bluez5: implement Bluetooth MIDI device enumeration

Add monitor for enumerating connected Bluetooth MIDI devices.

spa/include/spa/utils/names.h

@@ -120,6 +120,8 @@ extern "C" {
 #define SPA_NAME_API_BLUEZ5_A2DP_SOURCE	"api.bluez5.a2dp.source"	/**< alias for media.source */
 #define SPA_NAME_API_BLUEZ5_SCO_SINK	"api.bluez5.sco.sink"		/**< a playback Node interface for HSP/HFP profiles */
 #define SPA_NAME_API_BLUEZ5_SCO_SOURCE	"api.bluez5.sco.source"		/**< a capture Node interface for HSP/HFP profiles */
+#define SPA_NAME_API_BLUEZ5_MIDI_ENUM	"api.bluez5.midi.enum"		/**< a dbus midi Device interface */
+#define SPA_NAME_API_BLUEZ5_MIDI_NODE	"api.bluez5.midi.node"		/**< a midi Node interface */
 
 /** keys for codec factory names */
 #define SPA_NAME_API_CODEC_BLUEZ5_MEDIA	"api.codec.bluez5.media"	/**< Bluez5 Media codec plugin */

spa/plugins/bluez5/meson.build

@@ -31,6 +31,7 @@ bluez5_sources = [
   'hci.c',
   'dbus-manager.c',
   'dbus-monitor.c',
+  'midi-enum.c',
 ]
 
 bluez5_data = ['bluez-hardware.conf']

