audk/IntelFrameworkModulePkg/Csm/LegacyBiosDxe/LegacyBda.c

/** @file
  This code fills in BDA (0x400) and EBDA (pointed to by 0x4xx)
  information. There is support for doing initializeation before
  Legacy16 is loaded and before a legacy boot is attempted.

Copyright (c) 2006 - 2010, Intel Corporation. All rights reserved.<BR>

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 "LegacyBiosInterface.h"

/**
  Fill in the standard BDA and EBDA stuff before Legacy16 load

  @param  Private     Legacy BIOS Instance data

  @retval EFI_SUCCESS It should always work.

**/
EFI_STATUS
LegacyBiosInitBda (
  IN  LEGACY_BIOS_INSTANCE    *Private
  )
{
  BDA_STRUC *Bda;
  UINT8     *Ebda;

  Bda   = (BDA_STRUC *) ((UINTN) 0x400);
  Ebda  = (UINT8 *) ((UINTN) 0x9fc00);

  ACCESS_PAGE0_CODE (
    ZeroMem (Bda, 0x100);
    //
    // 640k-1k for EBDA
    //
    Bda->MemSize        = 0x27f;
    Bda->KeyHead        = 0x1e;
    Bda->KeyTail        = 0x1e;
    Bda->FloppyData     = 0x00;
    Bda->FloppyTimeout  = 0xff;

    Bda->KeyStart       = 0x001E;
    Bda->KeyEnd         = 0x003E;
    Bda->KeyboardStatus = 0x10;
    Bda->Ebda           = 0x9fc0;

    //
    // Move LPT time out here and zero out LPT4 since some SCSI OPROMS
    // use this as scratch pad (LPT4 is Reserved)
    //
    Bda->Lpt1_2Timeout  = 0x1414;
    Bda->Lpt3_4Timeout  = 0x1400;

  );

  ZeroMem (Ebda, 0x400);
  *Ebda = 0x01;

  return EFI_SUCCESS;
}