FMA 2008/024 introduces a libtopo model for supporting indicators and
sensors.  The initial implementation provides sensors and indicators
over IPMI.  The SES (SCSI enclosure services) specification also allows
a fairly rich set of indicators and sensors.  This case extends the
enumerator introduced as part of FMA 2008/024 to support these sensors
and indicators.

The SES enumerator presents several different types of nodes.  The
following describes the sensors and indicators available for each.

NODE TYPE	CLASS		TYPE		NAME

ses-enclosure
		indicator	locate		ident
		indicator	service		fail
		sensor		temperature	<dynamic>
		sensor		voltage		<dynamic>
		sensor		current		<dynamic>
		sensor		discrete	fault

psu
		indicator	locate		ident
		indicator	service		fail
		sensor		power_supply	status

fan
		indicator	locate		ident
		indicator	service		fail
		sensor		speed		speed
		sensor		discrete	fault

bay
		indicator	locate		ident
		indicator	service		fail
		indicator	ok2rm		ok2rm
		sensor		discrete	fault

The 'ident', 'fail', and 'ok2rm' indicators all implement a boolean
indicator of the given type for the element.  SES has the unfortunate
property that there is no way to tell if a given indicator is supported
or not other than attempting to change it.  As such, we are forced to
export indicators that may not be functional on all platforms.  In
addition, some elements (bay and enclosure) support enclosure-detected
failures distinct from requested failure indication.  Either of these
properties will turn on the indicator, so the user may make a request to
explicitly turn off a failure indicator only to find that it is still
active because there is an enclosure-detected failure present.

The 'fault' discrete sensors are a representation of this array-detected
internal state.  In the future, it may be possible to diagnose these
failures by periodically scanning the available components and checking
their status.

The fan speed sensor presents the current speed in RPM.  Again, there is
no way to know know whether the fan supports monitoring speed.  Some
enclosures that don't support this seem to report an RPM of 0, but this
is indistinguishable from the fan being actually stopped.

The psu status sensor combines several different properties (acfail,
dcfail, overcurrent, undervoltage, etc) into a single discrete sensor
that matches the existing libtopo PSU state masks.

The temperature, voltage, and current sensors are all enclosure-wide,
and named according the SES element description (or class description if
there is no element-specific description).  While it is possible for
these sensors to monitor a particular component (such as PSU voltage),
SES does not provide a way to associate these sensors with any element.
This means that all analog sensors much be attached to the ses-enclosure
ndoe.  In the future, if we develop some way to describe this
relationship via vendor-specific libses plugins, the enumerator could
use this information to construct a more specific topology.

All temperature sensors are reported in degrees celsius, all voltage
sensors are reported in volts, and all current sensors are reported in
amps.

Reading a single SES sensor requires taking an entire snapshot of the
enclosure, so it is impractical to read these indicators and sensors
upon every request.  Instead, the last requested snapshot will be used
for an implementation-defined period of time (approximately one second)
such that a series of queries can be efficient while still allowing
changes to be observed over time.