Coding style modification.

[mirror_edk2.git] / IntelFrameworkModulePkg / Bus / Isa / IsaBusDxe / IsaIo.c

/**@file
  The implementation for EFI_ISA_IO_PROTOCOL. 
  
Copyright (c) 2006 - 2007, Intel Corporation.<BR>
All rights reserved. This program and the accompanying materials
are licensed and made available under the terms and conditions of the BSD License
which accompanies this distribution.  The full text of the license may be found at
http://opensource.org/licenses/bsd-license.php

THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.

**/

#include "InternalIsaIo.h"

//
// Driver Support Global Variables
//
EFI_ISA_IO_PROTOCOL IsaIoInterface = {
  {    
    IsaIoMemRead,
    IsaIoMemWrite
  },
  {   
    IsaIoIoRead,
    IsaIoIoWrite
  },
  IsaIoCopyMem,
  IsaIoMap,
  IsaIoUnmap,
  IsaIoAllocateBuffer,
  IsaIoFreeBuffer,
  IsaIoFlush,
  NULL,
  0,
  NULL
};

static EFI_ISA_DMA_REGISTERS  DmaRegisters[8] = {
  {
    0x00,
    0x87,
    0x01
  },
  {
    0x02,
    0x83,
    0x03
  },
  {
    0x04,
    0x81,
    0x05
  },
  {
    0x06,
    0x82,
    0x07
  },
  {
    0x00,
    0x00,
    0x00
  },  // Channel 4 is invalid
  {
    0xC4,
    0x8B,
    0xC6
  },
  {
    0xC8,
    0x89,
    0xCA
  },
  {
    0xCC,
    0x8A,
    0xCE
  },
};

/**
  report a error Status code of PCI bus driver controller

  @param Code         - The error status code.
  
  @Return EFI_SUCCESS  - Success to report status code.
**/
EFI_STATUS
ReportErrorStatusCode (
  EFI_STATUS_CODE_VALUE Code
  )

{
  return REPORT_STATUS_CODE (
                EFI_ERROR_CODE | EFI_ERROR_MINOR,
                Code
                );
}

//
// Driver Support Functions
//
/**

  Initializes an ISA I/O Instance

  @param IsaIoDevice            - The iso device to be initialized.
  @param IsaDeviceResourceList  - The resource list.
  
  @retval EFI_SUCCESS            - Initial success.
  
**/
EFI_STATUS
InitializeIsaIoInstance (
  IN ISA_IO_DEVICE               *IsaIoDevice,
  IN EFI_ISA_ACPI_RESOURCE_LIST  *IsaDeviceResourceList
  )
{
  //
  // Initializes an ISA I/O Instance
  //
  CopyMem (
    &IsaIoDevice->IsaIo,
    &IsaIoInterface,
    sizeof (EFI_ISA_IO_PROTOCOL)
    );

  IsaIoDevice->IsaIo.ResourceList = IsaDeviceResourceList;
  
  return EFI_SUCCESS;
}

/**
  Performs an ISA I/O Read Cycle

  @param This                  - A pointer to the EFI_ISA_IO_PROTOCOL instance.
  @param Width                 - Signifies the width of the I/O operation.
  @param Offset                - The offset in ISA I/O space to start the I/O operation.  
  @param Count                 - The number of I/O operations to perform. 
  @param Buffer                - The destination buffer to store the results

  @retval EFI_SUCCESS           - The data was read from the device sucessfully.
  @retval EFI_UNSUPPORTED       - The Offset is not valid for this device.
  @retval EFI_INVALID_PARAMETER - Width or Count, or both, were invalid.
  @retval EFI_OUT_OF_RESOURCES  - The request could not be completed due to a lack of resources.

**/
EFI_STATUS
EFIAPI
IsaIoIoRead (
  IN     EFI_ISA_IO_PROTOCOL                        *This,
  IN     EFI_ISA_IO_PROTOCOL_WIDTH                  Width,
  IN     UINT32                                     Offset,
  IN     UINTN                                      Count,
  IN OUT VOID                                       *Buffer
  )

{
  EFI_STATUS    Status;
  ISA_IO_DEVICE *IsaIoDevice;

  IsaIoDevice = ISA_IO_DEVICE_FROM_ISA_IO_THIS (This);

  //
  // Verify Isa IO Access
  //
  Status = IsaIoVerifyAccess (
             IsaIoDevice,
             IsaAccessTypeIo,
             Width,
             Count,
             &Offset
             );
  if (EFI_ERROR (Status)) {
    return Status;
  }
  //
  // Call PciIo->Io.Read
  //
  Status = IsaIoDevice->PciIo->Io.Read (
                                    IsaIoDevice->PciIo,
                                    (EFI_PCI_IO_PROTOCOL_WIDTH) Width,
                                    EFI_PCI_IO_PASS_THROUGH_BAR,
                                    Offset,
                                    Count,
                                    Buffer
                                    );

  if (EFI_ERROR (Status)) {
    ReportErrorStatusCode (EFI_IO_BUS_LPC | EFI_IOB_EC_CONTROLLER_ERROR);
  }

  return Status;
}

/**
  Performs an ISA I/O Write Cycle

  @param This                  - A pointer to the EFI_ISA_IO_PROTOCOL instance.
  @param Width                 - Signifies the width of the I/O operation.
  @param Offset                - The offset in ISA I/O space to start the I/O operation.  
  @param Count                 - The number of I/O operations to perform. 
  @param Buffer                - The source buffer to write data from

  @Retval EFI_SUCCESS           - The data was writen to the device sucessfully.
  @Retval EFI_UNSUPPORTED       - The Offset is not valid for this device.
  @Retval EFI_INVALID_PARAMETER - Width or Count, or both, were invalid.
  @Retval EFI_OUT_OF_RESOURCES  - The request could not be completed due to a lack of resources.

**/
EFI_STATUS
EFIAPI
IsaIoIoWrite (
  IN     EFI_ISA_IO_PROTOCOL                        *This,
  IN     EFI_ISA_IO_PROTOCOL_WIDTH                  Width,
  IN     UINT32                                     Offset,
  IN     UINTN                                      Count,
  IN OUT VOID                                       *Buffer
  )
{
  EFI_STATUS    Status;
  ISA_IO_DEVICE *IsaIoDevice;

  IsaIoDevice = ISA_IO_DEVICE_FROM_ISA_IO_THIS (This);

  //
  // Verify Isa IO Access
  //
  Status = IsaIoVerifyAccess (
             IsaIoDevice,
             IsaAccessTypeIo,
             Width,
             Count,
             &Offset
             );
  if (EFI_ERROR (Status)) {
    return Status;
  }
  //
  // Call PciIo->Io.Write
  //
  Status = IsaIoDevice->PciIo->Io.Write (
                                    IsaIoDevice->PciIo,
                                    (EFI_PCI_IO_PROTOCOL_WIDTH) Width,
                                    EFI_PCI_IO_PASS_THROUGH_BAR,
                                    Offset,
                                    Count,
                                    Buffer
                                    );

  if (EFI_ERROR (Status)) {
    ReportErrorStatusCode (EFI_IO_BUS_LPC | EFI_IOB_EC_CONTROLLER_ERROR);
  }

  return Status;
}

/**
  Writes an 8 bit I/O Port

  @param This                  - A pointer to the EFI_ISA_IO_PROTOCOL instance.
  @param Offset                - The offset in ISA IO space to start the IO operation.  
  @param Value                 - The data to write port.

