Oneplus 9 will support 30W fast wireless charging, OnePlus 9 will also support wireless reverse charging function, you can let the phone to other devices that support wireless charging reverse charging, Huawei and Xiaomi flagship mobile phones have been standard with this function, if the user has a real wireless Bluetooth headset supporting wireless charging, this wireless reverse charging function is still quite practical.
Mobile phone A plugs into the OTG cable, and the other end connects to mobile phone B through the data cable, and A can charge B. (Mobile phone A needs to support OTG)