diff --git a/sound/usb/card.h b/sound/usb/card.h
index da5fa1ac4eda..9acbd4a1228d 100644
--- a/sound/usb/card.h
+++ b/sound/usb/card.h
@@ -30,13 +30,17 @@ 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 {
@@ -46,6 +50,60 @@ 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_* */
+	unsigned long flags;
+
+	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;
+
+	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;
diff --git a/sound/usb/endpoint.c b/sound/usb/endpoint.c
index 08dcce53720b..ea25265427ad 100644
--- a/sound/usb/endpoint.c
+++ b/sound/usb/endpoint.c
@@ -20,9 +20,11 @@
 #include <linux/ratelimit.h>
 #include <linux/usb.h>
 #include <linux/usb/audio.h>
+#include <linux/slab.h>
 
 #include <sound/core.h>
 #include <sound/pcm.h>
+#include <sound/pcm_params.h>
 
 #include "usbaudio.h"
 #include "helper.h"
@@ -30,6 +32,9 @@
 #include "endpoint.h"
 #include "pcm.h"
 
+#define EP_FLAG_ACTIVATED	0
+#define EP_FLAG_RUNNING		1
+
 /*
  * convert a sampling rate into our full speed format (fs/1000 in Q16.16)
  * this will overflow at approx 524 kHz
@@ -51,7 +56,7 @@ static inline unsigned get_usb_high_speed_rate(unsigned int rate)
 /*
  * unlink active urbs.
  */
-static int deactivate_urbs(struct snd_usb_substream *subs, int force, int can_sleep)
+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;
@@ -113,7 +118,7 @@ static void release_urb_ctx(struct snd_urb_ctx *u)
 /*
  *  wait until all urbs are processed.
  */
-static int wait_clear_urbs(struct snd_usb_substream *subs)
+static int wait_clear_urbs_old(struct snd_usb_substream *subs)
 {
 	unsigned long end_time = jiffies + msecs_to_jiffies(1000);
 	unsigned int i;
@@ -148,8 +153,8 @@ void snd_usb_release_substream_urbs(struct snd_usb_substream *subs, int force)
 	int i;
 
 	/* stop urbs (to be sure) */
-	deactivate_urbs(subs, force, 1);
-	wait_clear_urbs(subs);
+	deactivate_urbs_old(subs, force, 1);
+	wait_clear_urbs_old(subs);
 
 	for (i = 0; i < MAX_URBS; i++)
 		release_urb_ctx(&subs->dataurb[i]);
@@ -164,7 +169,7 @@ void snd_usb_release_substream_urbs(struct snd_usb_substream *subs, int force)
 /*
  * complete callback from data urb
  */
-static void snd_complete_urb(struct urb *urb)
+static void snd_complete_urb_old(struct urb *urb)
 {
 	struct snd_urb_ctx *ctx = urb->context;
 	struct snd_usb_substream *subs = ctx->subs;
@@ -318,7 +323,7 @@ int snd_usb_init_substream_urbs(struct snd_usb_substream *subs,
 		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;
+		u->urb->complete = snd_complete_urb_old;
 	}
 
 	if (subs->syncpipe) {
@@ -856,7 +861,7 @@ static int start_urbs(struct snd_usb_substream *subs, struct snd_pcm_runtime *ru
 
  __error:
 	// snd_pcm_stop(subs->pcm_substream, SNDRV_PCM_STATE_XRUN);
-	deactivate_urbs(subs, 0, 0);
+	deactivate_urbs_old(subs, 0, 0);
 	return -EPIPE;
 }
 
@@ -917,7 +922,7 @@ int snd_usb_substream_playback_trigger(struct snd_pcm_substream *substream, int
 		subs->ops.prepare = prepare_playback_urb;
 		return 0;
 	case SNDRV_PCM_TRIGGER_STOP:
-		return deactivate_urbs(subs, 0, 0);
+		return deactivate_urbs_old(subs, 0, 0);
 	case SNDRV_PCM_TRIGGER_PAUSE_PUSH:
 		subs->ops.prepare = prepare_nodata_playback_urb;
 		return 0;
@@ -935,7 +940,7 @@ int snd_usb_substream_capture_trigger(struct snd_pcm_substream *substream, int c
 		subs->ops.retire = retire_capture_urb;
 		return start_urbs(subs, substream->runtime);
 	case SNDRV_PCM_TRIGGER_STOP:
