OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgSec.c

   1 /** @file
   2
   3   Stateless fw_cfg library implementation.
   4
   5   Clients must call QemuFwCfgIsAvailable() first.
   6
   7   Copyright (C) 2013, Red Hat, Inc.
   8   Copyright (c) 2011 - 2013, Intel Corporation. All rights reserved.<BR>
   9
  10   This program and the accompanying materials are licensed and made available
  11   under the terms and conditions of the BSD License which accompanies this
  12   distribution.  The full text of the license may be found at
  13   http://opensource.org/licenses/bsd-license.php
  14
  15   THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS, WITHOUT
  16   WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
  17 **/
  18
  19 #include <Library/DebugLib.h>
  20 #include <Library/QemuFwCfgLib.h>
  21
  22 #include "QemuFwCfgLibInternal.h"
  23
  24 /**
  25   Returns a boolean indicating if the firmware configuration interface
  26   is available or not.
  27
  28   This function may change fw_cfg state.
  29
  30   @retval    TRUE   The interface is available
  31   @retval    FALSE  The interface is not available
  32
  33 **/
  34 BOOLEAN
  35 EFIAPI
  36 QemuFwCfgIsAvailable (
  37   VOID
  38   )
  39 {
  40   UINT32 Signature;
  41   UINT32 Revision;
  42
  43   QemuFwCfgSelectItem (QemuFwCfgItemSignature);
  44   Signature = QemuFwCfgRead32 ();
  45   DEBUG ((EFI_D_INFO, "FW CFG Signature: 0x%x\n", Signature));
  46   QemuFwCfgSelectItem (QemuFwCfgItemInterfaceVersion);
  47   Revision = QemuFwCfgRead32 ();
  48   DEBUG ((EFI_D_INFO, "FW CFG Revision: 0x%x\n", Revision));
  49   if ((Signature != SIGNATURE_32 ('Q', 'E', 'M', 'U')) ||
  50       (Revision < 1)
  51      ) {
  52     DEBUG ((EFI_D_INFO, "QemuFwCfg interface not supported.\n"));
  53     return FALSE;
  54   }
  55
  56   DEBUG ((EFI_D_INFO, "QemuFwCfg interface is supported.\n"));
  57   return TRUE;
  58 }
  59
  60
  61 /**
  62   Returns a boolean indicating if the firmware configuration interface is
  63   available for library-internal purposes.
  64
  65   This function never changes fw_cfg state.
  66
  67   @retval    TRUE   The interface is available internally.
  68   @retval    FALSE  The interface is not available internally.
  69 **/
  70 BOOLEAN
  71 InternalQemuFwCfgIsAvailable (
  72   VOID
  73   )
  74 {
  75   //
  76   // We always return TRUE, because the consumer of this library ought to have
  77   // called QemuFwCfgIsAvailable before making other calls which would hit this
  78   // path.
  79   //
  80   return TRUE;
  81 }
  82
  83 /**
  84   Returns a boolean indicating whether QEMU provides the DMA-like access method
  85   for fw_cfg.
  86
  87   @retval    TRUE   The DMA-like access method is available.
  88   @retval    FALSE  The DMA-like access method is unavailable.
  89 **/
  90 BOOLEAN
  91 InternalQemuFwCfgDmaIsAvailable (
  92   VOID
  93   )
  94 {
  95   return FALSE;
  96 }