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   SPDX-License-Identifier: BSD-2-Clause-Patent
   8 **/
   9
  10 #include <Library/QemuFwCfgLib.h>
  11 #include <Library/QemuFwCfgS3Lib.h>
  12
  13 /**
  14   Determine if S3 support is explicitly enabled.
  15
  16   @retval  TRUE   If S3 support is explicitly enabled. Other functions in this
  17                   library may be called (subject to their individual
  18                   restrictions).
  19
  20            FALSE  Otherwise. This includes unavailability of the firmware
  21                   configuration interface. No other function in this library
  22                   must be called.
  23 **/
  24 BOOLEAN
  25 EFIAPI
  26 QemuFwCfgS3Enabled (
  27   VOID
  28   )
  29 {
  30   RETURN_STATUS         Status;
  31   FIRMWARE_CONFIG_ITEM  FwCfgItem;
  32   UINTN                 FwCfgSize;
  33   UINT8                 SystemStates[6];
  34
  35   Status = QemuFwCfgFindFile ("etc/system-states", &FwCfgItem, &FwCfgSize);
  36   if ((Status != RETURN_SUCCESS) || (FwCfgSize != sizeof SystemStates)) {
  37     return FALSE;
  38   }
  39
  40   QemuFwCfgSelectItem (FwCfgItem);
  41   QemuFwCfgReadBytes (sizeof SystemStates, SystemStates);
  42   return (BOOLEAN)(SystemStates[3] & BIT7);
  43 }