sensordatahandler: Support empty inventory interfaces

This commit adds support for empty inventory interfaces when
asserting a sensor into the inventory. This is something already
supported in ipmi-fru-parser, for example.

Currently, the notify::assertion function expects that each DBUS
interface also have a set of associated properties. One of the
use-cases this commit tries to solve is when a sensor being asserted
maps to an inventory item (accessed via
xyz.openbmc_project.Inventory.Manager DBUS service) that implements
a DBUS interface with no properties. For example, the GPU sensor
is mapped to a GPU inventory object that implements the DBUS
interface xyz.openbmc_project.Inventory.Item.Accelerator.
This commit enables phosphor-host-ipmid to correctly create/update
inventory objects even in cases where they implement DBUS interfaces
that contain no properties.

The sensor-example.yaml file has been updated to show an example
of a GPU sensor, the inventory object for which implements a
property-less DBUS interface.

Tested:

Tested on a witherspoon system that had some GPUs attached to it.
Pulled also https://gerrit.openbmc-project.xyz/c/openbmc/openbmc/+/21107
in order to generate the right sensor configs for testing.
Verified that the GPU invetory objects that are created when the host
asserts a GPU sensor now implement the empty interface
xyz.openbmc_project.Inventory.Item.Accelerator

Signed-off-by: Santosh Puranik <santosh.puranik@in.ibm.com>
Change-Id: I973580e285ae0fff1a513d3bbe8c03a89e0eeb83

1 files changed, 9 insertions, 0 deletions

diff --git a/sensordatahandler.cpp b/sensordatahandler.cpp
index 76dad69..923b96a 100644
--- a/sensordatahandler.cpp
+++ b/sensordatahandler.cpp
@@ -322,6 +322,15 @@ ipmi_ret_t assertion(const SetSensorReadingReq& cmdData, const Info& sensorInfo)
     ipmi::sensor::InterfaceMap interfaces;
     for (const auto& interface : sensorInfo.propertyInterfaces)
     {
+        // An interface with no properties - It is possible that the sensor
+        // object on DBUS implements a DBUS interface with no properties.
+        // Make sure we add the interface to the list if interfaces on the
+        // object with an empty property map.
+        if (interface.second.empty())
+        {
+            interfaces.emplace(interface.first, ipmi::sensor::PropertyMap{});
+            continue;
+        }
         // For a property like functional state the result will be
         // calculated based on the true value of all conditions.
         for (const auto& property : interface.second)