scripts: add bluez-midi monitor and its configuration

Add support for BLE MIDI devices and local endpoints.

Disabled by default for now, as the feature currently faces some
DBus/SELinux policy issues e.g. on Fedora.

src/config/bluetooth.conf

@@ -68,6 +68,9 @@ context.modules = [
 
   # Provides factories to make session manager objects.
   { name = libpipewire-module-session-manager }
+
+  # Provides factories to make SPA node objects.
+  { name = libpipewire-module-spa-node-factory }
 ]
 
 wireplumber.components = [

src/config/bluetooth.lua.d/30-bluez-midi-monitor.lua

@@ -0,0 +1,18 @@
+bluez_midi_monitor = {}
+bluez_midi_monitor.properties = {}
+bluez_midi_monitor.rules = {}
+
+function bluez_midi_monitor.enable()
+  if bluez_midi_monitor.enabled == false then
+    return
+  end
+
+  load_monitor("bluez-midi", {
+    properties = bluez_midi_monitor.properties,
+    rules = bluez_midi_monitor.rules,
+  })
+
+  if bluez_midi_monitor.properties["with-logind"] then
+    load_optional_module("logind")
+  end
+end

src/config/bluetooth.lua.d/50-bluez-midi-config.lua

@@ -0,0 +1,41 @@
+-- BLE MIDI is currently disabled by default, because it conflicts with
+-- the SELinux policy on Fedora 37 and potentially other systems using
+-- SELinux. For a workaround, see
+-- https://gitlab.freedesktop.org/pipewire/pipewire/-/blob/master/spa/plugins/bluez5/README-MIDI.md
+bluez_midi_monitor.enabled = false
+
+bluez_midi_monitor.properties = {
+  -- Enable the logind module, which arbitrates which user will be allowed
+  -- to have bluetooth audio enabled at any given time (particularly useful
+  -- if you are using GDM as a display manager, as the gdm user also launches
+  -- pipewire and wireplumber).
+  -- This requires access to the D-Bus user session; disable if you are running
+  -- a system-wide instance of wireplumber.
+  ["with-logind"] = true,
+
+  -- List of MIDI server node names. Each node name given will create a new instance
+  -- of a BLE MIDI service. Typical BLE MIDI instruments have on service instance,
+  -- so adding more than one here may confuse some clients. The node property matching
+  -- rules below apply also to these servers.
+  --["servers"] = { "bluez_midi.server" },
+}
+
+bluez_midi_monitor.rules = {
+  -- An array of matches/actions to evaluate.
+  {
+    matches = {
+      {
+        -- Matches all nodes.
+        { "node.name", "matches", "bluez_midi.*" },
+      },
+    },
+    apply_properties = {
+      --["node.nick"] = "My Node",
+      --["priority.driver"] = 100,
+      --["priority.session"] = 100,
+      --["node.pause-on-idle"] = false,
+      --["session.suspend-timeout-seconds"] = 5,  -- 0 disables suspend
+      --["monitor.channel-volumes"] = false,
+    },
+  },
+}

src/config/bluetooth.lua.d/90-enable-all.lua

@@ -1 +1,2 @@
 bluez_monitor.enable()
+bluez_midi_monitor.enable()

src/config/wireplumber.conf

@@ -71,6 +71,9 @@ context.modules = [
 
   # Provides factories to make session manager objects.
   { name = libpipewire-module-session-manager }
+
+  # Provides factories to make SPA node objects.
+  { name = libpipewire-module-spa-node-factory }
 ]
 
