使用QSocketNotifier在char设备上进行选择。 [英] Using QSocketNotifier to select on a char device.

问题描述

我写了一个char设备驱动程序，我现在正在写一个QT包装程序，它的一部分是获得一个信号，当设备变得可读通过轮询机制。我试图做：

I wrote a char device driver and am now writing a QT "wrapper" which part of it is to get a signal to fire when the device becomes readable via the poll mechanism. I had tried to do:

QFile file("/dev/testDriver");
if(file.open(QFile::ReadOnly)) {
  QSocketNotifier sn(file.handle(), , QSocketNotifier::Read);
  sn.setEnabled(true);
  connect(&sn, SIGNAL(activated(int)), &this, SLOT(readyRead()));
}

但是readyRead从来没有被调用，我的驱动程序从来没有报告调用它的poll方法。

But readyRead was never called and my driver never reported having its poll method called.

我可以得到下面的代码，所以我知道我的驱动程序正在工作

I was able to get the following code to work so I know my driver is working

QFile file("/dev/testDriver");
if(file.open(QFile::ReadOnly)) {
    struct pollfd fd;
    fd.fd = file.handle();
    fd.events = POLLIN;

    struct pollfd fds[] = {fd};
    int ready;
    qDebug() << "Started poll";
    ready = poll(fds, 1, -1);
    qDebug() << "Poll returned: " << ready;

    QTextStream in(&file);
    QTextStream out(stdout);
    out << in.readAll();
}

正确等待我的驱动程序调用wake_up，我可以看到两个轮询调用从我的司机。一个用于初始轮询注册，一个用于wake_up发生时。

This properly waits for my driver to call wake_up and I can see two poll calls from my driver. One for the initial poll registration and one for when the wake_up happens.

这样做可能会产生一个单独的线程，它所做的是在这个设备上轮询并抛出一个信号和循环。

Doing it this way I would probably have to spawn a separate thread which all it did was poll on this device and throw a signal and loop.

可以使用 QSocketNotifier 这样吗？ QFile :: handle（）的文档似乎表明它应该。

Is it possible to use QSocketNotifier in this way? The documentation of QFile::handle() seems to indicate it should be.

推荐答案

您的 QSocketNotifer $ c> if 块结束。它不会报告任何内容。

Your QSocketNotifer gets destroyed as soon as that if block ends. It doesn't stand a chance of reporting anything.

只要您希望监控该文件，您必须保持该套接字通知程序处于活动状态。这样做的最简单的方法是在你的一个类中保留一个 QSocketNotifer * 成员。

You must keep that socket notifier alive as long as you want that file to be monitored. The simplest way of doing that is probably keeping a QSocketNotifer* member in one of your classes.

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