Add support for BTLE write command (BlueZ/Linux)

So far, we only supported write requests which reply with write
responses.

Change-Id: Ibdad36dcf18dec23260f003911b9361cc4ab1e3d
Reviewed-by: Lars Knoll <lars.knoll@digia.com>

7 files changed, 100 insertions, 26 deletions

diff --git a/src/bluetooth/qlowenergycharacteristic.cpp b/src/bluetooth/qlowenergycharacteristic.cpp
index 69f68a59..8b7297d0 100644
--- a/src/bluetooth/qlowenergycharacteristic.cpp
+++ b/src/bluetooth/qlowenergycharacteristic.cpp
@@ -182,10 +182,19 @@ QLowEnergyCharacteristic::PropertyTypes QLowEnergyCharacteristic::properties() c
 }
 
 /*!
-    Returns the value of the characteristic.
+    Returns the cached value of the characteristic.
 
     If the characteristic's \l properties() permit writing of new values,
     the value can be updated using \l QLowEnergyService::writeCharacteristic().
+
+    The cache is updated during the associated service's
+    \l {QLowEnergyService::discoverDetails()} {detail discovery}, a successful
+    \l {QLowEnergyService::writeCharacteristic()}{write operation} or when an update
+    notification is received.
+
+    The returned \l QByteArray is empty if the characteristic does not have the
+    \l {QLowEnergyCharacteristic::Read}{read permission}. However, a non-readable
+    characteristic may obtain a non-empty value via a related notification or write operation.
 */
 QByteArray QLowEnergyCharacteristic::value() const
 {
diff --git a/src/bluetooth/qlowenergycontroller_bluez.cpp b/src/bluetooth/qlowenergycontroller_bluez.cpp
index 2540791f..97eb429b 100644
--- a/src/bluetooth/qlowenergycontroller_bluez.cpp
+++ b/src/bluetooth/qlowenergycontroller_bluez.cpp
@@ -64,11 +64,12 @@
 #define ATT_OP_READ_BLOB_RESPONSE       0xD
 #define ATT_OP_READ_BY_GROUP_REQUEST    0x10 //discover services
 #define ATT_OP_READ_BY_GROUP_RESPONSE   0x11
-#define ATT_OP_WRITE_REQUEST            0x12 //write characteristic
+#define ATT_OP_WRITE_REQUEST            0x12 //write characteristic with response
 #define ATT_OP_WRITE_RESPONSE           0x13
 #define ATT_OP_HANDLE_VAL_NOTIFICATION  0x1b //informs about value change
 #define ATT_OP_HANDLE_VAL_INDICATION    0x1d //informs about value change -> requires reply
 #define ATT_OP_HANDLE_VAL_CONFIRMATION  0x1e //answer for ATT_OP_HANDLE_VAL_INDICATION
+#define ATT_OP_WRITE_COMMAND            0x52 //write characteristic without response
 
 //GATT command sizes in bytes
 #define FIND_INFO_REQUEST_SIZE 5
@@ -76,7 +77,7 @@
 #define READ_BY_TYPE_REQ_SIZE 7
 #define READ_REQUEST_SIZE 3
 #define READ_BLOB_REQUEST_SIZE 5
-#define WRITE_REQUEST_SIZE 3
+#define WRITE_REQUEST_SIZE 3    // same size for WRITE_COMMAND
 #define MTU_EXCHANGE_SIZE 3
 
 // GATT error codes
@@ -1122,7 +1123,8 @@ void QLowEnergyControllerPrivate::discoverNextDescriptor(
 void QLowEnergyControllerPrivate::writeCharacteristic(
         const QSharedPointer<QLowEnergyServicePrivate> service,
         const QLowEnergyHandle charHandle,
-        const QByteArray &newValue)
+        const QByteArray &newValue,
+        bool writeWithResponse)
 {
     Q_ASSERT(!service.isNull());
 
@@ -1134,16 +1136,27 @@ void QLowEnergyControllerPrivate::writeCharacteristic(
     const int size = 1 + 2 + newValue.size();
 
     quint8 packet[WRITE_REQUEST_SIZE];
-    packet[0] = ATT_OP_WRITE_REQUEST;
-    bt_put_unaligned(htobs(valueHandle), (quint16 *) &packet[1]);
+    if (writeWithResponse)
+        packet[0] = ATT_OP_WRITE_REQUEST;
+    else
+        packet[0] = ATT_OP_WRITE_COMMAND;
 
+    bt_put_unaligned(htobs(valueHandle), (quint16 *) &packet[1]);
 
