#!/bin/sh
# This script uses sg_start from the sg3_utils (http://sg.torque.net/sg/) to
# automatically put a SCSI device into standby mode after a configurable idle
# time period. This should also work with USB storage devices.
# Based upon the ruby script of Steffen Rusitschka found at
# http://rusi.is-a-geek.org/files/rusi_sg_down, version 0.1.
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License version 2 as
# published by the Free Software Foundation.
#
# Copyright (c) 2007 Michael Heimpold <m.heimpold@web.de>
#
# Supported parameters of this script:
# ./spindown [device [idle_timeout [pc]]]
# Defaults: device = sda, idle_timeout = 900 (seconds), pc = 3
# pc is the 'power condition' value (see man page of sg_start),
# where 3 = standby and 5 = sleep

DEVICE="$1"
DEVICE="${DEVICE:=sda}"
IDLETIME="$2"
IDLETIME="${IDLETIME:=900}"
PC="$3"
PC="${PC:=3}"

SYSFS="$(grep sysfs /proc/mounts | head -n 1 | awk '{print $2}')"
[ ! -d "$SYSFS" ] && echo "Error: no sysfs found." && exit 1
IOCNTFILE="$SYSFS/block/$DEVICE/device/iorequest_cnt"

LASTIOCNT=0
LASTATIME=0
SLEEPTIME=0

echo "$$" > /var/run/spindown.$DEVICE.pid
trap "rm -f /var/run/spindown.$DEVICE.pid; exit 0" SIGTERM SIGINT

while true; do
	if [ -d $SYSFS/block/$DEVICE ]; then
		CURTIME="$(date +'%s')"
		CURIOCNT="$(cat $IOCNTFILE)"

		if [ "$LASTIOCNT" != "$CURIOCNT" ]; then
			LASTATIME=$CURTIME
		fi

		if [ "$(($LASTATIME + $IDLETIME))" -lt "$CURTIME" \
			-a "$SLEEPTIME" -lt "$LASTATIME" ]; then
			SLEEPTIME=$CURTIME
			sg_start --stop --pc=$PC /dev/$DEVICE
			CURIOCNT="$(cat $IOCNTFILE)"
		fi

		LASTIOCNT=$CURIOCNT
	else
		LASTIOCNT=0
		LASTATIME=0
		SLEEPTIME=0
	fi
	sleep 60
done