-		return deactivate_urbs(subs, 0, 0);
+		return deactivate_urbs_old(subs, 0, 0);
 	case SNDRV_PCM_TRIGGER_PAUSE_PUSH:
 		subs->ops.retire = retire_paused_capture_urb;
 		return 0;
@@ -951,8 +956,8 @@ int snd_usb_substream_prepare(struct snd_usb_substream *subs,
 			      struct snd_pcm_runtime *runtime)
 {
 	/* clear urbs (to be sure) */
-	deactivate_urbs(subs, 0, 1);
-	wait_clear_urbs(subs);
+	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 */
@@ -964,3 +969,904 @@ int snd_usb_substream_prepare(struct snd_usb_substream *subs,
 	return 0;
 }
 
+int snd_usb_endpoint_implict_feedback_sink(struct snd_usb_endpoint *ep)
+{
+	return  ep->sync_master &&
+		ep->sync_master->type == SND_USB_ENDPOINT_TYPE_DATA &&
+		ep->type == SND_USB_ENDPOINT_TYPE_DATA &&
+		usb_pipeout(ep->pipe);
+}
+
+/* determine the number of frames in the next packet */
+static int next_packet_size(struct snd_usb_endpoint *ep)
+{
+	unsigned long flags;
+	int ret;
+
+	if (ep->fill_max)
+		return ep->maxframesize;
+
+	spin_lock_irqsave(&ep->lock, flags);
+	ep->phase = (ep->phase & 0xffff)
+		+ (ep->freqm << ep->datainterval);
+	ret = min(ep->phase >> 16, ep->maxframesize);
+	spin_unlock_irqrestore(&ep->lock, flags);
+
+	return ret;
+}
+
+static void retire_outbound_urb(struct snd_usb_endpoint *ep,
+				struct snd_urb_ctx *urb_ctx)
+{
+	if (ep->retire_data_urb)
+		ep->retire_data_urb(ep->data_subs, urb_ctx->urb);
+}
+
+static void retire_inbound_urb(struct snd_usb_endpoint *ep,
+			       struct snd_urb_ctx *urb_ctx)
+{
+	struct urb *urb = urb_ctx->urb;
+
+	if (ep->sync_slave)
+		snd_usb_handle_sync_urb(ep->sync_slave, ep, urb);
+
+	if (ep->retire_data_urb)
+		ep->retire_data_urb(ep->data_subs, urb);
+}
+
+static void prepare_outbound_urb_sizes(struct snd_usb_endpoint *ep,
+				       struct snd_urb_ctx *ctx)
+{
+	int i;
+
+	for (i = 0; i < ctx->packets; ++i)
+		ctx->packet_size[i] = next_packet_size(ep);
+}
+
+/*
+ * Prepare a PLAYBACK urb for submission to the bus.
+ */
+static void prepare_outbound_urb(struct snd_usb_endpoint *ep,
+				 struct snd_urb_ctx *ctx)
+{
+	int i;
+	struct urb *urb = ctx->urb;
+	unsigned char *cp = urb->transfer_buffer;
+
+	urb->dev = ep->chip->dev; /* we need to set this at each time */
+
+	switch (ep->type) {
+	case SND_USB_ENDPOINT_TYPE_DATA:
+		if (ep->prepare_data_urb) {
+			ep->prepare_data_urb(ep->data_subs, urb);
+		} else {
+			/* no data provider, so send silence */
+			unsigned int offs = 0;
+			for (i = 0; i < ctx->packets; ++i) {
+				int counts = ctx->packet_size[i];
+				urb->iso_frame_desc[i].offset = offs * ep->stride;
+				urb->iso_frame_desc[i].length = counts * ep->stride;
+				offs += counts;
+			}
+
+			urb->number_of_packets = ctx->packets;
+			urb->transfer_buffer_length = offs * ep->stride;
+			memset(urb->transfer_buffer, ep->silence_value,
+			       offs * ep->stride);
+		}
+		break;
+
+	case SND_USB_ENDPOINT_TYPE_SYNC:
+		if (snd_usb_get_speed(ep->chip->dev) >= USB_SPEED_HIGH) {
+			/*
+			 * fill the length and offset of each urb descriptor.
+			 * the fixed 12.13 frequency is passed as 16.16 through the pipe.
+			 */
+			urb->iso_frame_desc[0].length = 4;
+			urb->iso_frame_desc[0].offset = 0;
+			cp[0] = ep->freqn;
+			cp[1] = ep->freqn >> 8;
+			cp[2] = ep->freqn >> 16;
+			cp[3] = ep->freqn >> 24;
+		} else {
+			/*
+			 * fill the length and offset of each urb descriptor.
+			 * the fixed 10.14 frequency is passed through the pipe.
