OvmfPkg/Include/Library/QemuFwCfgLib.h

/** @file
  QEMU/KVM Firmware Configuration access

  Copyright (c) 2011 - 2013, Intel Corporation. All rights reserved.<BR>
  Copyright (C) 2013, Red Hat, Inc.

  SPDX-License-Identifier: BSD-2-Clause-Patent

**/

#ifndef __FW_CFG_LIB__
#define __FW_CFG_LIB__

#include <IndustryStandard/QemuFwCfg.h>
#include <Library/PlatformInitLib.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
  );

/**
  Selects a firmware configuration item for reading.

  Following this call, any data read from this item will start from
  the beginning of the configuration item's data.

  @param[in] QemuFwCfgItem - Firmware Configuration item to read

**/
VOID
EFIAPI
QemuFwCfgSelectItem (
  IN FIRMWARE_CONFIG_ITEM  QemuFwCfgItem
  );

/**
  Reads firmware configuration bytes into a buffer

  If called multiple times, then the data read will
  continue at the offset of the firmware configuration
  item where the previous read ended.

  @param[in] Size - Size in bytes to read
  @param[in] Buffer - Buffer to store data into

**/
VOID
EFIAPI
QemuFwCfgReadBytes (
  IN UINTN  Size,
  IN VOID   *Buffer  OPTIONAL
  );

/**
  Writes firmware configuration bytes from a buffer

  If called multiple times, then the data written will
  continue at the offset of the firmware configuration
  item where the previous write ended.

  @param[in] Size - Size in bytes to write
  @param[in] Buffer - Buffer to read data from

**/
VOID
EFIAPI
QemuFwCfgWriteBytes (
  IN UINTN  Size,
  IN VOID   *Buffer
  );

/**
  Skip bytes in the firmware configuration item.

  Increase the offset of the firmware configuration item without transferring
  bytes between the item and a caller-provided buffer. Subsequent read, write
  or skip operations will commence at the increased offset.

  @param[in] Size  Number of bytes to skip.
**/
VOID
EFIAPI
QemuFwCfgSkipBytes (
  IN UINTN  Size
  );

/**
  Reads a UINT8 firmware configuration value

  @return    Value of Firmware Configuration item read

**/
UINT8
EFIAPI
QemuFwCfgRead8 (
  VOID
  );

/**
  Reads a UINT16 firmware configuration value

  @return    Value of Firmware Configuration item read

**/
UINT16
EFIAPI
QemuFwCfgRead16 (
  VOID
  );

/**
  Reads a UINT32 firmware configuration value

  @return    Value of Firmware Configuration item read

**/
UINT32
EFIAPI
QemuFwCfgRead32 (
  VOID
  );

/**
  Reads a UINT64 firmware configuration value

  @return    Value of Firmware Configuration item read

**/
UINT64
EFIAPI
QemuFwCfgRead64 (
  VOID
  );

/**
  Find the configuration item corresponding to the firmware configuration file.

  @param[in]  Name - Name of file to look up.
  @param[out] Item - Configuration item corresponding to the file, to be passed
                     to QemuFwCfgSelectItem ().
  @param[out] Size - Number of bytes in the file.

  @return    RETURN_SUCCESS       If file is found.
             RETURN_NOT_FOUND     If file is not found.
             RETURN_UNSUPPORTED   If firmware configuration is unavailable.

**/
RETURN_STATUS
EFIAPI
QemuFwCfgFindFile (
  IN   CONST CHAR8           *Name,
  OUT  FIRMWARE_CONFIG_ITEM  *Item,
  OUT  UINTN                 *Size
  );

/**
  OVMF reads configuration data from QEMU via fw_cfg.
  For Td-Guest VMM is out of TCB and the configuration data is untrusted.
  From the security perpective the configuration data shall be measured
  before it is consumed.
  This function reads the fw_cfg items and cached them. In the meanwhile these
  fw_cfg items are measured as well. This is to avoid changing the order when
  reading the fw_cfg process, which depends on multiple factors(depex, order in
  the Firmware volume).

  @retval  RETURN_SUCCESS   - Successfully cache with measurement
  @retval  Others           - As the error code indicates
 */
RETURN_STATUS
EFIAPI
QemuFwCfgInitCache (
  IN OUT EFI_HOB_PLATFORM_INFO  *PlatformInfoHob
  );

#endif