spa/plugins/bluez5/midi-enum.c

@@ -0,0 +1,775 @@
+/* Spa midi dbus
+ *
+ * Copyright © 2022 Pauli Virtanen
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice (including the next
+ * paragraph) shall be included in all copies or substantial portions of the
+ * Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+ * DEALINGS IN THE SOFTWARE.
+ */
+
+#include <errno.h>
+#include <stddef.h>
+
+#include <dbus/dbus.h>
+
+#include <spa/support/log.h>
+#include <spa/support/loop.h>
+#include <spa/support/dbus.h>
+#include <spa/support/plugin.h>
+#include <spa/monitor/device.h>
+#include <spa/monitor/utils.h>
+#include <spa/utils/hook.h>
+#include <spa/utils/type.h>
+#include <spa/utils/keys.h>
+#include <spa/utils/names.h>
+#include <spa/utils/result.h>
+#include <spa/utils/string.h>
+#include <spa/utils/json.h>
+#include <spa/node/node.h>
+#include <spa/node/keys.h>
+
+#include "dbus-monitor.h"
+#include "dbus-manager.h"
+
+#include "midi.h"
+#include "config.h"
+
+#define MIDI_OBJECT_PATH	"/midi"
+#define MIDI_PROFILE_PATH	MIDI_OBJECT_PATH "/profile"
+
+static struct spa_log_topic log_topic = SPA_LOG_TOPIC(0, "spa.bluez5.midi");
+#undef SPA_LOG_TOPIC_DEFAULT
+#define SPA_LOG_TOPIC_DEFAULT &log_topic
+
+struct impl
+{
+	struct spa_handle handle;
+	struct spa_device device;
+
+	struct spa_log *log;
+	struct spa_dbus *dbus;
+	struct spa_dbus_connection *dbus_connection;
+	DBusConnection *conn;
+
+	struct spa_dbus_monitor *dbus_monitor;
+
+	struct spa_dbus_object_manager *object_manager;
+	struct spa_dbus_local_object *profile;
+
+	struct spa_hook_list hooks;
+
+	uint32_t id;
+
+	unsigned int object_manager_registered:1;
+	unsigned int profile_registered:1;
+};
+
+struct adapter
+{
+	struct spa_dbus_object object;
+	DBusPendingCall *register_call;
+	unsigned int registered:1;
+};
+
+struct device
+{
+	struct spa_dbus_object object;
+	char *adapter_path;
+	char *name;
+	char *alias;
+	char *address;
+	char *icon;
+	uint32_t class;
+	uint16_t appearance;
+	unsigned int connected:1;
+	unsigned int services_resolved:1;
+};
+
+struct service
+{
+	struct spa_dbus_object object;
+	char *device_path;
+	unsigned int valid_uuid:1;
+};
+
+struct chr
+{
+	struct spa_dbus_object object;
+	char *service_path;
+	uint32_t id;
+	DBusPendingCall *read_call;
+	unsigned int node_emitted:1;
+	unsigned int valid_uuid:1;
+	unsigned int read_probed:1;
+	unsigned int read_done:1;
+};
+
+static void emit_chr_node(struct impl *impl, struct chr *chr, struct device *device)
+{
+	struct spa_device_object_info info;
+	char class[16];
+	struct spa_dict_item items[23];
+	uint32_t n_items = 0;
+
+	spa_log_debug(impl->log, "emit node for path=%s", chr->object.path);
+
+	info = SPA_DEVICE_OBJECT_INFO_INIT();
+	info.type = SPA_TYPE_INTERFACE_Node;
+	info.factory_name = SPA_NAME_API_BLUEZ5_MIDI_NODE;
+	info.change_mask = SPA_DEVICE_OBJECT_CHANGE_MASK_FLAGS |
+		SPA_DEVICE_OBJECT_CHANGE_MASK_PROPS;
+	info.flags = 0;
+
+	items[n_items++] = SPA_DICT_ITEM_INIT(SPA_KEY_DEVICE_API, "bluez5");
+	items[n_items++] = SPA_DICT_ITEM_INIT(SPA_KEY_DEVICE_BUS, "bluetooth");
+	items[n_items++] = SPA_DICT_ITEM_INIT(SPA_KEY_MEDIA_CLASS, "Midi/Bridge");
+	items[n_items++] = SPA_DICT_ITEM_INIT("node.description",
+			device->alias ? device->alias : device->name);
+	items[n_items++] = SPA_DICT_ITEM_INIT(SPA_KEY_API_BLUEZ5_ICON, device->icon);
+	items[n_items++] = SPA_DICT_ITEM_INIT(SPA_KEY_API_BLUEZ5_PATH, chr->object.path);
+	items[n_items++] = SPA_DICT_ITEM_INIT(SPA_KEY_API_BLUEZ5_ADDRESS, device->address);
+	snprintf(class, sizeof(class), "0x%06x", device->class);
+	items[n_items++] = SPA_DICT_ITEM_INIT(SPA_KEY_API_BLUEZ5_CLASS, class);
+
+	info.props = &SPA_DICT_INIT(items, n_items);
+	spa_device_emit_object_info(&impl->hooks, chr->id, &info);
+}
+
+static void remove_chr_node(struct impl *impl, struct chr *chr)
+{
+	spa_log_debug(impl->log, "remove node for path=%s", chr->object.path);
+
+	spa_device_emit_object_info(&impl->hooks, chr->id, NULL);
+}
+
+static void check_chr_node(struct impl *impl, struct chr *chr);
