Add support for sensor override value

Write support Value property under xyz.openbmc_project.Sensor.Value
interface is added which will be used to do sensor override.
Sensor can be overridden by setting a value, which will be preserved,
till the service is restarted or Value is overridden again with NaN.

Change-Id: Ia606031a97e532cd12d768e36f1feaa4c7350620
Signed-off-by: Richard Marian Thomaiyar <richard.marian.thomaiyar@linux.intel.com>
Signed-off-by: James Feist <james.feist@linux.intel.com>
diff --git a/include/sensor.hpp b/include/sensor.hpp
index dc9cdbe..62eec62 100644
--- a/include/sensor.hpp
+++ b/include/sensor.hpp
@@ -20,4 +20,17 @@
     std::shared_ptr<sdbusplus::asio::dbus_interface> thresholdInterfaceWarning;
     std::shared_ptr<sdbusplus::asio::dbus_interface> thresholdInterfaceCritical;
     double value = std::numeric_limits<double>::quiet_NaN();
+    double overriddenValue = std::numeric_limits<double>::quiet_NaN();
+    bool internalSet = false;
+    int setSensorValue(const double& newValue, double& oldValue)
+    {
+        if (internalSet)
+        {
+            internalSet = false;
+            oldValue = newValue;
+            return 1;
+        }
+        overriddenValue = newValue;
+        return 1;
+    }
 };
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