+			 */
+			urb->iso_frame_desc[0].length = 3;
+			urb->iso_frame_desc[0].offset = 0;
+			cp[0] = ep->freqn >> 2;
+			cp[1] = ep->freqn >> 10;
+			cp[2] = ep->freqn >> 18;
+		}
+
+		break;
+	}
+}
+
+/*
+ * Prepare a CAPTURE or SYNC urb for submission to the bus.
+ */
+static inline void prepare_inbound_urb(struct snd_usb_endpoint *ep,
+				       struct snd_urb_ctx *urb_ctx)
+{
+	int i, offs;
+	struct urb *urb = urb_ctx->urb;
+
+	urb->dev = ep->chip->dev; /* we need to set this at each time */
+
+	switch (ep->type) {
+	case SND_USB_ENDPOINT_TYPE_DATA:
+		offs = 0;
+		for (i = 0; i < urb_ctx->packets; i++) {
+			urb->iso_frame_desc[i].offset = offs;
+			urb->iso_frame_desc[i].length = ep->curpacksize;
+			offs += ep->curpacksize;
+		}
+
+		urb->transfer_buffer_length = offs;
+		urb->number_of_packets = urb_ctx->packets;
+		break;
+
+	case SND_USB_ENDPOINT_TYPE_SYNC:
+		urb->iso_frame_desc[0].length = min(4u, ep->syncmaxsize);
+		urb->iso_frame_desc[0].offset = 0;
+		break;
+	}
+}
+
+static void queue_pending_output_urbs(struct snd_usb_endpoint *ep)
+{
+	while (test_bit(EP_FLAG_RUNNING, &ep->flags)) {
+
+		unsigned long flags;
+		struct snd_usb_packet_info *packet;
+		struct snd_urb_ctx *ctx = NULL;
+		struct urb *urb;
+		int err, i;
+
+		spin_lock_irqsave(&ep->lock, flags);
+		if (ep->next_packet_read_pos != ep->next_packet_write_pos) {
+			packet = ep->next_packet + ep->next_packet_read_pos;
+			ep->next_packet_read_pos++;
+			ep->next_packet_read_pos %= MAX_URBS;
+
+			/* take URB out of FIFO */
+			if (!list_empty(&ep->ready_playback_urbs))
+				ctx = list_first_entry(&ep->ready_playback_urbs,
+					       struct snd_urb_ctx, ready_list);
+		}
+		spin_unlock_irqrestore(&ep->lock, flags);
+
+		if (ctx == NULL)
+			return;
+
+		list_del_init(&ctx->ready_list);
+		urb = ctx->urb;
+
+		/* copy over the length information */
+		for (i = 0; i < packet->packets; i++)
+			ctx->packet_size[i] = packet->packet_size[i];
+
+		prepare_outbound_urb(ep, ctx);
+
+		err = usb_submit_urb(ctx->urb, GFP_ATOMIC);
+		if (err < 0)
+			snd_printk(KERN_ERR "Unable to submit urb #%d: %d (urb %p)\n",
+				   ctx->index, err, ctx->urb);
+		else
+			set_bit(ctx->index, &ep->active_mask);
+	}
+}
+
+/*
+ * complete callback for urbs
+ */
+static void snd_complete_urb(struct urb *urb)
+{
+	struct snd_urb_ctx *ctx = urb->context;
+	struct snd_usb_endpoint *ep = ctx->ep;
+	int err;
+
+	if (unlikely(urb->status == -ENOENT ||		/* unlinked */
+		     urb->status == -ENODEV ||		/* device removed */
+		     urb->status == -ECONNRESET ||	/* unlinked */
+		     urb->status == -ESHUTDOWN ||	/* device disabled */
+		     ep->chip->shutdown))		/* device disconnected */
+		goto exit_clear;
+
+	if (usb_pipeout(ep->pipe)) {
+		retire_outbound_urb(ep, ctx);
+		/* can be stopped during retire callback */
+		if (unlikely(!test_bit(EP_FLAG_RUNNING, &ep->flags)))
+			goto exit_clear;
+
+		if (snd_usb_endpoint_implict_feedback_sink(ep)) {
+			unsigned long flags;
+
+			spin_lock_irqsave(&ep->lock, flags);
+			list_add_tail(&ctx->ready_list, &ep->ready_playback_urbs);
+			spin_unlock_irqrestore(&ep->lock, flags);
+			queue_pending_output_urbs(ep);
+
+			goto exit_clear;
+		}
+
+		prepare_outbound_urb_sizes(ep, ctx);
