OvmfPkg/PlatformDebugLibIoPort: fix port detection for use in the DXE Core

[mirror_edk2.git] / OvmfPkg / Library / PlatformDebugLibIoPort / DebugLibDetect.c

/** @file\r
  Detection code for QEMU debug port.\r
  Non-SEC instance, caches the result of detection.\r
\r
  Copyright (c) 2017, Red Hat, Inc.<BR>\r
  This program and the accompanying materials\r
  are licensed and made available under the terms and conditions of the BSD License\r
  which accompanies this distribution.  The full text of the license may be found at\r
  http://opensource.org/licenses/bsd-license.php.\r
\r
  THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,\r
  WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.\r
\r
**/\r
\r
#include <Base.h>\r
#include "DebugLibDetect.h"\r
\r
//\r
// Set to TRUE if the debug I/O port has been checked\r
//\r
STATIC BOOLEAN mDebugIoPortChecked = FALSE;\r
\r
//\r
// Set to TRUE if the debug I/O port is enabled\r
//\r
STATIC BOOLEAN mDebugIoPortFound = FALSE;\r
\r
/**\r
  This constructor function must not do anything.\r
\r
  Some modules consuming this library instance, such as the DXE Core, invoke\r
  the DEBUG() macro before they explicitly call\r
  ProcessLibraryConstructorList(). Therefore the auto-generated call from\r
  ProcessLibraryConstructorList() to this constructor function may be preceded\r
  by some calls to PlatformDebugLibIoPortFound() below. Hence\r
  PlatformDebugLibIoPortFound() must not rely on anything this constructor\r
  could set up.\r
\r
  @retval RETURN_SUCCESS   The constructor always returns RETURN_SUCCESS.\r
\r
**/\r
RETURN_STATUS\r
EFIAPI\r
PlatformDebugLibIoPortConstructor (\r
  VOID\r
  )\r
{\r
  return RETURN_SUCCESS;\r
}\r
\r
/**\r
  At the first call, check if the debug I/O port device is present, and cache\r
  the result for later use. At subsequent calls, return the cached result.\r
\r
  @retval TRUE   if the debug I/O port device was detected.\r
  @retval FALSE  otherwise\r
\r
**/\r
BOOLEAN\r
EFIAPI\r
PlatformDebugLibIoPortFound (\r
  VOID\r
  )\r
{\r
  if (!mDebugIoPortChecked) {\r
    mDebugIoPortFound = PlatformDebugLibIoPortDetect ();\r
    mDebugIoPortChecked = TRUE;\r
  }\r
  return mDebugIoPortFound;\r
}\r