  @retval EFI_SUCCESS           - Success.
  @retval EFI_INVALID_PARAMETER - Parameter is invalid.
  @retval EFI_UNSUPPORTED       - The address range specified by Offset is not valid.
  @retval EFI_OUT_OF_RESOURCES  - The request could not be completed due to a lack of resources.
  
**/
EFI_STATUS
WritePort (
  IN EFI_ISA_IO_PROTOCOL                  *This,
  IN UINT32                               Offset,
  IN UINT8                                Value
  )

{
  EFI_STATUS    Status;
  ISA_IO_DEVICE *IsaIoDevice;

  IsaIoDevice = ISA_IO_DEVICE_FROM_ISA_IO_THIS (This);

  //
  // Call PciIo->Io.Write
  //
  Status = IsaIoDevice->PciIo->Io.Write (
                                    IsaIoDevice->PciIo,
                                    EfiPciIoWidthUint8,
                                    EFI_PCI_IO_PASS_THROUGH_BAR,
                                    Offset,
                                    1,
                                    &Value
                                    );
  if (EFI_ERROR (Status)) {
    ReportErrorStatusCode (EFI_IO_BUS_LPC | EFI_IOB_EC_CONTROLLER_ERROR);
    return Status;
  }

  gBS->Stall (50);

  return EFI_SUCCESS;
}

/**
  Writes I/O operation base address and count number to a 8 bit I/O Port.

  @param This                  - A pointer to the EFI_ISA_IO_PROTOCOL instance.
  @param AddrOffset            - The address' offset.
  @param PageOffset            - The page's offest.
  @param CountOffset           - The count's offset.
  @param BaseAddress           - The base address.
  @param Count                 - The number of I/O operations to perform. 
  
  @retval EFI_SUCCESS           - Success.
  @retval EFI_INVALID_PARAMETER - Parameter is invalid.
  @retval EFI_UNSUPPORTED       - The address range specified by these Offsets and Count is not valid.
  @retval EFI_OUT_OF_RESOURCES  - The request could not be completed due to a lack of resources.

**/
EFI_STATUS
WriteDmaPort (
  IN EFI_ISA_IO_PROTOCOL                  *This,
  IN UINT32                               AddrOffset,
  IN UINT32                               PageOffset,
  IN UINT32                               CountOffset,
  IN UINT32                               BaseAddress,
  IN UINT16                               Count
  )

{
  EFI_STATUS  Status;

  Status = WritePort (This, AddrOffset, (UINT8) (BaseAddress & 0xff));
  if (EFI_ERROR (Status)) {
    return Status;
  }

  Status = WritePort (This, AddrOffset, (UINT8) ((BaseAddress >> 8) & 0xff));
  if (EFI_ERROR (Status)) {
    return Status;
  }

  Status = WritePort (This, PageOffset, (UINT8) ((BaseAddress >> 16) & 0xff));
  if (EFI_ERROR (Status)) {
    return Status;
  }

  Status = WritePort (This, CountOffset, (UINT8) (Count & 0xff));
  if (EFI_ERROR (Status)) {
    return Status;
  }

  Status = WritePort (This, CountOffset, (UINT8) ((Count >> 8) & 0xff));
  if (EFI_ERROR (Status)) {
    return Status;
  }

  return EFI_SUCCESS;
}

/**
  Unmaps a memory region for DMA

  @param This             - A pointer to the EFI_ISA_IO_PROTOCOL instance.
  @param Mapping          - The mapping value returned from EFI_ISA_IO.Map().

  @retval EFI_SUCCESS      - The range was unmapped.
  @retval EFI_DEVICE_ERROR - The data was not committed to the target system memory.

**/
EFI_STATUS
EFIAPI
IsaIoUnmap (
  IN EFI_ISA_IO_PROTOCOL                  *This,
  IN VOID                                 *Mapping
  )
{
  ISA_MAP_INFO  *IsaMapInfo;

  //
  // Unset Feature Flag PcdIsaBusSupportDma to disable support for ISA DMA.
  //
  if (!FeaturePcdGet (PcdIsaBusSupportDma)) {
    return EFI_UNSUPPORTED;
  }

  //
  // See if the Map() operation associated with this Unmap() required a mapping
  // buffer.If a mapping buffer was not required, then this function simply
  // returns EFI_SUCCESS.
  //
  if (Mapping != NULL) {
    //
    // Get the MAP_INFO structure from Mapping
    //
    IsaMapInfo = (ISA_MAP_INFO *) Mapping;

    //
    // If this is a write operation from the Agent's point of view,
    // then copy the contents of the mapped buffer into the real buffer
    // so the processor can read the contents of the real buffer.
    //
    if (IsaMapInfo->Operation == EfiIsaIoOperationBusMasterWrite) {
      CopyMem (
        (VOID *) (UINTN) IsaMapInfo->HostAddress,
        (VOID *) (UINTN) IsaMapInfo->MappedHostAddress,
        IsaMapInfo->NumberOfBytes
        );
    }
    //
    // Free the mapped buffer and the MAP_INFO structure.
    //
    gBS->FreePages (IsaMapInfo->MappedHostAddress, IsaMapInfo->NumberOfPages);
    gBS->FreePool (IsaMapInfo);
  }

  return EFI_SUCCESS;
}

/**
  Flushes a DMA buffer

  @param This             - A pointer to the EFI_ISA_IO_PROTOCOL instance.

  @retval  EFI_SUCCESS      - The buffers were flushed.
  @retval  EFI_DEVICE_ERROR - The buffers were not flushed due to a hardware error.

