Please consider the following formatting changes to #14824

Detectors/Align/Workflow/src/BarrelAlignmentSpec.cxx

@@ -37,7 +37,7 @@
 #include "CommonUtils/TreeStreamRedirector.h"
 #include "TPCCalibration/VDriftHelper.h"
 #include "TPCCalibration/CorrectionMapsLoader.h"
-#include "GPUO2Interface.h"
+#include "GPUO2ExternalUser.h"
 #include "GPUO2InterfaceUtils.h"
 #include "GPUParam.h"
 #include "Headers/DataHeader.h"

Detectors/Align/include/Align/Controller.h

@@ -54,7 +54,7 @@
 #include <TTree.h>
 #include <TFile.h>
 #include "Align/Mille.h"
-// #include "GPUO2Interface.h"
+// #include "GPUO2ExternalUsage.h"
 // #include "DataFormatsTPC/WorkflowHelper.h"
 
 namespace o2

Detectors/Align/src/AlignableDetectorTPC.cxx

@@ -24,7 +24,7 @@
 #include "DataFormatsTPC/WorkflowHelper.h"
 #include <TMath.h>
 #include <TGeoManager.h>
-#include "GPUO2Interface.h"
+#include "GPUO2ExternalUser.h"
 #include "DataFormatsTPC/WorkflowHelper.h"
 #include "GPUParam.inc"
 

Detectors/Align/src/Controller.cxx

@@ -44,7 +44,7 @@
 #include <TH1F.h>
 #include <TList.h>
 #include <cstdio>
-#include "GPUO2Interface.h"
+#include "GPUO2ExternalUser.h"
 #include "DataFormatsTPC/WorkflowHelper.h"
 #include <TGeoGlobalMagField.h>
 #include "CommonUtils/NameConf.h"

Detectors/GlobalTracking/src/MatchTPCITS.cxx

@@ -9,7 +9,7 @@
 // granted to it by virtue of its status as an Intergovernmental Organization
 // or submit itself to any jurisdiction.
 
-#include "GPUO2Interface.h" // Needed for propper settings in GPUParam.h
+#include "GPUO2ExternalUser.h" // Needed for propper settings in GPUParam.h
 #include "GPUParam.h"
 #include "GPUParam.inc"
 #ifdef WITH_OPENMP

Detectors/GlobalTrackingWorkflow/study/src/TrackingStudy.cxx

@@ -44,7 +44,7 @@
 #include "TPCCalibration/VDriftHelper.h"
 #include "TPCCalibration/CorrectionMapsLoader.h"
 #include "GPUO2InterfaceRefit.h"
-#include "GPUO2Interface.h" // Needed for propper settings in GPUParam.h
+#include "GPUO2ExternalUser.h" // Needed for propper settings in GPUParam.h
 #include "GPUParam.h"
 #include "GPUParam.inc"
 #include "GPUTPCGeometry.h"

Detectors/ITSMFT/ITS/tracking/include/ITStracking/TrackingInterface.h

@@ -25,7 +25,7 @@
 #include "DataFormatsCalibration/MeanVertexObject.h"
 
 #include "GPUDataTypes.h"
-#include "GPUO2Interface.h"
+#include "GPUO2ExternalUser.h"
 #include "GPUChainITS.h"
 
 #include <oneapi/tbb/task_arena.h>

Detectors/TPC/calibration/src/CalibPadGainTracks.cxx

@@ -22,7 +22,7 @@
 #include "CorrectionMapsHelper.h"
 #include "TPCReconstruction/TPCFastTransformHelperO2.h"
 #include "GPUO2InterfaceRefit.h"
-#include "GPUO2Interface.h"
+#include "GPUO2ExternalUser.h"
 #include "DataFormatsTPC/ClusterNative.h"
 #include "DataFormatsTPC/VDriftCorrFact.h"
 #include "DetectorsBase/Propagator.h"

Detectors/TPC/reconstruction/src/TPCTrackingDigitsPreCheck.cxx

@@ -19,7 +19,7 @@
 #include "DataFormatsTPC/Digit.h"
 #include "DataFormatsTPC/ClusterNative.h"
 