+
+static void read_probe_reply(DBusPendingCall **call_ptr, DBusMessage *r)
+{
+	struct chr *chr = SPA_CONTAINER_OF(call_ptr, struct chr, read_call);
+	struct impl *impl = chr->object.user_data;
+
+	if (dbus_message_get_type(r) == DBUS_MESSAGE_TYPE_ERROR) {
+		spa_log_error(impl->log, "%s.ReadValue() failed: %s",
+				BLUEZ_GATT_CHR_INTERFACE,
+				dbus_message_get_error_name(r));
+		return;
+	}
+
+	spa_log_debug(impl->log, "MIDI GATT read probe done for path=%s", chr->object.path);
+
+	chr->read_done = true;
+
+	check_chr_node(impl, chr);
+}
+
+static int read_probe(struct impl *impl, struct chr *chr)
+{
+	DBusMessageIter i, d;
+	DBusMessage *m;
+
+	/*
+	 * BLE MIDI-1.0 §5: The Central shall read the MIDI I/O characteristic
+	 * of the Peripheral after establishing a connection with the accessory.
+	 */
+
+	if (chr->read_probed)
+		return 0;
+	if (chr->read_call)
+		return -EBUSY;
+
+	chr->read_probed = true;
+
+	spa_log_debug(impl->log, "MIDI GATT read probe for path=%s",
+			chr->object.path);
+
+	m = dbus_message_new_method_call(BLUEZ_SERVICE,
+			chr->object.path,
+			BLUEZ_GATT_CHR_INTERFACE,
+			"ReadValue");
+	if (m == NULL)
+		return -ENOMEM;
+
+	dbus_message_iter_init_append(m, &i);
+	dbus_message_iter_open_container(&i, DBUS_TYPE_ARRAY, "{sv}", &d);
+	dbus_message_iter_close_container(&i, &d);
+
+	return spa_dbus_async_call(impl->conn, m, &chr->read_call,
+			read_probe_reply);
+}
+
+static int read_probe_reset(struct impl *impl, struct chr *chr)
+{
+	spa_dbus_async_call_cancel(&chr->read_call);
+	chr->read_probed = false;
+	chr->read_done = false;
+	return 0;
+}
+
+static void lookup_chr_node(struct impl *impl, struct chr *chr, struct service **service, struct device **device)
+{
+	*service = (struct service *)spa_dbus_monitor_find(impl->dbus_monitor,
+			chr->service_path, BLUEZ_GATT_SERVICE_INTERFACE);
+	if (*service)
+		*device = (struct device *)spa_dbus_monitor_find(impl->dbus_monitor,
+				(*service)->device_path, BLUEZ_DEVICE_INTERFACE);
+	else
+		*device = NULL;
+}
+
+static void check_chr_node(struct impl *impl, struct chr *chr)
+{
+	struct service *service;
+	struct device *device;
+	bool available;
+
+	lookup_chr_node(impl, chr, &service, &device);
+
+	if (!device || !device->connected) {
+		/* Retry read probe on each connection */
+		read_probe_reset(impl, chr);
+	}
+
+	available = service && device && device->connected &&
+		device->services_resolved && service->valid_uuid &&
+		chr->valid_uuid;
+
+	if (available && !chr->read_done) {
+		read_probe(impl, chr);
+		available = false;
+	}
+
+	if (chr->node_emitted && !available) {
+		remove_chr_node(impl, chr);
+		chr->node_emitted = false;
+	} else if (!chr->node_emitted && available) {
+		emit_chr_node(impl, chr, device);
+		chr->node_emitted = true;
+	}
+}
+
+static void check_all_nodes(struct impl *impl)
+{
+	/*
+	 * Check if the nodes we have emitted are in sync with connected devices.
+	 */
+
+	struct spa_list *chrs = spa_dbus_monitor_object_list(
+		impl->dbus_monitor, BLUEZ_GATT_CHR_INTERFACE);
+	struct chr *chr;
+
+	spa_assert(chrs);
+
+	spa_list_for_each(chr, chrs, object.link)
+		check_chr_node(impl, chr);
+}
+
+static void adapter_register_application_reply(DBusPendingCall **call_ptr, DBusMessage *r)
+{
+	struct adapter *adapter = SPA_CONTAINER_OF(call_ptr, struct adapter, register_call);
+	struct impl *impl = adapter->object.user_data;
+
+	if (dbus_message_get_type(r) == DBUS_MESSAGE_TYPE_ERROR) {
+		spa_log_error(impl->log, "%s.RegisterApplication() failed: %s",
+				BLUEZ_GATT_MANAGER_INTERFACE,
+				dbus_message_get_error_name(r));
+		return;
+	}
+
+	adapter->registered = true;
+}
+
+static int adapter_register_application(struct adapter *adapter)
+{
+	struct impl *impl = adapter->object.user_data;
+	DBusMessageIter i, d;
+	DBusMessage *m;
+
+	m = dbus_message_new_method_call(BLUEZ_SERVICE,
+			adapter->object.path,
+			BLUEZ_GATT_MANAGER_INTERFACE,
+			"RegisterApplication");
+	if (m == NULL)
+		return -ENOMEM;
+
+	dbus_message_iter_init_append(m, &i);
