QML on Raspberry

  • Qt version: Qt 5.6.2
    Simple Qt program without QML works fine with "-platform linuxfb"
    but Qt+QML program not working.
    No error is displayed and keyboard & mouse don't responds.

  • Moderators

    This is not relevant for non-accelerated platforms, for example the ones using the LinuxFB plugin, which is meant for software-based rendering only. This means Qt Quick 2 is not functional in such a setup as it depends on OpenGL for rendering.

    Taken from: http://doc.qt.io/archives/qt-5.6/embedded-linux.html#configuring-a-specific-device

    It looks like you need to use -platform eglfs instead.

  • I tried with -platform eglfs
    it is not working

    following are last few lines I got from strace command

    open("/dev/tty", O_RDONLY|O_LARGEFILE|O_CLOEXEC) = 5
    fcntl64(5, F_SETFD, FD_CLOEXEC) = 0
    close(5) = 0
    write(2, "Could not find DRM device!\n", 27) = 27
    rt_sigprocmask(SIG_UNBLOCK, [ABRT], NULL, 8) = 0
    tgkill(199, 199, SIGABRT) = 0
    --- SIGABRT {si_signo=SIGABRT, si_code=SI_TKILL, si_pid=199, si_uid=0} ---
    +++ killed by SIGABRT +++

  • Moderators

    You probably need to install missing dependencies (if any) and compile the EGLFS platform plugin for Qt.

    See this guide: https://wiki.qt.io/RaspberryPi2EGLFS

  • Following plugins are installed in /usr/lib/qt/plugins/platforms/
    libqeglfs.so libqlinuxfb.so libqminimalegl.so libqminimal.so libqoffscreen.so libqxcb.so

  • make command output
    $ make
    ./buildroot-2017.02.2/output/host/usr/bin/arm-buildroot-linux-gnueabihf-g++ -c -pipe -D_LARGEFILE_SOURCE -D_LARGEFILE64_SOURCE -D_FILE_OFFSET_BITS=64 -Os --sysroot=./buildroot-2017.02.2/output/host/usr/arm-buildroot-linux-gnueabihf/sysroot -O2 -O3 -std=gnu++0x -Wall -W -D_REENTRANT -fPIC -DQT_NO_DEBUG -DQT_QUICK_LIB -DQT_GUI_LIB -DQT_QML_LIB -DQT_NETWORK_LIB -DQT_CORE_LIB -I. -I ./buildroot-2017.02.2/output/host/usr/arm-buildroot-linux-gnueabihf/sysroot/usr/include/qt5 -I ./buildroot-2017.02.2/output/host/usr/arm-buildroot-linux-gnueabihf/sysroot/usr/include/qt5/QtQuick -I ./buildroot-2017.02.2/output/host/usr/arm-buildroot-linux-gnueabihf/sysroot/usr/include/qt5/QtGui -I ./buildroot-2017.02.2/output/host/usr/arm-buildroot-linux-gnueabihf/sysroot/usr/include/qt5/QtQml -I ./buildroot-2017.02.2/output/host/usr/arm-buildroot-linux-gnueabihf/sysroot/usr/include/qt5/QtNetwork -I ./buildroot-2017.02.2/output/host/usr/arm-buildroot-linux-gnueabihf/sysroot/usr/include/qt5/QtCore -I. -I ./buildroot-2017.02.2/output/host/usr/mkspecs/devices/linux-buildroot-g++ -o main.o main.cpp
    ./buildroot-2017.02.2/output/host/usr/bin/rcc -name qml qml.qrc -o qrc_qml.cpp
    ./buildroot-2017.02.2/output/host/usr/bin/arm-buildroot-linux-gnueabihf-g++ -c -pipe -D_LARGEFILE_SOURCE -D_LARGEFILE64_SOURCE -D_FILE_OFFSET_BITS=64 -Os --sysroot=./buildroot-2017.02.2/output/host/usr/arm-buildroot-linux-gnueabihf/sysroot -O2 -O3 -std=gnu++0x -Wall -W -D_REENTRANT -fPIC -DQT_NO_DEBUG -DQT_QUICK_LIB -DQT_GUI_LIB -DQT_QML_LIB -DQT_NETWORK_LIB -DQT_CORE_LIB -I. -I./buildroot-2017.02.2/output/host/usr/arm-buildroot-linux-gnueabihf/sysroot/usr/include/qt5 -I./buildroot-2017.02.2/output/host/usr/arm-buildroot-linux-gnueabihf/sysroot/usr/include/qt5/QtQuick -I ./buildroot-2017.02.2/output/host/usr/arm-buildroot-linux-gnueabihf/sysroot/usr/include/qt5/QtGui -I./buildroot-2017.02.2/output/host/usr/arm-buildroot-linux-gnueabihf/sysroot/usr/include/qt5/QtQml -I./buildroot-2017.02.2/output/host/usr/arm-buildroot-linux-gnueabihf/sysroot/usr/include/qt5/QtNetwork -I./buildroot-2017.02.2/output/host/usr/arm-buildroot-linux-gnueabihf/sysroot/usr/include/qt5/QtCore -I. -I./buildroot-2017.02.2/output/host/usr/mkspecs/devices/linux-buildroot-g++ -o qrc_qml.o qrc_qml.cpp
    ./buildroot-2017.02.2/output/host/usr/bin/arm-buildroot-linux-gnueabihf-g++ --sysroot=./buildroot-2017.02.2/output/host/usr/arm-buildroot-linux-gnueabihf/sysroot -Wl,-O1 -o Rectangle main.o qrc_qml.o -lQt5Quick -L./buildroot-2017.02.2/output/host/usr/arm-buildroot-linux-gnueabihf/sysroot/usr/lib -lQt5Gui -lQt5Qml -lQt5Network -lQt5Core -lrt -ldl -lGLESv2 -lpthread

