pipewire: set node.link-group on virtual and internal filter nodes

[ChristianPraiss]

Ran into this chasing a bug where my Bluetooth AirPods mic never worked in Slack when routed through Easy Effects - WirePlumber's Bluetooth autoswitch (bluetooth.autoswitch-to-headset-profile) never flipped the headset into HFP mode, so the mic stayed silent no matter what.

Turned out to be a node.link-group gap. Easy Effects sets node.group on its virtual sink/source and internal filter nodes, but never sets the sibling property node.link-group. WirePlumber's autoswitch-bluetooth-profile.lua relies on node.link-group to walk through a filter chain and find the real device behind it - since it's missing here, the script can never see past Easy Effects, and the profile switch never fires.

PipeWire's own module-filter-chain.c sets node.group and node.link-group together automatically whenever either is missing, so this just brings Easy Effects' own node creation in line with that existing convention.

This alone isn't quite enough on the WirePlumber side either. Its filter-chain walk also expects media.class == Stream/Input/Audio on internal nodes, which Easy Effects doesn't set, and its cycle guard needs a small fix too. Got a patch for that on the WirePlumber side as well, and tested both together: a Bluetooth mic captured through Easy Effects now correctly switches profile and reverts afterward.

Related to #4878

Here's the wireplumber patch for reference.

diff --git a/src/scripts/device/autoswitch-bluetooth-profile.lua b/src/scripts/device/autoswitch-bluetooth-profile.lua
index 27c79dd..4763346 100644
--- a/src/scripts/device/autoswitch-bluetooth-profile.lua
+++ b/src/scripts/device/autoswitch-bluetooth-profile.lua
@@ -293,9 +293,21 @@ function triggerRestoreProfile (source, dev_id)
   end)
 end

-function getLinkedBluetoothLoopbackSourceNodeForStream (stream, node_om, link_om, visited_link_groups)
+function getLinkedBluetoothLoopbackSourceNodeForStream (stream, node_om, link_om, visited_nodes)
   local stream_id = stream["bound-id"]

+  -- Cycle guard: per visited NODE, not per link-group. A single filter chain
+  -- (e.g. EasyEffects) can have several internal nodes sharing the same
+  -- link-group in series, so guarding on the group alone stops the walk one
+  -- hop too early: https://github.com/wwmm/easyeffects/issues/4878
+  if visited_nodes == nil then
+    visited_nodes = {}
+  end
+  if visited_nodes [stream_id] then
+    return nil
+  end
+  visited_nodes [stream_id] = true
+
   -- Make sure the node is linked
   local link = link_om:lookup {
     Constraint { "link.input.node", "=", stream_id, type = "pw-global"}
@@ -321,23 +333,22 @@ function getLinkedBluetoothLoopbackSourceNodeForStream (stream, node_om, link_om
     }
     if filter_main_node ~= nil then
       local filter_link_group = filter_main_node.properties ["node.link-group"]
-      if visited_link_groups == nil then
-        visited_link_groups = {}
-      end
-      if visited_link_groups [filter_link_group] then
-        return nil
-      else
-        visited_link_groups [filter_link_group] = true
-      end
       for filter_stream_node in node_om:iterate {
-          Constraint { "media.class", "matches", "Stream/Input/Audio", type = "pw-global" },
           Constraint { "stream.monitor", "!", "true", type = "pw" },
           Constraint { "bluez5.loopback", "!", "true", type = "pw" },
           Constraint { "node.link-group", "=", filter_link_group, type = "pw" }
         } do
-        local bt_node = getLinkedBluetoothLoopbackSourceNodeForStream (filter_stream_node, node_oms)
-        if bt_node ~= nil then
-          return bt_node
+        -- Accept regular capture streams as before, and also plain internal
+        -- Duplex filter nodes that never set media.class at all (e.g.
+        -- EasyEffects' per-plugin nodes): https://github.com/wwmm/easyeffects/issues/4878
+        local fsn_media_class = filter_stream_node.properties ["media.class"]
+        local fsn_media_category = filter_stream_node.properties ["media.category"]
+        if (fsn_media_class ~= nil and string.find (fsn_media_class, "Stream/Input/Audio", 1, true
+            fsn_media_category == "Duplex" then
+          local bt_node = getLinkedBluetoothLoopbackSourceNodeForStream (filter_stream_node, node_
+          if bt_node ~= nil then
+            return bt_node
+          end
         end
       end
     end

[github-actions]

Workflow failed, but the following artifacts are still available for this pull request:

• easyeffects-archlinux-merge-314d54292-into-5b6859564-x86_64.zip
• easyeffects-flatpak-merge-314d54292-into-5b6859564-x86_64.flatpak.zip
• easyeffects-flatpak-merge-314d54292-into-5b6859564-aarch64.flatpak.zip