udev

I am writing a Python Application running on linux. I want to be able to register and be notified by the system if a network cable is plugged in/ out . I am already using pyUdev (python bindings for libUdev) in order to get notified for USB plug in events. However, because the network eth0 module (for example) always remains loaded (regardless of the cable being plugged in) , I dont get the information I require. It only works for if up/down events. I have read a lot of posts on Windows WMI providing this functionality but none on linux. Am I looking in the right direction? A python way of

udev the workflow of udev: 启动初始化时, /dev目录使用tmpfs挂载. 然后, Udev 拷贝 /lib/udev/devices 的静态设备节点到 /dev 目录. Udev守护进程开始运行，为所有连接到系统的设备收集来自内核的uevents. Udev守护进程解析uevent数据，并且对/etc/udev/rules.d中指定的规则进行匹配. 根据指定的规则为设备创建设备节点和符号链接. Udev守护进程读取/etc/udev/rules.d/*.rules 中的规则并且保存到内存里面. Udev接收接收inotify事件，如果某个规则发生了改变，读取这些改变并更新内存副本. udev通过NetLink注册内核的设备事件，当有设备插入/拔除时，udev就会收到通知，它会从事件中所带参数和sysfs中的信息，加载适当的驱动程序，创建dev下的设备节点，使设备处于可用的状态。具体流程如下： udev通过kernel收到一个uevent，若是移除设备的uevent，则删除/dev中相应的设备文件；若是一个添加设备的uevent，则在配置文件/etc/udev/udev.conf或/lib/udev/udev.conf中查找规则文件所在目录（默认规则目录是：/lib/udev/rules.d/，客户规则目录/etc/udev/rules/（优先级最高），

uevents has been sent from kernel space to user space through netlink socket. In kernel, there must be something trigger uevent. I guess there are two possibilities: Hardware interrupt - this means, once hardware interruption happened, kernel sends event to user space to signal that there is some events happened. software polling - this means, there is always a daemon to check these file system to see if there is anything changed. If so, then update these info to upper layer. Could anyone provide your feedback? Thanks I can't agree with you about polling. uevent is event-based, so there is no

When I run docker container and list properties of some device with udevadm inside the container, there are only the basic information about the device. When I do the same thing on host, I can see much more. What can I do to get all the information inside the container? host$ udevadm info --query=property /dev/bus/usb/004/008 BUSNUM=004 DEVNAME=/dev/bus/usb/004/008 DEVNUM=008 DEVPATH=/devices/pci0000:00/0000:00:1d.0/usb4/4-1/4-1.1 DEVTYPE=usb_device DRIVER=usb ID_BUS=usb ID_MODEL=MCP2210_USB-to-SPI_Master ID_MODEL_ENC=MCP2210 USB-to-SPI Master ID_MODEL_ID=00de ID_REVISION=0002 ID_SERIAL

The normal way to create a videocapture is this: cam = cv2.VideoCapture(n) where n corresponds to the number of /dev/video0 , dev/video1 But because I'm building a robot that uses multiple cameras for different things, I needed to make sure that it was being assigned to the correct camera, I created udev rules that created devices with symbolic links to the correct port whenever a specific camera was plugged in. They appear to be working because when I look in the /dev directory I can see the link: /dev/front_cam -> video1 However I'm not sure how to actually use this now. I thought I could