RFC v2 for snd-usb endpoint logic rework

index 0f6dc0d..ccfe1c6 100644
@@ -276,6 +276,7 @@ static int snd_usb_create_streams(struct snd_usb_audio *chip, int ctrlif)
 
 static int snd_usb_audio_free(struct snd_usb_audio *chip)
 {
+	mutex_destroy(&chip->mutex);
 	kfree(chip);
 	return 0;
 }

@@ -336,6 +337,7 @@ static int snd_usb_audio_create(struct usb_device *dev, int idx,
 		return -ENOMEM;
 	}
 
+	mutex_init(&chip->mutex);
 	mutex_init(&chip->shutdown_mutex);
 	chip->index = idx;
 	chip->dev = dev;

index 3e2b035..a16c21d 100644
@@ -36,6 +36,7 @@ struct snd_usb_audio {
 	struct snd_card *card;
 	struct usb_interface *pm_intf;
 	u32 usb_id;
+	struct mutex mutex;
 	struct mutex shutdown_mutex;
 	unsigned int shutdown:1;
 	unsigned int probing:1;

index a39edcc..219a8cd 100644
@@ -29,13 +29,17 @@ struct audioformat {
 };
 
 struct snd_usb_substream;
+struct snd_usb_endpoint;
 
 struct snd_urb_ctx {
 	struct urb *urb;
 	unsigned int buffer_size;	/* size of data buffer, if data URB */
 	struct snd_usb_substream *subs;
+	struct snd_usb_endpoint *ep;
 	int index;	/* index for urb array */
 	int packets;	/* number of packets per urb */
+	int packet_size[MAX_PACKS_HS]; /* size of packets for next submission */
+	struct list_head ready_list;
 };
 
 struct snd_urb_ops {

@@ -45,6 +49,62 @@ struct snd_urb_ops {
 	int (*retire_sync)(struct snd_usb_substream *subs, struct snd_pcm_runtime *runtime, struct urb *u);
 };
 
+struct snd_usb_endpoint {
+	struct snd_usb_audio *chip;
+
+	int use_count;
+	int ep_num;     /* the referenced endpoint number */
+	int type;	/* SND_USB_ENDPOINT_TYPE_* */
+	int activated;
+
+	void (* prepare_data_urb) (struct snd_usb_substream *subs,
+				   struct urb *urb);
+	void (* retire_data_urb) (struct snd_usb_substream *subs,
+				  struct urb *urb);
+
+	struct snd_usb_substream *data_subs;
+	struct snd_usb_endpoint *sync_master;
+	struct snd_usb_endpoint *sync_slave;
+
+	struct snd_urb_ctx urb[MAX_URBS];
+	
+
+	struct snd_usb_packet_info {
+		uint32_t packet_size[MAX_PACKS_HS];
+		int packets;
+	} next_packet[MAX_URBS];
+	int next_packet_read_pos, next_packet_write_pos;
+	struct list_head ready_playback_urbs;
+	struct tasklet_struct outbound_tasklet;
+
+	unsigned int nurbs;			/* # urbs */
+	unsigned long active_mask;		/* bitmask of active urbs */
+	unsigned long unlink_mask;		/* bitmask of unlinked urbs */
+	char *syncbuf;			     /* sync buffer for all sync URBs */
+	dma_addr_t sync_dma;		      /* DMA address of syncbuf */
+
+	unsigned int pipe;      /* the data i/o pipe */
+	unsigned int freqn;     /* nominal sampling rate in fs/fps in Q16.16 format */
+	unsigned int freqm;      /* momentary sampling rate in fs/fps in Q16.16 format */
+	int	   freqshift;  /* how much to shift the feedback value to get Q16.16 */
+	unsigned int freqmax;    /* maximum sampling rate, used for buffer management */
+	unsigned int phase;      /* phase accumulator */
+	unsigned int maxpacksize;	/* max packet size in bytes */
+	unsigned int maxframesize;      /* max packet size in frames */
+	unsigned int curpacksize;	/* current packet size in bytes (for capture) */
+	unsigned int curframesize;      /* current packet size in frames (for capture) */
+	unsigned int syncmaxsize;	/* sync endpoint packet size */
+	unsigned int fill_max: 1;	/* fill max packet size always */
+	unsigned int datainterval;      /* log_2 of data packet interval */
+	unsigned int syncinterval;  /* P for adaptive mode, 0 otherwise */
+	unsigned char silence_value;
+	unsigned int stride;
+	int iface, alt_idx;
+
+	spinlock_t lock;
+	struct list_head list;
+};
+
 struct snd_usb_substream {
 	struct snd_usb_stream *stream;
 	struct usb_device *dev;

977 lines not on this page · raw message

index 88eb63a..84aaec7 100644
@@ -18,4 +18,29 @@ int snd_usb_substream_prepare(struct snd_usb_substream *subs,
 int snd_usb_substream_playback_trigger(struct snd_pcm_substream *substream, int cmd);
 int snd_usb_substream_capture_trigger(struct snd_pcm_substream *substream, int cmd);
 
+
+#define SND_USB_ENDPOINT_TYPE_DATA     0
+#define SND_USB_ENDPOINT_TYPE_SYNC     1
+
+struct snd_usb_endpoint *snd_usb_add_endpoint(struct snd_usb_audio *chip,
+					      struct usb_host_interface *alts,
+					      int ep_num, int direction, int type);
+
+int snd_usb_endpoint_set_params(struct snd_usb_endpoint *ep,
+				struct snd_pcm_hw_params *hw_params,
+				struct audioformat *fmt,
+				struct snd_usb_endpoint *sync_ep);
+
+int  snd_usb_endpoint_start(struct snd_usb_endpoint *ep);
+void snd_usb_endpoint_stop(struct snd_usb_endpoint *ep, int force, int can_sleep);
+int  snd_usb_endpoint_activate(struct snd_usb_endpoint *ep);
+int  snd_usb_endpoint_deactivate(struct snd_usb_endpoint *ep);
+void snd_usb_endpoint_free(struct list_head *head);
+
+int snd_usb_endpoint_implict_feedback_sink(struct snd_usb_endpoint *ep);
+
+void snd_usb_handle_sync_urb(struct snd_usb_endpoint *ep,
+			     struct snd_usb_endpoint *sender,
+			     const struct urb *urb);
+
 #endif /* __USBAUDIO_ENDPOINT_H */

index a16c21d..b8233eb 100644
@@ -47,6 +47,7 @@ struct snd_usb_audio {
 	int num_suspended_intf;
 
 	struct list_head pcm_list;	/* list of pcm streams */
+	struct list_head ep_list;	/* list of audio-related endpoints */
 	int pcm_devs;
 
 	struct list_head midi_list;	/* list of midi interfaces */

index ccfe1c6..23018f0 100644
@@ -131,7 +131,6 @@ static void snd_usb_stream_disconnect(struct list_head *head)
 		subs = &as->substream[idx];
 		if (!subs->num_formats)
 			continue;
-		snd_usb_release_substream_urbs(subs, 1);
 		subs->interface = -1;
 	}
 }