**/
EFI_STATUS
EFIAPI
IsaIoFlush (
  IN EFI_ISA_IO_PROTOCOL                  *This
  )

{
  EFI_STATUS    Status;
  ISA_IO_DEVICE *IsaIoDevice;

  IsaIoDevice = ISA_IO_DEVICE_FROM_ISA_IO_THIS (This);

  //
  // Call PciIo->Flush
  //
  Status = IsaIoDevice->PciIo->Flush (IsaIoDevice->PciIo);

  if (EFI_ERROR (Status)) {
    ReportErrorStatusCode (EFI_IO_BUS_LPC | EFI_IOB_EC_CONTROLLER_ERROR);
  }

  return Status;
}

/**
  Verifies access to an ISA device

  @param IsaIoDevice           - The ISA device to be verified.
  @param Type                  - The Access type. The input must be either IsaAccessTypeMem or IsaAccessTypeIo.
  @param Width                 - Signifies the width of the memory operation.
  @param Count                 - The number of memory operations to perform. 
  @param Offset                - The offset in ISA memory space to start the memory operation.  
  
  @retval EFI_SUCCESS           - Verify success.
  @retval EFI_INVALID_PARAMETER - One of the parameters has an invalid value.
  @retval EFI_UNSUPPORTED       - The device ont support the access type.

**/
EFI_STATUS
IsaIoVerifyAccess (
  IN     ISA_IO_DEVICE              *IsaIoDevice,
  IN     ISA_ACCESS_TYPE            Type,
  IN     EFI_ISA_IO_PROTOCOL_WIDTH  Width,
  IN     UINTN                      Count,
  IN OUT UINT32                     *Offset
  )

{
  EFI_ISA_ACPI_RESOURCE *Item;
  EFI_STATUS            Status;

  if (Width < EfiIsaIoWidthUint8 ||
      Width >= EfiIsaIoWidthMaximum ||
      Width == EfiIsaIoWidthReserved ||
      Width == EfiIsaIoWidthFifoReserved ||
      Width == EfiIsaIoWidthFillReserved
      ) {
    return EFI_INVALID_PARAMETER;
  }

  //
  // If Width is EfiIsaIoWidthFifoUintX then convert to EfiIsaIoWidthUintX
  // If Width is EfiIsaIoWidthFillUintX then convert to EfiIsaIoWidthUintX
  //
  if (Width >= EfiIsaIoWidthFifoUint8 && Width <= EfiIsaIoWidthFifoReserved) {
    Count = 1;
  }

  Width = (EFI_ISA_IO_PROTOCOL_WIDTH) (Width & 0x03);

  Status  = EFI_UNSUPPORTED;
  Item    = IsaIoDevice->IsaIo.ResourceList->ResourceItem;
  while (Item->Type != EfiIsaAcpiResourceEndOfList) {
    if ((Type == IsaAccessTypeMem && Item->Type == EfiIsaAcpiResourceMemory) ||
        (Type == IsaAccessTypeIo && Item->Type == EfiIsaAcpiResourceIo)
        ) {
      if (*Offset >= Item->StartRange && (*Offset + Count * (UINT32)(1 << Width)) - 1 <= Item->EndRange) {
        return EFI_SUCCESS;
      }

      if (*Offset >= Item->StartRange && *Offset <= Item->EndRange) {
        Status = EFI_INVALID_PARAMETER;
      }
    }

    Item++;
  }

  return Status;
}

/**

  Performs an ISA Memory Read Cycle

  @param This                  - A pointer to the EFI_ISA_IO_PROTOCOL instance.
  @param Width                 - Signifies the width of the memory operation.
  @param Offset                - The offset in ISA memory space to start the memory operation.  
  @param Count                 - The number of memory operations to perform. 
  @param Buffer                - The destination buffer to store the results
 
  @retval EFI_SUCCESS           - The data was read from the device successfully.
  @retval EFI_UNSUPPORTED       - The Offset is not valid for this device.
  @retval EFI_INVALID_PARAMETER - Width or Count, or both, were invalid.
  @retval EFI_OUT_OF_RESOURCES  - The request could not be completed due to a lack of resources.

**/
EFI_STATUS
EFIAPI
IsaIoMemRead (
  IN     EFI_ISA_IO_PROTOCOL                       *This,
  IN     EFI_ISA_IO_PROTOCOL_WIDTH                 Width,
  IN     UINT32                                    Offset,
  IN     UINTN                                     Count,
  IN OUT VOID                                      *Buffer
  )

{
  EFI_STATUS    Status;
  ISA_IO_DEVICE *IsaIoDevice;

  //
  // Set Feature Flag PcdIsaBusSupportBusMaster to FALSE to disable support for 
  // ISA Bus Master.
  //
  // So we just return EFI_UNSUPPORTED for these functions.
  //
  if (!FeaturePcdGet (PcdIsaBusSupportIsaMemory)) {
    return EFI_UNSUPPORTED;
  }

  IsaIoDevice = ISA_IO_DEVICE_FROM_ISA_IO_THIS (This);

  //
  // Verify the Isa Io Access
  //
  Status = IsaIoVerifyAccess (
             IsaIoDevice,
             IsaAccessTypeMem,
             Width,
             Count,
             &Offset
             );
  if (EFI_ERROR (Status)) {
    return Status;
  }
  //
  // Call PciIo->Mem.Read
  //
  Status = IsaIoDevice->PciIo->Mem.Read (
                                     IsaIoDevice->PciIo,
                                     (EFI_PCI_IO_PROTOCOL_WIDTH) Width,
                                     EFI_PCI_IO_PASS_THROUGH_BAR,
                                     Offset,
                                     Count,
                                     Buffer
                                     );

  if (EFI_ERROR (Status)) {
    ReportErrorStatusCode (EFI_IO_BUS_LPC | EFI_IOB_EC_CONTROLLER_ERROR);
  }

  return Status;
}

/**
  Performs an ISA Memory Write Cycle

  @param This                  - A pointer to the EFI_ISA_IO_PROTOCOL instance.  
  @param Width                 - Signifies the width of the memory operation.
  @param Offset                - The offset in ISA memory space to start the memory operation.  
  @param Count                 - The number of memory operations to perform. 
  @param Buffer                - The source buffer to write data from

  @retval EFI_SUCCESS           - The data was written to the device sucessfully.
  @retval EFI_UNSUPPORTED       - The Offset is not valid for this device.
  @retval EFI_INVALID_PARAMETER - Width or Count, or both, were invalid.
  @retval EFI_OUT_OF_RESOURCES  - The request could not be completed due to a lack of resources.

