Import OpenBSD's sysctl hardware sensors framework.

This commit includes the following core components:

 * sample configuration file for sensorsd
 * rc(8) script and glue code for sensorsd(8)
 * sysctl(3) doc fixes for CTL_HW tree
 * sysctl(3) documentation for hardware sensors
 * sysctl(8) documentation for hardware sensors
 * support for the sensor structure for sysctl(8)
 * rc.conf(5) documentation for starting sensorsd(8)
 * sensor_attach(9) et al documentation
 * /sys/kern/kern_sensors.c
   o sensor_attach(9) API for drivers to register ksensors
   o sensor_task_register(9) API for the update task
   o sysctl(3) glue code
   o hw.sensors shadow tree for sysctl(8) internal magic
 * <sys/sensors.h>
 * HW_SENSORS definition for <sys/sysctl.h>
 * sensors display for systat(1), including documentation
 * sensorsd(8) and all applicable documentation

The userland part of the framework is entirely source-code
compatible with OpenBSD 4.1, 4.2 and  -current as of today.

All sensor readings can be viewed with `sysctl hw.sensors`,
monitored in semi-realtime with `systat -sensors` and also
logged with `sensorsd`.

Submitted by:	Constantine A. Murenin <cnst@FreeBSD.org>
Sponsored by:	Google Summer of Code 2007 (GSoC2007/cnst-sensors)
Mentored by:	syrinx
Tested by:	many
OKed by:	kensmith
Obtained from:	OpenBSD (parts)

5 files changed, 71 insertions, 2 deletions

diff --git a/etc/Makefile b/etc/Makefile
index fb0e3e8..725dd24 100644
--- a/etc/Makefile
+++ b/etc/Makefile
@@ -17,7 +17,7 @@ BIN1=	amd.map apmd.conf auth.conf \
 	portsnap.conf pf.conf pf.os phones profile protocols \
 	rc rc.bsdextended rc.firewall rc.firewall6 rc.initdiskless \
 	rc.sendmail rc.shutdown \
-	rc.subr remote rpc services shells \
+	rc.subr remote rpc sensorsd.conf services shells \
 	snmpd.config sysctl.conf syslog.conf \
 	etc.${MACHINE_ARCH}/ttys \
 	${.CURDIR}/../gnu/usr.bin/man/manpath/manpath.config \
diff --git a/etc/defaults/rc.conf b/etc/defaults/rc.conf
index 7a18b9c..f941870 100644
--- a/etc/defaults/rc.conf
+++ b/etc/defaults/rc.conf
@@ -40,6 +40,8 @@ kldxref_clobber="NO"	# Overwrite old linker.hints at boot.
 kldxref_module_path=""	# Override kern.module_path. A ';'-delimited list.
 powerd_enable="NO" 	# Run powerd to lower our power usage.
 powerd_flags=""		# Flags to powerd (if enabled).
+sensorsd_enable="NO"	# Run sensorsd to monitor and log sensor state changes
+sensorsd_flags=""	# additional flags for sensorsd(8)
 tmpmfs="AUTO"		# Set to YES to always create an mfs /tmp, NO to never
 tmpsize="20m"		# Size of mfs /tmp if created
 tmpmfs_flags="-S"	# Extra mdmfs options for the mfs /tmp
diff --git a/etc/rc.d/Makefile b/etc/rc.d/Makefile
index 56aa598..5f58a6f 100755
--- a/etc/rc.d/Makefile
+++ b/etc/rc.d/Makefile
@@ -33,7 +33,7 @@ FILES=	DAEMON FILESYSTEMS LOGIN NETWORKING SERVERS \
 	random rarpd resolv root \
 	route6d routed routing rpcbind rtadvd rwho \
 	savecore sdpd securelevel sendmail \
-	serial sppp statd swap1 \
+	sensorsd serial sppp statd swap1 \
 	syscons sysctl syslogd \
 	timed tmp \
 	ugidfw \
diff --git a/etc/rc.d/sensorsd b/etc/rc.d/sensorsd
new file mode 100644
index 0000000..51bd970
--- /dev/null
+++ b/etc/rc.d/sensorsd
@@ -0,0 +1,17 @@
+#!/bin/sh
+#
+# $FreeBSD$
+#
+
+# PROVIDE: sensorsd
+# REQUIRE: syslogd
+#
+
+. /etc/rc.subr
+
+name="sensorsd"
+rcvar=`set_rcvar`
+command="/usr/sbin/${name}"
+
+load_rc_config $name
+run_rc_command "$1"
diff --git a/etc/sensorsd.conf b/etc/sensorsd.conf
new file mode 100644
index 0000000..3b41b28
--- /dev/null
+++ b/etc/sensorsd.conf
@@ -0,0 +1,50 @@
+# $FreeBSD$
+# $OpenBSD: sensorsd.conf,v 1.8 2007/08/14 19:02:02 cnst Exp $
+
+#
+# Sample sensorsd.conf file. See sensorsd.conf(5) for details.
+#
+
+# +5 voltage (volts)
+#hw.sensors.lm0.volt3:low=4.8V:high=5.2V
+
+# +12 voltage (volts)
+#hw.sensors.lm0.volt4:low=11.5V:high=12.5V
+
+# Chipset temperature (degrees Celsius)
+#hw.sensors.lm0.temp0:high=50C
+
+# CPU temperature (degrees Celsius)
+#hw.sensors.lm0.temp1:high=60C
+
+# CPU fan (RPM)
+#hw.sensors.lm0.fan1:low=3000
+
+# ignore certain indicators on ipmi(4)
+#hw.sensors.ipmi0.indicator1:istatus
+
+# Warn if any temperature sensor is over 70 degC.
+# This entry will match only those temperature sensors
+# that don't have their own entry.
+#temp:high=70C
+
+
+# By default, sensorsd(8) reports status changes of all sensors that 
+# keep their state. Uncomment the following lines if you want to 
+# suppress reports about status changes of specific sensor types.
+
+#temp:istatus
+#fan:istatus
+#volt:istatus
+#acvolt:istatus
+#resistance:istatus
+#power:istatus
+#current:istatus
+#watthour:istatus
+#amphour:istatus
+#indicator:istatus
+#raw:istatus
+#percentage:istatus
+#illuminance:istatus
+#drive:istatus
+#timedelta:istatus