@@ -350,6 +349,7 @@ static int snd_usb_audio_create(struct usb_device *dev, int idx,
 	chip->usb_id = USB_ID(le16_to_cpu(dev->descriptor.idVendor),
 			      le16_to_cpu(dev->descriptor.idProduct));
 	INIT_LIST_HEAD(&chip->pcm_list);
+	INIT_LIST_HEAD(&chip->ep_list);
 	INIT_LIST_HEAD(&chip->midi_list);
 	INIT_LIST_HEAD(&chip->mixer_list);
 

@@ -567,6 +567,10 @@ static void snd_usb_audio_disconnect(struct usb_device *dev,
 		list_for_each(p, &chip->pcm_list) {
 			snd_usb_stream_disconnect(p);
 		}
+		/* release the endpoint resources */
+		list_for_each(p, &chip->ep_list) {
+			snd_usb_endpoint_free(p);
+		}
 		/* release the midi resources */
 		list_for_each(p, &chip->midi_list) {
 			snd_usbmidi_disconnect(p);

index 219a8cd..530b75d 100644
@@ -146,6 +146,11 @@ struct snd_usb_substream {
 	struct snd_urb_ctx syncurb[SYNC_URBS];	/* sync urb table */
 	char *syncbuf;				/* sync buffer for all sync URBs */
 	dma_addr_t sync_dma;			/* DMA address of syncbuf */
+	/* data and sync endpoints for this stream */
+	struct snd_usb_endpoint *data_endpoint;
+	struct snd_usb_endpoint *sync_endpoint;
+	unsigned int data_endpoint_started:1;
+	unsigned int sync_endpoint_started:1;
 
 	u64 formats;			/* format bitmasks (all or'ed) */
 	unsigned int num_formats;		/* number of supported audio formats (list) */

index ebf4008..9345001 100644
@@ -908,46 +908,6 @@ void snd_usb_init_substream(struct snd_usb_stream *as,
 	subs->fmt_type = fp->fmt_type;
 }
 
-int snd_usb_substream_playback_trigger(struct snd_pcm_substream *substream, int cmd)
-{
-	struct snd_usb_substream *subs = substream->runtime->private_data;
-
-	switch (cmd) {
-	case SNDRV_PCM_TRIGGER_START:
-	case SNDRV_PCM_TRIGGER_PAUSE_RELEASE:
-		subs->ops.prepare = prepare_playback_urb;
-		return 0;
-	case SNDRV_PCM_TRIGGER_STOP:
-		return deactivate_urbs_old(subs, 0, 0);
-	case SNDRV_PCM_TRIGGER_PAUSE_PUSH:
-		subs->ops.prepare = prepare_nodata_playback_urb;
-		return 0;
-	}
-
-	return -EINVAL;
-}
-
-int snd_usb_substream_capture_trigger(struct snd_pcm_substream *substream, int cmd)
-{
-	struct snd_usb_substream *subs = substream->runtime->private_data;
-
-	switch (cmd) {
-	case SNDRV_PCM_TRIGGER_START:
-		subs->ops.retire = retire_capture_urb;
-		return start_urbs(subs, substream->runtime);
-	case SNDRV_PCM_TRIGGER_STOP:
-		return deactivate_urbs_old(subs, 0, 0);
-	case SNDRV_PCM_TRIGGER_PAUSE_PUSH:
-		subs->ops.retire = retire_paused_capture_urb;
-		return 0;
-	case SNDRV_PCM_TRIGGER_PAUSE_RELEASE:
-		subs->ops.retire = retire_capture_urb;
-		return 0;
-	}
-
-	return -EINVAL;
-}
-
 int snd_usb_substream_prepare(struct snd_usb_substream *subs,
 			      struct snd_pcm_runtime *runtime)
 {

index 84aaec7..a9f6c80 100644
@@ -15,9 +15,6 @@ void snd_usb_release_substream_urbs(struct snd_usb_substream *subs, int force);
 int snd_usb_substream_prepare(struct snd_usb_substream *subs,
 			      struct snd_pcm_runtime *runtime);
 
-int snd_usb_substream_playback_trigger(struct snd_pcm_substream *substream, int cmd);
-int snd_usb_substream_capture_trigger(struct snd_pcm_substream *substream, int cmd);
-
 
 #define SND_USB_ENDPOINT_TYPE_DATA     0
 #define SND_USB_ENDPOINT_TYPE_SYNC     1

500 lines not on this page · raw message

index 5ff8010..6b7d7a2 100644
@@ -73,6 +73,31 @@ static void snd_usb_audio_pcm_free(struct snd_pcm *pcm)
 	}
 }
 
+/*
+ * initialize the substream instance.
+ */
+
+static void snd_usb_init_substream(struct snd_usb_stream *as,
+				   int stream,
+				   struct audioformat *fp)
+{
+	struct snd_usb_substream *subs = &as->substream[stream];
+
+	INIT_LIST_HEAD(&subs->fmt_list);
+	spin_lock_init(&subs->lock);
+
+	subs->stream = as;
+	subs->direction = stream;
+	subs->dev = as->chip->dev;
+	subs->txfr_quirk = as->chip->txfr_quirk;
+
+	snd_usb_set_pcm_ops(as->pcm, stream);
+
+	list_add_tail(&fp->list, &subs->fmt_list);
+	subs->formats |= fp->formats;
+	subs->num_formats++;
+	subs->fmt_type = fp->fmt_type;
+}
 
 /*
  * add this endpoint to the chip instance.