**/
EFI_STATUS
EFIAPI
IsaIoMemWrite (
  IN     EFI_ISA_IO_PROTOCOL                        *This,
  IN     EFI_ISA_IO_PROTOCOL_WIDTH                  Width,
  IN     UINT32                                     Offset,
  IN     UINTN                                      Count,
  IN OUT VOID                                       *Buffer
  )
{
  EFI_STATUS    Status;
  ISA_IO_DEVICE *IsaIoDevice;

  //
  // Set Feature Flag PcdIsaBusSupportBusMaster to FALSE to disable support for 
  // ISA Bus Master.
  //
  // So we just return EFI_UNSUPPORTED for these functions.
  //
  if (!FeaturePcdGet (PcdIsaBusSupportIsaMemory)) {
    return EFI_UNSUPPORTED;
  }

  IsaIoDevice = ISA_IO_DEVICE_FROM_ISA_IO_THIS (This);

  //
  // Verify Isa IO Access
  //
  Status = IsaIoVerifyAccess (
             IsaIoDevice,
             IsaAccessTypeMem,
             Width,
             Count,
             &Offset
             );
  if (EFI_ERROR (Status)) {
    return Status;
  }
  //
  // Call PciIo->Mem.Write
  //
  Status = IsaIoDevice->PciIo->Mem.Write (
                                     IsaIoDevice->PciIo,
                                     (EFI_PCI_IO_PROTOCOL_WIDTH) Width,
                                     EFI_PCI_IO_PASS_THROUGH_BAR,
                                     Offset,
                                     Count,
                                     Buffer
                                     );

  if (EFI_ERROR (Status)) {
    ReportErrorStatusCode (EFI_IO_BUS_LPC | EFI_IOB_EC_CONTROLLER_ERROR);
  }

  return Status;
}

/**
  Performs an ISA I/O Copy Memory 

  @param This                  - A pointer to the EFI_ISA_IO_PROTOCOL instance.
  @param Width                 - Signifies the width of the memory copy operation.
  @param DestOffset            - The offset of the destination 
  @param SrcOffset             - The offset of the source
  @param Count                 - The number of memory copy  operations to perform

  @retval EFI_SUCCESS           - The data was copied sucessfully.
  @retval EFI_UNSUPPORTED       - The DestOffset or SrcOffset is not valid for this device.
  @retval EFI_INVALID_PARAMETER - Width or Count, or both, were invalid.
  @retval EFI_OUT_OF_RESOURCES  - The request could not be completed due to a lack of resources.

**/
EFI_STATUS
EFIAPI
IsaIoCopyMem (
  IN EFI_ISA_IO_PROTOCOL                        *This,
  IN EFI_ISA_IO_PROTOCOL_WIDTH                  Width,
  IN UINT32                                     DestOffset,
  IN UINT32                                     SrcOffset,
  IN UINTN                                      Count
  )

{
  EFI_STATUS    Status;
  ISA_IO_DEVICE *IsaIoDevice;

  //
  // Set Feature Flag PcdIsaBusSupportBusMaster to FALSE to disable support for 
  // ISA Bus Master.
  //
  // So we just return EFI_UNSUPPORTED for these functions.
  //
  if (!FeaturePcdGet (PcdIsaBusSupportIsaMemory)) {
    return EFI_UNSUPPORTED;
  }

  IsaIoDevice = ISA_IO_DEVICE_FROM_ISA_IO_THIS (This);

  //
  // Verify Isa IO Access for destination and source
  //
  Status = IsaIoVerifyAccess (
             IsaIoDevice,
             IsaAccessTypeMem,
             Width,
             Count,
             &DestOffset
             );
  if (EFI_ERROR (Status)) {
    return Status;
  }

  Status = IsaIoVerifyAccess (
             IsaIoDevice,
             IsaAccessTypeMem,
             Width,
             Count,
             &SrcOffset
             );
  if (EFI_ERROR (Status)) {
    return Status;
  }
  //
  // Call PciIo->CopyMem
  //
  Status = IsaIoDevice->PciIo->CopyMem (
                                 IsaIoDevice->PciIo,
                                 (EFI_PCI_IO_PROTOCOL_WIDTH) Width,
                                 EFI_PCI_IO_PASS_THROUGH_BAR,
                                 DestOffset,
                                 EFI_PCI_IO_PASS_THROUGH_BAR,
                                 SrcOffset,
                                 Count
                                 );

  if (EFI_ERROR (Status)) {
    ReportErrorStatusCode (EFI_IO_BUS_LPC | EFI_IOB_EC_CONTROLLER_ERROR);
  }

  return Status;
}

/**
  Maps a memory region for DMA, note this implementation
  only supports slave read/write operation to save code size.

  @param This                  - A pointer to the EFI_ISA_IO_PROTOCOL instance.
  @param Operation             - Indicates the type of DMA (slave or bus master), and if 
                          the DMA operation is going to read or write to system memory. 
  @param ChannelNumber         - The slave channel number to use for this DMA operation. 
                          If Operation and ChannelAttributes shows that this device 
                          performs bus mastering DMA, then this field is ignored.  
                          The legal range for this field is 0..7.  
  @param ChannelAttributes     - The attributes of the DMA channel to use for this DMA operation
  @param HostAddress           - The system memory address to map to the device.  
  @param NumberOfBytes         - On input the number of bytes to map.  On output the number 
                          of bytes that were mapped.
  @param DeviceAddress         - The resulting map address for the bus master device to use 
                          to access the hosts HostAddress.  
  @param Mapping               - A resulting value to pass to EFI_ISA_IO.Unmap().

  @retval EFI_SUCCESS           - The range was mapped for the returned NumberOfBytes.
  @retval EFI_INVALID_PARAMETER - The Operation or HostAddress is undefined.
  @retval EFI_UNSUPPORTED       - The HostAddress can not be mapped as a common buffer.
  @retval EFI_DEVICE_ERROR      - The system hardware could not map the requested address.
  @retval EFI_OUT_OF_RESOURCES  - The memory pages could not be allocated.

**/
STATIC
EFI_STATUS
IsaIoMap_OnlySupportSlaveReadWrite (
  IN     EFI_ISA_IO_PROTOCOL                                  *This,
  IN     EFI_ISA_IO_PROTOCOL_OPERATION                        Operation,
  IN     UINT8                                                ChannelNumber         OPTIONAL,
  IN     UINT32                                               ChannelAttributes,
  IN     VOID                                                 *HostAddress,
  IN OUT UINTN                                                *NumberOfBytes,
  OUT    EFI_PHYSICAL_ADDRESS                                 *DeviceAddress,
  OUT    VOID                                                 **Mapping
  )

{
  EFI_STATUS            Status;
  EFI_PHYSICAL_ADDRESS  PhysicalAddress;
  ISA_MAP_INFO          *IsaMapInfo;
  UINT8                 DmaMode;
  UINTN                 MaxNumberOfBytes;
  UINT32                BaseAddress;
  UINT16                Count;

  UINT8                 DmaMask;
  UINT8                 DmaClear;
  UINT8                 DmaChannelMode;
  
  if ((NULL == This) ||
      (NULL == HostAddress) ||
      (NULL == NumberOfBytes) ||
      (NULL == DeviceAddress) ||
      (NULL == Mapping)
      ) {
    return EFI_INVALID_PARAMETER;
  }


  //
  // Initialize the return values to their defaults
  //
  *Mapping = NULL;

