opengl es 1.x with QTE on brcm7413

qt : qt-everywhere-opensource-src-4.7.1
HW platform: broadcom7413

Broadcom7413 support openGL es 1.1(standard),and I'm porting QT on it.

But here below returns 0(qgl_qws.cpp),so nothing displayed on QGLWidget.
What can I do ?Do I need to implement the screen driver ?(but I have done this on qscreenlinuxfb_qws.cpp : setting display and framebuffer ,the 2D display is OK)Maybe only the QGLscreen?.

Code:

---

static QGLScreen *glScreenForDevice(QPaintDevice *device)
{
    QScreen *screen = qt_screen;
    if (screen->classId() == QScreen::MultiClass) {
 
	 int screenNumber;
        if (device && device->devType() == QInternal::Widget)
            screenNumber = qApp->desktop()->screenNumber(static_cast<QWidget *>(device));
        else
            screenNumber = 0;
        screen = screen->subScreens()[screenNumber];
    }
    while (screen->classId() == QScreen::ProxyClass ||
           screen->classId() == QScreen::TransformedClass) {
        screen = static_cast<QProxyScreen *>(screen)->screen();
    }
    if (screen->classId() == QScreen::GLClass)
    {
	return static_cast<QGLScreen *>(screen);
    }
    else
        return 0;
}

---