Simple script for testing USB gadget on Linux devices. Tested on F1C100s SoC, should work on Pi Pico as well

usb_gadget_setup.sh

#!/bin/bash

# Usage
# ./usb_gadget_setup.sh mass_storage <device> -> set up a mass storage gadget exposing <device> (it can be a block device, or a file). MAKE SURE IT'S NOT MOUNTED!!!
# ./usb_gadget_setup.sh eth -> setup an ethernet gadget
#
# /sys/kernel/config should be already mounted

mkdir /sys/kernel/config/usb_gadget/g1
pushd /sys/kernel/config/usb_gadget/g1

echo 0xabcd > idVendor
echo 0x1234 > idProduct

mkdir strings/0x409
echo 420 > strings/0x409/serialnumber
echo marcsello > strings/0x409/manufacturer
echo turbomeme > strings/0x409/product

mkdir configs/c.1

echo 120 > configs/c.1/MaxPower

FUNC=""

if [[ "$1" == "mass_storage" ]]; then

	# https://popovicu.com/posts/make-your-own-usb-storage-embedded-linux/

	mkdir functions/mass_storage.0

	# mkdir functions/mass_storage.0/lun.0 # should be already created
	echo "$2" > functions/mass_storage.0/lun.0/file

	FUNC="functions/mass_storage.0"


fi

if [[ "$1" == "eth" ]]; then

	# https://developer.ridgerun.com/wiki/index.php/How_to_create_USB_Ethernet_gadget_for_Jetson_through_configfs

	mkdir functions/ecm.usb0

	FUNC="functions/ecm.usb0"
fi

# bind the config to the function

ln -s $FUNC configs/c.1

echo "musb-hdrc.1.auto" > UDC