDD_PRIMARY               0x01
#define HDD_SECONDARY             0x02
#define HDD_MASTER_ATAPI_CDROM    0x04
#define HDD_SLAVE_ATAPI_CDROM     0x08
#define HDD_MASTER_IDE            0x20
#define HDD_SLAVE_IDE             0x40
#define HDD_MASTER_ATAPI_ZIPDISK  0x10
#define HDD_SLAVE_ATAPI_ZIPDISK   0x80

///
/// BBS_STATUS_FLAGS;\.
///
typedef struct {
  UINT16                            OldPosition : 4;    ///< Prior priority.
  UINT16                            Reserved1 : 4;      ///< Reserved for future use.
  UINT16                            Enabled : 1;        ///< If 0, ignore this entry.
  UINT16                            Failed : 1;         ///< 0 = Not known if boot failure occurred.
                                                        ///< 1 = Boot attempted failed.

  ///
  /// State of media present.
  ///   00 = No bootable media is present in the device.
  ///   01 = Unknown if a bootable media present.
  ///   10 = Media is present and appears bootable.
  ///   11 = Reserved.
  ///
  UINT16                            MediaPresent : 2;
  UINT16                            Reserved2 : 4;      ///< Reserved for future use.
} BBS_STATUS_FLAGS;

///
/// BBS_TABLE, device type values & boot priority values.
///
typedef struct {
  ///
  /// The boot priority for this boot device. Values are defined below.
  ///
  UINT16                            BootPriority;

  ///
  /// The PCI bus for this boot device.
  ///
  UINT32                            Bus;

  ///
  /// The PCI device for this boot device.
  ///
  UINT32                            Device;

  ///
  /// The PCI function for the boot device.
  ///
  UINT32                            Function;

  ///
  /// The PCI class for this boot device.
  ///
  UINT8                             Class;

  ///
  /// The PCI Subclass for this boot device.
  ///
  UINT8                             SubClass;

  ///
  /// Segment:offset address of an ASCIIZ description string describing the manufacturer.
  ///
  UINT16                            MfgStringOffset;

  ///
  /// Segment:offset address of an ASCIIZ description string describing the manufacturer.
  ///
  UINT16                            MfgStringSegment;

  ///
  /// BBS device type. BBS device types are defined below.
  ///
  UINT16                            DeviceType;

  ///
  /// Status of this boot device. Type BBS_STATUS_FLAGS is defined below.
  ///
  BBS_STATUS_FLAGS                  StatusFlags;

  ///
  /// Segment:Offset address of boot loader for IPL devices or install INT13 handler for
  /// BCV devices.
  ///
  UINT16                            BootHandlerOffset;

  ///
  /// Segment:Offset address of boot loader for IPL devices or install INT13 handler for
  /// BCV devices.
  ///
  UINT16                            BootHandlerSegment;

  ///
  /// Segment:offset address of an ASCIIZ description string describing this device.
  ///
  UINT16                            DescStringOffset;

  ///
  /// Segment:offset address of an ASCIIZ description string describing this device.
  ///
  UINT16                            DescStringSegment;

  ///
  /// Reserved.
  ///
  UINT32                            InitPerReserved;

  ///
  /// The use of these fields is IBV dependent. They can be used to flag that an OpROM
  /// has hooked the specified IRQ. The OpROM may be BBS compliant as some SCSI
  /// BBS-compliant OpROMs also hook IRQ vectors in order to run their BIOS Setup
  ///
  UINT32                            AdditionalIrq13Handler;

  ///
  /// The use of these fields is IBV dependent. They can be used to flag that an OpROM
  /// has hooked the specified IRQ. The OpROM may be BBS compliant as some SCSI
  /// BBS-compliant OpROMs also hook IRQ vectors in order to run their BIOS Setup
  ///
  UINT32                            AdditionalIrq18Handler;

  ///
  /// The use of these fields is IBV dependent. They can be used to flag that an OpROM
  /// has hooked the specified IRQ. The OpROM may be BBS compliant as some SCSI
  /// BBS-compliant OpROMs also hook IRQ vectors in order to run their BIOS Setup
  ///
  UINT32                            AdditionalIrq19Handler;

  ///
  /// The use of these fields is IBV dependent. They can be used to flag that an OpROM
  /// has hooked the specified IRQ. The OpROM may be BBS compliant as some SCSI
  /// BBS-compliant OpROMs also hook IRQ vectors in order to run their BIOS Setup
  ///
  UINT32                            AdditionalIrq40Handler;
  UINT8                             AssignedDriveNumber;
  UINT32                            AdditionalIrq41Handler;
  UINT32                            AdditionalIrq46Handler;
  UINT32                            IBV1;
  UINT32                            IBV2;
} BBS_TABLE;

