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   Copyright (c) 2017, Advanced Micro Devices. All rights reserved.<BR>
  10
  11   This program and the accompanying materials are licensed and made available
  12   under the terms and conditions of the BSD License which accompanies this
  13   distribution.  The full text of the license may be found at
  14   http://opensource.org/licenses/bsd-license.php
  15
  16   THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS, WITHOUT
  17   WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
  18 **/
  19
  20 #include <Library/BaseLib.h>
  21 #include <Library/DebugLib.h>
  22 #include <Library/QemuFwCfgLib.h>
  23
  24 #include "QemuFwCfgLibInternal.h"
  25
  26 /**
  27   Returns a boolean indicating if the firmware configuration interface
  28   is available or not.
  29
  30   This function may change fw_cfg state.
  31
  32   @retval    TRUE   The interface is available
  33   @retval    FALSE  The interface is not available
  34
  35 **/
  36 BOOLEAN
  37 EFIAPI
  38 QemuFwCfgIsAvailable (
  39   VOID
  40   )
  41 {
  42   UINT32 Signature;
  43   UINT32 Revision;
  44
  45   QemuFwCfgSelectItem (QemuFwCfgItemSignature);
  46   Signature = QemuFwCfgRead32 ();
  47   DEBUG ((EFI_D_INFO, "FW CFG Signature: 0x%x\n", Signature));
  48   QemuFwCfgSelectItem (QemuFwCfgItemInterfaceVersion);
  49   Revision = QemuFwCfgRead32 ();
  50   DEBUG ((EFI_D_INFO, "FW CFG Revision: 0x%x\n", Revision));
  51   if ((Signature != SIGNATURE_32 ('Q', 'E', 'M', 'U')) ||
  52       (Revision < 1)
  53      ) {
  54     DEBUG ((EFI_D_INFO, "QemuFwCfg interface not supported.\n"));
  55     return FALSE;
  56   }
  57
  58   DEBUG ((EFI_D_INFO, "QemuFwCfg interface is supported.\n"));
  59   return TRUE;
  60 }
  61
  62
  63 /**
  64   Returns a boolean indicating if the firmware configuration interface is
  65   available for library-internal purposes.
  66
  67   This function never changes fw_cfg state.
  68
  69   @retval    TRUE   The interface is available internally.
  70   @retval    FALSE  The interface is not available internally.
  71 **/
  72 BOOLEAN
  73 InternalQemuFwCfgIsAvailable (
  74   VOID
  75   )
  76 {
  77   //
  78   // We always return TRUE, because the consumer of this library ought to have
  79   // called QemuFwCfgIsAvailable before making other calls which would hit this
  80   // path.
  81   //
  82   return TRUE;
  83 }
  84
  85 /**
  86   Returns a boolean indicating whether QEMU provides the DMA-like access method
  87   for fw_cfg.
  88
  89   @retval    TRUE   The DMA-like access method is available.
  90   @retval    FALSE  The DMA-like access method is unavailable.
  91 **/
  92 BOOLEAN
  93 InternalQemuFwCfgDmaIsAvailable (
  94   VOID
  95   )
  96 {
  97   return FALSE;
  98 }
  99
 100 /**
 101   Transfer an array of bytes, or skip a number of bytes, using the DMA
 102   interface.
 103
 104   @param[in]     Size     Size in bytes to transfer or skip.
 105
 106   @param[in,out] Buffer   Buffer to read data into or write data from. Ignored,
 107                           and may be NULL, if Size is zero, or Control is
 108                           FW_CFG_DMA_CTL_SKIP.
 109
 110   @param[in]     Control  One of the following:
 111                           FW_CFG_DMA_CTL_WRITE - write to fw_cfg from Buffer.
 112                           FW_CFG_DMA_CTL_READ  - read from fw_cfg into Buffer.
 113                           FW_CFG_DMA_CTL_SKIP  - skip bytes in fw_cfg.
 114 **/
 115 VOID
 116 InternalQemuFwCfgDmaBytes (
 117   IN     UINT32   Size,
 118   IN OUT VOID     *Buffer OPTIONAL,
 119   IN     UINT32   Control
 120   )
 121 {
 122   //
 123   // We should never reach here
 124   //
 125   ASSERT (FALSE);
 126   CpuDeadLoop ();
 127 }