3 files changed, 53 insertions, 1 deletions

diff --git a/src/serialport/qserialport.cpp b/src/serialport/qserialport.cpp
index 690eb65..369be62 100644
--- a/src/serialport/qserialport.cpp
+++ b/src/serialport/qserialport.cpp
@@ -1409,7 +1409,7 @@ qint64 QSerialPort::readData(char *data, qint64 maxSize)
     Q_UNUSED(data);
     Q_UNUSED(maxSize);
 
-#ifdef Q_OS_WIN32
+#if defined(Q_OS_WIN32)
     // We need try to start async reading to read a remainder from a driver's queue
     // in case we have a limited read buffer size. Because the read notification can
     // be stalled since Windows do not re-triggered an EV_RXCHAR event if a driver's
@@ -1417,6 +1417,12 @@ qint64 QSerialPort::readData(char *data, qint64 maxSize)
     Q_D(QSerialPort);
     if (d->readBufferMaxSize || d->flowControl == QSerialPort::HardwareControl)
         d->startAsyncRead();
+#elif defined(Q_OS_UNIX)
+    // We need try to re-trigger the read notification to read a remainder from a
+    // driver's queue in case we have a limited read buffer size.
+    Q_D(QSerialPort);
+    if (d->readBufferMaxSize && !d->isReadNotificationEnabled())
+        d->setReadNotificationEnabled(true);
 #endif
 
     // return 0 indicating there may be more data in the future
diff --git a/src/serialport/qserialport_unix.cpp b/src/serialport/qserialport_unix.cpp
index 4659a18..c243319 100644
--- a/src/serialport/qserialport_unix.cpp
+++ b/src/serialport/qserialport_unix.cpp
@@ -727,6 +727,7 @@ bool QSerialPortPrivate::readNotification()
         if (bytesToRead == 0) {
             // Buffer is full. User must read data from the buffer
             // before we can read more from the port.
+            setReadNotificationEnabled(false);
             return false;
         }
     }
diff --git a/tests/auto/qserialport/tst_qserialport.cpp b/tests/auto/qserialport/tst_qserialport.cpp
index d50afe9..3a62bfa 100644
--- a/tests/auto/qserialport/tst_qserialport.cpp
+++ b/tests/auto/qserialport/tst_qserialport.cpp
@@ -120,6 +120,8 @@ private slots:
     void asynchronousWriteByTimer_data();
     void asynchronousWriteByTimer();
 
+    void asyncReadWithLimitedReadBufferSize();
+
     void readBufferOverflow();
     void readAfterInputClear();
     void synchronousReadWriteAfterAsynchronousReadWrite();
@@ -808,6 +810,49 @@ void tst_QSerialPort::asynchronousWriteByTimer()
     QCOMPARE(receiverPort.readAll(), alphabetArray);
 }
 
+class AsyncReader2 : public QObject
+{
+    Q_OBJECT
+public:
+    explicit AsyncReader2(QSerialPort &port, const QByteArray &expectedData)
+        : serialPort(port), expectedData(expectedData)
+    {
+        connect(&serialPort, &QSerialPort::readyRead, this, &AsyncReader2::receive);
+    }
+
+private slots:
+    void receive()
+    {
+        receivedData.append(serialPort.readAll());
+        if (receivedData == expectedData)
+            tst_QSerialPort::exitLoop();
+    }
+
+private:
+    QSerialPort &serialPort;
+    const QByteArray expectedData;
+    QByteArray receivedData;
+};
+
+void tst_QSerialPort::asyncReadWithLimitedReadBufferSize()
+{
+    QSerialPort senderPort(m_senderPortName);
+    QVERIFY(senderPort.open(QSerialPort::WriteOnly));
+
+    QSerialPort receiverPort(m_receiverPortName);
+    QVERIFY(receiverPort.open(QSerialPort::ReadOnly));
+
+    receiverPort.setReadBufferSize(1);
+    QCOMPARE(receiverPort.readBufferSize(), qint64(1));
+
+    AsyncReader2 reader(receiverPort, alphabetArray);
+
+    QCOMPARE(senderPort.write(alphabetArray), qint64(alphabetArray.size()));
+
+    enterLoop(1);
+    QVERIFY2(!timeout(), "Timed out when waiting for the read or write.");
+}
+
 void tst_QSerialPort::readBufferOverflow()
 {
     QSerialPort senderPort(m_senderPortName);