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 STATIC BOOLEAN mQemuFwCfgSupported = FALSE;
  21
  22
  23 /**
  24   Returns a boolean indicating if the firmware configuration interface
  25   is available or not.
  26
  27   This function may change fw_cfg state.
  28
  29   @retval    TRUE   The interface is available
  30   @retval    FALSE  The interface is not available
  31
  32 **/
  33 BOOLEAN
  34 EFIAPI
  35 QemuFwCfgIsAvailable (
  36   VOID
  37   )
  38 {
  39   return InternalQemuFwCfgIsAvailable ();
  40 }
  41
  42
  43 RETURN_STATUS
  44 EFIAPI
  45 QemuFwCfgInitialize (
  46   VOID
  47   )
  48 {
  49   UINT32 Signature;
  50   UINT32 Revision;
  51
  52   //
  53   // Enable the access routines while probing to see if it is supported.
  54   //
  55   mQemuFwCfgSupported = TRUE;
  56
  57   QemuFwCfgSelectItem (QemuFwCfgItemSignature);
  58   Signature = QemuFwCfgRead32 ();
  59   DEBUG ((EFI_D_INFO, "FW CFG Signature: 0x%x\n", Signature));
  60   QemuFwCfgSelectItem (QemuFwCfgItemInterfaceVersion);
  61   Revision = QemuFwCfgRead32 ();
  62   DEBUG ((EFI_D_INFO, "FW CFG Revision: 0x%x\n", Revision));
  63   if ((Signature != SIGNATURE_32 ('Q', 'E', 'M', 'U')) ||
  64       (Revision < 1)
  65      ) {
  66     DEBUG ((EFI_D_INFO, "QemuFwCfg interface not supported.\n"));
  67     mQemuFwCfgSupported = FALSE;
  68     return RETURN_SUCCESS;
  69   }
  70
  71   DEBUG ((EFI_D_INFO, "QemuFwCfg interface is supported.\n"));
  72   return RETURN_SUCCESS;
  73 }
  74
  75
  76 /**
  77   Returns a boolean indicating if the firmware configuration interface is
  78   available for library-internal purposes.
  79
  80   This function never changes fw_cfg state.
  81
  82   @retval    TRUE   The interface is available internally.
  83   @retval    FALSE  The interface is not available internally.
  84 **/
  85 BOOLEAN
  86 EFIAPI
  87 InternalQemuFwCfgIsAvailable (
  88   VOID
  89   )
  90 {
  91   return mQemuFwCfgSupported;
  92 }