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ISSUE Qt-5.11.3 for USB device plugout and plugin, Qt events not working

  • Hi,

    In QT5.9.4, when USB device unplug and plug in, we could see the below code behavior.
    During Plugout
    Void QDeviceDiscoveryUDev::handleUDevNotification () handle gets called and internally, device removed function gets called.
    During Plugin
    Void QDeviceDiscoveryUDev::handleUDevNotification (handle gets called and internally, device detected function gets called.

    ISSUE Qt-5.11.3

    Whereas In QT 5.11.3, when USB device unplug and plugin, we are facing below issue.
    During Plugout
    Void QDeviceDiscoveryUDev::handleUDevNotification () handler is not called. In which case, USB device removal is not properly handled, due to which device is not getting detected whenever we plugin the USB device again.

    This works, only when we restart the QT application, dynamic USB detection after Plug out and Plugin is not working.

    Below is the path of the file where debug prints were added and found the flow.


  • Lifetime Qt Champion

    Hi and welcome to devnet,

    You should add what Linux distribution you are using as well as device.

    Did you check with a current version of Qt ? The latest Qt 5.12 or even beta of Qt 5.13.

  • Hi SGaist,

    Thanks for your quick reply.

    i am not using the any Linux distributions, i am using the Embedded Linux for arm (Linux kernel 4.9 using).
    i am using the - linuxfb and udev
    i am using the yocto-2.6 build system.


  • Lifetime Qt Champion

    Good, then please update the recipe you use and build an image using a more recent version of Qt.

  • I used the Qt5.12.3 but I am getting same issue.

    It is not solved the latest version Qt5.12.3

  • Lifetime Qt Champion

    In that case, you should check the bug report system to see if there's anything related. If not then please open a new report providing a much details as you can.

    If you by any chance you can, please check the latest release of Qt 5.9 and onward to pinpoint when the functionality broke.

  • We are using the eudev-3.2.2 older version for Qt-5.9 here is working.
    currently we updated the Qt-5.11 and eudev-3.2.7 here the problem if i changed the eudev-3.2.2 it is working Qt-5.11 also.
    The issue is eudev-3.2.7 , Qt-5.11 is not receiving events for eudev-3.2.7 rules.

    Finlay we are suspecting the eudev rules .

    One question :
    Qt-5.11 eudev rules are not rec-ionized any rules or syntax is changed the Qt-5.11 ?, would you please confirm me.

  • Lifetime Qt Champion

    I would rather check the other way around since version 3.2.2 is working properly, they may have changed something that broke Qt's handling.

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