@@ -94,9 +119,9 @@ int snd_usb_add_audio_stream(struct snd_usb_audio *chip,
 		if (as->fmt_type != fp->fmt_type)
 			continue;
 		subs = &as->substream[stream];
-		if (!subs->endpoint)
+		if (!subs->data_endpoint)
 			continue;
-		if (subs->endpoint == fp->endpoint) {
+		if (subs->data_endpoint->ep_num == fp->endpoint) {
 			list_add_tail(&fp->list, &subs->fmt_list);
 			subs->num_formats++;
 			subs->formats |= fp->formats;

@@ -109,7 +134,7 @@ int snd_usb_add_audio_stream(struct snd_usb_audio *chip,
 		if (as->fmt_type != fp->fmt_type)
 			continue;
 		subs = &as->substream[stream];
-		if (subs->endpoint)
+		if (subs->data_endpoint)
 			continue;
 		err = snd_pcm_new_stream(as->pcm, stream, 1);
 		if (err < 0)

index 9345001..a667cf4 100644
@@ -49,882 +49,6 @@ static inline unsigned get_usb_high_speed_rate(unsigned int rate)
 	return ((rate << 10) + 62) / 125;
 }
 
-/*
- * unlink active urbs.
- */
-static int deactivate_urbs_old(struct snd_usb_substream *subs, int force, int can_sleep)
-{
-	struct snd_usb_audio *chip = subs->stream->chip;
-	unsigned int i;
-	int async;
-
-	subs->running = 0;
-
-	if (!force && subs->stream->chip->shutdown) /* to be sure... */
-		return -EBADFD;
-
-	async = !can_sleep && chip->async_unlink;
-
-	if (!async && in_interrupt())
-		return 0;
-
-	for (i = 0; i < subs->nurbs; i++) {
-		if (test_bit(i, &subs->active_mask)) {
-			if (!test_and_set_bit(i, &subs->unlink_mask)) {
-				struct urb *u = subs->dataurb[i].urb;
-				if (async)
-					usb_unlink_urb(u);
-				else
-					usb_kill_urb(u);
-			}
-		}
-	}
-	if (subs->syncpipe) {
-		for (i = 0; i < SYNC_URBS; i++) {
-			if (test_bit(i+16, &subs->active_mask)) {
-				if (!test_and_set_bit(i+16, &subs->unlink_mask)) {
-					struct urb *u = subs->syncurb[i].urb;
-					if (async)
-						usb_unlink_urb(u);
-					else
-						usb_kill_urb(u);
-				}
-			}
-		}
-	}
-	return 0;
-}
-
-
-/*
- * release a urb data
- */
-static void release_urb_ctx(struct snd_urb_ctx *u)
-{
-	if (u->urb) {
-		if (u->buffer_size)
-			usb_free_coherent(u->subs->dev, u->buffer_size,
-					u->urb->transfer_buffer,
-					u->urb->transfer_dma);
-		usb_free_urb(u->urb);
-		u->urb = NULL;
-	}
-}
-
-/*
- *  wait until all urbs are processed.
- */
-static int wait_clear_urbs_old(struct snd_usb_substream *subs)
-{
-	unsigned long end_time = jiffies + msecs_to_jiffies(1000);
-	unsigned int i;
-	int alive;
-
-	do {
-		alive = 0;
-		for (i = 0; i < subs->nurbs; i++) {
-			if (test_bit(i, &subs->active_mask))
-				alive++;
-		}
-		if (subs->syncpipe) {
-			for (i = 0; i < SYNC_URBS; i++) {
-				if (test_bit(i + 16, &subs->active_mask))
-					alive++;
-			}
-		}
-		if (! alive)
-			break;
-		schedule_timeout_uninterruptible(1);
-	} while (time_before(jiffies, end_time));
-	if (alive)
-		snd_printk(KERN_ERR "timeout: still %d active urbs..\n", alive);
-	return 0;
-}
-
-/*
- * release a substream
- */
-void snd_usb_release_substream_urbs(struct snd_usb_substream *subs, int force)
-{
-	int i;
-
-	/* stop urbs (to be sure) */
-	deactivate_urbs_old(subs, force, 1);
-	wait_clear_urbs_old(subs);
-
-	for (i = 0; i < MAX_URBS; i++)
-		release_urb_ctx(&subs->dataurb[i]);
-	for (i = 0; i < SYNC_URBS; i++)
-		release_urb_ctx(&subs->syncurb[i]);
-	usb_free_coherent(subs->dev, SYNC_URBS * 4,
-			subs->syncbuf, subs->sync_dma);
-	subs->syncbuf = NULL;
-	subs->nurbs = 0;
-}
-
-/*
- * complete callback from data urb
- */
-static void snd_complete_urb_old(struct urb *urb)
-{
-	struct snd_urb_ctx *ctx = urb->context;
-	struct snd_usb_substream *subs = ctx->subs;
-	struct snd_pcm_substream *substream = ctx->subs->pcm_substream;
-	int err = 0;
-
-	if ((subs->running && subs->ops.retire(subs, substream->runtime, urb)) ||
-	    !subs->running || /* can be stopped during retire callback */
-	    (err = subs->ops.prepare(subs, substream->runtime, urb)) < 0 ||
-	    (err = usb_submit_urb(urb, GFP_ATOMIC)) < 0) {
-		clear_bit(ctx->index, &subs->active_mask);
-		if (err < 0) {
-			snd_printd(KERN_ERR "cannot submit urb (err = %d)\n", err);
-			snd_pcm_stop(substream, SNDRV_PCM_STATE_XRUN);
-		}
-	}
-}
-
-
-/*
- * complete callback from sync urb
- */
-static void snd_complete_sync_urb(struct urb *urb)
-{
-	struct snd_urb_ctx *ctx = urb->context;
-	struct snd_usb_substream *subs = ctx->subs;
-	struct snd_pcm_substream *substream = ctx->subs->pcm_substream;
-	int err = 0;
-
-	if ((subs->running && subs->ops.retire_sync(subs, substream->runtime, urb)) ||
-	    !subs->running || /* can be stopped during retire callback */
-	    (err = subs->ops.prepare_sync(subs, substream->runtime, urb)) < 0 ||
-	    (err = usb_submit_urb(urb, GFP_ATOMIC)) < 0) {
-		clear_bit(ctx->index + 16, &subs->active_mask);
-		if (err < 0) {
-			snd_printd(KERN_ERR "cannot submit sync urb (err = %d)\n", err);
-			snd_pcm_stop(substream, SNDRV_PCM_STATE_XRUN);
-		}
-	}
-}
-
-
-/*
- * initialize a substream for plaback/capture
- */
-int snd_usb_init_substream_urbs(struct snd_usb_substream *subs,
-				unsigned int period_bytes,
-				unsigned int rate,
-				unsigned int frame_bits)
-{
-	unsigned int maxsize, i;
-	int is_playback = subs->direction == SNDRV_PCM_STREAM_PLAYBACK;
-	unsigned int urb_packs, total_packs, packs_per_ms;
