#!/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.
#
AWK=${AWK:-/bin/awk}
CONFIG=${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="no"
MAPPING=linux


usage() {
	cat << EOF
Usage: zpool_layout [-th] [-c file] [-b buses] [-p ports] [-n channels] [-m map]
  -c    Alternate config file [default=${CONFIG}]
  -b    Enumerate buses [default="${BUSES[*]}"]
  -p    Enumerate ports [default="${PORTS[*]}"]
  -n    Channel names [default="A..Z"]
  -t    Trigger and wait for udev to settle [default=${TRIGGER}]
  -m    Slot mapping [default=${MAPPING}]
  -h    Show this message
EOF
	exit 0
}

while getopts 'c:b:p:n:m:th' OPTION; do
	case ${OPTION} in
	c)
		CONFIG=${OPTARG}
		;;
	b)
		BUSES=(${OPTARG})
		;;
	p)
		PORTS=(${OPTARG})
		;;
	n)
		CHANNELS=(${OPTARG})
		;;
	m)
		MAPPING=`readlink -e ${OPTARG}`
		;;
	t)
		TRIGGER=yes
		;;
	h)
		usage
		;;
	esac
done

# Verify mapping file exists if specified.
# Linux-Slot	Custom-Slot
if [ ${MAPPING} != "linux" ] && [ ! -e ${MAPPING} ]; then
	echo "Error: Mapping file '${MAPPING}' does not exist"
	exit 1
fi

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

map_slot() {
	local LINUX_SLOT=$1
	local MAPPED_SLOT=

	if [ ${MAPPING} = "linux" ]; then
		MAPPED_SLOT=${LINUX_SLOT}
	else
		MAPPED_SLOT=`${AWK} "\\$1 == ${LINUX_SLOT} && !/^#/ \
			{ print \\$2; exit }" $MAPPING`
	fi
	printf "%d" ${MAPPED_SLOT}
}

# 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.
for (( i=0, k=0; i<${#BUSES[*]}; i++ )); do
	for (( j=0; j<${#PORTS[*]}; j++, k++ )); do
		BYPATH=(`ls *:${BUSES[$i]}:*:${PORTS[$j]}* 2>/dev/null | \
			grep -v part | sort -n -k7 -t'-' | cut -f1-6 -d'-'`)
		SLOTS=(`ls *:${BUSES[$i]}:*:${PORTS[$j]}* 2>/dev/null |  \
			grep -v part | sort -n -k7 -t'-' | cut -f7 -d'-'`)
		TMP_FILE=`mktemp`

		for (( l=0; l<${#SLOTS[*]}; l++ )); do
			MAPPED_SLOT=`map_slot ${SLOTS[$l]}`
			printf "%s%d\t%s-%d\n" \
				${CHANNELS[$k]} ${MAPPED_SLOT} \
				${BYPATH[$l]} ${SLOTS[$l]} >>${TMP_FILE}
		done

		echo
		echo -n "# Channel ${CHANNELS[$k]}, "
		echo "Bus ${BUSES[$i]}, Port ${PORTS[$j]}"
		cat ${TMP_FILE} | sort -n -k2 -t${CHANNELS[$k]}
		rm -f ${TMP_FILE}
	done
done

# Restore stdout from fd #8 and close fd #8.
exec 1>&8 8>&-
popd >/dev/null

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

exit 0