Question

假设在等待从设备读取输入的pthread中调用以下代码，但设备本身在启动期间最初不可用，并且稍后通过USB端口[比如键盘]插入。

有没有比使用do..while更好的等待方式？我看到do..while在获取文件描述符之前CPU利用率很高。

#define DEV "/dev/input/event2"

int fd; 
fd = open(DEV, O_RDONLY);
if (fd == -1) {
    fprintf(stderr, "Cannot open %s: %s.\n", dev, strerror(errno));
    //return EXIT_FAILURE;
    do{     
        fd = open(dev, O_RDONLY);
    }       
    while(fd < 0);
}

while (1)
{
    //Logic to read from say keyboard device
}

Answer 1

您可以使用libudev的通知功能：

http://www.signal11.us/oss/udev/

https://www.freedesktop.org/software/systemd/man/libudev.html

Answer 2

You can use inotify as:

Create inotify object: 
    fd=inotify_init();

Add your path in watcher list:
    inotify_add_watch(fd,<YOUR_PATH>, IN_CREATE | IN_DELETE)<0)

Continuously watch in infinite loop and use select for timeout and wait  for event  on fd.
    ret = pselect(fd+1, &fds, NULL, NULL, &tv, NULL);

When the event will occur, read the event.
    rsize = read(fd, buf, BUF_LEN);
    event=(struct inotify_event *)buf;

Check for event:
if((event->mask & IN_CREATE)){
    //USB added
}else if((event->mask & IN_DELETE)){
    //USB deleted
}

我希望这会有所帮助。

什么是更好的实现以下 - 民意调查，inotify或其他任何东西

2 个答案: