First draft

ScriptableRenderPipeline/HDRenderPipeline/HDRP/Editor/Sky/HDRISky/HDRISkyEditor.cs

     public class HDRISkyEditor
         : SkySettingsEditor
     {
-        SerializedDataParameter m_hdriSky;
+        SerializedDataParameter m_HdriSky;
+        SerializedDataParameter m_Intensity;
+        SerializedDataParameter m_EnableIntensity;
 
         public override void OnEnable()
         {
-            m_hdriSky = Unpack(o.Find(x => x.hdriSky));
+            m_HdriSky = Unpack(o.Find(x => x.hdriSky));
+            m_Intensity = Unpack(o.Find(x => x.intensity));
+            m_EnableIntensity = Unpack(o.Find(x => x.enableIntensity));
-            PropertyField(m_hdriSky);
+            EditorGUI.BeginChangeCheck();
+            PropertyField(m_HdriSky);
+            PropertyField(m_EnableIntensity);
+            using (new UnityEditor.EditorGUI.DisabledScope(m_EnableIntensity.value.boolValue))
+            {
+                PropertyField(m_Intensity);
+            }
+            if (EditorGUI.EndChangeCheck())
+            {
+              //  target. NeedComputeMultiplier();
+            }
 
             EditorGUILayout.Space();
 

ScriptableRenderPipeline/HDRenderPipeline/HDRP/Sky/HDRISky/HDRISky.cs

     {
         [Tooltip("Cubemap used to render the sky.")]
         public CubemapParameter hdriSky = new CubemapParameter(null);
+        [Tooltip("Desired intensity in Lux for the upper hemisphere of the HDRI")]
+        public float intensity = 10000;
+        [Tooltip("If enabled the HDRI will be calibrated based on the desired intensity provided")]
+        public bool enableIntensity = false;
+
+        public bool NeedComputeMultiplier()
+        {
+            return m_needComputeMultiplier;
+        }
+
+        bool m_needComputeMultiplier = false;
 
         public override SkyRenderer CreateRenderer()
         {