AdapterStatusListener[1] and DBTAdapter[2] API Refinement: [1] non const DBTAdapter, [2] use HCIStatusCode for start/stopDiscovery

and well as [2] return boolean for set[Discoverable|Bondable|Powered](..).

AdapterStatusListener needs to pass non-const DBTAdapter to allow actionable modification of adapter state,
e.g. start/stopDiscovery.

HCIStatusCode is desired for start/stopDiscovery, allowing user to read actual HCI status code on failure.

boolean return value for set[Discoverable|Bondable|Powered](..) reflecting general success or failure
on these basic commands.

17 files changed, 214 insertions, 169 deletions

diff --git a/api/direct_bt/DBTAdapter.hpp b/api/direct_bt/DBTAdapter.hpp
index 46ff0c65..c137d676 100644
--- a/api/direct_bt/DBTAdapter.hpp
+++ b/api/direct_bt/DBTAdapter.hpp
@@ -77,23 +77,23 @@ namespace direct_bt {
 
             /**
              * DBTAdapter setting(s) changed.
-             * @param a the adapter which settings have changed.
+             * @param adapter the adapter which settings have changed.
              * @param oldmask the previous settings mask
              * @param newmask the new settings mask
              * @param changedmask the changes settings mask
              * @param timestamp the time in monotonic milliseconds when this event occurred. See BasicTypes::getCurrentMilliseconds().
              */
-            virtual void adapterSettingsChanged(DBTAdapter const &a, const AdapterSetting oldmask, const AdapterSetting newmask,
+            virtual void adapterSettingsChanged(DBTAdapter &adapter, const AdapterSetting oldmask, const AdapterSetting newmask,
                                                 const AdapterSetting changedmask, const uint64_t timestamp) = 0;
 
             /**
              * DBTAdapter's discovery state has changed, i.e. enabled or disabled.
-             * @param a the adapter which discovering state has changed.
+             * @param adapter the adapter which discovering state has changed.
              * @param enabled the new discovery state
              * @param keepAlive if {@code true}, the discovery will be re-enabled if disabled by the underlying Bluetooth implementation.
              * @param timestamp the time in monotonic milliseconds when this event occurred. See BasicTypes::getCurrentMilliseconds().
              */
-            virtual void discoveringChanged(DBTAdapter const &a, const bool enabled, const bool keepAlive, const uint64_t timestamp) = 0;
+            virtual void discoveringChanged(DBTAdapter &adapter, const bool enabled, const bool keepAlive, const uint64_t timestamp) = 0;
 
             /**
              * A DBTDevice has been newly discovered.
@@ -336,17 +336,17 @@ namespace direct_bt {
             /**
              * Set the discoverable state of the adapter.
              */
-            void setDiscoverable(bool value) noexcept;
+            bool setDiscoverable(bool value) noexcept;
 
             /**
              * Set the bondable (aka pairable) state of the adapter.
              */
-            void setBondable(bool value) noexcept;
+            bool setBondable(bool value) noexcept;
 
             /**
              * Set the power state of the adapter.
              */
-            void setPowered(bool value) noexcept;
+            bool setPowered(bool value) noexcept;
 
             /**
              * Reset the adapter.
@@ -444,7 +444,7 @@ namespace direct_bt {
             /**
              * Starts a new discovery session.
              * <p>
-             * Returns true if successful, otherwise false;
+             * Returns HCIStatusCode::SUCCESS if successful, otherwise the HCIStatusCode error state;
              * </p>
              * <p>
              * if {@code keepAlive} is {@code  true}, discovery state will be re-enabled
@@ -482,10 +482,10 @@ namespace direct_bt {
              * @param own_mac_type
              * @param le_scan_interval in units of 0.625ms, default value 24 for 15ms; Value range [4 .. 0x4000] for [2.5ms .. 10.24s]
              * @param le_scan_window in units of 0.625ms, default value 24 for 15ms; Value range [4 .. 0x4000] for [2.5ms .. 10.24s]. Shall be <= le_scan_interval
-             * @return
+             * @return HCIStatusCode::SUCCESS if successful, otherwise the HCIStatusCode error state
              */
-            bool startDiscovery(const bool keepAlive=true, const HCILEOwnAddressType own_mac_type=HCILEOwnAddressType::PUBLIC,
-                                const uint16_t le_scan_interval=24, const uint16_t le_scan_window=24);
+            HCIStatusCode startDiscovery(const bool keepAlive=true, const HCILEOwnAddressType own_mac_type=HCILEOwnAddressType::PUBLIC,
+                                         const uint16_t le_scan_interval=24, const uint16_t le_scan_window=24);
 
             /**
              * Closes the discovery session.
@@ -493,9 +493,9 @@ namespace direct_bt {
              * This adapter's HCIHandler instance is used to stop scanning,
              * see HCIHandler::le_enable_scan().
              * </p>
-             * @return true if no error, otherwise false.
+             * @return HCIStatusCode::SUCCESS if successful, otherwise the HCIStatusCode error state
              */
-            bool stopDiscovery() noexcept;
+            HCIStatusCode stopDiscovery() noexcept;
 
             /**
              * Returns the meta discovering state. It can be modified through startDiscovery(..) and stopDiscovery().
diff --git a/examples/direct_bt_scanner00/dbt_scanner00.cpp b/examples/direct_bt_scanner00/dbt_scanner00.cpp
index df37a103..0940de7e 100644
--- a/examples/direct_bt_scanner00/dbt_scanner00.cpp
+++ b/examples/direct_bt_scanner00/dbt_scanner00.cpp
@@ -51,7 +51,7 @@ std::mutex mtxDeviceFound;
 std::condition_variable cvDeviceFound;
 
 class MyAdapterStatusListener : public AdapterStatusListener {
-    void adapterSettingsChanged(DBTAdapter const &a, const AdapterSetting oldmask, const AdapterSetting newmask,
+    void adapterSettingsChanged(DBTAdapter &a, const AdapterSetting oldmask, const AdapterSetting newmask,
                                 const AdapterSetting changedmask, const uint64_t timestamp) override {
         fprintf(stderr, "****** Native Adapter SETTINGS_CHANGED: %s -> %s, changed %s\n",
                 getAdapterSettingsString(oldmask).c_str(),
@@ -62,7 +62,7 @@ class MyAdapterStatusListener : public AdapterStatusListener {
         (void)timestamp;
     }
 
-    void discoveringChanged(DBTAdapter const &a, const bool enabled, const bool keepAlive, const uint64_t timestamp) override {
+    void discoveringChanged(DBTAdapter &a, const bool enabled, const bool keepAlive, const uint64_t timestamp) override {
         fprintf(stderr, "****** DISCOVERING: enabled %d, keepAlive %d: %s\n", enabled, keepAlive, a.toString().c_str());
         (void)timestamp;
     }
@@ -204,7 +204,7 @@ int main(int argc, char *argv[])
     const int64_t t0 = getCurrentMilliseconds();
 
     while( ok && ( forever || !foundDevice ) ) {
-        ok = adapter.startDiscovery(true /* keepAlive */);
+        ok = HCIStatusCode::SUCCESS == adapter.startDiscovery(true /* keepAlive */);
         if( !ok) {
             perror("Adapter start discovery failed");
             goto out;
diff --git a/examples/direct_bt_scanner01/dbt_scanner01.cpp b/examples/direct_bt_scanner01/dbt_scanner01.cpp
index db7fd78c..a63deb25 100644
--- a/examples/direct_bt_scanner01/dbt_scanner01.cpp
+++ b/examples/direct_bt_scanner01/dbt_scanner01.cpp
@@ -48,7 +48,7 @@ std::mutex mtxDeviceFound;
 std::condition_variable cvDeviceFound;
 
 class MyAdapterStatusListener : public AdapterStatusListener {
-    void adapterSettingsChanged(DBTAdapter const &a, const AdapterSetting oldmask, const AdapterSetting newmask,
+    void adapterSettingsChanged(DBTAdapter &a, const AdapterSetting oldmask, const AdapterSetting newmask,
                                 const AdapterSetting changedmask, const uint64_t timestamp) override {
         fprintf(stderr, "****** Native Adapter SETTINGS_CHANGED: %s -> %s, changed %s\n",
                 getAdapterSettingsString(oldmask).c_str(),
@@ -59,7 +59,7 @@ class MyAdapterStatusListener : public AdapterStatusListener {
         (void)timestamp;
     }
 
