USB LED Triggers

configname: CONFIG_USB_LED_TRIG

Linux Kernel Configuration
└─>Device Drivers
└─>USB support
└─>USB LED Triggers
In linux kernel since version 3.18 (release Date: 2014-12-07)  
This option adds LED triggers for USB host and/or gadget activity.

Say Y here if you are working on a system with led-class supported
LEDs and you want to use them as activity indicators for USB host or
gadget.