///
/// BBS device type values
///@{
#define BBS_FLOPPY              0x01
#define BBS_HARDDISK            0x02
#define BBS_CDROM               0x03
#define BBS_PCMCIA              0x04
#define BBS_USB                 0x05
#define BBS_EMBED_NETWORK       0x06
#define BBS_BEV_DEVICE          0x80
#define BBS_UNKNOWN             0xff
///@}

///
/// BBS boot priority values
///@{
#define BBS_DO_NOT_BOOT_FROM    0xFFFC
#define BBS_LOWEST_PRIORITY     0xFFFD
#define BBS_UNPRIORITIZED_ENTRY 0xFFFE
#define BBS_IGNORE_ENTRY        0xFFFF
///@}

///
/// SMM_ATTRIBUTES
///
typedef struct {
  ///
  /// Access mechanism used to generate the soft SMI. Defined types are below. The other
  /// values are reserved for future usage.
  ///
  UINT16                            Type : 3;

  ///
  /// The size of "port" in bits. Defined values are below.
  ///
  UINT16                            PortGranularity : 3;

  ///
  /// The size of data in bits. Defined values are below.
  ///
  UINT16                            DataGranularity : 3;

  ///
  /// Reserved for future use.
  ///
  UINT16                            Reserved : 7;
} SMM_ATTRIBUTES;

///
/// SMM_ATTRIBUTES type values.
///@{
#define STANDARD_IO       0x00
#define STANDARD_MEMORY   0x01
///@}

///
/// SMM_ATTRIBUTES port size constants.
///@{
#define PORT_SIZE_8       0x00
#define PORT_SIZE_16      0x01
#define PORT_SIZE_32      0x02
#define PORT_SIZE_64      0x03
///@}

///
/// SMM_ATTRIBUTES data size constants.
///@{
#define DATA_SIZE_8       0x00
#define DATA_SIZE_16      0x01
#define DATA_SIZE_32      0x02
#define DATA_SIZE_64      0x03
///@}

///
/// SMM_FUNCTION & relating constants.
///
typedef struct {
  UINT16                            Function : 15;
  UINT16                            Owner : 1;
} SMM_FUNCTION;

///
/// SMM_FUNCTION Function constants.
///@{
#define INT15_D042        0x0000
#define GET_USB_BOOT_INFO 0x0001
#define DMI_PNP_50_57     0x0002
///@}

///
/// SMM_FUNCTION Owner constants.
///@{
#define STANDARD_OWNER    0x0
#define OEM_OWNER         0x1
///@}

///
/// This structure assumes both port and data sizes are 1. SmmAttribute must be
/// properly to reflect that assumption.
///
typedef struct {
  ///
  /// Describes the access mechanism, SmmPort, and SmmData sizes. Type
  /// SMM_ATTRIBUTES is defined below.
  ///
  SMM_ATTRIBUTES                    SmmAttributes;

  ///
  /// Function Soft SMI is to perform. Type SMM_FUNCTION is defined below.
  ///
  SMM_FUNCTION                      SmmFunction;

  ///
  /// SmmPort size depends upon SmmAttributes and ranges from2 bytes to 16 bytes.
  ///
  UINT8                             SmmPort;

  ///
  /// SmmData size depends upon SmmAttributes and ranges from2 bytes to 16 bytes.
  ///
  UINT8                             SmmData;
} SMM_ENTRY;

///
/// SMM_TABLE
///
typedef struct {
  UINT16                            NumSmmEntries;    ///< Number of entries represented by SmmEntry.
  SMM_ENTRY                         SmmEntry;         ///< One entry per function. Type SMM_ENTRY is defined below.
} SMM_TABLE;

///
/// UDC_ATTRIBUTES
///
typedef struct {
  ///
  /// This bit set indicates that the ServiceAreaData is valid.
  ///
  UINT8                             DirectoryServiceValidity : 1;

  ///
  /// This bit set indicates to use the Reserve Area Boot Code Address (RACBA) only if
  /// DirectoryServiceValidity is 0.
  ///
  UINT8                             RabcaUsedFlag : 1;

  ///
  /// This bit set indicates to execute hard disk diagnostics.
  ///
  UINT8                             ExecuteHddDiagnosticsFlag : 1;

  ///
  /// Reserved for future use. Set to 0.
  ///
  UINT8                             Reserved : 5;
} UDC_ATTRIBUTES;