-    void discoveringChanged(DBTAdapter const &a, const bool enabled, const bool keepAlive, const uint64_t timestamp) override {
+    void discoveringChanged(DBTAdapter &a, const bool enabled, const bool keepAlive, const uint64_t timestamp) override {
         fprintf(stderr, "****** DISCOVERING: enabled %d, keepAlive %d: %s\n", enabled, keepAlive, a.toString().c_str());
         (void)timestamp;
     }
@@ -200,7 +200,7 @@ int main(int argc, char *argv[])
     const int64_t t0 = getCurrentMilliseconds();
 
     while( ok && ( forever || !foundDevice ) ) {
-        ok = adapter.startDiscovery(true /* keepAlive */);
+        ok = HCIStatusCode::SUCCESS == adapter.startDiscovery(true /* keepAlive */);
         if( !ok) {
             perror("Adapter start discovery failed");
             goto out;
diff --git a/examples/direct_bt_scanner10/dbt_scanner10.cpp b/examples/direct_bt_scanner10/dbt_scanner10.cpp
index f8bbbc51..a7e0b505 100644
--- a/examples/direct_bt_scanner10/dbt_scanner10.cpp
+++ b/examples/direct_bt_scanner10/dbt_scanner10.cpp
@@ -77,7 +77,7 @@ static void connectDiscoveredDevice(std::shared_ptr<DBTDevice> device);
 static void processConnectedDevice(std::shared_ptr<DBTDevice> device);
 
 static void removeDevice(std::shared_ptr<DBTDevice> device);
-static void resetAdapter(DBTAdapter *a);
+static void resetAdapter(DBTAdapter *a, int mode);
 
 static std::vector<EUI48> devicesInProcessing;
 static std::recursive_mutex mtx_devicesProcessing;
@@ -147,7 +147,7 @@ static size_t getDeviceProcessingCount() {
 
 class MyAdapterStatusListener : public AdapterStatusListener {
 
-    void adapterSettingsChanged(DBTAdapter const &a, const AdapterSetting oldmask, const AdapterSetting newmask,
+    void adapterSettingsChanged(DBTAdapter &a, const AdapterSetting oldmask, const AdapterSetting newmask,
                                 const AdapterSetting changedmask, const uint64_t timestamp) override {
         const bool initialSetting = AdapterSetting::NONE == oldmask;
         if( initialSetting ) {
@@ -162,7 +162,7 @@ class MyAdapterStatusListener : public AdapterStatusListener {
         (void)timestamp;
     }
 
-    void discoveringChanged(DBTAdapter const &a, const bool enabled, const bool keepAlive, const uint64_t timestamp) override {
+    void discoveringChanged(DBTAdapter &a, const bool enabled, const bool keepAlive, const uint64_t timestamp) override {
         fprintf(stderr, "****** DISCOVERING: enabled %d, keepAlive %d: %s\n", enabled, keepAlive, a.toString().c_str());
         (void)timestamp;
     }
@@ -303,7 +303,8 @@ static void connectDiscoveredDevice(std::shared_ptr<DBTDevice> device) {
     }
     fprintf(stderr, "****** Connecting Device: End result %s of %s\n", getHCIStatusCodeString(res).c_str(), device->toString().c_str());
     if( !USE_WHITELIST && 0 == getDeviceProcessingCount() && HCIStatusCode::SUCCESS != res ) {
-        device->getAdapter().startDiscovery( true );
+        const HCIStatusCode r = device->getAdapter().startDiscovery( true );
+        fprintf(stderr, "****** Connecting Device: startDiscovery result %s\n", getHCIStatusCodeString(r).c_str());
     }
 }
 
@@ -429,7 +430,8 @@ static void processConnectedDevice(std::shared_ptr<DBTDevice> device) {
 
 exit:
     if( !USE_WHITELIST && 0 == getDeviceProcessingCount() ) {
-        device->getAdapter().startDiscovery( true );
+        const HCIStatusCode r = device->getAdapter().startDiscovery( true );
+        fprintf(stderr, "****** Processing Device: startDiscovery.0 result %s\n", getHCIStatusCodeString(r).c_str());
     }
 
     if( KEEP_CONNECTED && GATT_PING_ENABLED && success ) {
@@ -457,7 +459,8 @@ exit:
 
         device->remove();
         if( !USE_WHITELIST && 0 == getDeviceProcessingCount() ) {
-            device->getAdapter().startDiscovery( true );
+            const HCIStatusCode r = device->getAdapter().startDiscovery( true );
+            fprintf(stderr, "****** Processing Device: startDiscovery.1 result %s\n", getHCIStatusCodeString(r).c_str());
         }
     }
 
@@ -476,14 +479,15 @@ static void removeDevice(std::shared_ptr<DBTDevice> device) {
     device->remove();
 
     if( !USE_WHITELIST && 0 == getDeviceProcessingCount() ) {
-        device->getAdapter().startDiscovery( true );
+        const HCIStatusCode r = device->getAdapter().startDiscovery( true );
+        fprintf(stderr, "****** Remove Device: startDiscovery result %s\n", getHCIStatusCodeString(r).c_str());
     }
 }
 
-static void resetAdapter(DBTAdapter *a) {
-    fprintf(stderr, "****** Reset Adapter: reset start: %s\n", a->toString().c_str());
+static void resetAdapter(DBTAdapter *a, int mode) {
+    fprintf(stderr, "****** Reset Adapter: reset[%d] start: %s\n", mode, a->toString().c_str());
     HCIStatusCode res = a->reset();
-    fprintf(stderr, "****** Reset Adapter: reset end: %s, %s\n", getHCIStatusCodeString(res).c_str(), a->toString().c_str());
+    fprintf(stderr, "****** Reset Adapter: reset[%d] end: %s, %s\n", mode, getHCIStatusCodeString(res).c_str(), a->toString().c_str());
 }
 