+		prepare_outbound_urb(ep, ctx);
+	} else {
+		retire_inbound_urb(ep, ctx);
+		/* can be stopped during retire callback */
+		if (unlikely(!test_bit(EP_FLAG_RUNNING, &ep->flags)))
+			goto exit_clear;
+
+		prepare_inbound_urb(ep, ctx);
+	}
+
+	err = usb_submit_urb(urb, GFP_ATOMIC);
+	if (err == 0)
+		return;
+
+	snd_printk(KERN_ERR "cannot submit urb (err = %d)\n", err);
+	//snd_pcm_stop(substream, SNDRV_PCM_STATE_XRUN);
+
+exit_clear:
+	clear_bit(ctx->index, &ep->active_mask);
+}
+
+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)
+{
+	struct list_head *p;
+	struct snd_usb_endpoint *ep;
+	int ret, is_playback = direction == SNDRV_PCM_STREAM_PLAYBACK;
+
+	mutex_lock(&chip->mutex);
+
+	list_for_each(p, &chip->ep_list) {
+		ep = list_entry(p, struct snd_usb_endpoint, list);
+		if (ep->ep_num == ep_num &&
+		    ep->iface == alts->desc.bInterfaceNumber &&
+		    ep->alt_idx == alts->desc.bAlternateSetting) {
+			snd_printdd(KERN_DEBUG "Re-using EP %x in iface %d,%d @%p\n",
+					ep_num, ep->iface, ep->alt_idx, ep);
+			goto __exit_unlock;
+		}
+	}
+
+	snd_printdd(KERN_DEBUG "Creating new %s %s endpoint #%x\n",
+		    is_playback ? "playback" : "capture",
+		    type == SND_USB_ENDPOINT_TYPE_DATA ? "data" : "sync",
+		    ep_num);
+
+	/* select the alt setting once so the endpoints become valid */
+	ret = usb_set_interface(chip->dev, alts->desc.bInterfaceNumber,
+				alts->desc.bAlternateSetting);
+	if (ret < 0) {
+		snd_printk(KERN_ERR "%s(): usb_set_interface() failed, ret = %d\n",
+					__func__, ret);
+		ep = NULL;
+		goto __exit_unlock;
+	}
+
+	ep = kzalloc(sizeof(*ep), GFP_KERNEL);
+	if (!ep)
+		goto __exit_unlock;
+
+	ep->chip = chip;
+	spin_lock_init(&ep->lock);
+	ep->type = type;
+	ep->ep_num = ep_num;
+	ep->iface = alts->desc.bInterfaceNumber;
+	ep->alt_idx = alts->desc.bAlternateSetting;
+	INIT_LIST_HEAD(&ep->ready_playback_urbs);
+	ep_num &= USB_ENDPOINT_NUMBER_MASK;
+
+	if (is_playback)
+		ep->pipe = usb_sndisocpipe(chip->dev, ep_num);
+	else
+		ep->pipe = usb_rcvisocpipe(chip->dev, ep_num);
+
+	if (type == SND_USB_ENDPOINT_TYPE_SYNC) {
+		if (get_endpoint(alts, 1)->bLength >= USB_DT_ENDPOINT_AUDIO_SIZE &&
+		    get_endpoint(alts, 1)->bRefresh >= 1 &&
+		    get_endpoint(alts, 1)->bRefresh <= 9)
+			ep->syncinterval = get_endpoint(alts, 1)->bRefresh;
+		else if (snd_usb_get_speed(chip->dev) == USB_SPEED_FULL)
+			ep->syncinterval = 1;
+		else if (get_endpoint(alts, 1)->bInterval >= 1 &&
+			 get_endpoint(alts, 1)->bInterval <= 16)
+			ep->syncinterval = get_endpoint(alts, 1)->bInterval - 1;
+		else
+			ep->syncinterval = 3;
+
+		ep->syncmaxsize = le16_to_cpu(get_endpoint(alts, 1)->wMaxPacketSize);
+	}
+
+	list_add_tail(&ep->list, &chip->ep_list);
+
+__exit_unlock:
+	mutex_unlock(&chip->mutex);
+
+	return ep;
+}
+
+/*
+ *  wait until all urbs are processed.
+ */
+static int wait_clear_urbs(struct snd_usb_endpoint *ep)
+{
+	unsigned long end_time = jiffies + msecs_to_jiffies(1000);
+	unsigned int i;
+	int alive;
+
+	do {
+		alive = 0;
+		for (i = 0; i < ep->nurbs; i++)
+			if (test_bit(i, &ep->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 on EP #%x\n",
+					alive, ep->ep_num);
+
+	return 0;
+}
+
+/*
+ * unlink active urbs.