///
/// UD_TABLE
///
typedef struct {
  ///
  /// This field contains the bit-mapped attributes of the PARTIES information. Type
  /// UDC_ATTRIBUTES is defined below.
  ///
  UDC_ATTRIBUTES                    Attributes;

  ///
  /// This field contains the zero-based device on which the selected
  /// ServiceDataArea is present. It is 0 for master and 1 for the slave device.
  ///
  UINT8                             DeviceNumber;

  ///
  /// This field contains the zero-based index into the BbsTable for the parent device.
  /// This index allows the user to reference the parent device information such as PCI
  /// bus, device function.
  ///
  UINT8                             BbsTableEntryNumberForParentDevice;

  ///
  /// This field contains the zero-based index into the BbsTable for the boot entry.
  ///
  UINT8                             BbsTableEntryNumberForBoot;

  ///
  /// This field contains the zero-based index into the BbsTable for the HDD diagnostics entry.
  ///
  UINT8                             BbsTableEntryNumberForHddDiag;

  ///
  /// The raw Beer data.
  ///
  UINT8                             BeerData[128];

  ///
  /// The raw data of selected service area.
  ///
  UINT8                             ServiceAreaData[64];
} UD_TABLE;

#define EFI_TO_LEGACY_MAJOR_VERSION 0x02
#define EFI_TO_LEGACY_MINOR_VERSION 0x00
#define MAX_IDE_CONTROLLER          8

///
/// EFI_TO_COMPATIBILITY16_BOOT_TABLE
///
typedef struct {
  UINT16                            MajorVersion;                 ///< The EfiCompatibility major version number.
  UINT16                            MinorVersion;                 ///< The EfiCompatibility minor version number.
  UINT32                            AcpiTable;                    ///< The location of the RSDT ACPI table. < 4G range.
  UINT32                            SmbiosTable;                  ///< The location of the SMBIOS table in EFI memory. < 4G range.
  UINT32                            SmbiosTableLength;
  //
  // Legacy SIO state
  //
  DEVICE_PRODUCER_DATA_HEADER       SioData;                      ///< Standard traditional device information.
  UINT16                            DevicePathType;               ///< The default boot type.
  UINT16                            PciIrqMask;                   ///< Mask of which IRQs have been assigned to PCI.
  UINT32                            NumberE820Entries;            ///< Number of E820 entries. The number can change from the
                                                                  ///< Compatibility16InitializeYourself() function.
  //
  // Controller & Drive Identify[2] per controller information
  //
  HDD_INFO                          HddInfo[MAX_IDE_CONTROLLER];  ///< Hard disk drive information, including raw Identify Drive data.
  UINT32                            NumberBbsEntries;             ///< Number of entries in the BBS table
  UINT32                            BbsTable;                     ///< A pointer to the BBS table. Type BBS_TABLE is defined below.
  UINT32                            SmmTable;                     ///< A pointer to the SMM table. Type SMM_TABLE is defined below.
  UINT32                            OsMemoryAbove1Mb;             ///< The amount of usable memory above 1 MB, i.e. E820 type 1 memory. This value can
                                                                  ///< differ from the value in EFI_TO_COMPATIBILITY16_INIT_TABLE as more
                                                                  ///< memory may have been discovered.
  UINT32                            UnconventionalDeviceTable;    ///< Information to boot off an unconventional device like a PARTIES partition. Type
                                                                  ///< UD_TABLE is defined below.
} EFI_TO_COMPATIBILITY16_BOOT_TABLE;

///
/// EFI_LEGACY_INSTALL_PCI_HANDLER
///
typedef struct {
  UINT8                             PciBus;             ///< The PCI bus of the device.
  UINT8                             PciDeviceFun;       ///< The PCI device in bits 7:3 and function in bits 2:0.
  UINT8                             PciSegment;         ///< The PCI segment of the device.
  UINT8                             PciClass;           ///< The PCI class code of the device.
  UINT8                             PciSubclass;        ///< The PCI subclass code of the device.
  UINT8                             PciInterface;       ///< The PCI interface code of the device.
  //
  // Primary section
  //
  UINT8                             PrimaryIrq;         ///< The primary device IRQ.
  UINT8                             PrimaryReserved;    ///< Reserved.
  UINT16                            PrimaryControl;     ///< The primary device control I/O base.
  UINT16                            PrimaryBase;        ///< The primary device I/O base.
  UINT16                            PrimaryBusMaster;   ///< The primary device bus master I/O base.
  //
  // Secondary Section
  //
  UINT8                             SecondaryIrq;       ///< The secondary device IRQ.
  UINT8                             SecondaryReserved;  ///< Reserved.
  UINT16                            SecondaryControl;   ///< The secondary device control I/O base.
  UINT16                            SecondaryBase;      ///< The secondary device I/O base.
  UINT16                            SecondaryBusMaster; ///< The secondary device bus master I/O base.
} EFI_LEGACY_INSTALL_PCI_HANDLER;

