Any usage case for USB device mode of linux side?

Official Hardware Classic Yún
1

Yun has two USB port, one for ATmega32u4 is device/client mode, and one for AR9331 is host mode. But AR9331 does support device mode( but not USB OTG/On-The-Go). I have hard time to find out usage case for device mode application. Any one?

I come cross 2 applications;-

  1. emulate keyboard and mouse
  2. replace UART console TTY, now serial port is clean.

any one?

2

AR9331 does not support USB OTG, this shows rough edge of chip.