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.
+=head2 Plugin C<cpusleep>
+
+This plugin doesn't have any options. It reads CLOCK_BOOTTIME and
+CLOCK_MONOTONIC and reports the difference between these clocks. Since
+BOOTTIME clock increments while device is suspended and MONOTONIC
+clock does not, the derivative of the difference between these clocks
+gives the relative amount of time the device has spent in suspend
+state. The recorded value is in milliseconds of sleep per seconds of
+wall clock.
+
=head2 Plugin C<csv>
=over 4
reports disks as asleep because it has not been updated to incorporate support
for newer idle states in the ATA spec.
+=item B<UseSerial> B<true>|B<false>
+
+A disk's kernel name (e.g., sda) can change from one boot to the next. If this
+option is enabled, the C<smart> plugin will use the disk's serial number (e.g.,
+HGST_HUH728080ALE600_2EJ8VH8X) instead of the kernel name as the key for
+storing data. This ensures that the data for a given disk will be kept together
+even if the kernel name changes.
+
=back
=head2 Plugin C<snmp>