// SPDX-License-Identifier: GPL-2.0-or-later

  /*

   */

  #include <linux/gfp.h>
  #include <linux/init.h>

  #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"
  #include "card.h"
  #include "endpoint.h"
  #include "pcm.h"

  #include "quirks.h"

  #define EP_FLAG_RUNNING		1

  #define EP_FLAG_STOPPING	2

  /*

   * snd_usb_endpoint is a model that abstracts everything related to an
   * USB endpoint and its streaming.
   *
   * There are functions to activate and deactivate the streaming URBs and

   * optional callbacks to let the pcm logic handle the actual content of the

   * packets for playback and record. Thus, the bus streaming and the audio
   * handlers are fully decoupled.
   *

   * There are two different types of endpoints in audio applications.

   *
   * SND_USB_ENDPOINT_TYPE_DATA handles full audio data payload for both
   * inbound and outbound traffic.
   *

   * SND_USB_ENDPOINT_TYPE_SYNC endpoints are for inbound traffic only and
   * expect the payload to carry Q10.14 / Q16.16 formatted sync information
   * (3 or 4 bytes).

   *

   * Each endpoint has to be configured prior to being used by calling
   * snd_usb_endpoint_set_params().

   *
   * The model incorporates a reference counting, so that multiple users
   * can call snd_usb_endpoint_start() and snd_usb_endpoint_stop(), and
   * only the first user will effectively start the URBs, and only the last

   * one to stop it will tear the URBs down again.

   */
  
  /*

   * convert a sampling rate into our full speed format (fs/1000 in Q16.16)
   * this will overflow at approx 524 kHz
   */
  static inline unsigned get_usb_full_speed_rate(unsigned int rate)
  {
  	return ((rate << 13) + 62) / 125;
  }
  
  /*
   * convert a sampling rate into USB high speed format (fs/8000 in Q16.16)
   * this will overflow at approx 4 MHz
   */
  static inline unsigned get_usb_high_speed_rate(unsigned int rate)
  {
  	return ((rate << 10) + 62) / 125;
  }
  
  /*

   * release a urb data
   */
  static void release_urb_ctx(struct snd_urb_ctx *u)
  {

  	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;

  }
  
  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";
  	}
  }

  /**
   * snd_usb_endpoint_implicit_feedback_sink: Report endpoint usage type
   *

   * @ep: The snd_usb_endpoint

   *
   * Determine whether an endpoint is driven by an implicit feedback
   * data endpoint source.
   */

  int snd_usb_endpoint_implicit_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);
  }

  /*
   * For streaming based on information derived from sync endpoints,

   * prepare_outbound_urb_sizes() will call slave_next_packet_size() to

   * determine the number of samples to be sent in the next packet.
   *

   * For implicit feedback, slave_next_packet_size() is unused.

   */

  int snd_usb_endpoint_slave_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;
  }

  /*
   * For adaptive and synchronous endpoints, prepare_outbound_urb_sizes()
   * will call next_packet_size() to determine the number of samples to be
   * sent in the next packet.
   */
  int snd_usb_endpoint_next_packet_size(struct snd_usb_endpoint *ep)
  {
  	int ret;
  
  	if (ep->fill_max)
  		return ep->maxframesize;
  
  	ep->sample_accum += ep->sample_rem;

  	if (ep->sample_accum >= ep->pps) {
  		ep->sample_accum -= ep->pps;
  		ret = ep->packsize[1];

  	} else {

  		ret = ep->packsize[0];

  	}
  
  	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 (unlikely(ep->skip_packets > 0)) {
  		ep->skip_packets--;
  		return;
  	}

  	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_silent_urb(struct snd_usb_endpoint *ep,
  			       struct snd_urb_ctx *ctx)
  {
  	struct urb *urb = ctx->urb;
  	unsigned int offs = 0;

  	unsigned int extra = 0;
  	__le32 packet_length;

  	int i;