 void test(int dev_id) {
@@ -516,8 +520,9 @@ void test(int dev_id) {
             fprintf(stderr, "Added to WHITELIST: res %d, address %s\n", res, it->toString().c_str());
         }
     } else {
-        if( !adapter.startDiscovery( true ) ) {
-            perror("Adapter start discovery failed");
+        HCIStatusCode status = adapter.startDiscovery( true );
+        if( HCIStatusCode::SUCCESS != status ) {
+            fprintf(stderr, "Adapter: Start discovery failed: %s", getHCIStatusCodeString(status).c_str());
             done = true;
         }
     }
diff --git a/examples/java/DBTScanner10.java b/examples/java/DBTScanner10.java
index a7027008..75a35f75 100644
--- a/examples/java/DBTScanner10.java
+++ b/examples/java/DBTScanner10.java
@@ -122,8 +122,9 @@ public class DBTScanner10 {
                 newmask.isSet(AdapterSettings.SettingType.POWERED) )
             {
                 // powered on adapter ....
-                if( !adapter.startDiscovery( true ) ) {
-                    println("Adapter (powered-on): Start discovery failed");
+                final HCIStatusCode res = adapter.startDiscovery( true );
+                if( res != HCIStatusCode.SUCCESS ) {
+                    println("Adapter (powered-on): Start discovery failed: "+res);
                 }
             }
         }
@@ -186,7 +187,8 @@ public class DBTScanner10 {
                 )
               )
             {
-                println("****** CONNECTED-0: Processing "+device.toString());
+                connectionCount.incrementAndGet();
+                println("****** CONNECTED-0: Processing["+connectionCount.get()+"] "+device.toString());
                 {
                     final long td = BluetoothUtils.getCurrentMilliseconds() - timestamp_t0; // adapter-init -> now
                     println("PERF: adapter-init -> CONNECTED-0 " + td + " ms");
@@ -221,11 +223,11 @@ public class DBTScanner10 {
             } else {
                 devicesInProcessing.remove(device.getAddress());
             }
-            if( 0 == connectionCount.addAndGet(1) % RESET_ADAPTER_EACH_CONN ) {
+            if( 0 < RESET_ADAPTER_EACH_CONN && 0 == connectionCount.get() % RESET_ADAPTER_EACH_CONN ) {
                 final Thread adapterResetTask = new Thread( new Runnable() {
                     @Override
                     public void run() {
-                        resetAdapter(device.getAdapter());
+                        resetAdapter(device.getAdapter(), 1);
                     }
                 }, "DBT-Reset-"+device.getAdapter().getAddress());
                 adapterResetTask.setDaemon(true); // detach thread
@@ -237,7 +239,7 @@ public class DBTScanner10 {
     private void connectDiscoveredDevice(final BluetoothDevice device) {
         println("****** Connecting Device: Start " + device.toString());
         {
-            final boolean r = device.getAdapter().stopDiscovery();
+            final HCIStatusCode r = device.getAdapter().stopDiscovery();
             println("****** Connecting Device: stopDiscovery result "+r);
         }
         HCIStatusCode res;
@@ -248,7 +250,7 @@ public class DBTScanner10 {
         }
         println("****** Connecting Device Command, res "+res+": End result "+res+" of " + device.toString());
         if( !USE_WHITELIST && 0 == devicesInProcessing.size() && HCIStatusCode.SUCCESS != res ) {
-            final boolean r = device.getAdapter().startDiscovery( true );
+            final HCIStatusCode r = device.getAdapter().startDiscovery( true );
             println("****** Connecting Device: startDiscovery result "+r);
         }
     }
@@ -290,7 +292,7 @@ public class DBTScanner10 {
         println("****** Processing Device: Start " + device.toString());
         {
             // make sure for pending connections on failed connect*(..) command
-            final boolean r = device.getAdapter().stopDiscovery();
+            final HCIStatusCode r = device.getAdapter().stopDiscovery();
             println("****** Processing Device: stopDiscovery result "+r);
         }
 
@@ -454,8 +456,8 @@ public class DBTScanner10 {
         }
 
         if( !USE_WHITELIST && 0 == devicesInProcessing.size() ) {
-            final boolean r = device.getAdapter().startDiscovery( true );
-            println("****** Processing Device: startDiscovery result "+r);
+            final HCIStatusCode r = device.getAdapter().startDiscovery( true );
+            println("****** Processing Device: startDiscovery.0 result "+r);
         }
 
         if( KEEP_CONNECTED && GATT_PING_ENABLED && success ) {
@@ -483,11 +485,15 @@ public class DBTScanner10 {
             device.remove();
 
             if( !USE_WHITELIST && 0 == devicesInProcessing.size() ) {
-                final boolean r = device.getAdapter().startDiscovery( true );
-                println("****** Processing Device: startDiscovery result "+r);
+                final HCIStatusCode r = device.getAdapter().startDiscovery( true );
+                println("****** Processing Device: startDiscovery.1 result "+r);
             }
         }
 
+        if( 0 < RESET_ADAPTER_EACH_CONN && 0 == connectionCount.get() % RESET_ADAPTER_EACH_CONN ) {
+            resetAdapter(device.getAdapter(), 2);
+        }
+
         if( 0 < MULTI_MEASUREMENTS.get() ) {
             MULTI_MEASUREMENTS.decrementAndGet();
             println("****** Processing Device: MULTI_MEASUREMENTS left "+MULTI_MEASUREMENTS.get()+": "+device.getAddress());
@@ -503,15 +509,15 @@ public class DBTScanner10 {
         device.remove();
 
         if( !USE_WHITELIST && 0 == devicesInProcessing.size() ) {
-            final boolean r = device.getAdapter().startDiscovery( true );
+            final HCIStatusCode r = device.getAdapter().startDiscovery( true );
             println("****** Remove Device: startDiscovery result "+r);
         }
     }
 
-    private void resetAdapter(final BluetoothAdapter adapter) {
-        println("****** Reset Adapter: reset start: "+adapter.toString());
+    private void resetAdapter(final BluetoothAdapter adapter, final int mode) {
+        println("****** Reset Adapter: reset["+mode+"] start: "+adapter.toString());
         final HCIStatusCode res = adapter.reset();
-        println("****** Reset Adapter: reset end: "+res+", "+adapter.toString());
+        println("****** Reset Adapter: reset["+mode+"] end: "+res+", "+adapter.toString());
     }
 
     public void runTest(final BluetoothManager manager) {
@@ -556,8 +562,9 @@ public class DBTScanner10 {
                 println("Added to whitelist: res "+res+", address "+addr);
             }
         } else {
-            if( !adapter.startDiscovery( true ) ) {
-                println("Adapter start discovery failed");
+            final HCIStatusCode status = adapter.startDiscovery( true );
+            if( HCIStatusCode.SUCCESS != status ) {
+                println("Adapter start discovery failed: "+status);
                 done = true;
             }
         }
diff --git a/examples/java/ScannerTinyB00.java b/examples/java/ScannerTinyB00.java
index 9b49fda5..fe7f2475 100644
--- a/examples/java/ScannerTinyB00.java
+++ b/examples/java/ScannerTinyB00.java
@@ -137,9 +137,9 @@ public class ScannerTinyB00 {
             if( useAdapter ) {
                 adapter.removeDevices();
             }
-            final boolean discoveryStarted = useAdapter ? adapter.startDiscovery(true) : manager.startDiscovery();
+            final HCIStatusCode discoveryStatus = useAdapter ? adapter.startDiscovery(true) : manager.startDiscovery(true);
 
-            System.err.println("The discovery started: " + (discoveryStarted ? "true" : "false") + " for mac "+mac+", mode "+mode+", useAdapter "+useAdapter);
+            System.err.println("The discovery started: " + discoveryStatus + " for mac "+mac+", mode "+mode+", useAdapter "+useAdapter);
             BluetoothDevice sensor = null;
 
             if( 0 == mode ) {
diff --git a/examples/java/ScannerTinyB01.java b/examples/java/ScannerTinyB01.java
index d62aee88..d2a03ffb 100644
--- a/examples/java/ScannerTinyB01.java
+++ b/examples/java/ScannerTinyB01.java
@@ -225,10 +225,10 @@ public class ScannerTinyB01 {
 
                 final long t0 = BluetoothUtils.getCurrentMilliseconds();
 
-                final boolean discoveryStarted = adapter.startDiscovery(true);
+                final HCIStatusCode discoveryStatus = adapter.startDiscovery(true);
 
-                System.err.println("The discovery started: " + (discoveryStarted ? "true" : "false") + " for mac "+waitForDevice+", mode "+mode);
-                if( !discoveryStarted ) {
+                System.err.println("The discovery started: " + discoveryStatus + " for mac "+waitForDevice+", mode "+mode);
+                if( HCIStatusCode.SUCCESS != discoveryStatus ) {
                     break;
                 }
                 BluetoothDevice sensor = null;
diff --git a/java/direct_bt/tinyb/DBTAdapter.java b/java/direct_bt/tinyb/DBTAdapter.java
index c53b712b..3e3e3973 100644
--- a/java/direct_bt/tinyb/DBTAdapter.java
+++ b/java/direct_bt/tinyb/DBTAdapter.java
@@ -199,13 +199,13 @@ public class DBTAdapter extends DBTObject implements BluetoothAdapter
     public long getDiscoverableTimeout() { throw new UnsupportedOperationException(); } // FIXME
 
