OvmfPkg/Library/QemuFwCfgS3Lib/QemuFwCfgS3PeiDxe.c

   1 /** @file
   2   Shared code for the PEI fw_cfg and DXE fw_cfg instances of the QemuFwCfgS3Lib
   3   class.
   4
   5   Copyright (C) 2017, Red Hat, Inc.
   6
   7   This program and the accompanying materials are licensed and made available
   8   under the terms and conditions of the BSD License which accompanies this
   9   distribution.  The full text of the license may be found at
  10   http://opensource.org/licenses/bsd-license.php
  11
  12   THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS, WITHOUT
  13   WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
  14 **/
  15
  16 #include <Library/QemuFwCfgLib.h>
  17 #include <Library/QemuFwCfgS3Lib.h>
  18
  19 /**
  20   Determine if S3 support is explicitly enabled.
  21
  22   @retval  TRUE   If S3 support is explicitly enabled. Other functions in this
  23                   library may be called (subject to their individual
  24                   restrictions).
  25
  26            FALSE  Otherwise. This includes unavailability of the firmware
  27                   configuration interface. No other function in this library
  28                   must be called.
  29 **/
  30 BOOLEAN
  31 EFIAPI
  32 QemuFwCfgS3Enabled (
  33   VOID
  34   )
  35 {
  36   RETURN_STATUS        Status;
  37   FIRMWARE_CONFIG_ITEM FwCfgItem;
  38   UINTN                FwCfgSize;
  39   UINT8                SystemStates[6];
  40
  41   Status = QemuFwCfgFindFile ("etc/system-states", &FwCfgItem, &FwCfgSize);
  42   if (Status != RETURN_SUCCESS || FwCfgSize != sizeof SystemStates) {
  43     return FALSE;
  44   }
  45   QemuFwCfgSelectItem (FwCfgItem);
  46   QemuFwCfgReadBytes (sizeof SystemStates, SystemStates);
  47   return (BOOLEAN) (SystemStates[3] & BIT7);
  48 }