Expose BLE-MIDI server as a local ALSA sequencer

NEWS

@@ -1,6 +1,7 @@
 unreleased
 ==========
 
+- optional support for BLE MIDI 1.0 profile as a GATT server
 - command line option to set real-time priority for IO threads
 - allow to select individual extended controls in ALSA plug-in
 - codec-specific delay adjustment with ALSA control and persistency

src/Makefile.am

@@ -85,7 +85,9 @@ endif
 
 if ENABLE_MIDI
 bluealsa_SOURCES += \
-	bluez-midi.c
+	ble-midi.c \
+	bluez-midi.c \
+	midi.c
 endif
 
 if ENABLE_MPEG
@@ -111,6 +113,7 @@ endif
 
 AM_CFLAGS = \
 	@AAC_CFLAGS@ \
+	@ALSA_CFLAGS@ \
 	@APTX_CFLAGS@ \
 	@APTX_HD_CFLAGS@ \
 	@BLUEZ_CFLAGS@ \
@@ -127,6 +130,7 @@ AM_CFLAGS = \
 
 LDADD = \
 	@AAC_LIBS@ \
+	@ALSA_LIBS@ \
 	@APTX_HD_LIBS@ \
 	@APTX_LIBS@ \
 	@BLUEZ_LIBS@ \

src/ba-transport.c

@@ -42,6 +42,7 @@
 #include "bluez.h"
 #include "hci.h"
 #include "hfp.h"
+#include "midi.h"
 #include "sco.h"
 #include "storage.h"
 #include "shared/a2dp-codecs.h"
@@ -860,12 +861,13 @@ struct ba_transport *ba_transport_new_sco(
 #if ENABLE_MIDI
 
 static int transport_acquire_bt_midi(struct ba_transport *t) {
-	(void)t;
-	return 0;
+	return midi_transport_alsa_seq_create(t);
 }
 
 static int transport_release_bt_midi(struct ba_transport *t) {
 
+	midi_transport_alsa_seq_delete(t);
+
 	if (t->midi.ble_fd_write != -1) {
 		debug("Releasing BLE-MIDI write link: %d", t->midi.ble_fd_write);
 		close(t->midi.ble_fd_write);
@@ -893,10 +895,28 @@ struct ba_transport *ba_transport_new_midi(
 
 	t->profile = profile;
 
+	t->midi.seq_port = -1;
+	t->midi.ble_fd_write = -1;
+	t->midi.ble_fd_notify = -1;
+
+	int err;
+	if ((err = snd_midi_event_new(1024, &t->midi.seq_parser)) < 0) {
+		error("Couldn't create MIDI event decoder: %s", snd_strerror(err));
+		goto fail;
+	}
+
+	/* Disable MIDI running status generated by the decoder. */
+	snd_midi_event_no_status(t->midi.seq_parser, 1);
+
 	t->acquire = transport_acquire_bt_midi;
 	t->release = transport_release_bt_midi;
 
 	return t;
+
+fail:
+	ba_transport_unref(t);
+	errno = -err;
+	return NULL;
 }
 
 #endif
@@ -1124,6 +1144,12 @@ void ba_transport_unref(struct ba_transport *t) {
 		free(t->sco.ofono_dbus_path_modem);
 #endif
 	}
+#if ENABLE_MIDI
+	else if (t->profile & BA_TRANSPORT_PROFILE_MIDI) {
+		if (t->midi.seq_parser != NULL)
+			snd_midi_event_free(t->midi.seq_parser);
+	}
+#endif
 
 #if DEBUG
 	/* If IO threads are not terminated yet, we can not go any further.
@@ -1316,6 +1342,11 @@ void ba_transport_set_codec(
  *   errno is set to indicate the error. */
 int ba_transport_start(struct ba_transport *t) {
 
