OvmfPkg/PlatformDebugLibIoPort: factor out debug port detection

Factor out debug port detection in PlatformDebugLibIoPort.

Signed-off-by: Anthony PERARD <anthony.perard@citrix.com>
Message-Id: <20200423095358.2518197-4-anthony.perard@citrix.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Reviewed-by: Laszlo Ersek <lersek@redhat.com>

OvmfPkg/Library/PlatformDebugLibIoPort/DebugIoPortQemu.c

@@ -0,0 +1,34 @@
+/** @file
+  Detection code for QEMU debug port.
+
+  Copyright (c) 2006 - 2019, Intel Corporation. All rights reserved.<BR>
+  Copyright (c) 2012, Red Hat, Inc.<BR>
+  Copyright (c) 2020, Citrix Systems, Inc.
+  SPDX-License-Identifier: BSD-2-Clause-Patent
+
+**/
+
+#include <Library/IoLib.h>
+#include <Library/PcdLib.h>
+#include "DebugLibDetect.h"
+
+//
+// The constant value that is read from the debug I/O port
+//
+#define BOCHS_DEBUG_PORT_MAGIC    0xE9
+
+/**
+  Return the result of detecting the debug I/O port device.
+
+  @retval TRUE   if the debug I/O port device was detected.
+  @retval FALSE  otherwise
+
+**/
+BOOLEAN
+EFIAPI
+PlatformDebugLibIoPortDetect (
+  VOID
+  )
+{
+  return IoRead8 (PcdGet16 (PcdDebugIoPort)) == BOCHS_DEBUG_PORT_MAGIC;
+}