  	/* For tx_length_quirk, put packet length at start of packet */
  	if (ep->chip->tx_length_quirk)
  		extra = sizeof(packet_length);

  	for (i = 0; i < ctx->packets; ++i) {

  		unsigned int offset;
  		unsigned int length;

  		int counts;
  
  		if (ctx->packet_size[i])
  			counts = ctx->packet_size[i];

  		else if (ep->sync_master)
  			counts = snd_usb_endpoint_slave_next_packet_size(ep);

  		else
  			counts = snd_usb_endpoint_next_packet_size(ep);

  		length = counts * ep->stride; /* number of silent bytes */
  		offset = offs * ep->stride + extra * i;
  		urb->iso_frame_desc[i].offset = offset;
  		urb->iso_frame_desc[i].length = length + extra;
  		if (extra) {
  			packet_length = cpu_to_le32(length);
  			memcpy(urb->transfer_buffer + offset,
  			       &packet_length, sizeof(packet_length));
  		}
  		memset(urb->transfer_buffer + offset + extra,
  		       ep->silence_value, length);

  		offs += counts;
  	}
  
  	urb->number_of_packets = ctx->packets;

  	urb->transfer_buffer_length = offs * ep->stride + ctx->packets * extra;

  }

  /*
   * Prepare a PLAYBACK urb for submission to the bus.
   */
  static void prepare_outbound_urb(struct snd_usb_endpoint *ep,
  				 struct snd_urb_ctx *ctx)
  {

  	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 */

  			prepare_silent_urb(ep, ctx);

  		}
  		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;
  	}
  }

  /*

   * Send output urbs that have been prepared previously. URBs are dequeued

   * from ep->ready_playback_urbs and in case there aren't any available

   * or there are no packets that have been prepared, this function does
   * nothing.
   *

   * The reason why the functionality of sending and preparing URBs is separated
   * is that host controllers don't guarantee the order in which they return
   * inbound and outbound packets to their submitters.

   *
   * This function is only used for implicit feedback endpoints. For endpoints

   * driven by dedicated sync endpoints, URBs are immediately re-submitted
   * from their completion handler.

   */

  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;

  		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);

  				list_del_init(&ctx->ready_list);
  			}

  		}
  		spin_unlock_irqrestore(&ep->lock, flags);
  
  		if (ctx == NULL)
  			return;

  		/* copy over the length information */
  		for (i = 0; i < packet->packets; i++)
  			ctx->packet_size[i] = packet->packet_size[i];

  		/* call the data handler to fill in playback data */

  		prepare_outbound_urb(ep, ctx);
  
  		err = usb_submit_urb(ctx->urb, GFP_ATOMIC);
  		if (err < 0)

  			usb_audio_err(ep->chip,
  				"Unable to submit urb #%d: %d (urb %p)
  ",
  				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;

  	struct snd_pcm_substream *substream;
  	unsigned long flags;

  	int err;
  
  	if (unlikely(urb->status == -ENOENT ||		/* unlinked */
  		     urb->status == -ENODEV ||		/* device removed */
  		     urb->status == -ECONNRESET ||	/* unlinked */

  		     urb->status == -ESHUTDOWN))	/* device disabled */
  		goto exit_clear;
  	/* device disconnected */
  	if (unlikely(atomic_read(&ep->chip->shutdown)))

  		goto exit_clear;

  	if (unlikely(!test_bit(EP_FLAG_RUNNING, &ep->flags)))
  		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_implicit_feedback_sink(ep)) {

  			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(ep, ctx);

  		/* can be stopped during prepare callback */
  		if (unlikely(!test_bit(EP_FLAG_RUNNING, &ep->flags)))
  			goto exit_clear;

  	} 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;

  	usb_audio_err(ep->chip, "cannot submit urb (err = %d)
  ", err);

  	if (ep->data_subs && ep->data_subs->pcm_substream) {
  		substream = ep->data_subs->pcm_substream;

  		snd_pcm_stop_xrun(substream);

  	}

  
  exit_clear:
  	clear_bit(ctx->index, &ep->active_mask);
  }

  /**

   * snd_usb_add_endpoint: Add an endpoint to an USB audio chip

   *
   * @chip: The chip
   * @alts: The USB host interface
   * @ep_num: The number of the endpoint to use
   * @direction: SNDRV_PCM_STREAM_PLAYBACK or SNDRV_PCM_STREAM_CAPTURE
   * @type: SND_USB_ENDPOINT_TYPE_DATA or SND_USB_ENDPOINT_TYPE_SYNC
   *
   * If the requested endpoint has not been added to the given chip before,
   * a new instance is created. Otherwise, a pointer to the previoulsy
   * created instance is returned. In case of any error, NULL is returned.
   *
   * New endpoints will be added to chip->ep_list and must be freed by
   * calling snd_usb_endpoint_free().

