[PATCH v4 02/21] ArmPkg/ArmMonitorLib: Definition for ArmMonitorLib library class

["PierreGondois" <pierre.gondois@arm.com>]

From: Pierre Gondois <Pierre.Gondois@arm.com>

The ArmMonitorLib provides an abstract interface to issue
an HyperVisor Call (HVC) or System Monitor Call (SMC) depending
on the default conduit.
The PcdMonitorConduitHvc PCD allows to select the default conduit.

The new library relies on the ArmHvcLib and ArmSmcLib libraries.
A Null instance of these libraries can be used for the unused conduit.

Signed-off-by: Pierre Gondois <Pierre.Gondois@arm.com>
---
 ArmPkg/ArmPkg.dec                      |  5 +++
 ArmPkg/Include/Library/ArmMonitorLib.h | 42 ++++++++++++++++++++++++++
 2 files changed, 47 insertions(+)
 create mode 100644 ArmPkg/Include/Library/ArmMonitorLib.h

diff --git a/ArmPkg/ArmPkg.dec b/ArmPkg/ArmPkg.dec
index bb5cbecbc228..653942ff63c3 100644
--- a/ArmPkg/ArmPkg.dec
+++ b/ArmPkg/ArmPkg.dec
@@ -71,6 +71,11 @@ [LibraryClasses.common]
   #
   ArmSvcLib|Include/Library/ArmSvcLib.h
 
+  ##  @libraryclass  Provides a Monitor Call interface that will use the
+  #   default conduit (HVC or SMC).
+  #
+  ArmMonitorLib|Include/Library/ArmMonitorLib.h
+
   ##  @libraryclass  Provides a default exception handler.
   #
   DefaultExceptionHandlerLib|Include/Library/DefaultExceptionHandlerLib.h
diff --git a/ArmPkg/Include/Library/ArmMonitorLib.h b/ArmPkg/Include/Library/ArmMonitorLib.h
new file mode 100644
index 000000000000..8bc430f92036
--- /dev/null
+++ b/ArmPkg/Include/Library/ArmMonitorLib.h
@@ -0,0 +1,42 @@
+/** @file
+
+  Copyright (c) 2022, Arm Limited. All rights reserved.<BR>
+
+  SPDX-License-Identifier: BSD-2-Clause-Patent
+
+**/
+
+#ifndef ARM_MONITOR_LIB_H_
+#define ARM_MONITOR_LIB_H_
+
+/** The size of the SMC arguments is different between AArch64 and AArch32.
+
+  The native size is used for the arguments.
+  It will be casted to either HVC or SMC args.
+*/
+typedef struct {
+  UINTN    Arg0;
+  UINTN    Arg1;
+  UINTN    Arg2;
+  UINTN    Arg3;
+  UINTN    Arg4;
+  UINTN    Arg5;
+  UINTN    Arg6;
+  UINTN    Arg7;
+} ARM_MONITOR_ARGS;
+
+/** Monitor call.
+
+  An HyperVisor Call (HVC) or System Monitor Call (SMC) will be issued
+  depending on the default conduit. PcdMonitorConduitHvc determines the type
+  of the call: if true, do an HVC.
+
+  @param [in, out]  Args    Arguments for the HVC/SMC.
+**/
+VOID
+EFIAPI
+ArmMonitorCall (
+  IN OUT ARM_MONITOR_ARGS  *Args
+  );
+
+#endif // ARM_MONITOR_LIB_H_
-- 
2.25.1