  //
  // Make sure the Operation parameter is valid.
  // Light IsaIo only supports two operations.
  //
  if (!(Operation == EfiIsaIoOperationSlaveRead || 
        Operation == EfiIsaIoOperationSlaveWrite)) {
    return EFI_INVALID_PARAMETER;
  }

  if (ChannelNumber >= 4) {
    //
    // The Light IsaIo doesn't support channelNumber larger than 4.
    //
    return EFI_INVALID_PARAMETER;
  }

  //
  // Map the HostAddress to a DeviceAddress.
  //
  PhysicalAddress = (EFI_PHYSICAL_ADDRESS) (UINTN) HostAddress;
  if ((PhysicalAddress +*NumberOfBytes) > ISA_MAX_MEMORY_ADDRESS) {
    //
    // Common Buffer operations can not be remapped.  If the common buffer
    // is above 16MB, then it is not possible to generate a mapping, so return
    // an error.
    //
    if (Operation == EfiIsaIoOperationBusMasterCommonBuffer) {
      return EFI_UNSUPPORTED;
    }
    //
    // Allocate an ISA_MAP_INFO structure to remember the mapping when Unmap()
    // is called later.
    //
    IsaMapInfo = AllocatePool (sizeof (ISA_MAP_INFO));
    if (IsaMapInfo == NULL) {
      *NumberOfBytes = 0;
      return EFI_OUT_OF_RESOURCES;
    }
    //
    // Return a pointer to the MAP_INFO structure in Mapping
    //
    *Mapping = IsaMapInfo;

    //
    // Initialize the MAP_INFO structure
    //
    IsaMapInfo->Operation         = Operation;
    IsaMapInfo->NumberOfBytes     = *NumberOfBytes;
    IsaMapInfo->NumberOfPages     = EFI_SIZE_TO_PAGES (*NumberOfBytes);
    IsaMapInfo->HostAddress       = PhysicalAddress;
    IsaMapInfo->MappedHostAddress = ISA_MAX_MEMORY_ADDRESS - 1;

    //
    // Allocate a buffer below 16MB to map the transfer to.
    //
    Status = gBS->AllocatePages (
                    AllocateMaxAddress,
                    EfiBootServicesData,
                    IsaMapInfo->NumberOfPages,
                    &IsaMapInfo->MappedHostAddress
                    );
    if (EFI_ERROR (Status)) {
      gBS->FreePool (IsaMapInfo);
      *NumberOfBytes  = 0;
      *Mapping        = NULL;
      return Status;
    }
    //
    // If this is a read operation from the DMA agents's point of view,
    // then copy the contents of the real buffer into the mapped buffer
    // so the DMA agent can read the contents of the real buffer.
    //
    if (Operation == EfiIsaIoOperationSlaveRead) {
      CopyMem (
        (VOID *) (UINTN) IsaMapInfo->MappedHostAddress,
        (VOID *) (UINTN) IsaMapInfo->HostAddress,
        IsaMapInfo->NumberOfBytes
        );
    }
    //
    // The DeviceAddress is the address of the maped buffer below 16 MB
    //
    *DeviceAddress = IsaMapInfo->MappedHostAddress;
  } else {
    //
    // The transfer is below 16 MB, so the DeviceAddress is simply the
    // HostAddress
    //
    *DeviceAddress = PhysicalAddress;
  }
  
  //
  // Figure out what to program into the DMA Channel Mode Register
  //
  DmaMode = (UINT8) (B_8237_DMA_CHMODE_INCREMENT | (ChannelNumber & 0x03));
  if (Operation == EfiIsaIoOperationSlaveRead) {
    DmaMode |= V_8237_DMA_CHMODE_MEM2IO;
  } else {
    DmaMode |= V_8237_DMA_CHMODE_IO2MEM;
  }
  //
  // We only support EFI_ISA_IO_SLAVE_DMA_ATTRIBUTE_SINGLE_MODE in simplified IsaIo
  //
  DmaMode |= V_8237_DMA_CHMODE_SINGLE;

  //
  // A Slave DMA transfer can not cross a 64K boundary.
  // Compute *NumberOfBytes based on this restriction.
  //
  MaxNumberOfBytes = 0x10000 - ((UINT32) (*DeviceAddress) & 0xffff);
  if (*NumberOfBytes > MaxNumberOfBytes) {
    *NumberOfBytes = MaxNumberOfBytes;
  }
  //
  // Compute the values to program into the BaseAddress and Count registers
  // of the Slave DMA controller
  //
  BaseAddress = (UINT32) (*DeviceAddress);
  Count       = (UINT16) (*NumberOfBytes - 1);
  //
  // Program the DMA Write Single Mask Register for ChannelNumber
  // Clear the DMA Byte Pointer Register
  //
  DmaMask         = R_8237_DMA_WRSMSK_CH0_3;
  DmaClear        = R_8237_DMA_CBPR_CH0_3;
  DmaChannelMode  = R_8237_DMA_CHMODE_CH0_3;

  Status = WritePort (
             This,
             DmaMask,
             (UINT8) (B_8237_DMA_WRSMSK_CMS | (ChannelNumber & 0x03))
             );
  if (EFI_ERROR (Status)) {
    return Status;
  }

  Status = WritePort (
             This,
             DmaClear,
             (UINT8) (B_8237_DMA_WRSMSK_CMS | (ChannelNumber & 0x03))
             );
  if (EFI_ERROR (Status)) {
    return Status;
  }

  Status = WritePort (This, DmaChannelMode, DmaMode);
  if (EFI_ERROR (Status)) {
    return Status;
  }

  Status = WriteDmaPort (
             This,
             DmaRegisters[ChannelNumber].Address,
             DmaRegisters[ChannelNumber].Page,
             DmaRegisters[ChannelNumber].Count,
             BaseAddress,
             Count
             );
  if (EFI_ERROR (Status)) {
    return Status;
  }

  Status = WritePort (
             This,
             DmaMask,
             (UINT8) (ChannelNumber & 0x03)
             );
  if (EFI_ERROR (Status)) {
    return Status;
  }

  return EFI_SUCCESS;
}

/**
  Maps a memory region for DMA. This implementation implement the 
  the full mapping support.

  @param This                  - A pointer to the EFI_ISA_IO_PROTOCOL instance.
  @param Operation             - Indicates the type of DMA (slave or bus master), and if 
                          the DMA operation is going to read or write to system memory. 
  @param ChannelNumber         - The slave channel number to use for this DMA operation. 
                          If Operation and ChannelAttributes shows that this device 
                          performs bus mastering DMA, then this field is ignored.  
                          The legal range for this field is 0..7.  
  @param ChannelAttributes     - The attributes of the DMA channel to use for this DMA operation
  @param HostAddress           - The system memory address to map to the device.  
  @param NumberOfBytes         - On input the number of bytes to map.  On output the number 
                          of bytes that were mapped.
  @param DeviceAddress         - The resulting map address for the bus master device to use 
                        - to access the hosts HostAddress.  
  @param Mapping               - A resulting value to pass to EFI_ISA_IO.Unmap().

