scripts: cleaned and improved policy scripts

The policy scripts can handle now client nodes that want to be linked with other
client nodes. This is needed for nodes created by the Pulse Audio Volume Control
to monitor audio comming from other application client nodes.

src/scripts/policy-endpoint-device.lua

@@ -95,21 +95,28 @@ function createLink (si_ep, si_target)
     return
   end
 
-  -- activate and register
-  si_link:activate (Feature.SessionItem.ACTIVE, function (link)
-    Log.info (link, "link activated")
-    link:register ()
-  end)
+  -- register
+  si_link:register ()
+
+  -- activate
+  si_link:activate (Feature.SessionItem.ACTIVE)
 end
 
-function getSiLinkAndSiPeer (si_ep)
+function getSiLinkAndSiPeer (si_ep, target_media_class)
   for silink in silinks_om:iterate() do
     local out_id = tonumber(silink.properties["out.item.id"])
     local in_id = tonumber(silink.properties["in.item.id"])
-    if out_id == si_ep.id then
-      return silink, getSessionItemById (in_id, siportinfos_om)
-    elseif in_id == si_ep.id then
-      return silink, getSessionItemById (out_id, siportinfos_om)
+    if out_id == si_ep.id or in_id == si_ep.id then
+      local is_out = out_id == si_ep.id and true or false
+      for peer in siportinfos_om:iterate() do
+        if peer.id == (is_out and in_id or out_id) then
+          local peer_node = peer:get_associated_proxy ("node")
+          local peer_media_class = peer_node.properties["media.class"]
+          if peer_media_class == target_media_class then
+            return silink, peer
+          end
+        end
+      end
     end
   end
   return nil, nil
@@ -133,7 +140,7 @@ function handleSiEndpoint (si_ep)
   end
 
   -- Check if item is linked to proper target endpoint, otherwise re-link
-  local si_link, si_peer = getSiLinkAndSiPeer (si_ep)
+  local si_link, si_peer = getSiLinkAndSiPeer (si_ep, target_media_class)
   if si_link then
     if si_peer and si_peer.id == si_target.id then
       Log.info (si_ep, "already linked to proper target")