-	struct snd_usb_audio *chip = subs->stream->chip;
-
-	/* calculate the frequency in 16.16 format */
-	if (snd_usb_get_speed(subs->dev) == USB_SPEED_FULL)
-		subs->freqn = get_usb_full_speed_rate(rate);
-	else
-		subs->freqn = get_usb_high_speed_rate(rate);
-	subs->freqm = subs->freqn;
-	subs->freqshift = INT_MIN;
-	/* calculate max. frequency */
-	if (subs->maxpacksize) {
-		/* whatever fits into a max. size packet */
-		maxsize = subs->maxpacksize;
-		subs->freqmax = (maxsize / (frame_bits >> 3))
-				<< (16 - subs->datainterval);
-	} else {
-		/* no max. packet size: just take 25% higher than nominal */
-		subs->freqmax = subs->freqn + (subs->freqn >> 2);
-		maxsize = ((subs->freqmax + 0xffff) * (frame_bits >> 3))
-				>> (16 - subs->datainterval);
-	}
-	subs->phase = 0;
-
-	if (subs->fill_max)
-		subs->curpacksize = subs->maxpacksize;
-	else
-		subs->curpacksize = maxsize;
-
-	if (snd_usb_get_speed(subs->dev) != USB_SPEED_FULL)
-		packs_per_ms = 8 >> subs->datainterval;
-	else
-		packs_per_ms = 1;
-
-	if (is_playback) {
-		urb_packs = max(chip->nrpacks, 1);
-		urb_packs = min(urb_packs, (unsigned int)MAX_PACKS);
-	} else
-		urb_packs = 1;
-	urb_packs *= packs_per_ms;
-	if (subs->syncpipe)
-		urb_packs = min(urb_packs, 1U << subs->syncinterval);
-
-	/* decide how many packets to be used */
-	if (is_playback) {
-		unsigned int minsize, maxpacks;
-		/* determine how small a packet can be */
-		minsize = (subs->freqn >> (16 - subs->datainterval))
-			  * (frame_bits >> 3);
-		/* with sync from device, assume it can be 12% lower */
-		if (subs->syncpipe)
-			minsize -= minsize >> 3;
-		minsize = max(minsize, 1u);
-		total_packs = (period_bytes + minsize - 1) / minsize;
-		/* we need at least two URBs for queueing */
-		if (total_packs < 2) {
-			total_packs = 2;
-		} else {
-			/* and we don't want too long a queue either */
-			maxpacks = max(MAX_QUEUE * packs_per_ms, urb_packs * 2);
-			total_packs = min(total_packs, maxpacks);
-		}
-	} else {
-		while (urb_packs > 1 && urb_packs * maxsize >= period_bytes)
-			urb_packs >>= 1;
-		total_packs = MAX_URBS * urb_packs;
-	}
-	subs->nurbs = (total_packs + urb_packs - 1) / urb_packs;
-	if (subs->nurbs > MAX_URBS) {
-		/* too much... */
-		subs->nurbs = MAX_URBS;
-		total_packs = MAX_URBS * urb_packs;
-	} else if (subs->nurbs < 2) {
-		/* too little - we need at least two packets
-		 * to ensure contiguous playback/capture
-		 */
-		subs->nurbs = 2;
-	}
-
-	/* allocate and initialize data urbs */
-	for (i = 0; i < subs->nurbs; i++) {
-		struct snd_urb_ctx *u = &subs->dataurb[i];
-		u->index = i;
-		u->subs = subs;
-		u->packets = (i + 1) * total_packs / subs->nurbs
-			- i * total_packs / subs->nurbs;
-		u->buffer_size = maxsize * u->packets;
-		if (subs->fmt_type == UAC_FORMAT_TYPE_II)
-			u->packets++; /* for transfer delimiter */
-		u->urb = usb_alloc_urb(u->packets, GFP_KERNEL);
-		if (!u->urb)
-			goto out_of_memory;
-		u->urb->transfer_buffer =
-			usb_alloc_coherent(subs->dev, u->buffer_size,
-					   GFP_KERNEL, &u->urb->transfer_dma);
-		if (!u->urb->transfer_buffer)
-			goto out_of_memory;
-		u->urb->pipe = subs->datapipe;
-		u->urb->transfer_flags = URB_ISO_ASAP | URB_NO_TRANSFER_DMA_MAP;
-		u->urb->interval = 1 << subs->datainterval;
-		u->urb->context = u;
-		u->urb->complete = snd_complete_urb_old;
-	}
-
-	if (subs->syncpipe) {
-		/* allocate and initialize sync urbs */
-		subs->syncbuf = usb_alloc_coherent(subs->dev, SYNC_URBS * 4,
-						 GFP_KERNEL, &subs->sync_dma);
-		if (!subs->syncbuf)
-			goto out_of_memory;
-		for (i = 0; i < SYNC_URBS; i++) {
-			struct snd_urb_ctx *u = &subs->syncurb[i];
-			u->index = i;
-			u->subs = subs;
-			u->packets = 1;
-			u->urb = usb_alloc_urb(1, GFP_KERNEL);
-			if (!u->urb)
-				goto out_of_memory;
-			u->urb->transfer_buffer = subs->syncbuf + i * 4;
-			u->urb->transfer_dma = subs->sync_dma + i * 4;
-			u->urb->transfer_buffer_length = 4;
-			u->urb->pipe = subs->syncpipe;
-			u->urb->transfer_flags = URB_ISO_ASAP |
-						 URB_NO_TRANSFER_DMA_MAP;
-			u->urb->number_of_packets = 1;
-			u->urb->interval = 1 << subs->syncinterval;
-			u->urb->context = u;
-			u->urb->complete = snd_complete_sync_urb;
-		}
-	}
-	return 0;
-
-out_of_memory:
-	snd_usb_release_substream_urbs(subs, 0);
-	return -ENOMEM;
-}
-
-/*
- * prepare urb for full speed capture sync pipe
- *
- * fill the length and offset of each urb descriptor.
- * the fixed 10.14 frequency is passed through the pipe.
- */
-static int prepare_capture_sync_urb(struct snd_usb_substream *subs,
-				    struct snd_pcm_runtime *runtime,
-				    struct urb *urb)
-{
-	unsigned char *cp = urb->transfer_buffer;
-	struct snd_urb_ctx *ctx = urb->context;
-
-	urb->dev = ctx->subs->dev; /* we need to set this at each time */
-	urb->iso_frame_desc[0].length = 3;
-	urb->iso_frame_desc[0].offset = 0;
-	cp[0] = subs->freqn >> 2;
-	cp[1] = subs->freqn >> 10;
-	cp[2] = subs->freqn >> 18;
-	return 0;
-}
-
-/*
- * prepare urb for high speed capture sync pipe
- *
- * fill the length and offset of each urb descriptor.
- * the fixed 12.13 frequency is passed as 16.16 through the pipe.
- */
-static int prepare_capture_sync_urb_hs(struct snd_usb_substream *subs,