     QByteArray data(size, Qt::Uninitialized);
     memcpy(data.data(), packet, WRITE_REQUEST_SIZE);
     memcpy(&(data.data()[WRITE_REQUEST_SIZE]), newValue.constData(), newValue.size());
 
     qCDebug(QT_BT_BLUEZ) << "Writing characteristic" << hex << charHandle
-                         << "(size:" << size << ")";
+                         << "(size:" << size << "response:" << writeWithResponse << ")";
+
+    // Advantage of write without response is the quick turnaround.
+    // It can be send at any time and does not produce responses.
+    // Therefore we will not put them into the openRequest queue at all.
+    if (!writeWithResponse) {
+        sendCommand(data);
+        return;
+    }
 
     Request request;
     request.payload = data;
diff --git a/src/bluetooth/qlowenergycontroller_p.cpp b/src/bluetooth/qlowenergycontroller_p.cpp
index 0135df1c..7de0c604 100644
--- a/src/bluetooth/qlowenergycontroller_p.cpp
+++ b/src/bluetooth/qlowenergycontroller_p.cpp
@@ -66,10 +66,10 @@ void QLowEnergyControllerPrivate::discoverServiceDetails(const QBluetoothUuid &/
 
 }
 
-void QLowEnergyControllerPrivate::writeCharacteristic(
-        const QSharedPointer<QLowEnergyServicePrivate> /*service*/,
+void QLowEnergyControllerPrivate::writeCharacteristic(const QSharedPointer<QLowEnergyServicePrivate> /*service*/,
         const QLowEnergyHandle /*charHandle*/,
-        const QByteArray &/*newValue*/)
+        const QByteArray &/*newValue*/,
+        bool /*writeWithResponse*/)
 {
 
 }
diff --git a/src/bluetooth/qlowenergycontroller_p.h b/src/bluetooth/qlowenergycontroller_p.h
index 150c1690..d9f75625 100644
--- a/src/bluetooth/qlowenergycontroller_p.h
+++ b/src/bluetooth/qlowenergycontroller_p.h
@@ -89,7 +89,7 @@ public:
     // write data
     void writeCharacteristic(const QSharedPointer<QLowEnergyServicePrivate> service,
                              const QLowEnergyHandle charHandle,
-                             const QByteArray &newValue);
+                             const QByteArray &newValue, bool writeWithResponse = true);
     void writeDescriptor(const QSharedPointer<QLowEnergyServicePrivate> service,
                          const QLowEnergyHandle charHandle,
                          const QLowEnergyHandle descriptorHandle,
diff --git a/src/bluetooth/qlowenergydescriptor.cpp b/src/bluetooth/qlowenergydescriptor.cpp
index c7ee87ad..976ee73f 100644
--- a/src/bluetooth/qlowenergydescriptor.cpp
+++ b/src/bluetooth/qlowenergydescriptor.cpp
@@ -229,7 +229,7 @@ QLowEnergyHandle QLowEnergyDescriptor::handle() const
 }
 
 /*!
-    Returns the value of the descriptor.
+    Returns the cached value of the descriptor.
 
     A descriptor value may be updated using
     \l QLowEnergyService::writeDescriptor().
diff --git a/src/bluetooth/qlowenergyservice.cpp b/src/bluetooth/qlowenergyservice.cpp
index a55ed6e9..d60b4e81 100644
--- a/src/bluetooth/qlowenergyservice.cpp
+++ b/src/bluetooth/qlowenergyservice.cpp
@@ -1,6 +1,7 @@
 /****************************************************************************
 **
 ** Copyright (C) 2014 Digia Plc and/or its subsidiary(-ies).
+** Copyright (C) 2013 Javier S. Pedro <maemo@javispedro.com>
 ** Contact: http://www.qt-project.org/legal
 **
 ** This file is part of the QtBluetooth module of the Qt Toolkit.
@@ -166,6 +167,32 @@ QT_BEGIN_NAMESPACE
  */
 
 /*!
+  \enum QLowEnergyService::WriteMode
+
+  This enum describes the mode to be used when writing a characteristic value.
+  The characteristic advertises its supported write modes via its
+  \l {QLowEnergyCharacteristic::properties()}{properties}.
+
+  \value WriteWithResponse      If a characteristic is written using this mode, the peripheral
+                                shall send a write confirmation. If the operation is
+                                successful, the confirmation is emitted via the
+                                \l characteristicChanged() signal. Otherwise the
+                                \l CharacteristicWriteError is emitted.
+                                A characteristic must have set the
+                                \l QLowEnergyCharacteristic::Write property to support this
+                                write mode.
+
+  \value WriteWithoutResponse   If a characteristic is written using this mode, the remote peripheral
+                                shall not send a write confirmation. The operation's success
+                                cannot be determined and the payload must not be longer than 20 bytes.
+                                A characteristic must have set the
+                                \l QLowEnergyCharacteristic::WriteNoResponse property to support this
+                                write mode. Its adavantage is a quicker
+                                write operation as it may happen in between other
+                                device interactions.
+ */
+
+/*!
     \fn void QLowEnergyService::stateChanged(QLowEnergyService::ServiceState newState)
 
     This signal is emitted when the service's state changes. The \a newState can also be
@@ -189,6 +216,10 @@ QT_BEGIN_NAMESPACE
     by calling \l writeCharacteristic() or otherwise triggering a change
     notification on the peripheral device.
 
