nav-sdcard-format.sh

#!/bin/bash

if [ "${EUID}" -ne 0 ]; then
    (>&2 echo "only support exec as root.")
    exit 1
fi

set -euo pipefail

# global errors
ERR_ARGS=1
ERR_DEV_PERMISSION=2
ERR_UNSUPPORTED_DISK_TYPE=3
ERR_DEV_SIZE=4

# globals
BLOCK_DEV=""
SHOW_HELP=0
FORCE_FORMAT=0
NAVDEV=""
OFFDEV=""
# Minimal partition size in sectors:
# - 15388655 Sector * 512 (Byte/Sector) = 7878991360 Bytes
# - 7878991360 Bytes / 1024 / 1024 / 1024 = 7.34GiB
MIN_PART_SECTOR=15388655
HALF_DEV_SECTOR=0
PARTITION_MARK=""

print_help() {
    (>&2 cat <<EOF
Usage:
  nav-sdcard-format.sh [option] [dev]

Partition a block device into two 7.9GB (7.34GiB) ext4 partitions
Means you need more than 16GB (30777312 Sector) on your device

option:
  -h, --help     display the help
  -f, --force    force repartioning

dev:
  Path to block device. Accept sdx, mmcblkx type devices.
EOF
    )
    exit "${ERR_ARGS}"
}

parse_args() {
    # show help when there're no args
    if [ "$#" -eq 0 ]; then
        SHOW_HELP=1
    fi

    # Process options
    while [ "$#" -gt 1 ]; do
        case $1 in
            -h | --help)
                echo 'in help'
                SHOW_HELP=1
                shift
                ;;
            -f | --force)
                FORCE_FORMAT=1
                shift
                ;;
        esac
    done

    # print help and exit
    if [ "${SHOW_HELP}" -ne 0 ]; then
        print_help
    fi

    # Process required parameters
    BLOCK_DEV="$1"
    shift
}

get_partition_prefix() {
    local P_

    # auto detect if it's testing & set disk partition name
    # (e.g.  /dev/sdb     -> /dev/sdb1 & /dev/sdb2
    #        /dev/mmcblk1 -> /dev/mmcblk1p1 & /dev/mmcblk1p2)
    case "${BLOCK_DEV}" in
        /dev/sd* ) P_="";;
        /dev/mmcblk* ) P_="p";;
        * ) echo "Support only sdx, mmc."; exit "${ERR_UNSUPPORTED_DISK_TYPE}";;
    esac

    echo -n "${P_}"
}

check_device_partition() {
    # Check device write permission
    if [ ! -w "${BLOCK_DEV}" ] || [ ! -r "${BLOCK_DEV}" ]; then
        (>&2 echo "Device ${BLOCK_DEV} is not readable/writeable")
        return 1
    fi

    if [ -e "${NAVDEV}" ] || [ -e "${OFFDEV}" ]; then
        return 1
    fi

    return 0
}

do_partition() {
    local PART_LAYOUT
    PART_LAYOUT="$(
cat <<EOF
,${MIN_PART_SECTOR},L
,${MIN_PART_SECTOR},L
EOF
)"
    echo "${PART_LAYOUT}" | sfdisk -f "${BLOCK_DEV}"
    return 0
}

# main() function

parse_args "$@"

PARTITION_MARK="$(get_partition_prefix)"

NAVDEV="${BLOCK_DEV}${PARTITION_MARK}1"
OFFDEV="${BLOCK_DEV}${PARTITION_MARK}2"

HALF_DEV_SECTOR=$(( $(blockdev --getsz "${BLOCK_DEV}") / 2 - 1 ))

check_device_partition || if [ "${FORCE_FORMAT}" -eq 0 ]; then
    echo "Block device appears to already be partitioned and formated. Use -f to force repartion."
    exit "${ERR_DEV_PERMISSION}"
fi
grep -q /opt/navigon /proc/mounts && umount /opt/navigon
grep -q "${NAVDEV}"  /proc/mounts && umount "${NAVDEV}"
grep -q "${OFFDEV}"  /proc/mounts && umount "${OFFDEV}"

if [ "${HALF_DEV_SECTOR}" -lt "${MIN_PART_SECTOR}" ] ; then
    echo "Two partitions of needed size will not fit."
    echo "Need minium: 16 GB"
    echo "Available: $(($(blockdev --getsz "${BLOCK_DEV}") / 1024 / 1024 / 2)) GiB"
    exit "${ERR_DEV_SIZE}"
fi


do_partition || (>&2 echo 'partition failed')
sync
sfdisk -l "${BLOCK_DEV}"

# Wait until NAVDEV and OFFDEV partitions are created
while [ ! -r "${NAVDEV}" ] || [ ! -r "${OFFDEV}" ]; do sleep 1; done
ls /dev/mmc*

# Natually the SDCard should be fully formatted to its expected size as the following:
# - mke2fs -F -t ext4 -E nodiscard -Lempty_nav "${NAVDEV}"
# - mke2fs -F -t ext4 -E nodiscard -Lalt_nav "${OFFDEV}"
# However, on tegra platform for Model S/X, formatting speed is incredibly slow, which
# we choose to optimize to format a very small amount on these two partitions for storing
# only the "empty.txt" file.
# Free to change to `nodiscard` when tegra platform is retired.
mke2fs -F -t ext4 -b4096 -Lempty_nav "${NAVDEV}" 2048
mke2fs -F -t ext4 -b4096 -Lalt_nav "${OFFDEV}" 2048

mkdir -p /opt/navigon
mount "${NAVDEV}" /opt/navigon
touch /opt/navigon/empty.txt
umount -l "${NAVDEV}"

mkdir -p /opt/navigoff
mount "${OFFDEV}" /opt/navigoff
touch /opt/navigoff/empty.txt
umount -l "${OFFDEV}"