+ */
+static int deactivate_urbs(struct snd_usb_endpoint *ep, int force, int can_sleep)
+{
+	unsigned long flags;
+	unsigned int i;
+	int async;
+
+	if (!force && ep->chip->shutdown) /* to be sure... */
+		return -EBADFD;
+
+	async = !can_sleep && ep->chip->async_unlink;
+
+	clear_bit(EP_FLAG_RUNNING, &ep->flags);
+
+	INIT_LIST_HEAD(&ep->ready_playback_urbs);
+	ep->next_packet_read_pos = 0;
+	ep->next_packet_write_pos = 0;
+
+	if (!async && in_interrupt())
+		return 0;
+
+	for (i = 0; i < ep->nurbs; i++) {
+		if (test_bit(i, &ep->active_mask)) {
+			if (!test_and_set_bit(i, &ep->unlink_mask)) {
+				struct urb *u = ep->urb[i].urb;
+				if (async)
+					usb_unlink_urb(u);
+				else
+					usb_kill_urb(u);
+			}
+		}
+	}
+
+	return 0;
+}
+
+/*
+ * release an endpoint's urbs
+ */
+static void release_urbs(struct snd_usb_endpoint *ep, int force)
+{
+	int i;
+
+	/* route incoming urbs to nirvana */
+	ep->retire_data_urb = NULL;
+	ep->prepare_data_urb = NULL;
+
+	/* stop urbs */
+	deactivate_urbs(ep, force, 1);
+	wait_clear_urbs(ep);
+
+	for (i = 0; i < ep->nurbs; i++)
+		release_urb_ctx(&ep->urb[i]);
+
+	if (ep->syncbuf)
+		usb_free_coherent(ep->chip->dev, SYNC_URBS * 4,
+				  ep->syncbuf, ep->sync_dma);
+
+	ep->syncbuf = NULL;
+	ep->nurbs = 0;
+}
+
+static int data_ep_set_params(struct snd_usb_endpoint *ep,
+			      struct snd_pcm_hw_params *hw_params,
+			      struct audioformat *fmt,
+			      struct snd_usb_endpoint *sync_ep)
+{
+	unsigned int maxsize, i, urb_packs, total_packs, packs_per_ms;
+	int period_bytes = params_period_bytes(hw_params);
+	int format = params_format(hw_params);
+	int is_playback = usb_pipeout(ep->pipe);
+	int frame_bits = snd_pcm_format_physical_width(params_format(hw_params)) *
+							params_channels(hw_params);
+
+	ep->datainterval = fmt->datainterval;
+	ep->stride = frame_bits >> 3;
+	ep->silence_value = format == SNDRV_PCM_FORMAT_U8 ? 0x80 : 0;
+
+	/* calculate max. frequency */
+	if (ep->maxpacksize) {
+		/* whatever fits into a max. size packet */
+		maxsize = ep->maxpacksize;
+		ep->freqmax = (maxsize / (frame_bits >> 3))
+				<< (16 - ep->datainterval);
+	} else {
+		/* no max. packet size: just take 25% higher than nominal */
+		ep->freqmax = ep->freqn + (ep->freqn >> 2);
+		maxsize = ((ep->freqmax + 0xffff) * (frame_bits >> 3))
+				>> (16 - ep->datainterval);
+	}
+
+	if (ep->fill_max)
+		ep->curpacksize = ep->maxpacksize;
+	else
+		ep->curpacksize = maxsize;
+
+	if (snd_usb_get_speed(ep->chip->dev) != USB_SPEED_FULL)
+		packs_per_ms = 8 >> ep->datainterval;
+	else
+		packs_per_ms = 1;
+
+	if (is_playback && !snd_usb_endpoint_implict_feedback_sink(ep)) {
+		urb_packs = max(ep->chip->nrpacks, 1);
+		urb_packs = min(urb_packs, (unsigned int) MAX_PACKS);
+	} else {
+		urb_packs = 1;
+	}
+
+	urb_packs *= packs_per_ms;
+
+	if (sync_ep && !snd_usb_endpoint_implict_feedback_sink(ep))
+		urb_packs = min(urb_packs, 1U << sync_ep->syncinterval);
+
+	/* decide how many packets to be used */
+	if (is_playback && !snd_usb_endpoint_implict_feedback_sink(ep)) {
+		unsigned int minsize, maxpacks;
+		/* determine how small a packet can be */
+		minsize = (ep->freqn >> (16 - ep->datainterval))
+			  * (frame_bits >> 3);
+		/* with sync from device, assume it can be 12% lower */
+		if (sync_ep)
+			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;
+	}
+
+	ep->nurbs = (total_packs + urb_packs - 1) / urb_packs;
+	if (ep->nurbs > MAX_URBS) {
+		/* too much... */
+		ep->nurbs = MAX_URBS;
+		total_packs = MAX_URBS * urb_packs;
+	} else if (ep->nurbs < 2) {
+		/* too little - we need at least two packets
+		 * to ensure contiguous playback/capture
