#!/bin/sh
# Given an iso image, runs isohybrid on it to allow it to be booted from
# USB stick as well as CD. Then it adds a small second FAT partition, which
# the user can use to provide firmware files to the installer on the same
# USB stick.

# This needs to be big enough to hold the uncompressed firmware.tar.gz
# file. Currently that is 4.4M; add a few more to grow.
firmware_volume_size_M=6
# max size 11 chars:  ----------- 
firmware_volume_name="Firmware"

iso="$1"

if [ -z "$iso" ]; then
	echo "usage: $0 iso" >&2
	exit 1
fi

set -e

# isohybrid's defaults, but let's insure against future changes.
heads=64
sectors=32

isohybrid -h "$heads" -s "$sectors" "$iso"

# Make the firmware volume.
tmpdir="$(mktemp -d)"
firmware_volume_file="$tmpdir/fat"
mkfs.msdos -n "$firmware_volume_name" -C "$firmware_volume_file" \
	$(expr $firmware_volume_size_M \* 1024)

# Combine images. 
# XXX This wastes some space because isohybrid pads the iso to one
# megabyte. Could reuse that padding for the start of the firmware volume.
cat "$firmware_volume_file" >> "$iso"
rm -r "$tmpdir"

cylinders="$(($(stat -c %s "$iso") / $heads / $sectors))"

# Now adjust the partition table of the hybrid iso.
# It has a first partition which is the iso; add a second partition for the
# firmware volume.
(

# Make new partition #2
echo n
echo p
echo 2
echo # use default start sector
echo # use default end sector

# Pedantically, set partition type to 1: FAT 16
echo t
echo 2
echo 1

# Done!
echo w
) | fdisk -C "$cylinders" -H "$heads" -S "$sectors" "$iso"