-				       struct snd_pcm_runtime *runtime,
-				       struct urb *urb)
-{
-	unsigned char *cp = urb->transfer_buffer;
-	struct snd_urb_ctx *ctx = urb->context;
-
-	urb->dev = ctx->subs->dev; /* we need to set this at each time */
-	urb->iso_frame_desc[0].length = 4;
-	urb->iso_frame_desc[0].offset = 0;
-	cp[0] = subs->freqn;
-	cp[1] = subs->freqn >> 8;
-	cp[2] = subs->freqn >> 16;
-	cp[3] = subs->freqn >> 24;
-	return 0;
-}
-
-/*
- * process after capture sync complete
- * - nothing to do
- */
-static int retire_capture_sync_urb(struct snd_usb_substream *subs,
-				   struct snd_pcm_runtime *runtime,
-				   struct urb *urb)
-{
-	return 0;
-}
-
-/*
- * prepare urb for capture data pipe
- *
- * fill the offset and length of each descriptor.
- *
- * we use a temporary buffer to write the captured data.
- * since the length of written data is determined by host, we cannot
- * write onto the pcm buffer directly...  the data is thus copied
- * later at complete callback to the global buffer.
- */
-static int prepare_capture_urb(struct snd_usb_substream *subs,
-			       struct snd_pcm_runtime *runtime,
-			       struct urb *urb)
-{
-	int i, offs;
-	struct snd_urb_ctx *ctx = urb->context;
-
-	offs = 0;
-	urb->dev = ctx->subs->dev; /* we need to set this at each time */
-	for (i = 0; i < ctx->packets; i++) {
-		urb->iso_frame_desc[i].offset = offs;
-		urb->iso_frame_desc[i].length = subs->curpacksize;
-		offs += subs->curpacksize;
-	}
-	urb->transfer_buffer_length = offs;
-	urb->number_of_packets = ctx->packets;
-	return 0;
-}
-
-/*
- * process after capture complete
- *
- * copy the data from each desctiptor to the pcm buffer, and
- * update the current position.
- */
-static int retire_capture_urb(struct snd_usb_substream *subs,
-			      struct snd_pcm_runtime *runtime,
-			      struct urb *urb)
-{
-	unsigned long flags;
-	unsigned char *cp;
-	int i;
-	unsigned int stride, frames, bytes, oldptr;
-	int period_elapsed = 0;
-
-	stride = runtime->frame_bits >> 3;
-
-	for (i = 0; i < urb->number_of_packets; i++) {
-		cp = (unsigned char *)urb->transfer_buffer + urb->iso_frame_desc[i].offset;
-		if (urb->iso_frame_desc[i].status) {
-			snd_printd(KERN_ERR "frame %d active: %d\n", i, urb->iso_frame_desc[i].status);
-			// continue;
-		}
-		bytes = urb->iso_frame_desc[i].actual_length;
-		frames = bytes / stride;
-		if (!subs->txfr_quirk)
-			bytes = frames * stride;
-		if (bytes % (runtime->sample_bits >> 3) != 0) {
-#ifdef CONFIG_SND_DEBUG_VERBOSE
-			int oldbytes = bytes;
-#endif
-			bytes = frames * stride;
-			snd_printdd(KERN_ERR "Corrected urb data len. %d->%d\n",
-							oldbytes, bytes);
-		}
-		/* update the current pointer */
-		spin_lock_irqsave(&subs->lock, flags);
-		oldptr = subs->hwptr_done;
-		subs->hwptr_done += bytes;
-		if (subs->hwptr_done >= runtime->buffer_size * stride)
-			subs->hwptr_done -= runtime->buffer_size * stride;
-		frames = (bytes + (oldptr % stride)) / stride;
-		subs->transfer_done += frames;
-		if (subs->transfer_done >= runtime->period_size) {
-			subs->transfer_done -= runtime->period_size;
-			period_elapsed = 1;
-		}
-		spin_unlock_irqrestore(&subs->lock, flags);
-		/* copy a data chunk */
-		if (oldptr + bytes > runtime->buffer_size * stride) {
-			unsigned int bytes1 =
-					runtime->buffer_size * stride - oldptr;
-			memcpy(runtime->dma_area + oldptr, cp, bytes1);
-			memcpy(runtime->dma_area, cp + bytes1, bytes - bytes1);
-		} else {
-			memcpy(runtime->dma_area + oldptr, cp, bytes);
-		}
-	}
-	if (period_elapsed)
-		snd_pcm_period_elapsed(subs->pcm_substream);
-	return 0;
-}
-
-/*
- * Process after capture complete when paused.  Nothing to do.
- */
-static int retire_paused_capture_urb(struct snd_usb_substream *subs,
-				     struct snd_pcm_runtime *runtime,
-				     struct urb *urb)
-{
-	return 0;
-}
-
-
-/*
- * prepare urb for playback sync pipe
- *
- * set up the offset and length to receive the current frequency.
- */
-static int prepare_playback_sync_urb(struct snd_usb_substream *subs,
-				     struct snd_pcm_runtime *runtime,
-				     struct urb *urb)
-{
-	struct snd_urb_ctx *ctx = urb->context;
-
-	urb->dev = ctx->subs->dev; /* we need to set this at each time */
-	urb->iso_frame_desc[0].length = min(4u, ctx->subs->syncmaxsize);
-	urb->iso_frame_desc[0].offset = 0;
-	return 0;
-}
-
-/*
- * process after playback sync complete
- *
- * Full speed devices report feedback values in 10.14 format as samples per
- * frame, high speed devices in 16.16 format as samples per microframe.
- * Because the Audio Class 1 spec was written before USB 2.0, many high speed
- * devices use a wrong interpretation, some others use an entirely different
- * format.  Therefore, we cannot predict what format any particular device uses
- * and must detect it automatically.
- */
-static int retire_playback_sync_urb(struct snd_usb_substream *subs,
-				    struct snd_pcm_runtime *runtime,
-				    struct urb *urb)
-{
-	unsigned int f;
-	int shift;
-	unsigned long flags;
-
-	if (urb->iso_frame_desc[0].status != 0 ||
-	    urb->iso_frame_desc[0].actual_length < 3)
-		return 0;
-
-	f = le32_to_cpup(urb->transfer_buffer);
-	if (urb->iso_frame_desc[0].actual_length == 3)