+		 */
+		ep->nurbs = 2;
+	}
+
+	/* allocate and initialize data urbs */
+	for (i = 0; i < ep->nurbs; i++) {
+		struct snd_urb_ctx *u = &ep->urb[i];
+		u->index = i;
+		u->ep = ep;
+		u->packets = (i + 1) * total_packs / ep->nurbs
+			- i * total_packs / ep->nurbs;
+		u->buffer_size = maxsize * u->packets;
+
+		if (fmt->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(ep->chip->dev, u->buffer_size,
+					   GFP_KERNEL, &u->urb->transfer_dma);
+		if (!u->urb->transfer_buffer)
+			goto out_of_memory;
+		u->urb->pipe = ep->pipe;
+		u->urb->transfer_flags = URB_ISO_ASAP | URB_NO_TRANSFER_DMA_MAP;
+		u->urb->interval = 1 << ep->datainterval;
+		u->urb->context = u;
+		u->urb->complete = snd_complete_urb;
+		INIT_LIST_HEAD(&u->ready_list);
+	}
+
+	return 0;
+
+out_of_memory:
+	release_urbs(ep, 0);
+	return -ENOMEM;
+}
+
+static int sync_ep_set_params(struct snd_usb_endpoint *ep,
+			      struct snd_pcm_hw_params *hw_params,
+			      struct audioformat *fmt)
+{
+	int i;
+
+	ep->syncbuf = usb_alloc_coherent(ep->chip->dev, SYNC_URBS * 4,
+					 GFP_KERNEL, &ep->sync_dma);
+	if (!ep->syncbuf)
+		return -ENOMEM;
+
+	for (i = 0; i < SYNC_URBS; i++) {
+		struct snd_urb_ctx *u = &ep->urb[i];
+		u->index = i;
+		u->ep = ep;
+		u->packets = 1;
+		u->urb = usb_alloc_urb(1, GFP_KERNEL);
+		if (!u->urb)
+			goto out_of_memory;
+		u->urb->transfer_buffer = ep->syncbuf + i * 4;
+		u->urb->transfer_dma = ep->sync_dma + i * 4;
+		u->urb->transfer_buffer_length = 4;
+		u->urb->pipe = ep->pipe;
+		u->urb->transfer_flags = URB_ISO_ASAP |
+					 URB_NO_TRANSFER_DMA_MAP;
+		u->urb->number_of_packets = 1;
+		u->urb->interval = 1 << ep->syncinterval;
+		u->urb->context = u;
+		u->urb->complete = snd_complete_urb;
+	}
+
+	ep->nurbs = SYNC_URBS;
+
+	return 0;
+
+out_of_memory:
+	release_urbs(ep, 0);
+	return -ENOMEM;
+}
+
+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 err;
+
+	if (ep->use_count != 0) {
+		snd_printk(KERN_WARNING "Unable to change format on ep #%x: already in use\n",
+			   ep->ep_num);
+		return -EBUSY;
+	}
+
+	/* release old buffers, if any */
+	release_urbs(ep, 0);
+
+	ep->datainterval = fmt->datainterval;
+	ep->maxpacksize = fmt->maxpacksize;
+	ep->fill_max = fmt->attributes & UAC_EP_CS_ATTR_FILL_MAX;
+
+	if (snd_usb_get_speed(ep->chip->dev) == USB_SPEED_FULL)
+		ep->freqn = get_usb_full_speed_rate(params_rate(hw_params));
+	else
+		ep->freqn = get_usb_high_speed_rate(params_rate(hw_params));
+
+	/* calculate the frequency in 16.16 format */
+	ep->freqm = ep->freqn;
+	ep->freqshift = INT_MIN;
+
+	ep->phase = 0;
+
+	switch (ep->type) {
+	case  SND_USB_ENDPOINT_TYPE_DATA:
+		err = data_ep_set_params(ep, hw_params, fmt, sync_ep);
+		break;
+	case  SND_USB_ENDPOINT_TYPE_SYNC:
+		err = sync_ep_set_params(ep, hw_params, fmt);
+		break;
+	default:
+		err = -EINVAL;
+	}
+
+	snd_printdd(KERN_DEBUG "Setting params for ep #%x (type %d, %d urbs), ret=%d\n",
+		   ep->ep_num, ep->type, ep->nurbs, err);
+
+	return err;
+}
+
+int snd_usb_endpoint_start(struct snd_usb_endpoint *ep)
+{
+	int err;
+	unsigned int i;
+
+	if (ep->chip->shutdown)
+		return -EBADFD;
+
+	/* already running? */
+	if (++ep->use_count != 1)
+		return 0;
+
+	if (snd_BUG_ON(!test_bit(EP_FLAG_ACTIVATED, &ep->flags)))
+		return -EINVAL;
+
+	/* just to be sure */
+	deactivate_urbs(ep, 0, 1);
+	wait_clear_urbs(ep);
+
+	ep->active_mask = 0;
+	ep->unlink_mask = 0;
+	ep->phase = 0;
+
+	/*
+	 * If this endpoint has a data endpoint as implicit feedback source,
+	 * don't start the urbs here. Instead, mark them all as available,
+	 * wait for the record urbs to arrive and queue from that context.
