pwmconfig: Properly deal with multiple fan control

When a given PWM output controls more than one fan,
fanactive_min is no longer a space-separated list of numbers, it will
also include items of the form "A+B". The tests in the rest of the
code do not expect that and choke with errors like:

/usr/sbin/pwmconfig: line 926: [: 538+799: integer expression expected
/usr/sbin/pwmconfig: line 952: [: 538+799: integer expression expected

As the only thing we really care about is whether any fan stops
completely when PWM is 0, we can simply record the minimum of the
lowest speed of all affected fans.

CHANGES

@@ -6,6 +6,7 @@ SVN HEAD
   sensors: Clarify what option -u is good for
   pwmconfig: Print the initial PWM values
              Raise the detection threshold to 3/4
+             Properly deal with multiple fan control
   sensors-detect: Add detection of AMD family 16h power sensors
                   Map IT8771E, IT8772E, IT8782F and IT8783F to it87
                   Use /sys/module instead of /proc/modules where available

prog/pwm/pwmconfig

@@ -444,6 +444,7 @@ do
 
 	let pwmactivecount=0
 	let count=1
+	S_MIN=
 	for j in $GOODFAN
 	do
 		OS=`echo $SPEEDS | cut -d' ' -f$count`
@@ -462,7 +463,6 @@ do
 				let pwmactivecount=1
 				pwmactive="$i ${pwmactive}"
 				fanactive="$j ${fanactive}"
-				fanactive_min="$S ${fanactive_min}"
 
 				# Give all correlated fans time to return to full speed
 				sleep $DELAY
@@ -473,8 +473,14 @@ do
 				fi
 			else
 				fanactive="$j+${fanactive}"
-				fanactive_min="$S+${fanactive_min}"
 			fi
+
+			# Keep track of the slowest fan controlled by one PWM
+			if [ -z "$S_MIN" ] || [ $S -lt $S_MIN ]
+			then
+				S_MIN=$S
+			fi
+
 			S=`cat $j`
 			if [ $S -lt $threshold ]
 			then
@@ -507,8 +513,11 @@ do
 		if [ "$X" = "y" -o "$X" = "Y" ]
 		then
 			pwmactive="$i ${pwmactive}"
+			fanactive_min="0 $fanactive_min"
 		fi
 		echo
+	else
+		fanactive_min="$S_MIN $fanactive_min"
 	fi
 done