#!/bin/bash
#
# Set BUSES and PORTS to match the topology of your system.  As each
# port is enumerated it will be assigned the next channel name.  The
# current script enumerates each port on a bus before moving on to
# enumerate the next bus.
#
# Every distribution, version of udev, and type of attached storage
# seems to result in slightly different formatting of the by-path
# name.   For this reason you may need to adjust the parsing below
# to suit your needs.  This is one of the reasons to use a custom
# /etc/zfs/zdev.conf file, it allows the by-path naming convertion
# to change and still keep the simple <channel><rank> naming.
#
CONFIG=${CONFIG:-/etc/zfs/zdev.conf}
BUSES=( 01 02 03 )
PORTS=( 4 0 )
CHANNELS=( A B C D E F G H I J K L M N O P Q R S T U V W X Y Z )
TRIGGER=

usage() {
	cat << EOF
Usage: zpool_layout [-th] [-c file] [-b buses] [-p ports] [-n channels]
  -c    Alternate config file [default=/etc/zfs/zdev.conf]
  -b    Enumerate buses [default="01 02 03"]
  -p    Enumerate ports [default="4 0"]
  -n    Channel names [default="A..Z"]
  -t    Trigger and wait for udev to settle [default=no]
  -h    Show this message
EOF
	exit 0
}

while getopts 'c:b:p:n:th' OPTION; do
	case ${OPTION} in
	c)
		CONFIG=${OPTARG}
		;;
	b)
		BUSES=(${OPTARG})
		;;
	p)
		PORTS=(${OPTARG})
		;;
	n)
		CHANNELS=(${OPTARG})
		;;
	t)
		TRIGGER=1
		;;
	h)
		usage
		;;
	esac
done

# Save stdout as fd #8, then redirect stdout to the config file.
exec 8>&1
exec >${CONFIG}
pushd /dev/disk/by-path >/dev/null

# Generate comment header.
echo "#"
echo "# Custom /dev/disk/by-path to /dev/disk/zpool mapping, "
echo "# based of the following physical cable layout."
echo "#"

# Generate host port layout table for comment header.
echo "# ------------------ Host Port Layout ---------------------"
echo -n "#          "
for (( i=0; i<${#BUSES[*]}; i++ )); do
	printf "%-8d" ${BUSES[$i]}
done
echo

for (( i=0, k=0; i<${#PORTS[*]}; i++ )); do
	printf "# Port %-2d  " ${PORTS[$i]}

	for (( j=0; j<${#BUSES[*]}; j++, k++ )); do
		let k=$j*${#PORTS[*]}+$i
		printf "%-8s" ${CHANNELS[$k]}
	done
	echo
done
echo "#"

# Generate channel/disk layout table for comment header.
echo "# ----------------- Channel/Disk Layout -------------------"
echo "# Channel  Disks"
for (( i=0, k=0; i<${#BUSES[*]}; i++ )); do
	for (( j=0; j<${#PORTS[*]}; j++, k++ )); do
		printf "# %-9s" ${CHANNELS[$k]}
		ls *:${BUSES[$i]}:*:${PORTS[$j]}* 2>/dev/null | \
			cut -f7 -d'-' | sort -u -n | tr '\n' ','
		echo
	done
done
echo "#"

# Generate mapping from <channel><rank> to by-path name.
TMP_FILE=`mktemp`
AWK=${AWK:-/bin/awk}

for (( i=0, k=0; i<${#BUSES[*]}; i++ )); do
	for (( j=0; j<${#PORTS[*]}; j++, k++ )); do
		ls *:${BUSES[$i]}:*:${PORTS[$j]}*  2>/dev/null | \
			grep -v part | sort -n -k7 -t'-'>${TMP_FILE}

		echo
		echo -n "# Channel ${CHANNELS[$k]}, "
		echo "Bus ${BUSES[$i]}, Port ${PORTS[$j]}"
		${AWK} -F '-' -v ch="${CHANNELS[$k]}" \
			'{print ch$7 "\t" $0 }' ${TMP_FILE}
	done
done

# Restore stdout from fd #8 and close fd #8.
exec 1>&8 8>&-
rm -f ${TMP_FILE}
popd >/dev/null

if [ ${TRIGGER} ]; then
	udevadm trigger
	udevadm settle
fi

exit 0