+	 */
+
+	set_bit(EP_FLAG_RUNNING, &ep->flags);
+
+	if (snd_usb_endpoint_implict_feedback_sink(ep)) {
+		for (i = 0; i < ep->nurbs; i++) {
+			struct snd_urb_ctx *ctx = ep->urb + i;
+			list_add_tail(&ctx->ready_list, &ep->ready_playback_urbs);
+		}
+
+		return 0;
+	}
+
+	for (i = 0; i < ep->nurbs; i++) {
+		struct urb *urb = ep->urb[i].urb;
+
+		if (snd_BUG_ON(!urb))
+			goto __error;
+
+		if (usb_pipeout(ep->pipe)) {
+			prepare_outbound_urb_sizes(ep, urb->context);
+			prepare_outbound_urb(ep, urb->context);
+		} else {
+			prepare_inbound_urb(ep, urb->context);
+		}
+
+		err = usb_submit_urb(urb, GFP_ATOMIC);
+		if (err < 0) {
+			snd_printk(KERN_ERR "cannot submit urb %d, error %d: %s\n",
+				   i, err, usb_error_string(err));
+			goto __error;
+		}
+		set_bit(i, &ep->active_mask);
+	}
+
+	return 0;
+
+__error:
+	clear_bit(EP_FLAG_RUNNING, &ep->flags);
+	ep->use_count--;
+	deactivate_urbs(ep, 0, 0);
+	return -EPIPE;
+}
+
+void snd_usb_endpoint_stop(struct snd_usb_endpoint *ep,
+			   int force, int can_sleep, int wait)
+{
+	if (!ep)
+		return;
+
+	if (snd_BUG_ON(ep->use_count == 0))
+		return;
+
+	if (snd_BUG_ON(!test_bit(EP_FLAG_ACTIVATED, &ep->flags)))
+		return;
+
+	if (--ep->use_count == 0) {
+		deactivate_urbs(ep, force, can_sleep);
+		ep->data_subs = NULL;
+		ep->sync_slave = NULL;
+		ep->retire_data_urb = NULL;
+		ep->prepare_data_urb = NULL;
+
+		if (wait)
+			wait_clear_urbs(ep);
+	}
+}
+
+int snd_usb_endpoint_activate(struct snd_usb_endpoint *ep)
+{
+	if (ep->use_count != 0)
+		return 0;
+
+	if (!ep->chip->shutdown &&
+	    !test_and_set_bit(EP_FLAG_ACTIVATED, &ep->flags)) {
+		int ret;
+
+		ret = usb_set_interface(ep->chip->dev, ep->iface, ep->alt_idx);
+		if (ret < 0) {
+			snd_printk(KERN_ERR "%s() usb_set_interface() failed, ret = %d\n",
+						__func__, ret);
+			clear_bit(EP_FLAG_ACTIVATED, &ep->flags);
+			return ret;
+		}
+
+		return 0;
+	}
+
+	return -EBUSY;
+}
+
+int snd_usb_endpoint_deactivate(struct snd_usb_endpoint *ep)
+{
+	if (!ep)
+		return -EINVAL;
+
+	if (ep->use_count != 0)
+		return 0;
+
+	if (!ep->chip->shutdown &&
+	    test_and_clear_bit(EP_FLAG_ACTIVATED, &ep->flags)) {
+		int ret;
+
+		ret = usb_set_interface(ep->chip->dev, ep->iface, 0);
+		if (ret < 0) {
+			snd_printk(KERN_ERR "%s(): usb_set_interface() failed, ret = %d\n",
+						__func__, ret);
+			return ret;
+		}
+
+		return 0;
+	}
+
+	return -EBUSY;
+}
+
+void snd_usb_endpoint_free(struct list_head *head)
+{
+	struct snd_usb_endpoint *ep;
+
+	ep = list_entry(head, struct snd_usb_endpoint, list);
+	release_urbs(ep, 1);
+	kfree(ep);
+}
+
+/*
+ * 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.