+	dbus_message_iter_append_basic(&i, DBUS_TYPE_OBJECT_PATH, &impl->object_manager->path);
+	dbus_message_iter_open_container(&i, DBUS_TYPE_ARRAY, "{sv}", &d);
+	dbus_message_iter_close_container(&i, &d);
+
+	return spa_dbus_async_call(impl->conn, m, &adapter->register_call,
+			adapter_register_application_reply);
+}
+
+/*
+ * DBus monitoring
+ */
+
+static const char *get_dbus_string(DBusMessageIter *value)
+{
+	const char *v = NULL;
+	int type = dbus_message_iter_get_arg_type(value);
+	if (value && (type == DBUS_TYPE_STRING || type == DBUS_TYPE_OBJECT_PATH))
+		dbus_message_iter_get_basic(value, &v);
+	return v;
+}
+
+static void dup_dbus_string(DBusMessageIter *value, char **v)
+{
+	const char *str = get_dbus_string(value);
+	free(*v);
+	*v = str ? strdup(str) : NULL;
+}
+
+static bool get_dbus_bool(DBusMessageIter *value)
+{
+	dbus_bool_t v = FALSE;
+	if (value && dbus_message_iter_get_arg_type(value) == DBUS_TYPE_BOOLEAN)
+		dbus_message_iter_get_basic(value, &v);
+	return v ? true : false;
+}
+
+static uint32_t get_dbus_uint32(DBusMessageIter *value)
+{
+	uint32_t v = 0;
+	if (value && dbus_message_iter_get_arg_type(value) == DBUS_TYPE_UINT32)
+		dbus_message_iter_get_basic(value, &v);
+	return v;
+}
+
+static uint16_t get_dbus_uint16(DBusMessageIter *value)
+{
+	uint16_t v = 0;
+	if (value && dbus_message_iter_get_arg_type(value) == DBUS_TYPE_UINT16)
+		dbus_message_iter_get_basic(value, &v);
+	return v;
+}
+
+static void adapter_update(struct spa_dbus_object *object)
+{
+	struct adapter *adapter = SPA_CONTAINER_OF(object, struct adapter, object);
+
+	if (adapter->registered || adapter->register_call)
+		return;
+
+	adapter_register_application(adapter);
+}
+
+static void adapter_remove(struct spa_dbus_object *object)
+{
+	struct adapter *adapter = SPA_CONTAINER_OF(object, struct adapter, object);
+
+	spa_dbus_async_call_cancel(&adapter->register_call);
+}
+
+static void device_update(struct spa_dbus_object *object)
+{
+	struct impl *impl = object->user_data;
+
+	check_all_nodes(impl);
+}
+
+static void device_remove(struct spa_dbus_object *object)
+{
+	struct device *device = SPA_CONTAINER_OF(object, struct device, object);
+
+	free(device->adapter_path);
+	free(device->name);
+	free(device->alias);
+	free(device->address);
+	free(device->icon);
+}
+
+static void device_property(struct spa_dbus_object *object, const char *key, DBusMessageIter *value)
+{
+	struct device *device = SPA_CONTAINER_OF(object, struct device, object);
+
+	if (spa_streq(key, "Adapter"))
+		dup_dbus_string(value, &device->adapter_path);
+	else if (spa_streq(key, "Connected"))
+		device->connected = get_dbus_bool(value);
+	else if (spa_streq(key, "ServicesResolved"))
+		device->services_resolved = get_dbus_bool(value);
+	else if (spa_streq(key, "Name"))
+		dup_dbus_string(value, &device->name);
+	else if (spa_streq(key, "Alias"))
+		dup_dbus_string(value, &device->alias);
+	else if (spa_streq(key, "Address"))
+		dup_dbus_string(value, &device->address);
+	else if (spa_streq(key, "Icon"))
+		dup_dbus_string(value, &device->icon);
+	else if (spa_streq(key, "Class"))
+		device->class = get_dbus_uint32(value);
+	else if (spa_streq(key, "Appearance"))
+		device->appearance = get_dbus_uint16(value);
+}
+
+static void service_update(struct spa_dbus_object *object)
+{
+	struct service *service = SPA_CONTAINER_OF(object, struct service, object);
+	struct impl *impl = object->user_data;
+
+	if (!service->valid_uuid) {
+		spa_dbus_monitor_ignore_object(impl->dbus_monitor, object);
+		return;
+	}
+
+	check_all_nodes(impl);
+}
+
+static void service_remove(struct spa_dbus_object *object)
+{
+	struct service *service = SPA_CONTAINER_OF(object, struct service, object);
+
+	free(service->device_path);
+}
+
+static void service_property(struct spa_dbus_object *object, const char *key, DBusMessageIter *value)
+{
+	struct service *service = SPA_CONTAINER_OF(object, struct service, object);
+
+	if (spa_streq(key, "UUID"))
+		service->valid_uuid = spa_streq(get_dbus_string(value), BT_MIDI_SERVICE_UUID);