+#if ENABLE_MIDI
+	if (t->profile & BA_TRANSPORT_PROFILE_MIDI)
+		return midi_transport_start(t);
+#endif
+
 	/* For A2DP Source profile only, it is possible that BlueZ will
 	 * activate the transport following a D-Bus "Acquire" request before the
 	 * client thread has completed the acquisition procedure by initializing
@@ -1353,6 +1384,12 @@ int ba_transport_start(struct ba_transport *t) {
  * to call it from IO thread itself - it will cause deadlock! */
 int ba_transport_stop(struct ba_transport *t) {
 
+#if ENABLE_MIDI
+	if (t->profile & BA_TRANSPORT_PROFILE_MIDI)
+		// FIXME: Skip thread termination for MIDI profile.
+		midi_transport_stop(t);
+#endif
+
 	if (ba_transport_thread_state_check_terminated(&t->thread_enc) &&
 			ba_transport_thread_state_check_terminated(&t->thread_dec))
 		return 0;

src/ba-transport.h

@@ -22,9 +22,12 @@
 #include <stdint.h>
 #include <time.h>
 
+#include <alsa/asoundlib.h>
+
 #include "a2dp.h"
 #include "ba-device.h"
 #include "ba-transport-pcm.h"
+#include "ble-midi.h"
 #include "bluez.h"
 #include "shared/a2dp-codecs.h"
 
@@ -264,11 +267,29 @@ struct ba_transport {
 #if ENABLE_MIDI
 		struct {
 
+			/* ALSA sequencer. */
+			snd_seq_t *seq;
+			/* Associated sequencer port. */
+			int seq_port;
+
+			/* ALSA MIDI event parser. */
+			snd_midi_event_t *seq_parser;
+
 			/* BLE-MIDI input link */
 			int ble_fd_write;
 			/* BLE-MIDI output (notification) link */
 			int ble_fd_notify;
 
+			/* BLE-MIDI parser for the incoming data. */
+			struct ble_midi_dec ble_decoder;
+			/* BLE-MIDI parser for the outgoing data. */
+			struct ble_midi_enc ble_encoder;
+
+			/* Watch ID associated with the BLE-MIDI link. */
+			unsigned int watch_id_ble;
+			/* Watch ID associated with ALSA sequencer. */
+			unsigned int watch_id_seq;
+
 		} midi;
 #endif
 

src/bluez-midi.c

@@ -38,6 +38,7 @@
 #include "bluealsa-config.h"
 #include "bluez-iface.h"
 #include "dbus.h"
+#include "midi.h"
 #include "shared/bluetooth.h"
 #include "shared/defs.h"
 #include "shared/log.h"
@@ -208,6 +209,8 @@ static void bluez_midi_characteristic_acquire_write(
 
 	/* TODO: Find a way to detect "device" disconnection condition. */
 
+	midi_transport_start_watch_ble_midi(t);
+
 	GUnixFDList *fd_list = g_unix_fd_list_new_from_array(&fds[1], 1);
 	g_dbus_method_invocation_return_value_with_unix_fd_list(inv,
 			g_variant_new("(hq)", 0, mtu), fd_list);
@@ -262,6 +265,7 @@ static void bluez_midi_characteristic_acquire_notify(
 	debug("New BLE-MIDI notify link (MTU: %u): %d", mtu, fds[0]);
 	app->notify_acquired = true;
 	t->midi.ble_fd_notify = fds[0];
+	ble_midi_encode_set_mtu(&t->midi.ble_encoder, mtu);
 	t->mtu_write = mtu;
 
 	/* Setup IO watch for checking HUP condition on the socket. HUP means
@@ -377,6 +381,8 @@ GDBusObjectManagerServer *bluez_midi_app_new(
 		error("Couldn't create local MIDI transport: %s", strerror(errno));
 	else if (ba_transport_acquire(t) == -1)
 		error("Couldn't acquire local MIDI transport: %s", strerror(errno));
+	else if (ba_transport_start(t) == -1)
+		error("Couldn't start local MIDI transport: %s", strerror(errno));
 	app->t = t;
 
 	GDBusObjectManagerServer *manager = g_dbus_object_manager_server_new(path);