     @Override
-    public void setDiscoverableTimout(final long value) { throw new UnsupportedOperationException(); } // FIXME
+    public boolean setDiscoverableTimout(final long value) { return false; } // FIXME
 
     @Override
     public long getPairableTimeout() { throw new UnsupportedOperationException(); } // FIXME
 
     @Override
-    public void setPairableTimeout(final long value) { throw new UnsupportedOperationException(); } // FIXME
+    public boolean setPairableTimeout(final long value) { return false; } // FIXME
 
     @Override
     public String getModalias() { throw new UnsupportedOperationException(); } // FIXME
@@ -301,7 +301,7 @@ public class DBTAdapter extends DBTObject implements BluetoothAdapter
     private native String toStringImpl();
 
     @Override
-    public native void setPowered(boolean value);
+    public native boolean setPowered(boolean value);
 
     @Override
     public final HCIStatusCode reset() {
@@ -316,13 +316,13 @@ public class DBTAdapter extends DBTObject implements BluetoothAdapter
     public native void setAlias(final String value);
 
     @Override
-    public native void setDiscoverable(boolean value);
+    public native boolean setDiscoverable(boolean value);
 
     @Override
     public native BluetoothDevice connectDevice(String address, String addressType);
 
     @Override
-    public native void setPairable(boolean value);
+    public native boolean setPairable(boolean value);
 
     @Override
     public native boolean isEnabled();
@@ -336,28 +336,28 @@ public class DBTAdapter extends DBTObject implements BluetoothAdapter
 
     @Override
     public boolean startDiscovery() throws BluetoothException {
-        return startDiscovery(true);
+        return HCIStatusCode.SUCCESS == startDiscovery(true);
     }
 
     @Override
-    public boolean startDiscovery(final boolean keepAlive) throws BluetoothException {
+    public HCIStatusCode startDiscovery(final boolean keepAlive) throws BluetoothException {
         synchronized( discoveryLock ) {
             // Ignoring 'isDiscovering', as native implementation also handles change of 'keepAlive'.
             // The discoveredDevices shall always get cleared.
             removeDevices();
-            return startDiscoveryImpl(keepAlive); // event callbacks will be generated by implementation
+            return HCIStatusCode.get( startDiscoveryImpl(keepAlive) ); // event callbacks will be generated by implementation
         }
     }
-    private native boolean startDiscoveryImpl(boolean keepAlive) throws BluetoothException;
+    private native byte startDiscoveryImpl(boolean keepAlive) throws BluetoothException;
 
     @Override
-    public boolean stopDiscovery() throws BluetoothException {
+    public HCIStatusCode stopDiscovery() throws BluetoothException {
         synchronized( discoveryLock ) {
             // Ignoring 'isDiscovering', be consistent with startDiscovery
-            return stopDiscoveryImpl();  // event callbacks will be generated by implementation
+            return HCIStatusCode.get( stopDiscoveryImpl() );  // event callbacks will be generated by implementation
         }
     }
-    private native boolean stopDiscoveryImpl() throws BluetoothException;
+    private native byte stopDiscoveryImpl() throws BluetoothException;
 
     @Override
     public List<BluetoothDevice> getDevices() {
diff --git a/java/direct_bt/tinyb/DBTManager.java b/java/direct_bt/tinyb/DBTManager.java
index c903b7ba..82b25166 100644
--- a/java/direct_bt/tinyb/DBTManager.java
+++ b/java/direct_bt/tinyb/DBTManager.java
@@ -41,6 +41,7 @@ import org.tinyb.BluetoothGattService;
 import org.tinyb.BluetoothObject;
 import org.tinyb.BluetoothManager;
 import org.tinyb.BluetoothType;
+import org.tinyb.HCIStatusCode;
 
 public class DBTManager implements BluetoothManager
 {
@@ -259,13 +260,13 @@ public class DBTManager implements BluetoothManager
     public BluetoothAdapter getDefaultAdapter() { return adapters.get(defaultAdapterIndex); }
 
     @Override
-    public boolean startDiscovery() throws BluetoothException { return startDiscovery(true); }
+    public boolean startDiscovery() throws BluetoothException { return HCIStatusCode.SUCCESS == startDiscovery(true); }
 
     @Override
-    public boolean startDiscovery(final boolean keepAlive) throws BluetoothException { return getDefaultAdapter().startDiscovery(keepAlive); }
+    public HCIStatusCode startDiscovery(final boolean keepAlive) throws BluetoothException { return getDefaultAdapter().startDiscovery(keepAlive); }
 
     @Override
-    public boolean stopDiscovery() throws BluetoothException { return getDefaultAdapter().stopDiscovery(); }
+    public HCIStatusCode stopDiscovery() throws BluetoothException { return getDefaultAdapter().stopDiscovery(); }
 
     @Override
     public boolean getDiscovering() throws BluetoothException { return getDefaultAdapter().getDiscovering(); }
diff --git a/java/jni/direct_bt/DBTAdapter.cxx b/java/jni/direct_bt/DBTAdapter.cxx
index 80ca0ccb..6bdf58fa 100644
--- a/java/jni/direct_bt/DBTAdapter.cxx
+++ b/java/jni/direct_bt/DBTAdapter.cxx
@@ -230,7 +230,7 @@ class JNIAdapterStatusListener : public AdapterStatusListener {
         return device == *deviceMatchRef;
     }
 
-    void adapterSettingsChanged(DBTAdapter const &a, const AdapterSetting oldmask, const AdapterSetting newmask,
+    void adapterSettingsChanged(DBTAdapter &a, const AdapterSetting oldmask, const AdapterSetting newmask,
                                 const AdapterSetting changedmask, const uint64_t timestamp) override {
         JNIEnv *env = *jni_env;
         (void)a;
@@ -254,7 +254,7 @@ class JNIAdapterStatusListener : public AdapterStatusListener {
         env->DeleteLocalRef(adapterSettingChanged);
     }
 
-    void discoveringChanged(DBTAdapter const &a, const bool enabled, const bool keepAlive, const uint64_t timestamp) override {
+    void discoveringChanged(DBTAdapter &a, const bool enabled, const bool keepAlive, const uint64_t timestamp) override {
         JNIEnv *env = *jni_env;
         (void)a;
         env->CallVoidMethod(listenerObjRef.getObject(), mDiscoveringChanged, JavaGlobalObj::GetObject(adapterObjRef),
@@ -545,26 +545,26 @@ jboolean Java_direct_1bt_tinyb_DBTAdapter_isEnabled(JNIEnv *env, jobject obj)
     return JNI_FALSE;
 }
 
-jboolean Java_direct_1bt_tinyb_DBTAdapter_startDiscoveryImpl(JNIEnv *env, jobject obj, jboolean keepAlive)
+jbyte Java_direct_1bt_tinyb_DBTAdapter_startDiscoveryImpl(JNIEnv *env, jobject obj, jboolean keepAlive)
 {
     try {
         DBTAdapter *adapter = getDBTObject<DBTAdapter>(env, obj);
-        return adapter->startDiscovery(keepAlive);
+        return (jbyte) number( adapter->startDiscovery(keepAlive) );
     } catch(...) {
         rethrow_and_raise_java_exception(env);
     }
-    return JNI_FALSE;
+    return (jbyte) number(HCIStatusCode::INTERNAL_FAILURE);
 }
 
-jboolean Java_direct_1bt_tinyb_DBTAdapter_stopDiscoveryImpl(JNIEnv *env, jobject obj)
+jbyte Java_direct_1bt_tinyb_DBTAdapter_stopDiscoveryImpl(JNIEnv *env, jobject obj)
 {
     try {
         DBTAdapter *adapter = getDBTObject<DBTAdapter>(env, obj);
-        return adapter->stopDiscovery();
+        return (jbyte) number( adapter->stopDiscovery() );
     } catch(...) {
         rethrow_and_raise_java_exception(env);
     }
-    return JNI_FALSE;
+    return (jbyte) number(HCIStatusCode::INTERNAL_FAILURE);
 }
 
 jobject Java_direct_1bt_tinyb_DBTAdapter_getDiscoveredDevicesImpl(JNIEnv *env, jobject obj)
@@ -594,14 +594,15 @@ jint Java_direct_1bt_tinyb_DBTAdapter_removeDevicesImpl(JNIEnv *env, jobject obj
 // misc
 //
 