//
// Restore default pack value
//
#pragma pack()

#define EFI_LEGACY_BIOS_PROTOCOL_GUID \
  { \
    0xdb9a1e3d, 0x45cb, 0x4abb, {0x85, 0x3b, 0xe5, 0x38, 0x7f, 0xdb, 0x2e, 0x2d } \
  }

typedef struct _EFI_LEGACY_BIOS_PROTOCOL EFI_LEGACY_BIOS_PROTOCOL;

///
/// Flags returned by CheckPciRom().
///
#define NO_ROM            0x00
#define ROM_FOUND         0x01
#define VALID_LEGACY_ROM  0x02
#define ROM_WITH_CONFIG   0x04     ///< Not defined in the Framework CSM Specification.

///
/// The following macros do not appear in the Framework CSM Specification and
/// are kept for backward compatibility only.  They convert 32-bit address (_Adr)
/// to Segment:Offset 16-bit form.
///
///@{
#define EFI_SEGMENT(_Adr)     (UINT16) ((UINT16) (((UINTN) (_Adr)) >> 4) & 0xf000)
#define EFI_OFFSET(_Adr)      (UINT16) (((UINT16) ((UINTN) (_Adr))) & 0xffff)
///@}

#define CARRY_FLAG            0x01

///
/// EFI_EFLAGS_REG
///
typedef struct {
  UINT32 CF:1;
  UINT32 Reserved1:1;
  UINT32 PF:1;
  UINT32 Reserved2:1;
  UINT32 AF:1;
  UINT32 Reserved3:1;
  UINT32 ZF:1;
  UINT32 SF:1;
  UINT32 TF:1;
  UINT32 IF:1;
  UINT32 DF:1;
  UINT32 OF:1;
  UINT32 IOPL:2;
  UINT32 NT:1;
  UINT32 Reserved4:2;
  UINT32 VM:1;
  UINT32 Reserved5:14;
} EFI_EFLAGS_REG;

///
/// EFI_DWORD_REGS
///
typedef struct {
    UINT32           EAX;
    UINT32           EBX;
    UINT32           ECX;
    UINT32           EDX;
    UINT32           ESI;
    UINT32           EDI;
    EFI_EFLAGS_REG   EFlags;
    UINT16           ES;
    UINT16           CS;
    UINT16           SS;
    UINT16           DS;
    UINT16           FS;
    UINT16           GS;
    UINT32           EBP;
    UINT32           ESP;
} EFI_DWORD_REGS;

///
/// EFI_FLAGS_REG
///
typedef struct {
  UINT16     CF:1;
  UINT16     Reserved1:1;
  UINT16     PF:1;
  UINT16     Reserved2:1;
  UINT16     AF:1;
  UINT16     Reserved3:1;
  UINT16     ZF:1;
  UINT16     SF:1;
  UINT16     TF:1;
  UINT16     IF:1;
  UINT16     DF:1;
  UINT16     OF:1;
  UINT16     IOPL:2;
  UINT16     NT:1;
  UINT16     Reserved4:1;
} EFI_FLAGS_REG;

///
/// EFI_WORD_REGS
///
typedef struct {
    UINT16           AX;
    UINT16           ReservedAX;
    UINT16           BX;
    UINT16           ReservedBX;
    UINT16           CX;
    UINT16           ReservedCX;
    UINT16           DX;
    UINT16           ReservedDX;
    UINT16           SI;
    UINT16           ReservedSI;
    UINT16           DI;
    UINT16           ReservedDI;
    EFI_FLAGS_REG    Flags;
    UINT16           ReservedFlags;
    UINT16           ES;
    UINT16           CS;
    UINT16           SS;
    UINT16           DS;
    UINT16           FS;
    UINT16           GS;
    UINT16           BP;
    UINT16           ReservedBP;
    UINT16           SP;
    UINT16           ReservedSP;
} EFI_WORD_REGS;

///
/// EFI_BYTE_REGS
///
typedef struct {
    UINT8   AL, AH;
    UINT16  ReservedAX;
    UINT8   BL, BH;
    UINT16  ReservedBX;
    UINT8   CL, CH;
    UINT16  ReservedCX;
    UINT8   DL, DH;
    UINT16  ReservedDX;
} EFI_BYTE_REGS;

///
/// EFI_IA32_REGISTER_SET
///
typedef union {
  EFI_DWORD_REGS  E;
  EFI_WORD_REGS   X;
  EFI_BYTE_REGS   H;
} EFI_IA32_REGISTER_SET;

/**
  Thunk to 16-bit real mode and execute a software interrupt with a vector
  of BiosInt. Regs will contain the 16-bit register context on entry and
  exit.