-#include "GPUO2Interface.h"
+#include "GPUO2ExternalUser.h"
 #include "GPUO2InterfaceConfiguration.h"
 #include "TPCBase/Sector.h"
 #include "Framework/Logger.h"

Detectors/TRD/workflow/include/TRDWorkflow/TRDGlobalTrackingSpec.h

@@ -18,7 +18,7 @@
 #include "Framework/Task.h"
 #include "TStopwatch.h"
 #include "TRDBase/GeometryFlat.h"
-#include "GPUO2Interface.h"
+#include "GPUO2ExternalUser.h"
 #include "GPUTRDTracker.h"
 #include "ReconstructionDataFormats/GlobalTrackID.h"
 #include "DataFormatsGlobalTracking/RecoContainer.h"

GPU/GPUTracking/Definitions/GPUDefConstantsAndSettings.h

@@ -23,7 +23,7 @@
 #include "GPUCommonDef.h"
 
 #if !defined(GPUCA_STANDALONE) && !defined(GPUCA_O2_LIB) && !defined(GPUCA_O2_INTERFACE)
-  #error You are using the CA GPU tracking without defining the build type (O2/Standalone). If you are running an O2 ROOT macro, please include GPUO2Interface.h first!
+  #error You are using the CA GPU tracking without defining the build type (O2/Standalone). If you are running an O2 ROOT macro, please include GPUO2ExternalUser.h first!
 #endif
 
 #if (defined(GPUCA_O2_LIB) && defined(GPUCA_STANDALONE))

GPU/GPUTracking/Definitions/GPUSettingsList.h

@@ -19,7 +19,7 @@
 // Create plain-C struct for GPU code.
 // Create static constexpr with default values for GPU run time compilation
 
-#include "GPUDefConstantsAndSettings.h"
+#include "GPUCommonDef.h"
 #ifndef GPUSETTINGS_H
 #error Please include GPUSettings.h!
 #endif

GPU/GPUTracking/Interface/CMakeLists.txt

@@ -23,7 +23,7 @@ if(OPENGL_FOUND
 endif()
 
 string(REPLACE ".cxx" ".h" HDRS_TMP "${SRCS}")
-set(HDRS ${HDRS_TMP})
+set(HDRS ${HDRS_TMP} GPUO2ExternalUser.h)
 
 o2_add_library(${MODULE}
                SOURCES ${SRCS}

GPU/GPUTracking/Interface/GPUO2ExternalUser.h

@@ -0,0 +1,26 @@
+// Copyright 2019-2020 CERN and copyright holders of ALICE O2.
+// See https://alice-o2.web.cern.ch/copyright for details of the copyright holders.
+// All rights not expressly granted are reserved.
+//
+// This software is distributed under the terms of the GNU General Public
+// License v3 (GPL Version 3), copied verbatim in the file "COPYING".
+//
+// In applying this license CERN does not waive the privileges and immunities
+// granted to it by virtue of its status as an Intergovernmental Organization
+// or submit itself to any jurisdiction.
+
+/// \file GPUO2ExternalUser.h
+/// \author David Rohr
+
+#ifndef GPUO2EXTERNALUSER_H
+#define GPUO2EXTERNALUSER_H
+
+// Some defines denoting that we are compiling for O2
+#ifndef GPUCA_TPC_GEOMETRY_O2
+#define GPUCA_TPC_GEOMETRY_O2
+#endif
+#ifndef GPUCA_O2_INTERFACE
+#define GPUCA_O2_INTERFACE
+#endif
+
+#endif

GPU/GPUTracking/Interface/GPUO2Interface.h

@@ -15,19 +15,13 @@
 #ifndef GPUO2INTERFACE_H
 #define GPUO2INTERFACE_H
 
-// Some defines denoting that we are compiling for O2
-#ifndef GPUCA_TPC_GEOMETRY_O2
-#define GPUCA_TPC_GEOMETRY_O2
-#endif
-#ifndef GPUCA_O2_INTERFACE
-#define GPUCA_O2_INTERFACE
-#endif
+#include "GPUO2ExternalUser.h"
+#include "GPUCommonDef.h"
+#include "GPUDataTypes.h"
 