   *
   * For SND_USB_ENDPOINT_TYPE_SYNC, the caller needs to guarantee that
   * bNumEndpoints > 1 beforehand.

   */

  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 snd_usb_endpoint *ep;

  	int is_playback = direction == SNDRV_PCM_STREAM_PLAYBACK;

  	if (WARN_ON(!alts))
  		return NULL;

  	mutex_lock(&chip->mutex);

  	list_for_each_entry(ep, &chip->ep_list, list) {

  		if (ep->ep_num == ep_num &&
  		    ep->iface == alts->desc.bInterfaceNumber &&

  		    ep->altsetting == alts->desc.bAlternateSetting) {

  			usb_audio_dbg(ep->chip,
  				      "Re-using EP %x in iface %d,%d @%p
  ",

  					ep_num, ep->iface, ep->altsetting, ep);

  			goto __exit_unlock;
  		}
  	}

  	usb_audio_dbg(chip, "Creating new %s %s endpoint #%x
  ",

  		    is_playback ? "playback" : "capture",
  		    type == SND_USB_ENDPOINT_TYPE_DATA ? "data" : "sync",
  		    ep_num);

  	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->altsetting = 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);

  	ep->is_implicit_feedback = 0;

  __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);

  	int alive;
  
  	do {

  		alive = bitmap_weight(&ep->active_mask, ep->nurbs);

  		if (!alive)
  			break;
  
  		schedule_timeout_uninterruptible(1);
  	} while (time_before(jiffies, end_time));
  
  	if (alive)

  		usb_audio_err(ep->chip,
  			"timeout: still %d active urbs on EP #%x
  ",
  			alive, ep->ep_num);

  	clear_bit(EP_FLAG_STOPPING, &ep->flags);

  	ep->data_subs = NULL;
  	ep->sync_slave = NULL;
  	ep->retire_data_urb = NULL;
  	ep->prepare_data_urb = NULL;

  	return 0;
  }

  /* sync the pending stop operation;
   * this function itself doesn't trigger the stop operation
   */
  void snd_usb_endpoint_sync_pending_stop(struct snd_usb_endpoint *ep)
  {
  	if (ep && test_bit(EP_FLAG_STOPPING, &ep->flags))
  		wait_clear_urbs(ep);
  }

  /*
   * unlink active urbs.
   */

  static int deactivate_urbs(struct snd_usb_endpoint *ep, bool force)

  {

  	unsigned int i;

  	if (!force && atomic_read(&ep->chip->shutdown)) /* to be sure... */

  		return -EBADFD;

  	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;

  	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;

  				usb_unlink_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);

  	wait_clear_urbs(ep);
  
  	for (i = 0; i < ep->nurbs; i++)
  		release_urb_ctx(&ep->urb[i]);

  	usb_free_coherent(ep->chip->dev, SYNC_URBS * 4,
  			  ep->syncbuf, ep->sync_dma);

  
  	ep->syncbuf = NULL;
  	ep->nurbs = 0;
  }

  /*

   * Check data endpoint for format differences
   */
  static bool check_ep_params(struct snd_usb_endpoint *ep,
  			      snd_pcm_format_t pcm_format,
  			      unsigned int channels,
  			      unsigned int period_bytes,
  			      unsigned int frames_per_period,
  			      unsigned int periods_per_buffer,
  			      struct audioformat *fmt,
  			      struct snd_usb_endpoint *sync_ep)
  {
  	unsigned int maxsize, minsize, packs_per_ms, max_packs_per_urb;
  	unsigned int max_packs_per_period, urbs_per_period, urb_packs;
  	unsigned int max_urbs;
  	int frame_bits = snd_pcm_format_physical_width(pcm_format) * channels;
  	int tx_length_quirk = (ep->chip->tx_length_quirk &&
  			       usb_pipeout(ep->pipe));
  	bool ret = 1;
  
  	if (pcm_format == SNDRV_PCM_FORMAT_DSD_U16_LE && fmt->dsd_dop) {
  		/*
  		 * When operating in DSD DOP mode, the size of a sample frame
  		 * in hardware differs from the actual physical format width
  		 * because we need to make room for the DOP markers.
  		 */
  		frame_bits += channels << 3;
  	}
  
  	ret = ret && (ep->datainterval == fmt->datainterval);
  	ret = ret && (ep->stride == frame_bits >> 3);
  
