Where backends have the capability to collect from multiple devlib
Instruments, EnergyMeasurement currently appends 'device' keys to the
names of metrics reported by those Instruments. Where multiple
Instruments are indeed used, it then sums up equivalent metrics to
produce the 'normal' metric without the 'device' keys
appended.
E.g. If you have two ACME 'devices' enabled you will get something
like
'device_total_energy_iio:device0' and
'device_total_energy_iio:device1', which will be summed to produce
'device_total_energy'.
However when only one Instrument is actually instantiated, this is
not needed and not done. Therefore just directly produce the metric
with the name originally given by devlib (i.e. in the example,
'device_total_energy').
Devlib's get_data API can return None when something goes wrong -
this currently results in us attempting to add a non-existent
artifact.
To avoid this confusion, check and use the return value from
get_data, instead of assuming that it will write data to its
'outfile' parameter.
Devlib's ACME instrument uses iio-capture under the hood, which can
only capture data from one IIO device at a time. Devlib's instrument
API expects to produce a single CSV file for the Instrument, with a
single axis of sample timestamps. These two things cannot be
correctly reconciled without changing the devlib Instrument API -
get_data would need to be able to return two distinct sets of data.
Instead, where required WA will instantiate the ACME instrument
multiple times (once for each IIO device), producing two separate CSV
files. Aggregated energy info (as opposed to timestamped samples of
energy data) _can_ be meaningfully combined from multiple IIO
devices, so the derived stats are summed.
This requires altering the internal API of the energy_measurement
module - rather than a single instrument the super-instrument now has
a dictionary mapping 'device' keys (this is really an arbitrary key,
but I think that 'device' is a justifiable metaphor for whatever
might separate multiple instruments, plus it is the terminology used
by IIO/ACME) to Instrument objects. Existing instruments simply
return a dict with a single entry, with None as the key.
It may in future be possible to solve this problem in devlib's ACME
instrument by avoiding the use of the iio-capture tool. In that case,
it should be possible to basically revert this patch and get the
required funcitonality from devlib.
As paramters defined by energy_measurement instrument backends were not
used in instantiating the backends, but the underlying devlib
instrument, the values did not undergo the usual Plugin parameter
setting perocedure. In particuar, type conversion would not take place.
Make sure backend parameters are validated properly by setting them on
an obj_dict before passing them to the devlib instrument.
DerivedMeasurements in devlib was changed to return DerivedMetrics
instead of Measurements. The former do not have "channel" attribute, so
just pass its name to WA's metrics.
Delvib now is capable of performing postprocessing of MeasurementCSV
files, instead of calculating additional metrics in WA this will be
performed externally. Currently support has been added for calculating
average power and cumulative energy.