 #include <memory>
 #include <array>
 #include <vector>
-#include "GPUCommonDef.h"
-#include "GPUDataTypes.h"
 
 namespace o2::base
 {

GPU/GPUTracking/Interface/GPUO2InterfaceConfigurableParam.h

@@ -22,12 +22,8 @@
 #ifndef GPUO2INTERFACECONFIGURABLEPARAM_H
 #define GPUO2INTERFACECONFIGURABLEPARAM_H
 
-// Some defines denoting that we are compiling for O2
-#ifndef GPUCA_TPC_GEOMETRY_O2
-#define GPUCA_TPC_GEOMETRY_O2
-#endif
-#ifndef GPUCA_O2_INTERFACE
-#define GPUCA_O2_INTERFACE
+#if !defined(GPUCA_STANDALONE) && !defined(GPUCA_O2_LIB)
+#include "GPUO2ExternalUser.h"
 #endif
 
 #include "CommonUtils/ConfigurableParam.h"

GPU/GPUTracking/Interface/GPUO2InterfaceConfiguration.h

@@ -15,23 +15,17 @@
 #ifndef GPUO2INTERFACECONFIGURATION_H
 #define GPUO2INTERFACECONFIGURATION_H
 
-#ifndef GPUCA_TPC_GEOMETRY_O2
-#define GPUCA_TPC_GEOMETRY_O2
-#endif
-#ifndef GPUCA_O2_INTERFACE
-#define GPUCA_O2_INTERFACE
-#endif
-
-#include <memory>
-#include <array>
-#include <vector>
-#include <functional>
-#include <gsl/gsl>
+#include "GPUO2ExternalUser.h"
 #include "GPUSettings.h"
 #include "GPUDataTypes.h"
 #include "GPUHostDataTypes.h"
 #include "GPUOutputControl.h"
 #include "DataFormatsTPC/Constants.h"
+#include <memory>
+#include <array>
+#include <vector>
+#include <functional>
+#include <gsl/gsl> // TODO: Get rid of gsl
 
 class TH1F;
 class TH1D;

GPU/GPUTracking/Interface/GPUO2InterfaceDisplay.h

@@ -15,14 +15,7 @@
 #ifndef GPUO2INTERFACEDisplay_H
 #define GPUO2INTERFACEDisplay_H
 
-// Some defines denoting that we are compiling for O2
-#ifndef GPUCA_TPC_GEOMETRY_O2
-#define GPUCA_TPC_GEOMETRY_O2
-#endif
-#ifndef GPUCA_O2_INTERFACE
-#define GPUCA_O2_INTERFACE
-#endif
-
+#include "GPUO2ExternalUser.h"
 #include <memory>
 #include <vector>
 #include "GPUDataTypes.h"

GPU/GPUTracking/Interface/GPUO2InterfaceQA.h

@@ -15,14 +15,7 @@
 #ifndef GPUO2INTERFACEQA_H
 #define GPUO2INTERFACEQA_H
 
-// Some defines denoting that we are compiling for O2
-#ifndef GPUCA_TPC_GEOMETRY_O2
-#define GPUCA_TPC_GEOMETRY_O2
-#endif
-#ifndef GPUCA_O2_INTERFACE
-#define GPUCA_O2_INTERFACE
-#endif
-
+#include "GPUO2ExternalUser.h"
 #include <memory>
 #include <vector>
 

GPU/GPUTracking/Interface/GPUO2InterfaceRefit.h

@@ -15,14 +15,7 @@
 #ifndef GPUO2INTERFACEREFIT_H
 #define GPUO2INTERFACEREFIT_H
 
-// Some defines denoting that we are compiling for O2
-#ifndef GPUCA_TPC_GEOMETRY_O2
-#define GPUCA_TPC_GEOMETRY_O2
-#endif
-#ifndef GPUCA_O2_INTERFACE
-#define GPUCA_O2_INTERFACE
-#endif
-
+#include "GPUO2ExternalUser.h"
 #include <memory>
 #include <vector>
 #include <gsl/span>

GPU/GPUTracking/display/GPUDisplay.h

@@ -19,6 +19,7 @@
 #include "backend/GPUDisplayBackend.h"
 #include "GPUDisplayInterface.h"
 #include "GPUSettings.h"
+#include "GPUDefConstantsAndSettings.h"
 
 #include <array>
 #include <mutex>