-		f &= 0x00ffffff;
-	else
-		f &= 0x0fffffff;
-	if (f == 0)
-		return 0;
-
-	if (unlikely(subs->freqshift == INT_MIN)) {
-		/*
-		 * The first time we see a feedback value, determine its format
-		 * by shifting it left or right until it matches the nominal
-		 * frequency value.  This assumes that the feedback does not
-		 * differ from the nominal value more than +50% or -25%.
-		 */
-		shift = 0;
-		while (f < subs->freqn - subs->freqn / 4) {
-			f <<= 1;
-			shift++;
-		}
-		while (f > subs->freqn + subs->freqn / 2) {
-			f >>= 1;
-			shift--;
-		}
-		subs->freqshift = shift;
-	}
-	else if (subs->freqshift >= 0)
-		f <<= subs->freqshift;
-	else
-		f >>= -subs->freqshift;
-
-	if (likely(f >= subs->freqn - subs->freqn / 8 && f <= subs->freqmax)) {
-		/*
-		 * If the frequency looks valid, set it.
-		 * This value is referred to in prepare_playback_urb().
-		 */
-		spin_lock_irqsave(&subs->lock, flags);
-		subs->freqm = f;
-		spin_unlock_irqrestore(&subs->lock, flags);
-	} else {
-		/*
-		 * Out of range; maybe the shift value is wrong.
-		 * Reset it so that we autodetect again the next time.
-		 */
-		subs->freqshift = INT_MIN;
-	}
-
-	return 0;
-}
-
-/* determine the number of frames in the next packet */
-static int snd_usb_audio_next_packet_size(struct snd_usb_substream *subs)
-{
-	if (subs->fill_max)
-		return subs->maxframesize;
-	else {
-		subs->phase = (subs->phase & 0xffff)
-			+ (subs->freqm << subs->datainterval);
-		return min(subs->phase >> 16, subs->maxframesize);
-	}
-}
-
-/*
- * Prepare urb for streaming before playback starts or when paused.
- *
- * We don't have any data, so we send silence.
- */
-static int prepare_nodata_playback_urb(struct snd_usb_substream *subs,
-				       struct snd_pcm_runtime *runtime,
-				       struct urb *urb)
-{
-	unsigned int i, offs, counts;
-	struct snd_urb_ctx *ctx = urb->context;
-	int stride = runtime->frame_bits >> 3;
-
-	offs = 0;
-	urb->dev = ctx->subs->dev;
-	for (i = 0; i < ctx->packets; ++i) {
-		counts = snd_usb_audio_next_packet_size(subs);
-		urb->iso_frame_desc[i].offset = offs * stride;
-		urb->iso_frame_desc[i].length = counts * stride;
-		offs += counts;
-	}
-	urb->number_of_packets = ctx->packets;
-	urb->transfer_buffer_length = offs * stride;
-	memset(urb->transfer_buffer,
-	       runtime->format == SNDRV_PCM_FORMAT_U8 ? 0x80 : 0,
-	       offs * stride);
-	return 0;
-}
-
-/*
- * prepare urb for playback data pipe
- *
- * Since a URB can handle only a single linear buffer, we must use double
- * buffering when the data to be transferred overflows the buffer boundary.
- * To avoid inconsistencies when updating hwptr_done, we use double buffering
- * for all URBs.
- */
-static int prepare_playback_urb(struct snd_usb_substream *subs,
-				struct snd_pcm_runtime *runtime,
-				struct urb *urb)
-{
-	int i, stride;
-	unsigned int counts, frames, bytes;
-	unsigned long flags;
-	int period_elapsed = 0;
-	struct snd_urb_ctx *ctx = urb->context;
-
-	stride = runtime->frame_bits >> 3;
-
-	frames = 0;
-	urb->dev = ctx->subs->dev; /* we need to set this at each time */
-	urb->number_of_packets = 0;
-	spin_lock_irqsave(&subs->lock, flags);
-	for (i = 0; i < ctx->packets; i++) {
-		counts = snd_usb_audio_next_packet_size(subs);
-		/* set up descriptor */
-		urb->iso_frame_desc[i].offset = frames * stride;
-		urb->iso_frame_desc[i].length = counts * stride;
-		frames += counts;
-		urb->number_of_packets++;
-		subs->transfer_done += counts;
-		if (subs->transfer_done >= runtime->period_size) {
-			subs->transfer_done -= runtime->period_size;
-			period_elapsed = 1;
-			if (subs->fmt_type == UAC_FORMAT_TYPE_II) {
-				if (subs->transfer_done > 0) {
-					/* FIXME: fill-max mode is not
-					 * supported yet */
-					frames -= subs->transfer_done;
-					counts -= subs->transfer_done;
-					urb->iso_frame_desc[i].length =
-						counts * stride;
-					subs->transfer_done = 0;
-				}
-				i++;
-				if (i < ctx->packets) {
-					/* add a transfer delimiter */
-					urb->iso_frame_desc[i].offset =
-						frames * stride;
-					urb->iso_frame_desc[i].length = 0;
-					urb->number_of_packets++;
-				}
-				break;
-			}
-		}
-		if (period_elapsed) /* finish at the period boundary */
-			break;
-	}
-	bytes = frames * stride;
-	if (subs->hwptr_done + bytes > runtime->buffer_size * stride) {
-		/* err, the transferred area goes over buffer boundary. */
-		unsigned int bytes1 =
-			runtime->buffer_size * stride - subs->hwptr_done;
-		memcpy(urb->transfer_buffer,
-		       runtime->dma_area + subs->hwptr_done, bytes1);
-		memcpy(urb->transfer_buffer + bytes1,
-		       runtime->dma_area, bytes - bytes1);
-	} else {
-		memcpy(urb->transfer_buffer,
-		       runtime->dma_area + subs->hwptr_done, bytes);
-	}
-	subs->hwptr_done += bytes;
-	if (subs->hwptr_done >= runtime->buffer_size * stride)
-		subs->hwptr_done -= runtime->buffer_size * stride;
-
-	/* update delay with exact number of samples queued */
-	runtime->delay = subs->last_delay;
-	runtime->delay += frames;
-	subs->last_delay = runtime->delay;
-
-	/* realign last_frame_number */
-	subs->last_frame_number = usb_get_current_frame_number(subs->dev);
-	subs->last_frame_number &= 0xFF; /* keep 8 LSBs */
