1 files changed, 15 insertions, 1 deletions
diff --git a/ArmPkg/Include/Library/ArmGicLib.h b/ArmPkg/Include/Library/ArmGicLib.h
index f2d4c7b27c..e3ef228dba 100644
--- a/ArmPkg/Include/Library/ArmGicLib.h
+++ b/ArmPkg/Include/Library/ArmGicLib.h
@@ -140,10 +140,24 @@ ArmGicSendSgiTo (
   IN  INTN          SgiId
   );
 
+/*
+ * Acknowledge and return the value of the Interrupt Acknowledge Register
+ *
+ * InterruptId is returned separately from the register value because in
+ * the GICv2 the register value contains the CpuId and InterruptId while
+ * in the GICv3 the register value is only the InterruptId.
+ *
+ * @param GicInterruptInterfaceBase   Base Address of the GIC CPU Interface
+ * @param InterruptId                 InterruptId read from the Interrupt Acknowledge Register
+ *
+ * @retval value returned by the Interrupt Acknowledge Register
+ *
+ */
 UINTN
 EFIAPI
 ArmGicAcknowledgeInterrupt (
-  IN  UINTN          GicInterruptInterfaceBase
+  IN  UINTN          GicInterruptInterfaceBase,
+  OUT UINTN          *InterruptId
   );
 
 VOID