  • One more error I found through strace command

    "This plugin does not support cre"
    "Failed to create OpenGL context"

  • Moderators

    I don't know this error, sorry. So I am only guessing, but: are you sure you have all dependencies installed, including all OpenGL drivers?

  • Yes, I've installed all the dependencies.

    What is the meaning of
    could not open DRM device error

  • @Raviphulsundar This looks like an error reported by the eglfs plugin, but the details aren't clear to me. Can you try running it with the qt.qpa.eglfs.kms logging category enabled?

    ie $ QT_LOGGING_RULES="qt.qpa.eglfs.kms=true" program -platform eglfs

  • #export QT_LOGGING_RULES=qt.qpa.*=true
    #./Rectangle -platform eglfs
    qt.qpa.egldeviceintegration: EGL device integration plugin keys: ("eglfs_kms_egldevice","eglfs_kms","eglfs_X11")
    qt.qpa.egldeviceintegration: EGL device integration plugin keys (sorted): ("eglfs_kms","eglfs_kms_egldevice","eglfs_X11")
    qt.qpa.egldeviceintegration: Trying to load device EGL integration "eglfs_kms"
    qt.qpa.egldeviceintegration: Using EGL device integrtion "eglfs_kms"
    qt.qpa.input: udev device discovery for type QFlags(0x10)
    qt.qpa.input: Found matching devices ()
    qt.qpa.eglfs.kms: Found the following video devices ()
    Could not find DRM device!

  • It looks like querying libudev for DRM video devices is coming up empty. Is there anything in the /sys/class/drm/ directory on the target?

    From the Qt platform plugin side, the code of interest is QDeviceDiscoveryUDev::scanConnectedDevices() in qtbase/src/platformsupport/devicediscovery/qdevicediscovery_udev.cpp

  • $ls /sys/class/drm
    $cat /sys/class/drm/version
    drm 1.1.0 20060810

    $ls /lib/modules/4.4.43-v7/kernel/drivers/gpu/drm/
    drm_mipi_dsi.ko panel/ udl/ vc4/

    // No drm module is loaded, However DRM module is selected in Kernel configuration.

  • Now I've recompiled Kernel with
    instead of

    $ls /sys/class/ <---- no drm directory
    $ls /lib/modules/4.4.43-v7/kernel/drivers/gpu/drm/
    drm_kms_helper.ko drm.ko drm_mipi_dsi.ko panel udl vc4

    $lsmod -------> no drm module loaded
    #modprobe drm
    //DRM module loaded

    And now
    $ls /sys/class/drm
    version <----- Only version file

    $cat /sys/class/drm/version
    drm 1.1.0 20060810

  • @Raviphulsundar I suspect you need to get the Broadcom driver for the GPU. It might already be on the system, waiting to be loaded. Unfortunately I don't know what it is called. Have you checked raspberrypi.org?

  • @jeremy_k, I have checked in RaspberryPi forum for this pbm related to DRM. That thread is still unsolved.

    Regarding Broadcom driver for the GPU, I could not found it in Linux config.

    One thing I observed is drm module is not loading at boot time.
    Does it mean that Frame Buffer modules are selected instead of DRM ?

  • Unfortunately I don't have a pi to look at. Does the Raspbian distribution include X or some sort of gui? You can grab a copy of that, boot it, and see which modules are loaded.

    There's also this article about getting Qt to run with Arch on the pi 3: http://www.chaos-reins.com/2017-01-13-qt-pi3-arch-aarch64/

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