 wireplumber.components = [

src/scripts/monitors/bluez-midi.lua

@@ -0,0 +1,161 @@
+-- WirePlumber
+--
+-- Copyright © 2022 Pauli Virtanen
+--    @author Pauli Virtanen
+--
+-- SPDX-License-Identifier: MIT
+
+local config = ... or {}
+
+-- unique device/node name tables
+node_names_table = nil
+id_to_name_table = nil
+
+-- preprocess rules and create Interest objects
+for _, r in ipairs(config.rules or {}) do
+  r.interests = {}
+  for _, i in ipairs(r.matches) do
+    local interest_desc = { type = "properties" }
+    for _, c in ipairs(i) do
+      c.type = "pw"
+      table.insert(interest_desc, Constraint(c))
+    end
+    local interest = Interest(interest_desc)
+    table.insert(r.interests, interest)
+  end
+  r.matches = nil
+end
+
+-- applies properties from config.rules when asked to
+function rulesApplyProperties(properties)
+  for _, r in ipairs(config.rules or {}) do
+    if r.apply_properties then
+      for _, interest in ipairs(r.interests) do
+        if interest:matches(properties) then
+          for k, v in pairs(r.apply_properties) do
+            properties[k] = v
+          end
+        end
+      end
+    end
+  end
+end
+
+function createNode(parent, id, type, factory, properties)
+  properties["factory.name"] = factory
+
+  -- set the node description
+  local desc = properties["node.description"]
+  -- sanitize description, replace ':' with ' '
+  properties["node.description"] = desc:gsub("(:)", " ")
+
+  -- set the node name
+  local name =
+      "bluez_midi." .. properties["api.bluez5.address"]
+  -- sanitize name
+  name = name:gsub("([^%w_%-%.])", "_")
+  -- deduplicate nodes with the same name
+  properties["node.name"] = name
+  for counter = 2, 99, 1 do
+    if node_names_table[properties["node.name"]] ~= true then
+      node_names_table[properties["node.name"]] = true
+      break
+    end
+    properties["node.name"] = name .. "." .. counter
+  end
+
+  -- apply properties from config.rules
+  rulesApplyProperties(properties)
+
+  -- create the node
+  -- it doesn't necessarily need to be a local node,
+  -- the other Bluetooth parts run in the local process,
+  -- so it's consistent to have also this here
+  local node = LocalNode("spa-node-factory", properties)
+  node:activate(Feature.Proxy.BOUND)
+  parent:store_managed_object(id, node)
+  id_to_name_table[id] = properties["node.name"]
+end
+
+function createMonitor()
+  local monitor_props = {}
+  for k, v in pairs(config.properties or {}) do
+    monitor_props[k] = v
+  end
+  monitor_props["server"] = nil
+
+  local monitor = SpaDevice("api.bluez5.midi.enum", monitor_props)
+  if monitor then
+    monitor:connect("create-object", createNode)
+    monitor:connect("object-removed", function (parent, id)
+        node_names_table[id_to_name_table[id]] = nil
+        id_to_name_table[id] = nil
+    end)
+  else
+    Log.message("PipeWire's BlueZ MIDI SPA missing or broken. Bluetooth not supported.")
+    return nil
+  end
+
+  -- reset the name tables to make sure names are recycled
+  node_names_table = {}
+  id_to_name_table = {}
+
+  monitor:activate(Feature.SpaDevice.ENABLED)
+  return monitor
+end
+
+function createServers()
+  local props = config.properties or {}
+
+  if not props["servers"] then
+    return nil
+  end
+
+  local servers = {}
+  local i = 1
+
+  for k, v in pairs(props["servers"]) do
+    local node_props = {
+      ["node.name"] = v,
+      ["node.description"] = string.format(I18n.gettext("BLE MIDI %d"), i),
+      ["api.bluez5.role"] = "server",
+      ["factory.name"] = "api.bluez5.midi.node"
+    }
+    rulesApplyProperties(node_props)
+
+    local node = LocalNode("spa-node-factory", node_props)
+    if node then
+      node:activate(Feature.Proxy.BOUND)
+      table.insert(servers, node)
+    else
+      Log.message("Failed to create BLE MIDI server.")
+    end
+    i = i + 1
+  end
+
+  return servers
+end
+
+logind_plugin = Plugin.find("logind")
+if logind_plugin then
+  -- if logind support is enabled, activate
+  -- the monitor only when the seat is active
+  function startStopMonitor(seat_state)
+    Log.info(logind_plugin, "Seat state changed: " .. seat_state)
+
+    if seat_state == "active" then
+      monitor = createMonitor()
+      servers = createServers()
+    elseif monitor then
+      monitor:deactivate(Feature.SpaDevice.ENABLED)
+      monitor = nil
+      servers = nil
+    end
+  end
+
+  logind_plugin:connect("state-changed", function(p, s) startStopMonitor(s) end)
+  startStopMonitor(logind_plugin:call("get-state"))
+else
+  monitor = createMonitor()
+  servers = createServers()
+end