+	else if (spa_streq(key, "Device"))
+		dup_dbus_string(value, &service->device_path);
+}
+
+static void chr_update(struct spa_dbus_object *object)
+{
+	struct impl *impl = object->user_data;
+	struct chr *chr = SPA_CONTAINER_OF(object, struct chr, object);
+
+	if (!chr->valid_uuid) {
+		spa_dbus_monitor_ignore_object(impl->dbus_monitor, object);
+		return;
+	}
+
+	if (chr->id == 0)
+		chr->id = ++impl->id;
+
+	check_chr_node(impl, chr);
+}
+
+static void chr_remove(struct spa_dbus_object *object)
+{
+	struct impl *impl = object->user_data;
+	struct chr *chr = SPA_CONTAINER_OF(object, struct chr, object);
+
+	read_probe_reset(impl, chr);
+
+	if (chr->node_emitted)
+		remove_chr_node(impl, chr);
+
+	free(chr->service_path);
+}
+
+static void chr_property(struct spa_dbus_object *object, const char *key, DBusMessageIter *value)
+{
+	struct chr *chr = SPA_CONTAINER_OF(object, struct chr, object);
+
+	if (spa_streq(key, "UUID"))
+		chr->valid_uuid = spa_streq(get_dbus_string(value), BT_MIDI_CHR_UUID);
+	else if (spa_streq(key, "Service"))
+		dup_dbus_string(value, &chr->service_path);
+}
+
+static const struct spa_dbus_interface monitor_interfaces[] = {
+	{
+		.name = BLUEZ_ADAPTER_INTERFACE,
+		.update = adapter_update,
+		.remove = adapter_remove,
+		.object_size = sizeof(struct adapter),
+	},
+	{
+		.name = BLUEZ_DEVICE_INTERFACE,
+		.update = device_update,
+		.remove = device_remove,
+		.property = device_property,
+		.object_size = sizeof(struct device),
+	},
+	{
+		.name = BLUEZ_GATT_SERVICE_INTERFACE,
+		.update = service_update,
+		.remove = service_remove,
+		.property = service_property,
+		.object_size = sizeof(struct service),
+	},
+	{
+		.name = BLUEZ_GATT_CHR_INTERFACE,
+		.update = chr_update,
+		.remove = chr_remove,
+		.property = chr_property,
+		.object_size = sizeof(struct chr),
+	},
+	{NULL}
+};
+
+/*
+ * DBus GATT profile, to enable BlueZ autoconnect
+ */
+
+static DBusMessage *profile_release(struct spa_dbus_local_object *object, DBusMessage *m)
+{
+	/* noop */
+	return dbus_message_new_method_return(m);
+}
+
+static int profile_uuids_get(struct spa_dbus_local_object *object, DBusMessageIter *value)
+{
+	DBusMessageIter a;
+	const char *uuid = BT_MIDI_SERVICE_UUID;
+
+	dbus_message_iter_open_container(value, DBUS_TYPE_ARRAY, "s", &a);
+	dbus_message_iter_append_basic(&a, DBUS_TYPE_STRING, &uuid);
+	dbus_message_iter_close_container(value, &a);
+
+	return 0;
+}
+
+static const struct spa_dbus_local_interface profile_interfaces[] = {
+	{
+		.name = BLUEZ_GATT_PROFILE_INTERFACE,
+		.methods = (struct spa_dbus_method[]) {
+			{
+				.name = "Release",
+				.call = profile_release,
+			},
+			{NULL}
+		},
+		.properties = (struct spa_dbus_property[]) {
+			{
+				.name = "UUIDs",
+				.signature = "as",
+				.get = profile_uuids_get,
+			},
+			{NULL},
+		},
+	},
+	{NULL}
+};
+
+/*
+ * Monitor impl
+ */
+
+static int impl_device_add_listener(void *object, struct spa_hook *listener,
+		const struct spa_device_events *events, void *data)
+{
+	struct impl *this = object;
+	struct spa_hook_list save;
+	struct spa_list *chrs;
+	struct chr *chr;
+
+	spa_return_val_if_fail(this != NULL, -EINVAL);
+	spa_return_val_if_fail(events != NULL, -EINVAL);
+
+	chrs = spa_dbus_monitor_object_list(
+		this->dbus_monitor, BLUEZ_GATT_CHR_INTERFACE);
+
+	spa_hook_list_isolate(&this->hooks, &save, listener, events, data);
+
+	spa_list_for_each(chr, chrs, object.link) {
+		struct service *service;
+		struct device *device;
+
+		if (!chr->node_emitted)
+			continue;
+
+		lookup_chr_node(this, chr, &service, &device);
+		if (device)
+			emit_chr_node(this, chr, device);
+	}
+
+	spa_hook_list_join(&this->hooks, &save);
+
+	return 0;
+}
+
+static const struct spa_device_methods impl_device = {
+	SPA_VERSION_DEVICE_METHODS,
+	.add_listener = impl_device_add_listener,
+};
+
+static int impl_get_interface(struct spa_handle *handle, const char *type, void **interface)
+{
+	struct impl *this;
+
+	spa_return_val_if_fail(handle != NULL, -EINVAL);
