Add documentation for the FreeBSD bit for cpufreq

diff --git a/src/collectd.conf.pod b/src/collectd.conf.pod
index 0cc9a7c..2976f6d 100644 (file)
--- a/src/collectd.conf.pod
+++ b/src/collectd.conf.pod
@@ -1656,15 +1656,24 @@ Defaults to B<true>.
 
 =head2 Plugin C<cpufreq>
 
-This plugin doesn't have any options. It reads
+This plugin is available on Linux and FreeBSD only.  It doesn't have any
+options.  On Linux it reads
 F</sys/devices/system/cpu/cpu0/cpufreq/scaling_cur_freq> (for the first CPU
 installed) to get the current CPU frequency. If this file does not exist make
 sure B<cpufreqd> (L<http://cpufreqd.sourceforge.net/>) or a similar tool is
 installed and an "cpu governor" (that's a kernel module) is loaded.
 
-If the system has the I<cpufreq-stats> kernel module loaded, this plugin reports
-the rate of p-state (cpu frequency) transitions and the percentage of time spent
-in each p-state.
+On Linux, if the system has the I<cpufreq-stats> kernel module loaded, this
+plugin reports the rate of p-state (cpu frequency) transitions and the
+percentage of time spent in each p-state.
+
+On FreeBSD it does a sysctl dev.cpu.0.freq and submits this as instance 0.
+At this time FreeBSD only has one frequency setting for all cores.
+See the BUGS section in the FreeBSD man page for cpufreq(4) for more details.
+
+On FreeBSD the plugin checks the success of sysctl dev.cpu.0.freq and
+unregisters the plugin when this fails.  A message will be logged to indicate
+this.
 
 =head2 Plugin C<cpusleep>