使用设备文件符号链接查找总线号和设备号 [英] Find bus number and device number with device file symlink

问题描述

我有一个由udev规则生成的设备文件(SYMLINK)/dev/CDMAModem.我想找到实际设备的总线号和设备号.实际上，我想在我的C ++程序中的设备/dev/bus/usb/BUS_NO/DEVICE_NO上执行USBDEVFS_RESET ioctl.

I have a device file(SYMLINK) /dev/CDMAModem generated by a udev rule. I want to find the bus number and device number of the actual device. Actually I want to perform USBDEVFS_RESET ioctl on device /dev/bus/usb/BUS_NO/DEVICE_NO in my C++ program.

---- udev规则----

----udev rule----

SUBSYSTEMS=="usb", ACTION=="add", DRIVERS=="zte_ev", ATTRS{bNumEndpoints}=="03", SYMLINK+="CDMAModem"
SUBSYSTEMS=="usb", ACTION=="remove", DRIVERS=="zte_ev", ATTRS{bNumEndpoints}=="03", SYMLINK-="CDMAModem"

推荐答案

我认为libudev会为您提供:

I think libudev will give you that:

#include <libudev.h>
#include <stdio.h>
#include <stdlib.h>
#include <locale.h>
#include <unistd.h>

int main(int argc, char **argv)
{

    struct udev *udev;
    struct udev_enumerate *enumerate;
    struct udev_list_entry *devices, *dev_list_entry;
    struct udev_device *dev;

    udev = udev_new();

    enumerate = udev_enumerate_new(udev);
    udev_enumerate_add_match_subsystem(enumerate, "CDMAModem");
    udev_enumerate_scan_devices(enumerate);
    devices = udev_enumerate_get_list_entry(enumerate);

    udev_list_entry_foreach(dev_list_entry, devices) {
        const char *path;

        path = udev_list_entry_get_name(dev_list_entry);
        dev = udev_device_new_from_syspath(udev, path);

        fprintf(stderr, "devnum: %s\n",
            udev_device_get_sysattr_value(dev, "devnum"));
        fprintf(stderr, "busnum: %s\n",
            udev_device_get_sysattr_value(dev, 'busnum:));
        udev_device_unref(dev);
    }

    udev_enumerate_unref(enumerate);
    udev_unref(udev);

    return 0;
}

然后，我认为您可以在ioctl()中使用此信息，如:

You can then use this information with ioctl(), I think, as in:

[charles@localhost 2-1]$ cd /sys/class/mem/random
[charles@localhost 2-1]$echo $PWD
/sys/devices/pci0000:00/0000:00:11.0/0000:02:00.0/usb2/2-1

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