+	spa_return_val_if_fail(interface != NULL, -EINVAL);
+
+	this = (struct impl *) handle;
+
+	if (spa_streq(type, SPA_TYPE_INTERFACE_Device))
+		*interface = &this->device;
+	else
+		return -ENOENT;
+
+	return 0;
+}
+
+static int impl_clear(struct spa_handle *handle)
+{
+	struct impl *this;
+
+	this = (struct impl *) handle;
+
+	if (this->object_manager)
+		spa_dbus_object_manager_destroy(this->object_manager);
+	if (this->dbus_monitor)
+		spa_dbus_monitor_destroy(this->dbus_monitor);
+	if (this->conn)
+		dbus_connection_unref(this->conn);
+	if (this->dbus_connection)
+		spa_dbus_connection_destroy(this->dbus_connection);
+
+	spa_zero(*this);
+
+	return 0;
+}
+
+static size_t
+impl_get_size(const struct spa_handle_factory *factory,
+		const struct spa_dict *params)
+{
+	return sizeof(struct impl);
+}
+
+static int
+impl_init(const struct spa_handle_factory *factory,
+		struct spa_handle *handle,
+		const struct spa_dict *info,
+		const struct spa_support *support,
+		uint32_t n_support)
+{
+	struct impl *this;
+	int res = 0;
+
+	spa_return_val_if_fail(factory != NULL, -EINVAL);
+	spa_return_val_if_fail(handle != NULL, -EINVAL);
+
+	handle->get_interface = impl_get_interface;
+	handle->clear = impl_clear;
+
+	this = (struct impl *) handle;
+
+	this->log = spa_support_find(support, n_support, SPA_TYPE_INTERFACE_Log);
+	this->dbus = spa_support_find(support, n_support, SPA_TYPE_INTERFACE_DBus);
+
+	if (this->log == NULL)
+		return -EINVAL;
+
+	spa_log_topic_init(this->log, &log_topic);
+
+	if (this->dbus == NULL) {
+		spa_log_error(this->log, "a dbus is needed");
+		return -EINVAL;
+	}
+
+	this->conn = NULL;
+	this->dbus_connection = NULL;
+
+	this->dbus_connection = spa_dbus_get_connection(this->dbus, SPA_DBUS_TYPE_SYSTEM);
+	if (this->dbus_connection == NULL) {
+		spa_log_error(this->log, "no dbus connection");
+		res = -EIO;
+		goto fail;
+	}
+
+	this->conn = spa_dbus_connection_get(this->dbus_connection);
+	if (this->conn == NULL) {
+		spa_log_error(this->log, "failed to get dbus connection");
+		res = -EIO;
+		goto fail;
+	}
+
+	/*
+	 * XXX: We should handle spa_dbus reconnecting, but we don't, so ref
+	 * XXX: the handle so that we can keep it if spa_dbus unrefs it.
+	 */
+	dbus_connection_ref(this->conn);
+
+	spa_hook_list_init(&this->hooks);
+
+	this->device.iface = SPA_INTERFACE_INIT(
+		SPA_TYPE_INTERFACE_Device,
+				SPA_VERSION_DEVICE,
+				&impl_device, this);
+
+	this->dbus_monitor = spa_dbus_monitor_new(this->conn,
+			BLUEZ_SERVICE, "/", monitor_interfaces,
+			this->log, this);
+	if (!this->dbus_monitor)
+		goto fail;
+
+	this->object_manager = spa_dbus_object_manager_new(this->conn,
+			MIDI_OBJECT_PATH, this->log);
+	if (!this->object_manager)
+		goto fail;
+
+	this->profile = spa_dbus_object_manager_register(this->object_manager,
+			MIDI_PROFILE_PATH,
+			profile_interfaces,
+			sizeof(struct spa_dbus_local_object),
+			this);
+	if (!this->profile)
+		goto fail;
+
+	return 0;
+
+fail:
+	res = (res < 0) ? res : ((errno > 0) ? -errno : -EIO);
+	impl_clear(handle);
+	return res;
+}
+
+static const struct spa_interface_info impl_interfaces[] = {
+	{SPA_TYPE_INTERFACE_Device,},
+};
+
+static int
+impl_enum_interface_info(const struct spa_handle_factory *factory,
+		const struct spa_interface_info **info,
+		uint32_t *index)
+{
+	spa_return_val_if_fail(factory != NULL, -EINVAL);
+	spa_return_val_if_fail(info != NULL, -EINVAL);
+	spa_return_val_if_fail(index != NULL, -EINVAL);
+
+	if (*index >= SPA_N_ELEMENTS(impl_interfaces))
+		return 0;
+
+	*info = &impl_interfaces[(*index)++];
+
+	return 1;
+}
+
+static const struct spa_dict_item info_items[] = {
+	{ SPA_KEY_FACTORY_AUTHOR, "Pauli Virtanen <pav@iki.fi>" },
+	{ SPA_KEY_FACTORY_DESCRIPTION, "Bluez5 MIDI connection" },
+};
+
+static const struct spa_dict info = SPA_DICT_INIT_ARRAY(info_items);
+
+const struct spa_handle_factory spa_bluez5_midi_enum_factory = {
+	SPA_VERSION_HANDLE_FACTORY,
+	SPA_NAME_API_BLUEZ5_MIDI_ENUM,
+	&info,
+	impl_get_size,
+	impl_init,
+	impl_enum_interface_info,
+};