  @retval EFI_SUCCESS           - The range was mapped for the returned NumberOfBytes.
  @retval EFI_INVALID_PARAMETER - The Operation or HostAddress is undefined.
  @retval EFI_UNSUPPORTED       - The HostAddress can not be mapped as a common buffer.
  @retval EFI_DEVICE_ERROR      - The system hardware could not map the requested address.
  @retval EFI_OUT_OF_RESOURCES  - The memory pages could not be allocated.

**/
STATIC
EFI_STATUS
IsaIoMap_FullSupport (
  IN     EFI_ISA_IO_PROTOCOL                                  *This,
  IN     EFI_ISA_IO_PROTOCOL_OPERATION                        Operation,
  IN     UINT8                                                ChannelNumber         OPTIONAL,
  IN     UINT32                                               ChannelAttributes,
  IN     VOID                                                 *HostAddress,
  IN OUT UINTN                                                *NumberOfBytes,
  OUT    EFI_PHYSICAL_ADDRESS                                 *DeviceAddress,
  OUT    VOID                                                 **Mapping
  )

{
  EFI_STATUS            Status;
  BOOLEAN               Master;
  BOOLEAN               Read;
  EFI_PHYSICAL_ADDRESS  PhysicalAddress;
  ISA_MAP_INFO          *IsaMapInfo;
  UINT8                 DmaMode;
  UINTN                 MaxNumberOfBytes;
  UINT32                BaseAddress;
  UINT16                Count;

  UINT8                 DmaMask;
  UINT8                 DmaClear;
  UINT8                 DmaChannelMode;

  if ((NULL == This) ||
      (NULL == HostAddress) ||
      (NULL == NumberOfBytes) ||
      (NULL == DeviceAddress) ||
      (NULL == Mapping)
      ) {
    return EFI_INVALID_PARAMETER;
  }


  //
  // Initialize the return values to their defaults
  //
  *Mapping = NULL;

  //
  // Make sure the Operation parameter is valid
  //
  if (Operation < 0 || Operation >= EfiIsaIoOperationMaximum) {
    return EFI_INVALID_PARAMETER;
  }
  //
  // See if this is a Slave DMA Operation
  //
  Master  = TRUE;
  Read    = FALSE;
  if (Operation == EfiIsaIoOperationSlaveRead) {
    Operation = EfiIsaIoOperationBusMasterRead;
    Master    = FALSE;
    Read      = TRUE;
  }

  if (Operation == EfiIsaIoOperationSlaveWrite) {
    Operation = EfiIsaIoOperationBusMasterWrite;
    Master    = FALSE;
    Read      = FALSE;
  }

  if (!Master) {
    //
    // Make sure that ChannelNumber is a valid channel number
    // Channel 4 is used to cascade, so it is illegal.
    //
    if (ChannelNumber == 4 || ChannelNumber > 7) {
      return EFI_INVALID_PARAMETER;
    }
    //
    // This implementation only support COMPATIBLE DMA Transfers
    //
    if (!(ChannelAttributes & EFI_ISA_IO_SLAVE_DMA_ATTRIBUTE_SPEED_COMPATIBLE)) {
      return EFI_INVALID_PARAMETER;
    }

    if (ChannelAttributes &
       (
         EFI_ISA_IO_SLAVE_DMA_ATTRIBUTE_SPEED_A |
         EFI_ISA_IO_SLAVE_DMA_ATTRIBUTE_SPEED_B |
         EFI_ISA_IO_SLAVE_DMA_ATTRIBUTE_SPEED_C
       )
       ) {
      return EFI_INVALID_PARAMETER;
    }

    if (ChannelNumber < 4) {
      //
      // If this is Channel 0..3, then the width must be 8 bit
      //
      if (!(ChannelAttributes & EFI_ISA_IO_SLAVE_DMA_ATTRIBUTE_WIDTH_8) ||
          (ChannelAttributes & EFI_ISA_IO_SLAVE_DMA_ATTRIBUTE_WIDTH_16)
          ) {
        return EFI_INVALID_PARAMETER;
      }
    } else {
      //
      // If this is Channel 4..7, then the width must be 16 bit
      //
      if ((ChannelAttributes & EFI_ISA_IO_SLAVE_DMA_ATTRIBUTE_WIDTH_8) ||
          (!(ChannelAttributes & EFI_ISA_IO_SLAVE_DMA_ATTRIBUTE_WIDTH_16))
          ) {
        return EFI_INVALID_PARAMETER;
      }
    }
    //
    // Either Demand Mode or Single Mode must be selected, but not both
    //
    if (ChannelAttributes & EFI_ISA_IO_SLAVE_DMA_ATTRIBUTE_SINGLE_MODE) {
      if (ChannelAttributes & EFI_ISA_IO_SLAVE_DMA_ATTRIBUTE_DEMAND_MODE) {
        return EFI_INVALID_PARAMETER;
      }
    } else {
      if (!(ChannelAttributes & EFI_ISA_IO_SLAVE_DMA_ATTRIBUTE_DEMAND_MODE)) {
        return EFI_INVALID_PARAMETER;
      }
    }
  }
  //
  // Map the HostAddress to a DeviceAddress.
  //
  PhysicalAddress = (EFI_PHYSICAL_ADDRESS) (UINTN) HostAddress;
  if ((PhysicalAddress +*NumberOfBytes) > ISA_MAX_MEMORY_ADDRESS) {
    //
    // Common Buffer operations can not be remapped.  If the common buffer
    // is above 16MB, then it is not possible to generate a mapping, so return
    // an error.
    //
    if (Operation == EfiIsaIoOperationBusMasterCommonBuffer) {
      return EFI_UNSUPPORTED;
    }
    //
    // Allocate an ISA_MAP_INFO structure to remember the mapping when Unmap()
    // is called later.
    //
    IsaMapInfo = AllocatePool (sizeof (ISA_MAP_INFO));
    if (IsaMapInfo == NULL) {
      *NumberOfBytes = 0;
      return EFI_OUT_OF_RESOURCES;
    }
    //
    // Return a pointer to the MAP_INFO structure in Mapping
    //
    *Mapping = IsaMapInfo;

    //
    // Initialize the MAP_INFO structure
    //
    IsaMapInfo->Operation         = Operation;
    IsaMapInfo->NumberOfBytes     = *NumberOfBytes;
    IsaMapInfo->NumberOfPages     = EFI_SIZE_TO_PAGES (*NumberOfBytes);
    IsaMapInfo->HostAddress       = PhysicalAddress;
    IsaMapInfo->MappedHostAddress = ISA_MAX_MEMORY_ADDRESS - 1;