-void Java_direct_1bt_tinyb_DBTAdapter_setPowered(JNIEnv *env, jobject obj, jboolean value) {
+jboolean Java_direct_1bt_tinyb_DBTAdapter_setPowered(JNIEnv *env, jobject obj, jboolean value) {
     try {
         DBTAdapter *adapter = getDBTObject<DBTAdapter>(env, obj);
         JavaGlobalObj::check(adapter->getJavaObject(), E_FILE_LINE);
-        adapter->setPowered(JNI_TRUE == value ? true : false);
+        return adapter->setPowered(JNI_TRUE == value ? true : false) ? JNI_TRUE : JNI_FALSE;
     } catch(...) {
         rethrow_and_raise_java_exception(env);
     }
+    return JNI_FALSE;
 }
 
 jbyte Java_direct_1bt_tinyb_DBTAdapter_resetImpl(JNIEnv *env, jobject obj) {
@@ -638,14 +639,15 @@ void Java_direct_1bt_tinyb_DBTAdapter_setAlias(JNIEnv *env, jobject obj, jstring
     }
 }
 
-void Java_direct_1bt_tinyb_DBTAdapter_setDiscoverable(JNIEnv *env, jobject obj, jboolean value) {
+jboolean Java_direct_1bt_tinyb_DBTAdapter_setDiscoverable(JNIEnv *env, jobject obj, jboolean value) {
     try {
         DBTAdapter *adapter = getDBTObject<DBTAdapter>(env, obj);
         JavaGlobalObj::check(adapter->getJavaObject(), E_FILE_LINE);
-        adapter->setDiscoverable(JNI_TRUE == value ? true : false);
+        return adapter->setDiscoverable(JNI_TRUE == value ? true : false) ? JNI_TRUE : JNI_FALSE;
     } catch(...) {
         rethrow_and_raise_java_exception(env);
     }
+    return JNI_FALSE;
 }
 
 jobject Java_direct_1bt_tinyb_DBTAdapter_connectDevice(JNIEnv *env, jobject obj, jstring jaddress, jstring jaddressType) {
@@ -673,14 +675,15 @@ jobject Java_direct_1bt_tinyb_DBTAdapter_connectDevice(JNIEnv *env, jobject obj,
     return nullptr;
 }
 
-void Java_direct_1bt_tinyb_DBTAdapter_setPairable(JNIEnv *env, jobject obj, jboolean value) {
+jboolean Java_direct_1bt_tinyb_DBTAdapter_setPairable(JNIEnv *env, jobject obj, jboolean value) {
     try {
         DBTAdapter *adapter = getDBTObject<DBTAdapter>(env, obj);
         JavaGlobalObj::check(adapter->getJavaObject(), E_FILE_LINE);
-        adapter->setBondable(JNI_TRUE == value ? true : false);
+        return adapter->setBondable(JNI_TRUE == value ? true : false) ? JNI_TRUE : JNI_FALSE;
     } catch(...) {
         rethrow_and_raise_java_exception(env);
     }
+    return JNI_FALSE;
 }
 
 void Java_direct_1bt_tinyb_DBTAdapter_setDiscoveryFilter(JNIEnv *env, jobject obj, jobject juuids, jint rssi, jint pathloss, jint transportType) {
diff --git a/java/jni/tinyb/DBusAdapter.cxx b/java/jni/tinyb/DBusAdapter.cxx
index 6e0eda56..fdc40101 100644
--- a/java/jni/tinyb/DBusAdapter.cxx
+++ b/java/jni/tinyb/DBusAdapter.cxx
@@ -67,7 +67,7 @@ jboolean Java_tinyb_dbus_DBusAdapter_startDiscovery(JNIEnv *env, jobject obj)
     return JNI_FALSE;
 }
 
-jboolean Java_tinyb_dbus_DBusAdapter_stopDiscovery(JNIEnv *env, jobject obj)
+jboolean Java_tinyb_dbus_DBusAdapter_stopDiscoveryImpl(JNIEnv *env, jobject obj)
 {
     try {
         BluetoothAdapter *obj_adapter = getInstance<BluetoothAdapter>(env, obj);
@@ -192,16 +192,18 @@ jboolean Java_tinyb_dbus_DBusAdapter_getPowered(JNIEnv *env, jobject obj)
     return JNI_FALSE;
 }
 
-void Java_tinyb_dbus_DBusAdapter_setPowered(JNIEnv *env, jobject obj, jboolean val)
+jboolean Java_tinyb_dbus_DBusAdapter_setPowered(JNIEnv *env, jobject obj, jboolean val)
 {
     try {
         BluetoothAdapter *obj_adapter = getInstance<BluetoothAdapter>(env, obj);
 
         bool val_to_write = from_jboolean_to_bool(val);
         obj_adapter->set_powered(val_to_write);
+        return JNI_TRUE;
     } catch(...) {
         rethrow_and_raise_java_exception(env);
     }
+    return JNI_FALSE;
 }
 
 void Java_tinyb_dbus_DBusAdapter_enablePoweredNotifications(JNIEnv *env, jobject obj, jobject callback)
@@ -254,16 +256,18 @@ jboolean Java_tinyb_dbus_DBusAdapter_getDiscoverable(JNIEnv *env, jobject obj)
     return JNI_FALSE;
 }
 
-void Java_tinyb_dbus_DBusAdapter_setDiscoverable(JNIEnv *env, jobject obj, jboolean val)
+jboolean Java_tinyb_dbus_DBusAdapter_setDiscoverable(JNIEnv *env, jobject obj, jboolean val)
 {
     try {
         BluetoothAdapter *obj_adapter = getInstance<BluetoothAdapter>(env, obj);
 
         bool val_to_write = from_jboolean_to_bool(val);
         obj_adapter->set_discoverable(val_to_write);
+        return JNI_TRUE;
     } catch(...) {
         rethrow_and_raise_java_exception(env);
     }
+    return JNI_FALSE;
 }
 
 void Java_tinyb_dbus_DBusAdapter_enableDiscoverableNotifications(JNIEnv *env, jobject obj, jobject callback)
@@ -316,7 +320,7 @@ jlong Java_tinyb_dbus_DBusAdapter_getDiscoverableTimeout(JNIEnv *env, jobject ob
     return 0;
 }
 
-void Java_tinyb_dbus_DBusAdapter_setDiscoverableTimout(JNIEnv *env, jobject obj, jlong timeout)
+jboolean Java_tinyb_dbus_DBusAdapter_setDiscoverableTimout(JNIEnv *env, jobject obj, jlong timeout)
 {
     try {
         BluetoothAdapter *obj_adapter = getInstance<BluetoothAdapter>(env, obj);
@@ -326,9 +330,11 @@ void Java_tinyb_dbus_DBusAdapter_setDiscoverableTimout(JNIEnv *env, jobject obj,
             throw std::invalid_argument("timeout argument is negative\n");
         }
         obj_adapter->set_discoverable_timeout((unsigned int)timeout);
+        return JNI_TRUE;
     } catch(...) {
         rethrow_and_raise_java_exception(env);
     }
+    return JNI_FALSE;
 }
 
 jboolean Java_tinyb_dbus_DBusAdapter_getPairable(JNIEnv *env, jobject obj)
@@ -381,16 +387,18 @@ void Java_tinyb_dbus_DBusAdapter_disablePairableNotifications(JNIEnv *env, jobje
     }
 }
 
