Make the QSerialPort::flush() non-blocking

According to documentation, the flush() method shall be non-blocking.

Tested on Linux 64-bit with auto-tests with the on-board and the USB
serial ports for Qt4 and then Qt5.

Note: On Windows the flush() method still does not work.

Change-Id: Iaee80361e59e0c281206ca24c817a446cdbf6ed1
Reviewed-by: Sergey Belyashov <Sergey.Belyashov@gmail.com>
Reviewed-by: Denis Shienkov <denis.shienkov@gmail.com>

2 files changed, 2 insertions, 20 deletions

diff --git a/src/serialport/qserialport_unix.cpp b/src/serialport/qserialport_unix.cpp
index 11ab16f..d555805 100644
--- a/src/serialport/qserialport_unix.cpp
+++ b/src/serialport/qserialport_unix.cpp
@@ -337,12 +337,7 @@ bool QSerialPortPrivate::setRequestToSend(bool set)
 
 bool QSerialPortPrivate::flush()
 {
-    return completeAsyncWrite()
-#ifndef Q_OS_ANDROID
-            && (::tcdrain(descriptor) != -1);
-#else
-            && (::ioctl(descriptor, TCSBRK, 1) != -1);
-#endif
+    return completeAsyncWrite();
 }
 
 bool QSerialPortPrivate::clear(QSerialPort::Directions directions)
diff --git a/src/serialport/qserialport_win.cpp b/src/serialport/qserialport_win.cpp
index eccaca9..19f35b7 100644
--- a/src/serialport/qserialport_win.cpp
+++ b/src/serialport/qserialport_win.cpp
@@ -259,20 +259,7 @@ bool QSerialPortPrivate::setRequestToSend(bool set)
 
 bool QSerialPortPrivate::flush()
 {
-    Q_Q(QSerialPort);
-
-    bool returnValue = true;
-
-    if (!startAsyncWrite())
-        returnValue = false;
-
-    if (!::FlushFileBuffers(handle)) {
-        q->setError(decodeSystemError());
-        returnValue = false;
-    }
-
-    return returnValue;
-
+    return startAsyncWrite();
 }
 
 bool QSerialPortPrivate::clear(QSerialPort::Directions directions)