OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgPeiDxe.c

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