spa/plugins/bluez5/midi.h

@@ -0,0 +1,45 @@
+/* Spa V4l2 dbus
+ *
+ * Copyright © 2022 Pauli Virtanen
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice (including the next
+ * paragraph) shall be included in all copies or substantial portions of the
+ * Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+ * DEALINGS IN THE SOFTWARE.
+ */
+#ifndef SPA_BT_MIDI_H_
+#define SPA_BT_MIDI_H_
+
+#include <stddef.h>
+#include <stdint.h>
+#include <stdbool.h>
+
+#include <spa/utils/defs.h>
+#include <spa/support/log.h>
+
+#define BLUEZ_SERVICE			"org.bluez"
+#define BLUEZ_ADAPTER_INTERFACE		BLUEZ_SERVICE ".Adapter1"
+#define BLUEZ_DEVICE_INTERFACE		BLUEZ_SERVICE ".Device1"
+#define BLUEZ_GATT_MANAGER_INTERFACE	BLUEZ_SERVICE ".GattManager1"
+#define BLUEZ_GATT_PROFILE_INTERFACE	BLUEZ_SERVICE ".GattProfile1"
+#define BLUEZ_GATT_SERVICE_INTERFACE	BLUEZ_SERVICE ".GattService1"
+#define BLUEZ_GATT_CHR_INTERFACE	BLUEZ_SERVICE ".GattCharacteristic1"
+
+#define BT_MIDI_SERVICE_UUID		"03b80e5a-ede8-4b33-a751-6ce34ec4c700"
+#define BT_MIDI_CHR_UUID		"7772e5db-3868-4112-a1a9-f2669d106bf3"
+
+#endif

spa/plugins/bluez5/plugin.c

@@ -35,6 +35,7 @@ extern const struct spa_handle_factory spa_sco_sink_factory;
 extern const struct spa_handle_factory spa_sco_source_factory;
 extern const struct spa_handle_factory spa_a2dp_sink_factory;
 extern const struct spa_handle_factory spa_a2dp_source_factory;
+extern const struct spa_handle_factory spa_bluez5_midi_enum_factory;
 
 SPA_EXPORT
 int spa_handle_factory_enum(const struct spa_handle_factory **factory, uint32_t *index)
@@ -67,6 +68,9 @@ int spa_handle_factory_enum(const struct spa_handle_factory **factory, uint32_t
 	case 7:
 		*factory = &spa_a2dp_source_factory;
 		break;
+	case 8:
+		*factory = &spa_bluez5_midi_enum_factory;
+		break;
 	default:
 		return 0;
 	}