Ruigu Electronic

When a USB device is disconnected from the USB bus, the following steps are involved:

When a USB device is disconnected from a downstream port on a hub, the hub disables the port and reports the port change to the USB host via the IN interrupt channel.
After receiving the port change, the host sends a GetPortStatus request to obtain detailed information and performs the disconnect operation.
The system calls the USB driver’s disconnect callback function to release all system resources occupied by the device.
If the disconnected device is a USB hub, the USB host performs the disconnect operation on the hub and all connected devices.