OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgSec.c

/** @file

  Stateless fw_cfg library implementation.

  Clients must call QemuFwCfgIsAvailable() first.

  Copyright (C) 2013, Red Hat, Inc.
  Copyright (c) 2011 - 2013, Intel Corporation. All rights reserved.<BR>
  Copyright (c) 2017, Advanced Micro Devices. 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 <Library/BaseLib.h>
#include <Library/DebugLib.h>
#include <Library/QemuFwCfgLib.h>

#include "QemuFwCfgLibInternal.h"

/**
  Returns a boolean indicating if the firmware configuration interface
  is available or not.

  This function may change fw_cfg state.

  @retval    TRUE   The interface is available
  @retval    FALSE  The interface is not available

**/
BOOLEAN
EFIAPI
QemuFwCfgIsAvailable (
  VOID
  )
{
  UINT32 Signature;
  UINT32 Revision;

  QemuFwCfgSelectItem (QemuFwCfgItemSignature);
  Signature = QemuFwCfgRead32 ();
  DEBUG ((EFI_D_INFO, "FW CFG Signature: 0x%x\n", Signature));
  QemuFwCfgSelectItem (QemuFwCfgItemInterfaceVersion);
  Revision = QemuFwCfgRead32 ();
  DEBUG ((EFI_D_INFO, "FW CFG Revision: 0x%x\n", Revision));
  if ((Signature != SIGNATURE_32 ('Q', 'E', 'M', 'U')) ||
      (Revision < 1)
     ) {
    DEBUG ((EFI_D_INFO, "QemuFwCfg interface not supported.\n"));
    return FALSE;
  }

  DEBUG ((EFI_D_INFO, "QemuFwCfg interface is supported.\n"));
  return TRUE;
}


/**
  Returns a boolean indicating if the firmware configuration interface is
  available for library-internal purposes.

  This function never changes fw_cfg state.

  @retval    TRUE   The interface is available internally.
  @retval    FALSE  The interface is not available internally.
**/
BOOLEAN
InternalQemuFwCfgIsAvailable (
  VOID
  )
{
  //
  // We always return TRUE, because the consumer of this library ought to have
  // called QemuFwCfgIsAvailable before making other calls which would hit this
  // path.
  //
  return TRUE;
}

/**
  Returns a boolean indicating whether QEMU provides the DMA-like access method
  for fw_cfg.

  @retval    TRUE   The DMA-like access method is available.
  @retval    FALSE  The DMA-like access method is unavailable.
**/
BOOLEAN
InternalQemuFwCfgDmaIsAvailable (
  VOID
  )
{
  return FALSE;
}

/**
  Transfer an array of bytes, or skip a number of bytes, using the DMA
  interface.

  @param[in]     Size     Size in bytes to transfer or skip.

  @param[in,out] Buffer   Buffer to read data into or write data from. Ignored,
                          and may be NULL, if Size is zero, or Control is
                          FW_CFG_DMA_CTL_SKIP.

  @param[in]     Control  One of the following:
                          FW_CFG_DMA_CTL_WRITE - write to fw_cfg from Buffer.
                          FW_CFG_DMA_CTL_READ  - read from fw_cfg into Buffer.
                          FW_CFG_DMA_CTL_SKIP  - skip bytes in fw_cfg.
**/
VOID
InternalQemuFwCfgDmaBytes (
  IN     UINT32   Size,
  IN OUT VOID     *Buffer OPTIONAL,
  IN     UINT32   Control
  )
{
  //
  // We should never reach here
  //
  ASSERT (FALSE);
  CpuDeadLoop ();
}