#!/usr/bin/env bash

# mount configfs
mount -t configfs none /sys/kernel/config
# load libcomposite module
modprobe libcomposite
# create a gadget
mkdir /sys/kernel/config/usb_gadget/g1
# cd to its configfs node
cd /sys/kernel/config/usb_gadget/g1
# configure it (vid/pid can be anything if USB Class is used for driver compat)
echo 0xabcd > idVendor
echo 0x1234 > idProduct
# configure its serial/mfg/product
mkdir strings/0x409
echo myserial > strings/0x409/serialnumber
echo mymfg > strings/0x409/manufacturer
echo myproduct > strings/0x409/product
# create a config
mkdir configs/c.1
# configure it with attributes if needed
echo 120 > configs/c.1/MaxPower
# ensure function is loaded
modprobe usb_f_ecm
# create the function (name must match a usb_f_<name> module such as 'ecm')
mkdir functions/ecm.0
# associate function with config
ln -s functions/ecm.0 configs/c.1
# enable gadget by binding it to a UDC from /sys/class/udc
echo 0000:01:00.0 > UDC
# to unbind it: echo "" UDC; sleep 1; rm -rf /sys/kernel/config/usb_gadget/g1