# Udevadm 说明

## 1. 安装

```bash
# Ubuntu 16.04
apt install udev
```

## 2. 使用

### 2.1. 监控 UEvent

```bash
udevadm monitor

# 热插拔设备出现类似 Log
KERNEL[4907.940589] add      /devices/platform/soc/2100000.aips-bus/2184200.usb/ci_hdrc.1/usb2/2-1/2-1:1.9/ttyUSB7/tty/ttyUSB7 (tty)
UDEV  [4908.211629] add      /devices/platform/soc/2100000.aips-bus/2184200.usb/ci_hdrc.1/usb2/2-1/2-1:1.9/ttyUSB7/tty/ttyUSB7 (tty)
```

### 2.2. 获取 UDev 信息

```bash
udevadm info <device node>
# 如
udevadm info /dev/ttyUSB7

P: /devices/platform/soc/2100000.aips-bus/2184200.usb/ci_hdrc.1/usb2/2-1/2-1:1.9/ttyUSB7/tty/ttyUSB7
N: ttyUSB7
S: serial/by-id/usb-LONGSUNG_M5700-if09-port0
S: serial/by-path/platform-ci_hdrc.1-usb-0:1:1.9-port0
E: DEVLINKS=/dev/serial/by-id/usb-LONGSUNG_M5700-if09-port0 /dev/serial/by-path/platform-ci_hdrc.1-usb-0:1:1.9-port0
E: DEVNAME=/dev/ttyUSB7
E: DEVPATH=/devices/platform/soc/2100000.aips-bus/2184200.usb/ci_hdrc.1/usb2/2-1/2-1:1.9/ttyUSB7/tty/ttyUSB7
E: ID_BUS=usb
E: ID_MODEL=M5700
E: ID_MODEL_ENC=M5700
E: ID_MODEL_ID=4d11
E: ID_PATH=platform-ci_hdrc.1-usb-0:1:1.9
E: ID_PATH_TAG=platform-ci_hdrc_1-usb-0_1_1_9
E: ID_REVISION=0000
E: ID_SERIAL=LONGSUNG_M5700
E: ID_TYPE=generic
E: ID_USB_DRIVER=option
E: ID_USB_INTERFACES=:020600:0a0000:ff0000:
E: ID_USB_INTERFACE_NUM=09
E: ID_VENDOR=LONGSUNG
E: ID_VENDOR_ENC=LONGSUNG
E: ID_VENDOR_FROM_DATABASE=Spreadtrum Communications Inc.
E: ID_VENDOR_ID=1782
E: MAJOR=188
E: MINOR=7
E: SUBSYSTEM=tty
E: TAGS=:systemd:
E: USEC_INITIALIZED=4908169711
```

## 外部参考资料

1. [How to Use Udev for Device Detection and Management in Linux](https://www.tecmint.com/udev-for-device-detection-management-in-linux/)
2. [udevadm 命令详解](https://www.cnblogs.com/carriezhangyan/p/9564900.html)