+ */
+void snd_usb_handle_sync_urb(struct snd_usb_endpoint *ep,
+			     struct snd_usb_endpoint *sender,
+			     const struct urb *urb)
+{
+	int shift;
+	unsigned int f;
+	unsigned long flags;
+
+	snd_BUG_ON(ep == sender);
+
+	if (snd_usb_endpoint_implict_feedback_sink(ep) &&
+	    ep->use_count != 0) {
+
+		/* implicit feedback case */
+		int i, bytes = 0;
+		struct snd_urb_ctx *in_ctx;
+		struct snd_usb_packet_info *out_packet;
+
+		in_ctx = urb->context;
+
+		/* Count overall packet size */
+		for (i = 0; i < in_ctx->packets; i++)
+			if (urb->iso_frame_desc[i].status == 0)
+				bytes += urb->iso_frame_desc[i].actual_length;
+
+		/*
+		 * skip empty packets. At least M-Audio's Fast Track Ultra stops
+		 * streaming once it received a 0-byte OUT URB
+		 */
+		if (bytes == 0)
+			return;
+
+		spin_lock_irqsave(&ep->lock, flags);
+		out_packet = ep->next_packet + ep->next_packet_write_pos;
+
+		/*
+		 * Iterate through the inbound packet and prepare the lengths
+		 * for the output packet. The OUT packet we are about to send
+		 * will have the same amount of payload than the IN packet we
+		 * just received.
+		 */
+
+		out_packet->packets = in_ctx->packets;
+		for (i = 0; i < in_ctx->packets; i++) {
+			if (urb->iso_frame_desc[i].status == 0)
+				out_packet->packet_size[i] =
+					urb->iso_frame_desc[i].actual_length / ep->stride;
+			else
+				out_packet->packet_size[i] = 0;
+		}
+
+		ep->next_packet_write_pos++;
+		ep->next_packet_write_pos %= MAX_URBS;
+		spin_unlock_irqrestore(&ep->lock, flags);
+		queue_pending_output_urbs(ep);
+
+		return;
+	}
+
+	/* parse sync endpoint packet */
+
+	if (urb->iso_frame_desc[0].status != 0 ||
+	    urb->iso_frame_desc[0].actual_length < 3)
+		return;
+
+	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;
+
+	if (unlikely(ep->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 < ep->freqn - ep->freqn / 4) {
+			f <<= 1;
+			shift++;
+		}
+		while (f > ep->freqn + ep->freqn / 2) {
+			f >>= 1;
+			shift--;
+		}
+		ep->freqshift = shift;
+	} else if (ep->freqshift >= 0)
+		f <<= ep->freqshift;
+	else
+		f >>= -ep->freqshift;
+
+	if (likely(f >= ep->freqn - ep->freqn / 8 && f <= ep->freqmax)) {
+		/*
+		 * If the frequency looks valid, set it.
+		 * This value is referred to in prepare_playback_urb().
+		 */
+		spin_lock_irqsave(&ep->lock, flags);
+		ep->freqm = f;
+		spin_unlock_irqrestore(&ep->lock, flags);
+	} else {
+		/*
+		 * Out of range; maybe the shift value is wrong.
+		 * Reset it so that we autodetect again the next time.
+		 */
+		ep->freqshift = INT_MIN;
+	}
+}
+
diff --git a/sound/usb/endpoint.h b/sound/usb/endpoint.h
index 88eb63a636eb..9f083d7d6cf1 100644
--- a/sound/usb/endpoint.h
+++ b/sound/usb/endpoint.h
@@ -18,4 +18,30 @@ 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 wait);
+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 */
diff --git a/sound/usb/usbaudio.h b/sound/usb/usbaudio.h
index a16c21d2d7ed..b8233ebe250f 100644
--- a/sound/usb/usbaudio.h
+++ b/sound/usb/usbaudio.h
@@ -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 */