  @param[in]     This      The protocol instance pointer.
  @param[in]     BiosInt   The processor interrupt vector to invoke.
  @param[in,out] Reg       Register contexted passed into (and returned) from thunk to
                           16-bit mode.

  @retval TRUE                Thunk completed with no BIOS errors in the target code. See Regs for status.
  @retval FALSE                  There was a BIOS error in the target code.
**/
typedef
BOOLEAN
(EFIAPI *EFI_LEGACY_BIOS_INT86)(
  IN     EFI_LEGACY_BIOS_PROTOCOL  *This,
  IN     UINT8                     BiosInt,
  IN OUT EFI_IA32_REGISTER_SET     *Regs
  );

/**
  Thunk to 16-bit real mode and call Segment:Offset. Regs will contain the
  16-bit register context on entry and exit. Arguments can be passed on
  the Stack argument

  @param[in] This        The protocol instance pointer.
  @param[in] Segment     The segemnt of 16-bit mode call.
  @param[in] Offset      The offset of 16-bit mdoe call.
  @param[in] Reg         Register contexted passed into (and returned) from thunk to
                         16-bit mode.
  @param[in] Stack       The caller allocated stack used to pass arguments.
  @param[in] StackSize   The size of Stack in bytes.

  @retval FALSE                 Thunk completed with no BIOS errors in the target code.                                See Regs for status.  @retval TRUE                  There was a BIOS error in the target code.
**/
typedef
BOOLEAN
(EFIAPI *EFI_LEGACY_BIOS_FARCALL86)(
  IN EFI_LEGACY_BIOS_PROTOCOL  *This,
  IN UINT16                    Segment,
  IN UINT16                    Offset,
  IN EFI_IA32_REGISTER_SET     *Regs,
  IN VOID                      *Stack,
  IN UINTN                     StackSize
  );

/**
  Test to see if a legacy PCI ROM exists for this device. Optionally return
  the Legacy ROM instance for this PCI device.

  @param[in]  This        The protocol instance pointer.
  @param[in]  PciHandle   The PCI PC-AT OPROM from this devices ROM BAR will be loaded
  @param[out] RomImage    Return the legacy PCI ROM for this device.
  @param[out] RomSize     The size of ROM Image.
  @param[out] Flags       Indicates if ROM found and if PC-AT. Multiple bits can be set as follows:
                            - 00 = No ROM.
                            - 01 = ROM Found.
                            - 02 = ROM is a valid legacy ROM.

  @retval EFI_SUCCESS       The Legacy Option ROM available for this device
  @retval EFI_UNSUPPORTED   The Legacy Option ROM is not supported.

**/
typedef
EFI_STATUS
(EFIAPI *EFI_LEGACY_BIOS_CHECK_ROM)(
  IN  EFI_LEGACY_BIOS_PROTOCOL  *This,
  IN  EFI_HANDLE                PciHandle,
  OUT VOID                      **RomImage, OPTIONAL
  OUT UINTN                     *RomSize, OPTIONAL
  OUT UINTN                     *Flags
  );

/**
  Load a legacy PC-AT OPROM on the PciHandle device. Return information
  about how many disks were added by the OPROM and the shadow address and
  size. DiskStart & DiskEnd are INT 13h drive letters. Thus 0x80 is C:

  @param[in]  This               The protocol instance pointer.
  @param[in]  PciHandle          The PCI PC-AT OPROM from this devices ROM BAR will be loaded.
                                 This value is NULL if RomImage is non-NULL. This is the normal
                                 case.
  @param[in]  RomImage           A PCI PC-AT ROM image. This argument is non-NULL if there is
                                 no hardware associated with the ROM and thus no PciHandle,
                                 otherwise is must be NULL.
                                 Example is PXE base code.
  @param[out] Flags              The type of ROM discovered. Multiple bits can be set, as follows:
                                   - 00 = No ROM.
                                   - 01 = ROM found.
                                   - 02 = ROM is a valid legacy ROM.
  @param[out] DiskStart          The disk number of first device hooked by the ROM. If DiskStart
                                 is the same as DiskEnd no disked were hooked.
  @param[out] DiskEnd            disk number of the last device hooked by the ROM.
  @param[out] RomShadowAddress   Shadow address of PC-AT ROM.
  @param[out] RomShadowSize      Size of RomShadowAddress in bytes.