+    \note Change notifications must first be activated via the characteristic's
+    \l {QBluetoothUuid::ClientCharacteristicConfiguration}{ClientCharacteristicConfiguration}
+    descriptor.
+
     \sa writeCharacteristic()
  */
 
@@ -419,13 +450,21 @@ bool QLowEnergyService::contains(const QLowEnergyCharacteristic &characteristic)
     Writes \a newValue as value for the \a characteristic. If the operation is successful,
     the \l characteristicChanged() signal is emitted.
 
+    The \a mode parameter determines whether the remote device should send a write
+    confirmation. The to-be-written \a characteristic must support the relevant
+    write mode. The characteristic's supported write modes are indicated by its
+    \l QLowEnergyCharacteristic::Write and \l QLowEnergyCharacteristic::WriteNoResponse
+    properties.
+
     A characteristic can only be written if this service is in the \l ServiceDiscovered state,
     belongs to the service and is writable.
+
+    \sa QLowEnergyCharacteristic::properties()
  */
 void QLowEnergyService::writeCharacteristic(
-        const QLowEnergyCharacteristic &characteristic, const QByteArray &newValue)
+        const QLowEnergyCharacteristic &characteristic,
+        const QByteArray &newValue, QLowEnergyService::WriteMode mode)
 {
-    //TODO check behavior when writing to WriteNoResponse characteristic
     //TODO check behavior when writing to WriteSigned characteristic
     //TODO add support for write long characteristic value (newValue.size() > MTU - 3)
     Q_D(QLowEnergyService);
@@ -434,23 +473,29 @@ void QLowEnergyService::writeCharacteristic(
     if (!contains(characteristic))
         return;
 
-    // don't write if we don't have to
-    if (characteristic.value() == newValue)
-        return;
-
-    // don't write write-protected or undiscovered characteristic
-    if (!(characteristic.properties() & QLowEnergyCharacteristic::Write)
-            || state() != ServiceDiscovered) {
+    if (state() != ServiceDiscovered)
         d->setError(QLowEnergyService::OperationError);
-        return;
-    }
 
     if (!d->controller)
         return;
 
-    d->controller->writeCharacteristic(characteristic.d_ptr,
+    // don't write if properties don't permit it
+    if (mode == WriteWithResponse
+            && (characteristic.properties() & QLowEnergyCharacteristic::Write))
+    {
+        d->controller->writeCharacteristic(characteristic.d_ptr,
                                        characteristic.attributeHandle(),
-                                       newValue);
+                                       newValue,
+                                       true);
+    } else if (mode == WriteWithoutResponse
+               && (characteristic.properties() & QLowEnergyCharacteristic::WriteNoResponse)) {
+        d->controller->writeCharacteristic(characteristic.d_ptr,
+                                       characteristic.attributeHandle(),
+                                       newValue,
+                                       false);
+    } else {
+        d->setError(QLowEnergyService::OperationError);
+    }
 }
 
 /*!
diff --git a/src/bluetooth/qlowenergyservice.h b/src/bluetooth/qlowenergyservice.h
index 37fa82d7..7bb2c0d3 100644
--- a/src/bluetooth/qlowenergyservice.h
+++ b/src/bluetooth/qlowenergyservice.h
@@ -1,6 +1,7 @@
 /****************************************************************************
 **
 ** Copyright (C) 2014 Digia Plc and/or its subsidiary(-ies).
+** Copyright (C) 2013 Javier S. Pedro <maemo@javispedro.com>
 ** Contact: http://www.qt-project.org/legal
 **
 ** This file is part of the QtBluetooth module of the Qt Toolkit.
@@ -66,6 +67,11 @@ public:
         ServiceDiscovered,  // all details have been synchronized
     };
 
+    enum WriteMode {
+        WriteWithResponse = 0,
+        WriteWithoutResponse
+    };
+
     ~QLowEnergyService();
 
     QList<QBluetoothUuid> includedServices() const;
@@ -84,7 +90,8 @@ public:
 
     bool contains(const QLowEnergyCharacteristic &characteristic) const;
     void writeCharacteristic(const QLowEnergyCharacteristic &characteristic,
-                             const QByteArray &newValue);
+                             const QByteArray &newValue,
+                             WriteMode mode = WriteWithResponse);
 
     bool contains(const QLowEnergyDescriptor &descriptor) const;
     void writeDescriptor(const QLowEnergyDescriptor &descriptor,