Inventory data presented to the host CPU by host-sp-comms includes the VPD for removable components such as NVMe drives, the fan tray, and temperature sensors, in addition to reporting the components' type and presence and what sensor measurements they have available. This is not presented to the control plane via the control-plane-agent inventory interface. It really ought to be.

While the control plane could learn the VPD of such devices by asking the host OS to retrieve it from host-sp-comms, this requires that the host OS be up and capable of receiving underlay network traffic from Nexus, which may not always be the case. For switches and power shelf controllers, this is never the case (since, you know, they don't have a host CPU or OS), so there is presently no way for the control plane to receive VPD for FRUs such as power shelf rectifiers or Sidecar fans. This is important for future fault management work, as we'll need this sort of thing in order to implement the idea of control plane cached topology described in RFD 589.

I think we ought to solve this by adding VPD identity to the TLV-encoded ComponentDetails messages for components that have their own VPD. We should probably also consider adding a DeviceCapabilities bit so that components can say they have VPD in the inventory list.