  @retval EFI_SUCCESS             Thunk completed, see Regs for status.
  @retval EFI_INVALID_PARAMETER   PciHandle not found

**/
typedef
EFI_STATUS
(EFIAPI *EFI_LEGACY_BIOS_INSTALL_ROM)(
  IN  EFI_LEGACY_BIOS_PROTOCOL  *This,
  IN  EFI_HANDLE                PciHandle,
  IN  VOID                      **RomImage,
  OUT UINTN                     *Flags,
  OUT UINT8                     *DiskStart, OPTIONAL
  OUT UINT8                     *DiskEnd, OPTIONAL
  OUT VOID                      **RomShadowAddress, OPTIONAL
  OUT UINT32                    *ShadowedRomSize OPTIONAL
  );

/**
  This function attempts to traditionally boot the specified BootOption. If the EFI context has
  been compromised, this function will not return. This procedure is not used for loading an EFI-aware
  OS off a traditional device. The following actions occur:
  - Get EFI SMBIOS data structures, convert them to a traditional format, and copy to
    Compatibility16.
  - Get a pointer to ACPI data structures and copy the Compatibility16 RSD PTR to F0000 block.
  - Find the traditional SMI handler from a firmware volume and register the traditional SMI
    handler with the EFI SMI handler.
  - Build onboard IDE information and pass this information to the Compatibility16 code.
  - Make sure all PCI Interrupt Line registers are programmed to match 8259.
  - Reconfigure SIO devices from EFI mode (polled) into traditional mode (interrupt driven).
  - Shadow all PCI ROMs.
  - Set up BDA and EBDA standard areas before the legacy boot.
  - Construct the Compatibility16 boot memory map and pass it to the Compatibility16 code.
  - Invoke the Compatibility16 table function Compatibility16PrepareToBoot(). This
    invocation causes a thunk into the Compatibility16 code, which sets all appropriate internal
    data structures. The boot device list is a parameter.
  - Invoke the Compatibility16 Table function Compatibility16Boot(). This invocation
    causes a thunk into the Compatibility16 code, which does an INT19.
  - If the Compatibility16Boot() function returns, then the boot failed in a graceful
    manner--meaning that the EFI code is still valid. An ungraceful boot failure causes a reset because the state
    of EFI code is unknown.

  @param[in] This             The protocol instance pointer.
  @param[in] BootOption       The EFI Device Path from BootXXXX variable.
  @param[in] LoadOptionSize   The size of LoadOption in size.
  @param[in] LoadOption       LThe oadOption from BootXXXX variable.

  @retval EFI_DEVICE_ERROR      Failed to boot from any boot device and memory is uncorrupted.                                Note: This function normally does not returns. It will either boot the                                OS or reset the system if memory has been "corrupted" by loading                                a boot sector and passing control to it.
**/
typedef
EFI_STATUS
(EFIAPI *EFI_LEGACY_BIOS_BOOT)(
  IN EFI_LEGACY_BIOS_PROTOCOL  *This,
  IN BBS_BBS_DEVICE_PATH       *BootOption,
  IN UINT32                    LoadOptionsSize,
  IN VOID                      *LoadOptions
  );

/**
  This function takes the Leds input parameter and sets/resets the BDA accordingly.
  Leds is also passed to Compatibility16 code, in case any special processing is required.
  This function is normally called from EFI Setup drivers that handle user-selectable
  keyboard options such as boot with NUM LOCK on/off. This function does not
  touch the keyboard or keyboard LEDs but only the BDA.

  @param[in] This   The protocol instance pointer.
  @param[in] Leds   The status of current Scroll, Num & Cap lock LEDS:
                      - Bit 0 is Scroll Lock 0 = Not locked.
                      - Bit 1 is Num Lock.
                      - Bit 2 is Caps Lock.

  @retval EFI_SUCCESS   The BDA was updated successfully.

**/
typedef
EFI_STATUS
(EFIAPI *EFI_LEGACY_BIOS_UPDATE_KEYBOARD_LED_STATUS)(
  IN EFI_LEGACY_BIOS_PROTOCOL  *This,
  IN UINT8                     Leds
  );

/**
  Retrieve legacy BBS info and assign boot priority.

  @param[in]     This       The protocol instance pointer.
  @param[out]    HddCount   The number of HDD_INFO structures.
  @param[out]    HddInfo    Onboard IDE controller information.
  @param[out]    BbsCount   The number of BBS_TABLE structures.
  @param[in,out] BbsTable   Points to List of BBS_TABLE.

