ALSA: firewire-digi00x: delayed registration of sound card

When some digi00x units are connected sequentially, userspace
applications are involved at bus-reset state on IEEE 1394 bus. In the
state, any communications can be canceled. Therefore, sound card
registration should be delayed till the bus gets calm.

This commit achieves it.

Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

sound/firewire/digi00x/digi00x-transaction.c

@@ -126,12 +126,17 @@ int snd_dg00x_transaction_register(struct snd_dg00x *dg00x)
 	return err;
 error:
 	fw_core_remove_address_handler(&dg00x->async_handler);
-	dg00x->async_handler.address_callback = NULL;
+	dg00x->async_handler.callback_data = NULL;
 	return err;
 }
 
 void snd_dg00x_transaction_unregister(struct snd_dg00x *dg00x)
 {
+	if (dg00x->async_handler.callback_data == NULL)
+		return;
+
 	snd_fw_async_midi_port_destroy(&dg00x->out_control);
 	fw_core_remove_address_handler(&dg00x->async_handler);
+
+	dg00x->async_handler.callback_data = NULL;
 }

sound/firewire/digi00x/digi00x.c

@@ -40,10 +40,8 @@ static int name_card(struct snd_dg00x *dg00x)
 	return 0;
 }
 
-static void dg00x_card_free(struct snd_card *card)
+static void dg00x_free(struct snd_dg00x *dg00x)
 {
-	struct snd_dg00x *dg00x = card->private_data;
-
 	snd_dg00x_stream_destroy_duplex(dg00x);
 	snd_dg00x_transaction_unregister(dg00x);
 
@@ -52,28 +50,24 @@ static void dg00x_card_free(struct snd_card *card)
 	mutex_destroy(&dg00x->mutex);
 }
 
-static int snd_dg00x_probe(struct fw_unit *unit,
-			   const struct ieee1394_device_id *entry)
+static void dg00x_card_free(struct snd_card *card)
 {
-	struct snd_card *card;
-	struct snd_dg00x *dg00x;
+	dg00x_free(card->private_data);
+}
+
+static void do_registration(struct work_struct *work)
+{
+	struct snd_dg00x *dg00x =
+			container_of(work, struct snd_dg00x, dwork.work);
 	int err;
 
-	/* create card */
-	err = snd_card_new(&unit->device, -1, NULL, THIS_MODULE,
-			   sizeof(struct snd_dg00x), &card);
+	if (dg00x->registered)
+		return;
+
+	err = snd_card_new(&dg00x->unit->device, -1, NULL, THIS_MODULE, 0,
+			   &dg00x->card);
 	if (err < 0)
-		return err;
-	card->private_free = dg00x_card_free;
-
-	/* initialize myself */
-	dg00x = card->private_data;
-	dg00x->card = card;
-	dg00x->unit = fw_unit_get(unit);
-
-	mutex_init(&dg00x->mutex);
-	spin_lock_init(&dg00x->lock);
-	init_waitqueue_head(&dg00x->hwdep_wait);
+		return;
 
 	err = name_card(dg00x);
 	if (err < 0)
@@ -101,35 +95,86 @@ static int snd_dg00x_probe(struct fw_unit *unit,
 	if (err < 0)
 		goto error;
 
-	err = snd_card_register(card);
+	err = snd_card_register(dg00x->card);
 	if (err < 0)
 		goto error;
 
+	dg00x->card->private_free = dg00x_card_free;
+	dg00x->card->private_data = dg00x;
+	dg00x->registered = true;
+
+	return;
+error:
+	snd_dg00x_transaction_unregister(dg00x);
+	snd_dg00x_stream_destroy_duplex(dg00x);
+	snd_card_free(dg00x->card);
+	dev_info(&dg00x->unit->device,
+		 "Sound card registration failed: %d\n", err);
+}
+
+static int snd_dg00x_probe(struct fw_unit *unit,
+			   const struct ieee1394_device_id *entry)
+{
+	struct snd_dg00x *dg00x;
+
+	/* Allocate this independent of sound card instance. */
+	dg00x = kzalloc(sizeof(struct snd_dg00x), GFP_KERNEL);
+	if (dg00x == NULL)
+		return -ENOMEM;
+
+	dg00x->unit = fw_unit_get(unit);
 	dev_set_drvdata(&unit->device, dg00x);
 
-	return err;
-error:
-	snd_card_free(card);
-	return err;
+	mutex_init(&dg00x->mutex);
+	spin_lock_init(&dg00x->lock);
+	init_waitqueue_head(&dg00x->hwdep_wait);
+
+	/* Allocate and register this sound card later. */
+	INIT_DEFERRABLE_WORK(&dg00x->dwork, do_registration);
+	snd_fw_schedule_registration(unit, &dg00x->dwork);
+
+	return 0;
 }
 
 static void snd_dg00x_update(struct fw_unit *unit)
 {
 	struct snd_dg00x *dg00x = dev_get_drvdata(&unit->device);
 
+	/* Postpone a workqueue for deferred registration. */
+	if (!dg00x->registered)
+		snd_fw_schedule_registration(unit, &dg00x->dwork);
+
 	snd_dg00x_transaction_reregister(dg00x);
 
-	mutex_lock(&dg00x->mutex);
-	snd_dg00x_stream_update_duplex(dg00x);
-	mutex_unlock(&dg00x->mutex);
+	/*
+	 * After registration, userspace can start packet streaming, then this
+	 * code block works fine.
+	 */
+	if (dg00x->registered) {
+		mutex_lock(&dg00x->mutex);
+		snd_dg00x_stream_update_duplex(dg00x);
+		mutex_unlock(&dg00x->mutex);
+	}
 }
 
 static void snd_dg00x_remove(struct fw_unit *unit)
 {
 	struct snd_dg00x *dg00x = dev_get_drvdata(&unit->device);
 
-	/* No need to wait for releasing card object in this context. */
-	snd_card_free_when_closed(dg00x->card);
+	/*
+	 * Confirm to stop the work for registration before the sound card is
+	 * going to be released. The work is not scheduled again because bus
+	 * reset handler is not called anymore.
+	 */
+	cancel_delayed_work_sync(&dg00x->dwork);
+
+	if (dg00x->registered) {
+		/* No need to wait for releasing card object in this context. */
+		snd_card_free_when_closed(dg00x->card);
+	} else {
+		/* Don't forget this case. */
+		dg00x_free(dg00x);
+	}
 }
 
 static const struct ieee1394_device_id snd_dg00x_id_table[] = {

sound/firewire/digi00x/digi00x.h

@@ -37,6 +37,9 @@ struct snd_dg00x {
 	struct mutex mutex;
 	spinlock_t lock;
 
+	bool registered;
+	struct delayed_work dwork;
+
 	struct amdtp_stream tx_stream;
 	struct fw_iso_resources tx_resources;