IOCTL_EMI_GET_MEASUREMENT IOCTL

Description

The IOCTL_EMI_GET_MEASUREMENT control code retrieves the current energy measurement and the time at which the measurement was taken.

Parameters

Input buffer

<text> None. </text>

Input buffer length

<text> None. </text>

Output buffer

<text> The AssociatedIrp.SystemBuffer member specifies the address of a caller-allocated buffer that contains the measurement data from provider device driver. </text>

Output buffer length

<text> The length of output buffer should be the size of EMI_MEASUREMENT_DATA_V1 or EMI_MEASUREMENT_DATA_V2 multiply by number of channels, it is specified in the Parameters.DeviceIoControl.OutputBufferLength member. </text>

Status block

Irp->IoStatus.Status is set to STATUS_SUCCESS if the request is successful. Otherwise, Status to the appropriate error condition as a NTSTATUS code.

For more information, see NTSTATUS Values.

Remarks

For EMI version 1 and 2, the EMI measurement data reported from each channel should be accumulated and translated to the unit specified by the channel on each request, as the EMI interface of any device should be shared across the system, therefore how freqeunt the counters are being sampled and accumulated depends on how often each of its consumer requests and also the driver implementation.

For the EMI version 2, Multiple channels are exposed by the same device should be sampled at once on each request, hence the caller should use the ChannelCount in the EMI_METADATA_V2 to traverse the channels, for example:

  status = DeviceIoControl(DeviceHandle,
                           IOCTL_EMI_GET_MEASUREMENT,
                           NULL,
                           NULL,
                           Data,
                           ChannelDataSize,
                           BytesReturned,
                           NULL);

  EMI_CHANNEL_V2* Channel = &MetaData->Channels[0];
  for (int i = 0 ; i < MetaData->ChannelCount && status ; i++) {

      //
      // Get energy measurement for each energy counter.
      //

      AbsoluteEnergy = Measurement->ChannelData[i].AbsoluteEnergy;
      AbsoluteTime = Measurement->ChannelData[i].AbsoluteTime;
  }

See also

EMI_METADATA_V2
EMI_MEASUREMENT_DATA_V2
Energy Metering Interface