Add Bluez DBus peripheral role selection support

A preparatory commit for adding Bluez DBus peripheral role support.

Fixes: QTBUG-107508
Change-Id: Ifa2b12df9856011048a9bc311e5da96275700f5e
Reviewed-by: Ivan Solovev <ivan.solovev@qt.io>
Reviewed-by: Alex Blasche <alexander.blasche@qt.io>

3 files changed, 64 insertions, 6 deletions

diff --git a/src/bluetooth/bluez/bluez5_helper.cpp b/src/bluetooth/bluez/bluez5_helper.cpp
index 5f252026..e2e34669 100644
--- a/src/bluetooth/bluez/bluez5_helper.cpp
+++ b/src/bluetooth/bluez/bluez5_helper.cpp
@@ -512,6 +512,41 @@ QString findAdapterForAddress(const QBluetoothAddress &wantedAddress, bool *ok =
 }
 
 /*
+
+  Checks the presence of peripheral interface
+
+*/
+
+bool peripheralInterfaceAvailable(const QBluetoothAddress &localAddress)
+{
+    // First find the object path to the desired adapter
+    bool ok = false;
+    const QString hostAdapterPath = findAdapterForAddress(localAddress, &ok);
+    if (!ok || hostAdapterPath.isEmpty())
+        return false;
+
+    // Then check if that adapter provides peripheral dbus interface
+    OrgFreedesktopDBusObjectManagerInterface manager(QStringLiteral("org.bluez"),
+                                                     QStringLiteral("/"),
+                                                     QDBusConnection::systemBus());
+    QDBusPendingReply<ManagedObjectList> reply = manager.GetManagedObjects();
+    reply.waitForFinished();
+    if (reply.isError())
+        return false;
+
+    using namespace Qt::StringLiterals;
+    // For example /org/bluez/hci0 contains org.bluezLEAdvertisingManager1
+    const bool peripheralSupported = reply.value()
+                   .value(QDBusObjectPath(hostAdapterPath))
+                   .contains("org.bluez.LEAdvertisingManager1"_L1);
+
+    qCDebug(QT_BT_BLUEZ) << "Peripheral role"
+                         << (peripheralSupported ? "" : "not")
+                         << "supported on" << hostAdapterPath;
+    return peripheralSupported;
+}
+
+/*
     Removes every character that cannot be used in QDbusObjectPath
 
     See QDbusUtil::isValidObjectPath(QString) for more details.
diff --git a/src/bluetooth/bluez/bluez5_helper_p.h b/src/bluetooth/bluez/bluez5_helper_p.h
index 1904da90..2d23ba92 100644
--- a/src/bluetooth/bluez/bluez5_helper_p.h
+++ b/src/bluetooth/bluez/bluez5_helper_p.h
@@ -43,6 +43,8 @@ QString sanitizeNameForDBus(const QString& text);
 
 QString findAdapterForAddress(const QBluetoothAddress &wantedAddress, bool *ok);
 
+bool peripheralInterfaceAvailable(const QBluetoothAddress &localAddress);
+
 class QtBluezDiscoveryManagerPrivate;
 class QtBluezDiscoveryManager : public QObject
 {
diff --git a/src/bluetooth/qlowenergycontroller.cpp b/src/bluetooth/qlowenergycontroller.cpp
index 4e7c8e95..92e93f6d 100644
--- a/src/bluetooth/qlowenergycontroller.cpp
+++ b/src/bluetooth/qlowenergycontroller.cpp
@@ -301,30 +301,51 @@ void registerQLowEnergyControllerMetaType()
     }
 }
 
-static QLowEnergyControllerPrivate *privateController(QLowEnergyController::Role role)
+static QLowEnergyControllerPrivate *privateController(
+        QLowEnergyController::Role role,
+        const QBluetoothAddress& localDevice = QBluetoothAddress{})
 {
 #if QT_CONFIG(bluez) && !defined(QT_BLUEZ_NO_BTLE)
-    // The new DBUS implementation only supports Central role for now
-    // For Peripheral role support see QTBUG-66909
+    // Central role
+    // The minimum Bluez DBus version for central role is 5.42, otherwise we
+    // fall back to kernel ATT backend. Application can also force the choice
+    // with an environment variable (see bluetoothdVersion())
+    //
+    // Peripheral role
+    // For the dbus peripheral backend we check the presence of the required DBus APIs, and in
+    // addition the application needs to opt-in to the DBus peripheral role by setting the
+    // environment variable. Otherwise we fall back to the kernel ATT backend
+    //
+    // ### Qt 7 consider removing the non-dbus bluez (kernel ATT) support
     if (role == QLowEnergyController::CentralRole
             && bluetoothdVersion() >= QVersionNumber(5, 42)) {
-        qCWarning(QT_BT) << "Using BlueZ LE DBus API";
+        qCDebug(QT_BT) << "Using BlueZ LE DBus API for central";
+        return new QLowEnergyControllerPrivateBluezDBus();
+    } else if (role == QLowEnergyController::PeripheralRole
+               && qEnvironmentVariableIsSet("BLUETOOTH_USE_DBUS_PERIPHERAL")
+               && peripheralInterfaceAvailable(localDevice)) {
+        qCDebug(QT_BT) << "Using BlueZ LE DBus API for peripheral";
         return new QLowEnergyControllerPrivateBluezDBus();
     } else {
-        qCWarning(QT_BT) << "Using BlueZ kernel ATT interface";
+        qCDebug(QT_BT) << "Using BlueZ kernel ATT interface for"
+                       << (role == QLowEnergyController::CentralRole ? "central" : "peripheral");
         return new QLowEnergyControllerPrivateBluez();
     }
 #elif defined(QT_ANDROID_BLUETOOTH)
     Q_UNUSED(role);
+    Q_UNUSED(localDevice);
     return new QLowEnergyControllerPrivateAndroid();
 #elif defined(QT_WINRT_BLUETOOTH)
     Q_UNUSED(role);
+    Q_UNUSED(localDevice);
     return new QLowEnergyControllerPrivateWinRT();
 #elif defined(Q_OS_DARWIN)
     Q_UNUSED(role);
+    Q_UNUSED(localDevice);
     return new QLowEnergyControllerPrivateDarwin();
 #else
     Q_UNUSED(role);
+    Q_UNUSED(localDevice);
     return new QLowEnergyControllerPrivateCommon();
 #endif
 }
@@ -450,7 +471,7 @@ QLowEnergyController *QLowEnergyController::createPeripheral(const QBluetoothAdd
 QLowEnergyController::QLowEnergyController(const QBluetoothAddress &localDevice, QObject *parent)
     : QObject(parent)
 {
-    d_ptr = privateController(PeripheralRole);
+    d_ptr = privateController(PeripheralRole, localDevice);
 
     Q_D(QLowEnergyController);
     d->q_ptr = this;