# Args:
# $1: device to mount
# $rootmnt: where to try mounting it
# Returns 0 if able to mount, nonzero otherwise
canmount()
{
    mount -n -t iso9660 -o ro $1 $rootmnt
}

# Args:
# $1: device to check
# $2: $rootmnt: where to try mounting
# Returns 0 if device mountable and DFS, nonzero otherwise
checkvalidity()
{
    echo -n "Scanning $1: "
    if canmount $1; then
        if cmp /marker $rootmnt/opt/dfsruntime/marker; then
            # LEAVE IT MOUNTED; later mount attempts will be weird.
            echo "Found DFS CD."
            return 0
        else
            umount $rootmnt
            echo "Found a CD, but not the correct DFS one."
            return 1
        fi
    else
        echo "$1: Not mountable (empty drive, not a CD-ROM, or wrong device)"
        return 1
    fi
}

# Args: $rootmnt: where to mount the new item
# Returns 0 if a valid device was found, nonzero otherwise
# If a valid device was found, sets DFSDEVICE to that device and exports
# DFSDEVICE
scandevices()
{
    OLDCWD=`pwd`

    cat <<EOF

Scanning for DFS CD....

EOF

    cd /sys/block
    for DEVICE in *; do
        if [ `cat $DEVICE/removable` = 1 ]; then
            if checkvalidity /dev/$DEVICE; then
                DFSDEVICE=/dev/$DEVICE
                export DFSDEVICE
                cd $OLDCWD
                return 0
            fi
        fi
    done
    cd $OLDCWD
    return 1
}