-void Java_tinyb_dbus_DBusAdapter_setPairable(JNIEnv *env, jobject obj, jboolean val)
+jboolean Java_tinyb_dbus_DBusAdapter_setPairable(JNIEnv *env, jobject obj, jboolean val)
 {
     try {
         BluetoothAdapter *obj_adapter = getInstance<BluetoothAdapter>(env, obj);
 
         bool val_to_write = from_jboolean_to_bool(val);
         obj_adapter->set_pairable(val_to_write);
+        return JNI_TRUE;
     } catch(...) {
         rethrow_and_raise_java_exception(env);
     }
+    return JNI_FALSE;
 }
 
 jlong Java_tinyb_dbus_DBusAdapter_getPairableTimeout(JNIEnv *env, jobject obj)
@@ -405,7 +413,7 @@ jlong Java_tinyb_dbus_DBusAdapter_getPairableTimeout(JNIEnv *env, jobject obj)
     return 0;
 }
 
-void Java_tinyb_dbus_DBusAdapter_setPairableTimeout(JNIEnv *env, jobject obj, jlong timeout)
+jboolean Java_tinyb_dbus_DBusAdapter_setPairableTimeout(JNIEnv *env, jobject obj, jlong timeout)
 {
     try {
         BluetoothAdapter *obj_adapter = getInstance<BluetoothAdapter>(env, obj);
@@ -415,9 +423,11 @@ void Java_tinyb_dbus_DBusAdapter_setPairableTimeout(JNIEnv *env, jobject obj, jl
             throw std::invalid_argument("timeout argument is negative\n");
         }
         obj_adapter->set_pairable_timeout((unsigned int)timeout);
+        return JNI_TRUE;
     } catch(...) {
         rethrow_and_raise_java_exception(env);
     }
+    return JNI_FALSE;
 }
 
 jboolean Java_tinyb_dbus_DBusAdapter_getDiscovering(JNIEnv *env, jobject obj)
diff --git a/java/jni/tinyb/DBusManager.cxx b/java/jni/tinyb/DBusManager.cxx
index 28150a13..d8ee789e 100644
--- a/java/jni/tinyb/DBusManager.cxx
+++ b/java/jni/tinyb/DBusManager.cxx
@@ -293,7 +293,7 @@ jboolean Java_tinyb_dbus_DBusManager_startDiscovery(JNIEnv *env, jobject obj)
     return JNI_FALSE;
 }
 
-jboolean Java_tinyb_dbus_DBusManager_stopDiscovery(JNIEnv *env, jobject obj)
+jboolean Java_tinyb_dbus_DBusManager_stopDiscoveryImpl(JNIEnv *env, jobject obj)
 {
     try {
         BluetoothManager *manager = getInstance<BluetoothManager>(env, obj);
diff --git a/java/org/tinyb/BluetoothAdapter.java b/java/org/tinyb/BluetoothAdapter.java
index 5d9637a9..20915083 100644
--- a/java/org/tinyb/BluetoothAdapter.java
+++ b/java/org/tinyb/BluetoothAdapter.java
@@ -167,18 +167,21 @@ public interface BluetoothAdapter extends BluetoothObject
      *        Using {@link #startDiscovery(boolean) startDiscovery}({@code keepAlive=true})
      *        and {@link #stopDiscovery()} is the recommended workflow
      *        for a reliable discovery process.
-     * @return TRUE if discovery was successfully enabled
+     * @return {@link HCIStatusCode#SUCCESS} if successful, otherwise the {@link HCIStatusCode} error state
      * @throws BluetoothException
      * @since 2.0.0
      * @implNote {@code keepAlive} not implemented in tinyb.dbus
      * @see #getDiscovering()
      */
-    public boolean startDiscovery(final boolean keepAlive) throws BluetoothException;
+    public HCIStatusCode startDiscovery(final boolean keepAlive) throws BluetoothException;
 
-    /** Turns off device discovery if it is enabled.
-      * @return TRUE if discovery was successfully disabled
-      */
-    public boolean stopDiscovery() throws BluetoothException;
+    /**
+     * Turns off device discovery if it is enabled.
+     * @return {@link HCIStatusCode#SUCCESS} if successful, otherwise the {@link HCIStatusCode} error state
+     * @apiNote return {@link HCIStatusCode} since 2.0.0
+     * @since 2.0.0
+     */
+    public HCIStatusCode stopDiscovery() throws BluetoothException;
 
     /** Returns a list of BluetoothDevices visible from this adapter.
       * @return A list of BluetoothDevices visible on this adapter,
@@ -249,9 +252,12 @@ public interface BluetoothAdapter extends BluetoothObject
      */
     public void disablePoweredNotifications();
 
-    /** Sets the power state the adapter.
-      */
-    public void setPowered(boolean value);
+    /**
+     * Sets the power state the adapter.
+     * @apiNote return value boolean since 2.0.0
+     * @since 2.0.0
+     */
+    public boolean setPowered(boolean value);
 
     /**
      * Reset the adapter.
@@ -282,19 +288,25 @@ public interface BluetoothAdapter extends BluetoothObject
      */
     public void disableDiscoverableNotifications();
 
-    /** Sets the discoverable state the adapter.
-      */
-    public void setDiscoverable(boolean value);
+    /**
+     * Sets the discoverable state the adapter.
+     * @apiNote return value boolean since 2.0.0
+     * @since 2.0.0
+     */
+    public boolean setDiscoverable(boolean value);
 
     /** Returns the discoverable timeout the adapter.
       * @return The discoverable timeout of the adapter.
       */
     public long getDiscoverableTimeout();
 
-    /** Sets the discoverable timeout the adapter. A value of 0 disables
-      * the timeout.
-      */
-    public void setDiscoverableTimout(long value);
+    /**
+     * Sets the discoverable timeout the adapter. A value of 0 disables
+     * the timeout.
+     * @apiNote return value boolean since 2.0.0
+     * @since 2.0.0
+     */
+    public boolean setDiscoverableTimout(long value);
 
     /**
      * This method connects to device without need of
@@ -342,9 +354,12 @@ public interface BluetoothAdapter extends BluetoothObject
      */
     public void disablePairableNotifications();
 
-    /** Sets the discoverable state the adapter.
-      */
-    public void setPairable(boolean value);
+    /**
+     * Sets the discoverable state the adapter.
+     * @apiNote return value boolean since 2.0.0
+     * @since 2.0.0
+     */
+    public boolean setPairable(boolean value);
 
     /** Returns the timeout in seconds after which pairable state turns off
       * automatically, 0 means never.
@@ -352,9 +367,12 @@ public interface BluetoothAdapter extends BluetoothObject
       */
     public long getPairableTimeout();
 
-    /** Sets the timeout after which pairable state turns off automatically, 0 means never.
-      */
-    public void setPairableTimeout(long value);
+    /**
+     * Sets the timeout after which pairable state turns off automatically, 0 means never.
+     * @apiNote return value boolean since 2.0.0
+     * @since 2.0.0
+     */
+    public boolean setPairableTimeout(long value);
 
     /**
      * Returns the meta discovering state (of the adapter).
diff --git a/java/org/tinyb/BluetoothManager.java b/java/org/tinyb/BluetoothManager.java
index 2ddad81e..5c7eba23 100644
--- a/java/org/tinyb/BluetoothManager.java
+++ b/java/org/tinyb/BluetoothManager.java
@@ -229,18 +229,20 @@ public interface BluetoothManager
      *        Using {@link #startDiscovery(boolean) startDiscovery}({@code keepAlive=true})
      *        and {@link #stopDiscovery()} is the recommended workflow
      *        for a reliable discovery process.
-     * @return TRUE if discovery was successfully enabled
+     * @return {@link HCIStatusCode#SUCCESS} if successful, otherwise the {@link HCIStatusCode} error state
      * @throws BluetoothException
      * @since 2.0.0
      * @implNote {@code keepAlive} not implemented in tinyb.dbus
      */
-    public boolean startDiscovery(final boolean keepAlive) throws BluetoothException;
+    public HCIStatusCode startDiscovery(final boolean keepAlive) throws BluetoothException;
 
