The Mi 9 supports OTG(On-The-Go) which is a technical standard for direct connection and communication between USB devices. It allows OTG enabled devices to directly connect and exchange data without the need for a computer as an intermediary.
For your reference, here are more information regarding OTG as below:
1. OTG allows you to directly connect devices that support OTG standards (such as smartphones, tablets) to other USB devices, such as USB drives, keyboards, mice, game controllers, etc;
2. Through OTG, you can transfer files and data directly between OTG enabled devices without the need for a computer or other intermediary devices;
3. OTG devices can serve as both host devices to control the functions of other USB devices, as well as slave devices to respond to and receive commands from other host devices.