-
-	spin_unlock_irqrestore(&subs->lock, flags);
-	urb->transfer_buffer_length = bytes;
-	if (period_elapsed)
-		snd_pcm_period_elapsed(subs->pcm_substream);
-	return 0;
-}
-
-/*
- * process after playback data complete
- * - decrease the delay count again
- */
-static int retire_playback_urb(struct snd_usb_substream *subs,
-			       struct snd_pcm_runtime *runtime,
-			       struct urb *urb)
-{
-	unsigned long flags;
-	int stride = runtime->frame_bits >> 3;
-	int processed = urb->transfer_buffer_length / stride;
-	int est_delay;
-
-	spin_lock_irqsave(&subs->lock, flags);
-
-	est_delay = snd_usb_pcm_delay(subs, runtime->rate);
-	/* update delay with exact number of samples played */
-	if (processed > subs->last_delay)
-		subs->last_delay = 0;
-	else
-		subs->last_delay -= processed;
-	runtime->delay = subs->last_delay;
-
-	/*
-	 * Report when delay estimate is off by more than 2ms.
-	 * The error should be lower than 2ms since the estimate relies
-	 * on two reads of a counter updated every ms.
-	 */
-	if (abs(est_delay - subs->last_delay) * 1000 > runtime->rate * 2)
-		snd_printk(KERN_DEBUG "delay: estimated %d, actual %d\n",
-			est_delay, subs->last_delay);
-
-	spin_unlock_irqrestore(&subs->lock, flags);
-	return 0;
-}
-
-static const char *usb_error_string(int err)
-{
-	switch (err) {
-	case -ENODEV:
-		return "no device";
-	case -ENOENT:
-		return "endpoint not enabled";
-	case -EPIPE:
-		return "endpoint stalled";
-	case -ENOSPC:
-		return "not enough bandwidth";
-	case -ESHUTDOWN:
-		return "device disabled";
-	case -EHOSTUNREACH:
-		return "device suspended";
-	case -EINVAL:
-	case -EAGAIN:
-	case -EFBIG:
-	case -EMSGSIZE:
-		return "internal error";
-	default:
-		return "unknown error";
-	}
-}
-
-/*
- * set up and start data/sync urbs
- */
-static int start_urbs(struct snd_usb_substream *subs, struct snd_pcm_runtime *runtime)
-{
-	unsigned int i;
-	int err;
-
-	if (subs->stream->chip->shutdown)
-		return -EBADFD;
-
-	for (i = 0; i < subs->nurbs; i++) {
-		if (snd_BUG_ON(!subs->dataurb[i].urb))
-			return -EINVAL;
-		if (subs->ops.prepare(subs, runtime, subs->dataurb[i].urb) < 0) {
-			snd_printk(KERN_ERR "cannot prepare datapipe for urb %d\n", i);
-			goto __error;
-		}
-	}
-	if (subs->syncpipe) {
-		for (i = 0; i < SYNC_URBS; i++) {
-			if (snd_BUG_ON(!subs->syncurb[i].urb))
-				return -EINVAL;
-			if (subs->ops.prepare_sync(subs, runtime, subs->syncurb[i].urb) < 0) {
-				snd_printk(KERN_ERR "cannot prepare syncpipe for urb %d\n", i);
-				goto __error;
-			}
-		}
-	}
-
-	subs->active_mask = 0;
-	subs->unlink_mask = 0;
-	subs->running = 1;
-	for (i = 0; i < subs->nurbs; i++) {
-		err = usb_submit_urb(subs->dataurb[i].urb, GFP_ATOMIC);
-		if (err < 0) {
-			snd_printk(KERN_ERR "cannot submit datapipe "
-				   "for urb %d, error %d: %s\n",
-				   i, err, usb_error_string(err));
-			goto __error;
-		}
-		set_bit(i, &subs->active_mask);
-	}
-	if (subs->syncpipe) {
-		for (i = 0; i < SYNC_URBS; i++) {
-			err = usb_submit_urb(subs->syncurb[i].urb, GFP_ATOMIC);
-			if (err < 0) {
-				snd_printk(KERN_ERR "cannot submit syncpipe "
-					   "for urb %d, error %d: %s\n",
-					   i, err, usb_error_string(err));
-				goto __error;
-			}
-			set_bit(i + 16, &subs->active_mask);
-		}
-	}
-	return 0;
-
- __error:
-	// snd_pcm_stop(subs->pcm_substream, SNDRV_PCM_STATE_XRUN);
-	deactivate_urbs_old(subs, 0, 0);
-	return -EPIPE;
-}
-
-
-/*
- */
-static struct snd_urb_ops audio_urb_ops[2] = {
-	{
-		.prepare =	prepare_nodata_playback_urb,
-		.retire =	retire_playback_urb,
-		.prepare_sync =	prepare_playback_sync_urb,
-		.retire_sync =	retire_playback_sync_urb,
-	},
-	{
-		.prepare =	prepare_capture_urb,
-		.retire =	retire_capture_urb,
-		.prepare_sync =	prepare_capture_sync_urb,
-		.retire_sync =	retire_capture_sync_urb,
-	},
-};
-
-/*
- * initialize the substream instance.
- */
-
-void snd_usb_init_substream(struct snd_usb_stream *as,
-			    int stream, struct audioformat *fp)
-{
-	struct snd_usb_substream *subs = &as->substream[stream];
-
-	INIT_LIST_HEAD(&subs->fmt_list);
-	spin_lock_init(&subs->lock);
-
-	subs->stream = as;
-	subs->direction = stream;
-	subs->dev = as->chip->dev;
-	subs->txfr_quirk = as->chip->txfr_quirk;
-	subs->ops = audio_urb_ops[stream];
-	if (snd_usb_get_speed(subs->dev) >= USB_SPEED_HIGH)
-		subs->ops.prepare_sync = prepare_capture_sync_urb_hs;
-
-	snd_usb_set_pcm_ops(as->pcm, stream);
-
-	list_add_tail(&fp->list, &subs->fmt_list);
-	subs->formats |= fp->formats;
-	subs->endpoint = fp->endpoint;
-	subs->num_formats++;
-	subs->fmt_type = fp->fmt_type;
-}
-
-int snd_usb_substream_prepare(struct snd_usb_substream *subs,
-			      struct snd_pcm_runtime *runtime)
-{
-	/* clear urbs (to be sure) */
-	deactivate_urbs_old(subs, 0, 1);
-	wait_clear_urbs_old(subs);
-
-	/* for playback, submit the URBs now; otherwise, the first hwptr_done
-	 * updates for all URBs would happen at the same time when starting */
-	if (subs->direction == SNDRV_PCM_STREAM_PLAYBACK) {
-		subs->ops.prepare = prepare_nodata_playback_urb;
-		return start_urbs(subs, runtime);
-	}
-
-	return 0;
-}
-
 int snd_usb_endpoint_implict_feedback_sink(struct snd_usb_endpoint *ep)
 {
 	return  ep->sync_master &&

