Index: usr.sbin/powerd/powerd.8
diff -u usr.sbin/powerd/powerd.8.orig usr.sbin/powerd/powerd.8
--- usr.sbin/powerd/powerd.8.orig	Sat Jun 18 19:36:21 2005
+++ usr.sbin/powerd/powerd.8	Sun Jun 19 00:05:47 2005
@@ -38,6 +38,7 @@
 .Op Fl n Ar mode
 .Op Fl p Ar ival
 .Op Fl r Ar percent
+.Op Fl t
 .Op Fl v
 .Sh DESCRIPTION
 The
@@ -87,6 +88,10 @@
 adaptive
 mode should consider the CPU running and increase performance.
 The default is 65% or lower.
+.It Fl t
+When the temperature is too high, the
+.Nm
+switches the frequency to the lowest value for cooling down.
 .It Fl v
 Verbose mode.
 Messages about power changes will be printed to stdout and
Index: usr.sbin/powerd/powerd.c
diff -u -p usr.sbin/powerd/powerd.c.orig usr.sbin/powerd/powerd.c
--- usr.sbin/powerd/powerd.c.orig	Mon Apr 11 05:42:55 2005
+++ usr.sbin/powerd/powerd.c	Sun Jun 19 00:14:09 2005
@@ -83,6 +83,7 @@ static int	cp_time_mib[2];
 static int	freq_mib[4];
 static int	levels_mib[4];
 static int	acline_mib[3];
+static int	thermal_mib[5];
 
 /* Configuration */
 static int	cpu_running_mark;
@@ -91,6 +92,7 @@ static int	poll_ival;
 
 static int	apm_fd;
 static int	exit_requested;
+static int	thermal_control;
 
 static int
 read_usage_times(long *idle, long *total)
@@ -253,7 +255,8 @@ main(int argc, char * argv[])
 {
 	long idle, total;
 	int curfreq, *freqs, i, *mwatts, numfreqs;
-	int ch, mode_ac, mode_battery, mode_none, acline, mode, vflag;
+	int ch, mode_ac, mode_battery, mode_none, acline, mode, tflag, vflag;
+	int thermal_flags;
 	uint64_t mjoules_used;
 	size_t len;
 
@@ -263,10 +266,11 @@ main(int argc, char * argv[])
 	cpu_idle_mark = DEFAULT_IDLE_PERCENT;
 	poll_ival = DEFAULT_POLL_INTERVAL;
 	mjoules_used = 0;
+	tflag = 0;
 	vflag = 0;
 	apm_fd = -1;
 
-	while ((ch = getopt(argc, argv, "a:b:i:n:p:r:v")) != EOF)
+	while ((ch = getopt(argc, argv, "a:b:i:n:p:r:tv")) != EOF)
 		switch (ch) {
 		case 'a':
 			parse_mode(optarg, &mode_ac, ch);
@@ -300,6 +304,9 @@ main(int argc, char * argv[])
 				usage();
 			}
 			break;
+		case 't':
+			tflag = 1;
+			break;
 		case 'v':
 			vflag = 1;
 			break;
@@ -320,6 +327,12 @@ main(int argc, char * argv[])
 	len = 4;
 	if (sysctlnametomib("dev.cpu.0.freq_levels", levels_mib, &len))
 		err(1, "lookup freq_levels");
+	if (tflag) {
+		len = 5;
+		if (sysctlnametomib("hw.acpi.thermal.tz0.thermal_flags",
+		    thermal_mib, &len) == 0)
+			thermal_control = 1;
+	}
 
 	/* Check if we can read the idle time and supported freqs. */
 	if (read_usage_times(NULL, NULL))
@@ -381,6 +394,25 @@ main(int argc, char * argv[])
 			if (i < numfreqs && mwatts[i] != -1)
 				mjoules_used +=
 				    (mwatts[i] * (poll_ival / 1000)) / 1000;
+		}
+
+		/* Switch to the lowest frequency when too hot. */
+		if (thermal_control) {
+			len = sizeof(thermal_flags);
+			if (sysctl(thermal_mib, 5, &thermal_flags, &len,
+			    NULL, 0) == 0 && thermal_flags) {
+				if (curfreq == freqs[numfreqs - 1])
+					continue;
+				if (vflag) {
+					printf("high temperature; "
+					    "changing frequency to %d MHz\n",
+					    freqs[numfreqs - 1]);
+				}
+				if (set_freq(freqs[numfreqs - 1]))
+					err(1, "error setting CPU freq %d",
+					    freqs[numfreqs - 1]);
+				continue;
+			}
 		}
 
 		/* Always switch to the lowest frequency in min mode. */