    //
    // Allocate a buffer below 16MB to map the transfer to.
    //
    Status = gBS->AllocatePages (
                    AllocateMaxAddress,
                    EfiBootServicesData,
                    IsaMapInfo->NumberOfPages,
                    &IsaMapInfo->MappedHostAddress
                    );
    if (EFI_ERROR (Status)) {
      gBS->FreePool (IsaMapInfo);
      *NumberOfBytes  = 0;
      *Mapping        = NULL;
      return Status;
    }
    //
    // If this is a read operation from the DMA agents's point of view,
    // then copy the contents of the real buffer into the mapped buffer
    // so the DMA agent can read the contents of the real buffer.
    //
    if (Operation == EfiIsaIoOperationBusMasterRead) {
      CopyMem (
        (VOID *) (UINTN) IsaMapInfo->MappedHostAddress,
        (VOID *) (UINTN) IsaMapInfo->HostAddress,
        IsaMapInfo->NumberOfBytes
        );
    }
    //
    // The DeviceAddress is the address of the maped buffer below 16 MB
    //
    *DeviceAddress = IsaMapInfo->MappedHostAddress;
  } else {
    //
    // The transfer is below 16 MB, so the DeviceAddress is simply the
    // HostAddress
    //
    *DeviceAddress = PhysicalAddress;
  }
  //
  // If this is a Bus Master operation then return
  //
  if (Master) {
    return EFI_SUCCESS;
  }
  //
  // Figure out what to program into the DMA Channel Mode Register
  //
  DmaMode = (UINT8) (B_8237_DMA_CHMODE_INCREMENT | (ChannelNumber & 0x03));
  if (Read) {
    DmaMode |= V_8237_DMA_CHMODE_MEM2IO;
  } else {
    DmaMode |= V_8237_DMA_CHMODE_IO2MEM;
  }

  if (ChannelAttributes & EFI_ISA_IO_SLAVE_DMA_ATTRIBUTE_AUTO_INITIALIZE) {
    DmaMode |= B_8237_DMA_CHMODE_AE;
  }

  if (ChannelAttributes & EFI_ISA_IO_SLAVE_DMA_ATTRIBUTE_DEMAND_MODE) {
    DmaMode |= V_8237_DMA_CHMODE_DEMAND;
  }

  if (ChannelAttributes & EFI_ISA_IO_SLAVE_DMA_ATTRIBUTE_SINGLE_MODE) {
    DmaMode |= V_8237_DMA_CHMODE_SINGLE;
  }
  //
  // A Slave DMA transfer can not cross a 64K boundary.
  // Compute *NumberOfBytes based on this restriction.
  //
  MaxNumberOfBytes = 0x10000 - ((UINT32) (*DeviceAddress) & 0xffff);
  if (*NumberOfBytes > MaxNumberOfBytes) {
    *NumberOfBytes = MaxNumberOfBytes;
  }
  //
  // Compute the values to program into the BaseAddress and Count registers
  // of the Slave DMA controller
  //
  if (ChannelNumber < 4) {
    BaseAddress = (UINT32) (*DeviceAddress);
    Count       = (UINT16) (*NumberOfBytes - 1);
  } else {
    BaseAddress = (UINT32) (((UINT32) (*DeviceAddress) & 0xff0000) | (((UINT32) (*DeviceAddress) & 0xffff) >> 1));
    Count       = (UINT16) ((*NumberOfBytes - 1) >> 1);
  }
  //
  // Program the DMA Write Single Mask Register for ChannelNumber
  // Clear the DMA Byte Pointer Register
  //
  if (ChannelNumber < 4) {
    DmaMask         = R_8237_DMA_WRSMSK_CH0_3;
    DmaClear        = R_8237_DMA_CBPR_CH0_3;
    DmaChannelMode  = R_8237_DMA_CHMODE_CH0_3;
  } else {
    DmaMask         = R_8237_DMA_WRSMSK_CH4_7;
    DmaClear        = R_8237_DMA_CBPR_CH4_7;
    DmaChannelMode  = R_8237_DMA_CHMODE_CH4_7;
  }

  Status = WritePort (
             This,
             DmaMask,
             (UINT8) (B_8237_DMA_WRSMSK_CMS | (ChannelNumber & 0x03))
             );
  if (EFI_ERROR (Status)) {
    return Status;
  }

  Status = WritePort (
             This,
             DmaClear,
             (UINT8) (B_8237_DMA_WRSMSK_CMS | (ChannelNumber & 0x03))
             );
  if (EFI_ERROR (Status)) {
    return Status;
  }

  Status = WritePort (This, DmaChannelMode, DmaMode);
  if (EFI_ERROR (Status)) {
    return Status;
  }

  Status = WriteDmaPort (
             This,
             DmaRegisters[ChannelNumber].Address,
             DmaRegisters[ChannelNumber].Page,
             DmaRegisters[ChannelNumber].Count,
             BaseAddress,
             Count
             );
  if (EFI_ERROR (Status)) {
    return Status;
  }

  Status = WritePort (
             This,
             DmaMask,
             (UINT8) (ChannelNumber & 0x03)
             );
  if (EFI_ERROR (Status)) {
    return Status;
  }

  return EFI_SUCCESS;
}

/**
  Maps a memory region for DMA

  @param This                  - A pointer to the EFI_ISA_IO_PROTOCOL instance.
  @param Operation             - Indicates the type of DMA (slave or bus master), and if 
                          the DMA operation is going to read or write to system memory. 
  @param ChannelNumber         - The slave channel number to use for this DMA operation. 
                          If Operation and ChannelAttributes shows that this device 
                          performs bus mastering DMA, then this field is ignored.  
                          The legal range for this field is 0..7.  
  @param ChannelAttributes     - The attributes of the DMA channel to use for this DMA operation
  @param HostAddress           - The system memory address to map to the device.  
  @param NumberOfBytes         - On input the number of bytes to map.  On output the number 
                          of bytes that were mapped.
  @param DeviceAddress         - The resulting map address for the bus master device to use 
                        - to access the hosts HostAddress.  
  @param Mapping               - A resulting value to pass to EFI_ISA_IO.Unmap().


  @retval EFI_SUCCESS           - The range was mapped for the returned NumberOfBytes.
  @retval EFI_INVALID_PARAMETER - The Operation or HostAddress is undefined.
  @retval EFI_UNSUPPORTED       - The HostAddress can not be mapped as a common buffer.
  @retval EFI_DEVICE_ERROR      - The system hardware could not map the requested address.
  @retval EFI_OUT_OF_RESOURCES  - The memory pages could not be allocated.

