Touchscreen cannot rotate with linuxfb evdevtouch

[Edmond.Yu]

I'm using QT 5.11 on Raspbian GNU/Linux 10 (buster),
The display is rotated but the touchscreen cannot rotate by the following startup parameters:

pi@raspberrypi:~ $ export QT_QPA_EVDEV_TOUCHSCREEN_PARAMETERS="rotate=270"
pi@raspberrypi:~ $ ./ucapp -platform linuxfb  -plugin evdevtouch

Refer the document:
https://doc.qt.io/qt-5/embedded-linux.html
https://doc.qt.io/qt-5/inputs-linux-device.html

After hook the QEvent as the following:

bool MainWindow::eventFilter(QObject *obj, QEvent *event)
{
    if(event->type()==QEvent::HoverMove)
    {
        auto e = (QHoverEvent*) event;
        auto p = e->pos();
        qDebug()<<"rx "<<p.rx() <<";ry "<<p.ry()<<"\n";
    }

    return QMainWindow::eventFilter(obj, event);
}

There are two line messages when I touch the left-top point on touchscreen.
It seems one for original point and one for transformed point.

09-29 07:52:25 Debug: rx  39 ;ry  767
09-29 07:52:25 Debug: rx  19 ;ry  65

when I set rotate=0, there is only one line message for one touch:

export QT_QPA_EVDEV_TOUCHSCREEN_PARAMETERS="rotate=0",

I haven't digged into the source code qevdevtouchhandler.cpp.
https://github.com/qt/qtbase/blob/dev/src/platformsupport/input/evdevtouch/qevdevtouchhandler.cpp

Please give me ideals to fix the issue. I have struggled and searched for several days