#!/bin/sh

setup_image()
{
	set -x
	local storage="$1"
	local sz_mb="$2"
	# create the backing store
	dd if=/dev/zero of=$storage bs=1M seek=$sz_mb count=0 2>/dev/null
	# this shows up as 23FC-F676 in /dev/disk/by-uuid
	local diskid=0x23FCF676
	mkdosfs -n 'OPENBMC-FW' -i $diskid -I $storage >/dev/null 2>&1
}

mount_image()
{
	set -x
	local storage="$1"
	local stormnt="$2"
	mkdir -p $stormnt || exit 1
	mount -o loop -t vfat $storage $stormnt
}

cleanup_image()
{
	set -x
	local storage="$1"
	local stormnt="$2"
	umount -f "$stormnt"
	rm -f "$storage"
	rmdir "$stormnt"
}

GADGET_BASE=/sys/kernel/config/usb_gadget

which_dev()
{
	local in_use=$(cat $GADGET_BASE/*/UDC)
	cd /sys/class/udc
	for D in *; do
		case "$in_use" in
			*"$D"*) ;;
			*) echo "$D"; return 0;;
		esac
	done
	return 1
}

usb_ms_insert()
{
	local name="$1"
	local storage="$2"

	if [ -d $GADGET_BASE/$name ]; then
		echo "device $name already exists" >&2
		return 1
	fi
	mkdir $GADGET_BASE/$name
	cd $GADGET_BASE/$name

	echo 0x1d6b > idVendor  # Linux Foundation
	echo 0x0105 > idProduct # FunctionFS Gadget
	mkdir strings/0x409
	local machineid=$(cat /etc/machine-id)
	local data="OpenBMC USB mass storage gadget device serial number"
	local serial=$( echo -n "${machineid}${data}${machineid}" | \
		sha256sum | cut -b 0-12 )
	echo $serial > strings/0x409/serialnumber
	echo OpenBMC > strings/0x409/manufacturer
	echo "OpenBMC Mass Storage" > strings/0x409/product

	mkdir configs/c.1
	mkdir functions/mass_storage.$name
	echo $storage > functions/mass_storage.$name/lun.0/file
	echo 0 > functions/mass_storage.$name/lun.0/removable
	mkdir configs/c.1/strings/0x409

	echo "Conf 1" > configs/c.1/strings/0x409/configuration
	echo 120 > configs/c.1/MaxPower
	ln -s functions/mass_storage.$name configs/c.1
	local dev=$(which_dev)
	echo $dev > UDC
}

usb_ms_eject()
{
	local name="$1"

	echo '' > $GADGET_BASE/$name/UDC

	rm -f $GADGET_BASE/$name/configs/c.1/mass_storage.$name
	rmdir $GADGET_BASE/$name/configs/c.1/strings/0x409
	rmdir $GADGET_BASE/$name/configs/c.1
	rmdir $GADGET_BASE/$name/functions/mass_storage.$name
	rmdir $GADGET_BASE/$name/strings/0x409
	rmdir $GADGET_BASE/$name
}

usage()
{
	echo "Usage: $0 <action> ..."
	echo "       $0 setup <file> <sizeMB>"
	echo "       $0 insert <name> <file>"
	echo "       $0 eject <name>"
	echo "       $0 mount <file> <mnt>"
	echo "       $0 cleanup <file> <mnt>"
	exit 1
}

echo "$#: $0 $@"
case "$1" in
	insert)
		shift
		usb_ms_insert "$@"
		;;
	eject)
		shift
		usb_ms_eject "$@"
		;;
	setup)
		shift
		setup_image "$@"
		;;
	mount)
		shift
		mount_image "$@"
		;;
	cleanup)
		shift
		cleanup_image "$@"
		;;
	*)
		usage
		;;
esac
exit $?