-
-    /** Turns off device discovery on the default adapter if it is enabled.
-      * @return TRUE if discovery was successfully disabled
-      */
-    public boolean stopDiscovery() throws BluetoothException;
+    /**
+     * Turns off device discovery on the default adapter if it is enabled.
+     * @return {@link HCIStatusCode#SUCCESS} if successful, otherwise the {@link HCIStatusCode} error state
+     * @apiNote return {@link HCIStatusCode} since 2.0.0
+     * @since 2.0.0
+     */
+    public HCIStatusCode stopDiscovery() throws BluetoothException;
 
     /** Returns if the discovers is running or not.
       * @return TRUE if discovery is running
diff --git a/java/tinyb/dbus/DBusAdapter.java b/java/tinyb/dbus/DBusAdapter.java
index 964ee67a..a92beafa 100644
--- a/java/tinyb/dbus/DBusAdapter.java
+++ b/java/tinyb/dbus/DBusAdapter.java
@@ -105,12 +105,15 @@ public class DBusAdapter extends DBusObject implements BluetoothAdapter
     public native boolean startDiscovery() throws BluetoothException;
 
     @Override
-    public synchronized boolean startDiscovery(final boolean keepAlive) throws BluetoothException {
-        return startDiscovery(); // FIXME keepAlive
+    public synchronized HCIStatusCode startDiscovery(final boolean keepAlive) throws BluetoothException {
+        return startDiscovery() ? HCIStatusCode.SUCCESS : HCIStatusCode.INTERNAL_FAILURE; // FIXME keepAlive
     }
 
     @Override
-    public native boolean stopDiscovery() throws BluetoothException;
+    public HCIStatusCode stopDiscovery() throws BluetoothException {
+        return stopDiscoveryImpl() ? HCIStatusCode.SUCCESS : HCIStatusCode.INTERNAL_FAILURE;
+    }
+    private native boolean stopDiscoveryImpl() throws BluetoothException;
 
     @Override
     public native List<BluetoothDevice> getDevices();
@@ -145,7 +148,7 @@ public class DBusAdapter extends DBusObject implements BluetoothAdapter
     public native void disablePoweredNotifications();
 
     @Override
-    public native void setPowered(boolean value);
+    public native boolean setPowered(boolean value);
 
     @Override
     public final HCIStatusCode reset() { return HCIStatusCode.INTERNAL_FAILURE; }
@@ -160,13 +163,13 @@ public class DBusAdapter extends DBusObject implements BluetoothAdapter
     public native void disableDiscoverableNotifications();
 
     @Override
-    public native void setDiscoverable(boolean value);
+    public native boolean setDiscoverable(boolean value);
 
     @Override
     public native long getDiscoverableTimeout();
 
     @Override
-    public native void setDiscoverableTimout(long value);
+    public native boolean setDiscoverableTimout(long value);
 
     @Override
     public native BluetoothDevice connectDevice(String address, String addressType);
@@ -181,13 +184,13 @@ public class DBusAdapter extends DBusObject implements BluetoothAdapter
     public native void disablePairableNotifications();
 
     @Override
-    public native void setPairable(boolean value);
+    public native boolean setPairable(boolean value);
 
     @Override
     public native long getPairableTimeout();
 
     @Override
-    public native void setPairableTimeout(long value);
+    public native boolean setPairableTimeout(long value);
 
     @Override
     public native boolean getDiscovering();
diff --git a/java/tinyb/dbus/DBusManager.java b/java/tinyb/dbus/DBusManager.java
index 61d0935d..e815aeec 100644
--- a/java/tinyb/dbus/DBusManager.java
+++ b/java/tinyb/dbus/DBusManager.java
@@ -37,6 +37,7 @@ import org.tinyb.BluetoothGattService;
 import org.tinyb.BluetoothObject;
 import org.tinyb.BluetoothManager;
 import org.tinyb.BluetoothType;
+import org.tinyb.HCIStatusCode;
 
 public class DBusManager implements BluetoothManager
 {
@@ -109,12 +110,15 @@ public class DBusManager implements BluetoothManager
     public native boolean startDiscovery() throws BluetoothException;
 
     @Override
-    public boolean startDiscovery(final boolean keepAlive) throws BluetoothException {
-        return startDiscovery(); // FIXME keepAlive
+    public HCIStatusCode startDiscovery(final boolean keepAlive) throws BluetoothException {
+        return startDiscovery() ? HCIStatusCode.SUCCESS : HCIStatusCode.INTERNAL_FAILURE; // FIXME keepAlive
     }
 
     @Override
-    public native boolean stopDiscovery() throws BluetoothException;
+    public HCIStatusCode stopDiscovery() throws BluetoothException {
+        return stopDiscoveryImpl() ? HCIStatusCode.SUCCESS : HCIStatusCode.INTERNAL_FAILURE;
+    }
+    private native boolean stopDiscoveryImpl() throws BluetoothException;
 
     @Override
     public native boolean getDiscovering() throws BluetoothException;
diff --git a/src/direct_bt/DBTAdapter.cpp b/src/direct_bt/DBTAdapter.cpp
index 204b5560..8f3b0179 100644
--- a/src/direct_bt/DBTAdapter.cpp
+++ b/src/direct_bt/DBTAdapter.cpp
@@ -312,16 +312,16 @@ std::shared_ptr<NameAndShortName> DBTAdapter::setLocalName(const std::string &na
     return mgmt.setLocalName(dev_id, name, short_name);
 }
 
-void DBTAdapter::setDiscoverable(bool value) noexcept {
-    mgmt.setMode(dev_id, MgmtOpcode::SET_DISCOVERABLE, value ? 1 : 0);
+bool DBTAdapter::setDiscoverable(bool value) noexcept {
+    return mgmt.setMode(dev_id, MgmtOpcode::SET_DISCOVERABLE, value ? 1 : 0);
 }
 
-void DBTAdapter::setBondable(bool value) noexcept {
-    mgmt.setMode(dev_id, MgmtOpcode::SET_BONDABLE, value ? 1 : 0);
+bool DBTAdapter::setBondable(bool value) noexcept {
+    return mgmt.setMode(dev_id, MgmtOpcode::SET_BONDABLE, value ? 1 : 0);
 }
 
-void DBTAdapter::setPowered(bool value) noexcept {
-    mgmt.setMode(dev_id, MgmtOpcode::SET_POWERED, value ? 1 : 0);
+bool DBTAdapter::setPowered(bool value) noexcept {
+    return mgmt.setMode(dev_id, MgmtOpcode::SET_POWERED, value ? 1 : 0);
 }
 
 HCIStatusCode DBTAdapter::reset() noexcept {
@@ -456,13 +456,13 @@ void DBTAdapter::checkDiscoveryState() noexcept {
 
