OvmfPkg QemuFwCfgLib: determine if S3 support is explicitly enabled

[mirror_edk2.git] / OvmfPkg / Library / QemuFwCfgLib / QemuFwCfgLib.c

diff --git a/OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgLib.c b/OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgLib.c
index 3c5963f31b52ecfe1ec7f1671f558cd15425ed4b..92c85c1d3d52a27dd9a2a2240f6a5a998ff63368 100644 (file)
--- a/OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgLib.c
+++ b/OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgLib.c
@@ -294,3 +294,31 @@ QemuFwCfgFindFile (
 \r
   return RETURN_NOT_FOUND;\r
 }\r
+\r
+\r
+/**\r
+  Determine if S3 support is explicitly enabled.\r
+\r
+  @retval  TRUE   if S3 support is explicitly enabled.\r
+           FALSE  otherwise. This includes unavailability of the firmware\r
+                  configuration interface.\r
+**/\r
+BOOLEAN\r
+EFIAPI\r
+QemuFwCfgS3Enabled (\r
+  VOID\r
+  )\r
+{\r
+  RETURN_STATUS        Status;\r
+  FIRMWARE_CONFIG_ITEM FwCfgItem;\r
+  UINTN                FwCfgSize;\r
+  UINT8                SystemStates[6];\r
+\r
+  Status = QemuFwCfgFindFile ("etc/system-states", &FwCfgItem, &FwCfgSize);\r
+  if (Status != RETURN_SUCCESS || FwCfgSize != sizeof SystemStates) {\r
+    return FALSE;\r
+  }\r
+  QemuFwCfgSelectItem (FwCfgItem);\r
+  QemuFwCfgReadBytes (sizeof SystemStates, SystemStates);\r
+  return (BOOLEAN) (SystemStates[3] & BIT7);\r
+}\r