  @retval EFI_SUCCESS   Tables were returned.

**/
typedef
EFI_STATUS
(EFIAPI *EFI_LEGACY_BIOS_GET_BBS_INFO)(
  IN     EFI_LEGACY_BIOS_PROTOCOL  *This,
  OUT    UINT16                    *HddCount,
  OUT    HDD_INFO                  **HddInfo,
  OUT    UINT16                    *BbsCount,
  IN OUT BBS_TABLE                 **BbsTable
  );

/**
  Assign drive number to legacy HDD drives prior to booting an EFI
  aware OS so the OS can access drives without an EFI driver.

  @param[in]  This       The protocol instance pointer.
  @param[out] BbsCount   The number of BBS_TABLE structures
  @param[out] BbsTable   List of BBS entries

  @retval EFI_SUCCESS   Drive numbers assigned.

**/
typedef
EFI_STATUS
(EFIAPI *EFI_LEGACY_BIOS_PREPARE_TO_BOOT_EFI)(
  IN  EFI_LEGACY_BIOS_PROTOCOL  *This,
  OUT UINT16                    *BbsCount,
  OUT BBS_TABLE                 **BbsTable
  );

/**
  To boot from an unconventional device like parties and/or execute
  HDD diagnostics.

  @param[in]  This              The protocol instance pointer.
  @param[in]  Attributes        How to interpret the other input parameters.
  @param[in]  BbsEntry          The 0-based index into the BbsTable for the parent
                                device.
  @param[in]  BeerData          A pointer to the 128 bytes of ram BEER data.
  @param[in]  ServiceAreaData   A pointer to the 64 bytes of raw Service Area data. The
                                caller must provide a pointer to the specific Service
                                Area and not the start all Service Areas.

  @retval EFI_INVALID_PARAMETER   If error. Does NOT return if no error.

**/
typedef
EFI_STATUS
(EFIAPI *EFI_LEGACY_BIOS_BOOT_UNCONVENTIONAL_DEVICE)(
  IN EFI_LEGACY_BIOS_PROTOCOL  *This,
  IN UDC_ATTRIBUTES            Attributes,
  IN UINTN                     BbsEntry,
  IN VOID                      *BeerData,
  IN VOID                      *ServiceAreaData
  );

/**
  Shadow all legacy16 OPROMs that haven't been shadowed.
  Warning: Use this with caution. This routine disconnects all EFI
  drivers. If used externally, then  the caller must re-connect EFI
  drivers.

  @param[in]  This   The protocol instance pointer.

  @retval EFI_SUCCESS   OPROMs were shadowed.

**/
typedef
EFI_STATUS
(EFIAPI *EFI_LEGACY_BIOS_SHADOW_ALL_LEGACY_OPROMS)(
  IN EFI_LEGACY_BIOS_PROTOCOL  *This
  );

/**
  Get a region from the LegacyBios for S3 usage.

  @param[in]  This                  The protocol instance pointer.
  @param[in]  LegacyMemorySize      The size of required region.
  @param[in]  Region                The region to use.
                                    00 = Either 0xE0000 or 0xF0000 block.
                                      - Bit0 = 1 0xF0000 block.
                                      - Bit1 = 1 0xE0000 block.
  @param[in]  Alignment             Address alignment. Bit mapped. The first non-zero
                                    bit from right is alignment.
  @param[out] LegacyMemoryAddress   The Region Assigned

  @retval EFI_SUCCESS           The Region was assigned.
  @retval EFI_ACCESS_DENIED     The function was previously invoked.
  @retval Other                 The Region was not assigned.

**/
typedef
EFI_STATUS
(EFIAPI *EFI_LEGACY_BIOS_GET_LEGACY_REGION)(
  IN  EFI_LEGACY_BIOS_PROTOCOL  *This,
  IN  UINTN                     LegacyMemorySize,
  IN  UINTN                     Region,
  IN  UINTN                     Alignment,
  OUT VOID                      **LegacyMemoryAddress
  );

/**
  Get a region from the LegacyBios for Tiano usage. Can only be invoked once.

  @param[in]  This                        The protocol instance pointer.
  @param[in]  LegacyMemorySize            The size of data to copy.
  @param[in]  LegacyMemoryAddress         The Legacy Region destination address.
                                          Note: must be in region assigned by
                                          LegacyBiosGetLegacyRegion.
  @param[in]  LegacyMemorySourceAddress   The source of the data to copy.

  @retval EFI_SUCCESS           The Region assigned.
  @retval EFI_ACCESS_DENIED     Destination was outside an assigned region.