 #define USE_HCI_DISCOVERY 1
 
-bool DBTAdapter::startDiscovery(const bool keepAlive, const HCILEOwnAddressType own_mac_type,
-                                const uint16_t le_scan_interval, const uint16_t le_scan_window)
+HCIStatusCode DBTAdapter::startDiscovery(const bool keepAlive, const HCILEOwnAddressType own_mac_type,
+                                         const uint16_t le_scan_interval, const uint16_t le_scan_window)
 {
     // FIXME: Respect DBTAdapter::btMode, i.e. BTMode::BREDR, BTMode::LE or BTMode::DUAL to setup BREDR, LE or DUAL scanning!
     if( !isEnabled() ) {
         ERR_PRINT("DBTAdapter::startDiscovery: Adapter not enabled/powered: %s", toString().c_str());
-        return false;
+        return HCIStatusCode::INTERNAL_FAILURE;
     }
     const std::lock_guard<std::recursive_mutex> lock(mtx_discovery); // RAII-style acquire and relinquish via destructor
     if( ScanType::NONE != currentMetaScanType ) {
@@ -478,7 +478,7 @@ bool DBTAdapter::startDiscovery(const bool keepAlive, const HCILEOwnAddressType
             keepDiscoveringAlive = keepAlive;
         }
         checkDiscoveryState();
-        return true;
+        return HCIStatusCode::SUCCESS;
     }
     (void)own_mac_type;
     (void)le_scan_interval;
@@ -494,30 +494,25 @@ bool DBTAdapter::startDiscovery(const bool keepAlive, const HCILEOwnAddressType
     std::shared_ptr<HCIHandler> hci = getHCI();
     if( nullptr == hci ) {
         ERR_PRINT("DBTAdapter::startDiscovery: HCI not available: %s", toString().c_str());
-        return false;
+        return HCIStatusCode::INTERNAL_FAILURE;
     }
 
     HCIStatusCode status = hci->le_set_scan_param();
     if( HCIStatusCode::SUCCESS != status ) {
         ERR_PRINT("DBTAdapter::startDiscovery: le_set_scan_param failed: %s", getHCIStatusCodeString(status).c_str());
-    }
-
-    bool res;
-    // Will issue 'mgmtEvDeviceDiscoveringHCI(..)' immediately, don't change current scan-type state here
-    status = hci->le_enable_scan(true /* enable */);
-    if( HCIStatusCode::SUCCESS != status ) {
-        ERR_PRINT("DBTAdapter::startDiscovery: le_enable_scan failed: %s", getHCIStatusCodeString(status).c_str());
-        res = false;
     } else {
-        res = true;
+        // Will issue 'mgmtEvDeviceDiscoveringHCI(..)' immediately, don't change current scan-type state here
+        status = hci->le_enable_scan(true /* enable */);
+        if( HCIStatusCode::SUCCESS != status ) {
+            ERR_PRINT("DBTAdapter::startDiscovery: le_enable_scan failed: %s", getHCIStatusCodeString(status).c_str());
+        }
     }
-
-    DBG_PRINT("DBTAdapter::startDiscovery: End: Result %d, keepAlive %d -> %d, currentScanType[native %s, meta %s] ...",
-            res, keepDiscoveringAlive.load(), keepAlive,
+    DBG_PRINT("DBTAdapter::startDiscovery: End: Result %s, keepAlive %d -> %d, currentScanType[native %s, meta %s] ...",
+            getHCIStatusCodeString(status).c_str(), keepDiscoveringAlive.load(), keepAlive,
             getScanTypeString(currentNativeScanType).c_str(), getScanTypeString(currentMetaScanType).c_str());
     checkDiscoveryState();
 
-    return res;
+    return status;
 }
 
 void DBTAdapter::startDiscoveryBackground() noexcept {
@@ -542,7 +537,7 @@ void DBTAdapter::startDiscoveryBackground() noexcept {
     }
 }
 
-bool DBTAdapter::stopDiscovery() noexcept {
+HCIStatusCode DBTAdapter::stopDiscovery() noexcept {
     // We allow !isEnabled, to utilize method for adjusting discovery state and notifying listeners
     // FIXME: Respect DBTAdapter::btMode, i.e. BTMode::BREDR, BTMode::LE or BTMode::DUAL to stop BREDR, LE or DUAL scanning!
     const std::lock_guard<std::recursive_mutex> lock(mtx_discovery); // RAII-style acquire and relinquish via destructor
@@ -575,47 +570,44 @@ bool DBTAdapter::stopDiscovery() noexcept {
                 keepDiscoveringAlive.load(),
                 getScanTypeString(currentNativeScanType).c_str(), getScanTypeString(currentMetaScanType).c_str());
         checkDiscoveryState();
-        return true;
+        return HCIStatusCode::SUCCESS;
     }
-    bool res;
 
+    HCIStatusCode status;
     std::shared_ptr<HCIHandler> hci = getHCI();
     if( nullptr == hci ) {
         ERR_PRINT("DBTAdapter::stopDiscovery: HCI not available: %s", toString().c_str());
-        res = false; // send event
+        status = HCIStatusCode::INTERNAL_FAILURE;
         goto exit;
     }
 
     if( discoveryTempDisabled ) {
         // meta state transition [4] -> [5], w/o native disabling
         currentMetaScanType = currentNativeScanType.load();
-        res = true; // send event: discoveryTempDisabled
+        status = HCIStatusCode::SUCCESS; // send event: discoveryTempDisabled
     } else {
         // Actual disabling discovery
         HCIStatusCode status = hci->le_enable_scan(false /* enable */);
         if( HCIStatusCode::SUCCESS != status ) {
-            res = false; // send event
             ERR_PRINT("DBTAdapter::stopDiscovery: le_enable_scan failed: %s", getHCIStatusCodeString(status).c_str());
-        } else {
-            res = true;
         }
     }
 
 exit:
-    if( discoveryTempDisabled || !res ) {
+    if( discoveryTempDisabled || HCIStatusCode::SUCCESS != status ) {
         // In case of discoveryTempDisabled, power-off, le_enable_scane failure
         // or already pulled HCIHandler, send the event directly.
         // SEND_EVENT: Perform off-thread to avoid potential deadlock w/ application callbacks (similar when sent from HCIHandler's reader-thread)
-        std::thread bg(&DBTAdapter::mgmtEvDeviceDiscoveringHCI, this, std::shared_ptr<MgmtEvent>( new MgmtEvtDiscovering(dev_id, ScanType::LE, false) ) );
+        std::thread bg(&DBTAdapter::mgmtEvDeviceDiscoveringHCI, this, std::shared_ptr<MgmtEvent>( new MgmtEvtDiscovering(dev_id, ScanType::LE, false) ) ); // @suppress("Invalid arguments")
         bg.detach();
         // mgmtEvDeviceDiscoveringHCI( std::shared_ptr<MgmtEvent>( new MgmtEvtDiscovering(dev_id, ScanType::LE, false) ) );
     }
-    DBG_PRINT("DBTAdapter::stopDiscovery: End: Result %d, keepAlive %d, currentScanType[native %s, meta %s], discoveryTempDisabled %d ...",
-            res, keepDiscoveringAlive.load(),
+    DBG_PRINT("DBTAdapter::stopDiscovery: End: Result %s, keepAlive %d, currentScanType[native %s, meta %s], discoveryTempDisabled %d ...",
+            getHCIStatusCodeString(status).c_str(), keepDiscoveringAlive.load(),
             getScanTypeString(currentNativeScanType).c_str(), getScanTypeString(currentMetaScanType).c_str(), discoveryTempDisabled);
     checkDiscoveryState();
 
-    return res;
+    return status;
 }
 
 std::shared_ptr<DBTDevice> DBTAdapter::findDiscoveredDevice (EUI48 const & mac, const BDAddressType macType) noexcept {
@@ -754,7 +746,7 @@ bool DBTAdapter::mgmtEvDeviceDiscoveringMgmt(std::shared_ptr<MgmtEvent> e) noexc
         i++;
     });
     if( ScanType::NONE == currentNativeScanType && keepDiscoveringAlive ) {
-        std::thread bg(&DBTAdapter::startDiscoveryBackground, this);
+        std::thread bg(&DBTAdapter::startDiscoveryBackground, this); // @suppress("Invalid arguments")
         bg.detach();
     }
     return true;
@@ -777,7 +769,7 @@ bool DBTAdapter::mgmtEvNewSettingsMgmt(std::shared_ptr<MgmtEvent> e) noexcept {
 
     if( !isPowered() ) {
         // Adapter has been powered off, close connections and cleanup off-thread.
-        std::thread bg(&DBTAdapter::poweredOff, this);
+        std::thread bg(&DBTAdapter::poweredOff, this); // @suppress("Invalid arguments")
         bg.detach();
     }