**/
EFI_STATUS
EFIAPI
IsaIoMap (
  IN     EFI_ISA_IO_PROTOCOL                                  *This,
  IN     EFI_ISA_IO_PROTOCOL_OPERATION                        Operation,
  IN     UINT8                                                ChannelNumber         OPTIONAL,
  IN     UINT32                                               ChannelAttributes,
  IN     VOID                                                 *HostAddress,
  IN OUT UINTN                                                *NumberOfBytes,
  OUT    EFI_PHYSICAL_ADDRESS                                 *DeviceAddress,
  OUT    VOID                                                 **Mapping
  )

{
  //
  // Or unset Feature Flag PcdIsaBusSupportDma to disable support for ISA DMA.
  //
  if (!FeaturePcdGet (PcdIsaBusSupportDma)) {
    return EFI_UNSUPPORTED;
  }
  //
  // Set Feature Flag PcdIsaBusSupportBusMaster to FALSE to disable support for 
  // ISA Bus Master.
  //
  // So we just return EFI_UNSUPPORTED for these functions.
  //
  if (FeaturePcdGet (PcdIsaBusOnlySupportSlaveDma)) {
    return IsaIoMap_OnlySupportSlaveReadWrite (
              This,
              Operation,
              ChannelNumber,
              ChannelAttributes,
              HostAddress,
              NumberOfBytes,
              DeviceAddress,
              Mapping
             );

  } else {
    return IsaIoMap_FullSupport (
              This,
              Operation,
              ChannelNumber,
              ChannelAttributes,
              HostAddress,
              NumberOfBytes,
              DeviceAddress,
              Mapping
             );
  }
}

/**
  Allocates a common buffer for DMA

  @param This                  - A pointer to the EFI_ISA_IO_PROTOCOL instance.
  @param Type                  - The type allocation to perform.
  @param MemoryType            - The type of memory to allocate.
  @param Pages                 - The number of pages to allocate.
  @param HostAddress           - A pointer to store the base address of the allocated range.
  @param Attributes            - The requested bit mask of attributes for the allocated range.

  @retval EFI_SUCCESS           - The requested memory pages were allocated.
  @retval EFI_INVALID_PARAMETER - Type is invalid or MemoryType is invalid or HostAddress is NULL
  @retval EFI_UNSUPPORTED       - Attributes is unsupported or the memory range specified 
                          by HostAddress, Pages, and Type is not available for common buffer use.
  @retval EFI_OUT_OF_RESOURCES  - The memory pages could not be allocated.

**/
EFI_STATUS
EFIAPI
IsaIoAllocateBuffer (
  IN  EFI_ISA_IO_PROTOCOL                  *This,
  IN  EFI_ALLOCATE_TYPE                    Type,
  IN  EFI_MEMORY_TYPE                      MemoryType,
  IN  UINTN                                Pages,
  OUT VOID                                 **HostAddress,
  IN  UINT64                               Attributes
  )
{
  EFI_STATUS            Status;
  EFI_PHYSICAL_ADDRESS  PhysicalAddress;

  //
  // Set Feature Flag PcdIsaBusOnlySupportSlaveDma to FALSE to disable support for 
  // ISA Bus Master.
  // Or unset Feature Flag PcdIsaBusSupportDma to disable support for ISA DMA.
  //
  if (!FeaturePcdGet (PcdIsaBusSupportDma) || FeaturePcdGet (PcdIsaBusOnlySupportSlaveDma)) {
    return EFI_UNSUPPORTED;
  }

  if (HostAddress == NULL) {
    return EFI_INVALID_PARAMETER;
  }

  if (Type < AllocateAnyPages || Type >= MaxAllocateType) {
    return EFI_INVALID_PARAMETER;
  }
  //
  // The only valid memory types are EfiBootServicesData and EfiRuntimeServicesData
  //
  if (MemoryType != EfiBootServicesData && MemoryType != EfiRuntimeServicesData) {
    return EFI_INVALID_PARAMETER;
  }

  if (Attributes &~(EFI_ISA_IO_ATTRIBUTE_MEMORY_WRITE_COMBINE | EFI_ISA_IO_ATTRIBUTE_MEMORY_CACHED)) {
    return EFI_UNSUPPORTED;
  }

  PhysicalAddress = (EFI_PHYSICAL_ADDRESS) (UINTN) (ISA_MAX_MEMORY_ADDRESS - 1);
  if (Type == AllocateAddress) {
    if ((UINTN) (*HostAddress) >= ISA_MAX_MEMORY_ADDRESS) {
      return EFI_UNSUPPORTED;
    } else {
      PhysicalAddress = (UINTN) (*HostAddress);
    }
  }

  if (Type == AllocateAnyPages) {
    Type = AllocateMaxAddress;
  }

  Status = gBS->AllocatePages (Type, MemoryType, Pages, &PhysicalAddress);
  if (EFI_ERROR (Status)) {
    ReportErrorStatusCode (EFI_IO_BUS_LPC | EFI_IOB_EC_CONTROLLER_ERROR);
    return Status;
  }

  *HostAddress = (VOID *) (UINTN) PhysicalAddress;
  return Status;
}

/**

  Frees a common buffer 

  @param This                  - A pointer to the EFI_ISA_IO_PROTOCOL instance.
  @param Pages                 - The number of pages to free.
  @param HostAddress           - The base address of the allocated range.


  @retval EFI_SUCCESS           - The requested memory pages were freed.
  @retval EFI_INVALID_PARAMETER - The memory was not allocated with EFI_ISA_IO.AllocateBufer().

**/

EFI_STATUS
EFIAPI
IsaIoFreeBuffer (
  IN EFI_ISA_IO_PROTOCOL                  *This,
  IN UINTN                                Pages,
  IN VOID                                 *HostAddress
  )
{
  EFI_STATUS            Status;
  EFI_PHYSICAL_ADDRESS  PhysicalAddress;

  //
  // Set Feature Flag PcdIsaBusOnlySupportSlaveDma to FALSE to disable support for 
  // ISA Bus Master.
  // Or unset Feature Flag PcdIsaBusSupportDma to disable support for ISA DMA.
  //
  if (!FeaturePcdGet (PcdIsaBusSupportDma) || FeaturePcdGet (PcdIsaBusOnlySupportSlaveDma)) {
    return EFI_UNSUPPORTED;
  }

  PhysicalAddress = (EFI_PHYSICAL_ADDRESS) (UINTN) HostAddress;
  Status = gBS->FreePages (
                  PhysicalAddress,
                  Pages
                  );
  if (EFI_ERROR (Status)) {
    ReportErrorStatusCode (EFI_IO_BUS_LPC | EFI_IOB_EC_CONTROLLER_ERROR);
  }

  return Status;
}