@@ -1244,6 +368,47 @@ __exit_unlock:
 	return ep;
 }
 
+static const char *usb_error_string(int err)
+{
+	switch (err) {
+	case -ENODEV:
+		return "no device";
+	case -ENOENT:
+		return "endpoint not enabled";
+	case -EPIPE:
+		return "endpoint stalled";
+	case -ENOSPC:
+		return "not enough bandwidth";
+	case -ESHUTDOWN:
+		return "device disabled";
+	case -EHOSTUNREACH:
+		return "device suspended";
+	case -EINVAL:
+	case -EAGAIN:
+	case -EFBIG:
+	case -EMSGSIZE:
+		return "internal error";
+	default:
+		return "unknown error";
+	}
+}
+
+/*
+ * release a urb data
+ */
+static void release_urb_ctx(struct snd_urb_ctx *u)
+{
+	if (!u->urb)
+		return;
+
+	if (u->buffer_size)
+		usb_free_coherent(u->ep->chip->dev, u->buffer_size,
+				  u->urb->transfer_buffer,
+				  u->urb->transfer_dma);
+	usb_free_urb(u->urb);
+	u->urb = NULL;
+}
+
 /*
  *  wait until all urbs are processed.
  */

index a9f6c80..872deff 100644
@@ -1,21 +1,6 @@
 #ifndef __USBAUDIO_ENDPOINT_H
 #define __USBAUDIO_ENDPOINT_H
 
-void snd_usb_init_substream(struct snd_usb_stream *as,
-			    int stream,
-			    struct audioformat *fp);
-
-int snd_usb_init_substream_urbs(struct snd_usb_substream *subs,
-				unsigned int period_bytes,
-				unsigned int rate,
-				unsigned int frame_bits);
-
-void snd_usb_release_substream_urbs(struct snd_usb_substream *subs, int force);
-
-int snd_usb_substream_prepare(struct snd_usb_substream *subs,
-			      struct snd_pcm_runtime *runtime);
-
-
 #define SND_USB_ENDPOINT_TYPE_DATA     0
 #define SND_USB_ENDPOINT_TYPE_SYNC     1
 

index 34adb17..3cf23e3 100644
@@ -298,7 +298,7 @@ static int set_format(struct snd_usb_substream *subs, struct audioformat *fmt)
 	struct usb_interface *iface;
 	unsigned int ep, attr;
 	int is_playback = subs->direction == SNDRV_PCM_STREAM_PLAYBACK;
-	int err;
+	int err, implicit_fb = 0;
 
 	iface = usb_ifnum_to_if(dev, fmt->iface);
 	if (WARN_ON(!iface))

@@ -323,25 +323,34 @@ static int set_format(struct snd_usb_substream *subs, struct audioformat *fmt)
 	 * assume it as adaptive-out or sync-in.
 	 */
 	attr = fmt->ep_attr & USB_ENDPOINT_SYNCTYPE;
-	if (((is_playback && attr == USB_ENDPOINT_SYNC_ASYNC) ||
-	     (! is_playback && attr == USB_ENDPOINT_SYNC_ADAPTIVE)) &&
-	    altsd->bNumEndpoints >= 2) {
-		switch (subs->stream->chip->usb_id) {
-		case USB_ID(0x0763, 0x2080): /* M-Audio FastTrack Ultra */
-		case USB_ID(0x0763, 0x2081):
+
+	switch (subs->stream->chip->usb_id) {
+	case USB_ID(0x0763, 0x2080): /* M-Audio FastTrack Ultra */
+	case USB_ID(0x0763, 0x2081):
+		if (is_playback) {
+			implicit_fb = 1;
 			ep = 0x81;
 			iface = usb_ifnum_to_if(dev, 2);
+
+			if (!iface || iface->num_altsetting == 0)
+				return -EINVAL;
+
 			alts = &iface->altsetting[1];
 			goto add_sync_ep;
 		}
+	}
 
+	if (((is_playback && attr == USB_ENDPOINT_SYNC_ASYNC) ||
+	     (! is_playback && attr == USB_ENDPOINT_SYNC_ADAPTIVE)) &&
+	    altsd->bNumEndpoints >= 2) {
 		/* check sync-pipe endpoint */
 		/* ... and check descriptor size before accessing bSynchAddress
 		   because there is a version of the SB Audigy 2 NX firmware lacking
 		   the audio fields in the endpoint descriptors */
 		if ((get_endpoint(alts, 1)->bmAttributes & USB_ENDPOINT_XFERTYPE_MASK) != 0x01 ||
 		    (get_endpoint(alts, 1)->bLength >= USB_DT_ENDPOINT_AUDIO_SIZE &&
-		     get_endpoint(alts, 1)->bSynchAddress != 0)) {
+		     get_endpoint(alts, 1)->bSynchAddress != 0 &&
+		     !implicit_fb)) {
 			snd_printk(KERN_ERR "%d:%d:%d : invalid synch pipe\n",
 				   dev->devnum, fmt->iface, fmt->altsetting);
 			return -EINVAL;

@@ -349,16 +358,22 @@ static int set_format(struct snd_usb_substream *subs, struct audioformat *fmt)
 		ep = get_endpoint(alts, 1)->bEndpointAddress;
 		if (get_endpoint(alts, 0)->bLength >= USB_DT_ENDPOINT_AUDIO_SIZE &&
 		    (( is_playback && ep != (unsigned int)(get_endpoint(alts, 0)->bSynchAddress | USB_DIR_IN)) ||
-		     (!is_playback && ep != (unsigned int)(get_endpoint(alts, 0)->bSynchAddress & ~USB_DIR_IN)))) {
+		     (!is_playback && ep != (unsigned int)(get_endpoint(alts, 0)->bSynchAddress & ~USB_DIR_IN)) ||
+		     ( is_playback && !implicit_fb))) {
 			snd_printk(KERN_ERR "%d:%d:%d : invalid synch pipe\n",
 				   dev->devnum, fmt->iface, fmt->altsetting);
 			return -EINVAL;
 		}
+
+		implicit_fb = (get_endpoint(alts, 1)->bmAttributes & USB_ENDPOINT_USAGE_MASK)
+				== USB_ENDPOINT_USAGE_IMPLICIT_FB;
+
 add_sync_ep:
 		subs->sync_endpoint = snd_usb_add_endpoint(subs->stream->chip,
 							   alts, ep, !subs->direction,
-							   SND_USB_ENDPOINT_TYPE_SYNC);
-
+							   implicit_fb ?
+								SND_USB_ENDPOINT_TYPE_DATA :
+								SND_USB_ENDPOINT_TYPE_SYNC);
 		if (!subs->sync_endpoint)
 			return -EINVAL;