**/
typedef
EFI_STATUS
(EFIAPI *EFI_LEGACY_BIOS_COPY_LEGACY_REGION)(
  IN EFI_LEGACY_BIOS_PROTOCOL  *This,
  IN UINTN                     LegacyMemorySize,
  IN VOID                      *LegacyMemoryAddress,
  IN VOID                      *LegacyMemorySourceAddress
  );

///
/// Abstracts the traditional BIOS from the rest of EFI. The LegacyBoot()
/// member function allows the BDS to support booting a traditional OS.
/// EFI thunks drivers that make EFI bindings for BIOS INT services use
/// all the other member functions.
///
struct _EFI_LEGACY_BIOS_PROTOCOL {
  ///
  /// Performs traditional software INT. See the Int86() function description.
  ///
  EFI_LEGACY_BIOS_INT86                       Int86;

  ///
  /// Performs a far call into Compatibility16 or traditional OpROM code.
  ///
  EFI_LEGACY_BIOS_FARCALL86                   FarCall86;

  ///
  /// Checks if a traditional OpROM exists for this device.
  ///
  EFI_LEGACY_BIOS_CHECK_ROM                   CheckPciRom;

  ///
  /// Loads a traditional OpROM in traditional OpROM address space.
  ///
  EFI_LEGACY_BIOS_INSTALL_ROM                 InstallPciRom;

  ///
  /// Boots a traditional OS.
  ///
  EFI_LEGACY_BIOS_BOOT                        LegacyBoot;

  ///
  /// Updates BDA to reflect the current EFI keyboard LED status.
  ///
  EFI_LEGACY_BIOS_UPDATE_KEYBOARD_LED_STATUS  UpdateKeyboardLedStatus;

  ///
  /// Allows an external agent, such as BIOS Setup, to get the BBS data.
  ///
  EFI_LEGACY_BIOS_GET_BBS_INFO                GetBbsInfo;

  ///
  /// Causes all legacy OpROMs to be shadowed.
  ///
  EFI_LEGACY_BIOS_SHADOW_ALL_LEGACY_OPROMS    ShadowAllLegacyOproms;

  ///
  /// Performs all actions prior to boot. Used when booting an EFI-aware OS
  /// rather than a legacy OS.
  ///
  EFI_LEGACY_BIOS_PREPARE_TO_BOOT_EFI         PrepareToBootEfi;

  ///
  /// Allows EFI to reserve an area in the 0xE0000 or 0xF0000 block.
  ///
  EFI_LEGACY_BIOS_GET_LEGACY_REGION           GetLegacyRegion;

  ///
  /// Allows EFI to copy data to the area specified by GetLegacyRegion.
  ///
  EFI_LEGACY_BIOS_COPY_LEGACY_REGION          CopyLegacyRegion;

  ///
  /// Allows the user to boot off an unconventional device such as a PARTIES partition.
  ///
  EFI_LEGACY_BIOS_BOOT_UNCONVENTIONAL_DEVICE  BootUnconventionalDevice;
};

//
// Legacy BIOS needs to access memory in page 0 (0-4095), which is disabled if
// NULL pointer detection feature is enabled. Following macro can be used to
// enable/disable page 0 before/after accessing it.
//
#define ACCESS_PAGE0_CODE(statements)                           \
  do {                                                          \
    EFI_STATUS                            Status_;              \
    EFI_GCD_MEMORY_SPACE_DESCRIPTOR       Desc_;                \
                                                                \
    Desc_.Attributes = 0;                                       \
    Status_ = gDS->GetMemorySpaceDescriptor (0, &Desc_);        \
    ASSERT_EFI_ERROR (Status_);                                 \
    if ((Desc_.Attributes & EFI_MEMORY_RP) != 0) {              \
      Status_ = gDS->SetMemorySpaceAttributes (                 \
                      0,                                        \
                      EFI_PAGES_TO_SIZE(1),                     \
                      Desc_.Attributes & ~(UINT64)EFI_MEMORY_RP \
                      );                                        \
      ASSERT_EFI_ERROR (Status_);                               \
    }                                                           \
                                                                \
    {                                                           \
      statements;                                               \
    }                                                           \
                                                                \
    if ((Desc_.Attributes & EFI_MEMORY_RP) != 0) {              \
      Status_ = gDS->SetMemorySpaceAttributes (                 \
                      0,                                        \
                      EFI_PAGES_TO_SIZE(1),                     \
                      Desc_.Attributes                          \
                      );                                        \
      ASSERT_EFI_ERROR (Status_);                               \
    }                                                           \
  } while (FALSE)

extern EFI_GUID gEfiLegacyBiosProtocolGuid;

#endif