  	switch (pcm_format) {
  	case SNDRV_PCM_FORMAT_U8:
  		ret = ret && (ep->silence_value == 0x80);
  		break;
  	case SNDRV_PCM_FORMAT_DSD_U8:
  	case SNDRV_PCM_FORMAT_DSD_U16_LE:
  	case SNDRV_PCM_FORMAT_DSD_U32_LE:
  	case SNDRV_PCM_FORMAT_DSD_U16_BE:
  	case SNDRV_PCM_FORMAT_DSD_U32_BE:
  		ret = ret && (ep->silence_value == 0x69);
  		break;
  	default:
  		ret = ret && (ep->silence_value == 0);
  	}
  
  	/* assume max. frequency is 50% higher than nominal */
  	ret = ret && (ep->freqmax == ep->freqn + (ep->freqn >> 1));
  	/* Round up freqmax to nearest integer in order to calculate maximum
  	 * packet size, which must represent a whole number of frames.
  	 * This is accomplished by adding 0x0.ffff before converting the
  	 * Q16.16 format into integer.
  	 * In order to accurately calculate the maximum packet size when
  	 * the data interval is more than 1 (i.e. ep->datainterval > 0),
  	 * multiply by the data interval prior to rounding. For instance,
  	 * a freqmax of 41 kHz will result in a max packet size of 6 (5.125)
  	 * frames with a data interval of 1, but 11 (10.25) frames with a
  	 * data interval of 2.
  	 * (ep->freqmax << ep->datainterval overflows at 8.192 MHz for the
  	 * maximum datainterval value of 3, at USB full speed, higher for
  	 * USB high speed, noting that ep->freqmax is in units of
  	 * frames per packet in Q16.16 format.)
  	 */
  	maxsize = (((ep->freqmax << ep->datainterval) + 0xffff) >> 16) *
  			 (frame_bits >> 3);
  	if (tx_length_quirk)
  		maxsize += sizeof(__le32); /* Space for length descriptor */
  	/* but wMaxPacketSize might reduce this */
  	if (ep->maxpacksize && ep->maxpacksize < maxsize) {
  		/* whatever fits into a max. size packet */
  		unsigned int data_maxsize = maxsize = ep->maxpacksize;
  
  		if (tx_length_quirk)
  			/* Need to remove the length descriptor to calc freq */
  			data_maxsize -= sizeof(__le32);
  		ret = ret && (ep->freqmax == (data_maxsize / (frame_bits >> 3))
  				<< (16 - ep->datainterval));
  	}
  
  	if (ep->fill_max)
  		ret = ret && (ep->curpacksize == ep->maxpacksize);
  	else
  		ret = ret && (ep->curpacksize == maxsize);
  
  	if (snd_usb_get_speed(ep->chip->dev) != USB_SPEED_FULL) {
  		packs_per_ms = 8 >> ep->datainterval;
  		max_packs_per_urb = MAX_PACKS_HS;
  	} else {
  		packs_per_ms = 1;
  		max_packs_per_urb = MAX_PACKS;
  	}
  	if (sync_ep && !snd_usb_endpoint_implicit_feedback_sink(ep))
  		max_packs_per_urb = min(max_packs_per_urb,
  					1U << sync_ep->syncinterval);
  	max_packs_per_urb = max(1u, max_packs_per_urb >> ep->datainterval);
  
  	/*
  	 * Capture endpoints need to use small URBs because there's no way
  	 * to tell in advance where the next period will end, and we don't
  	 * want the next URB to complete much after the period ends.
  	 *
  	 * Playback endpoints with implicit sync much use the same parameters
  	 * as their corresponding capture endpoint.
  	 */
  	if (usb_pipein(ep->pipe) ||
  			snd_usb_endpoint_implicit_feedback_sink(ep)) {
  
  		urb_packs = packs_per_ms;
  		/*
  		 * Wireless devices can poll at a max rate of once per 4ms.
  		 * For dataintervals less than 5, increase the packet count to
  		 * allow the host controller to use bursting to fill in the
  		 * gaps.
  		 */
  		if (snd_usb_get_speed(ep->chip->dev) == USB_SPEED_WIRELESS) {
  			int interval = ep->datainterval;
  
  			while (interval < 5) {
  				urb_packs <<= 1;
  				++interval;
  			}
  		}
  		/* make capture URBs <= 1 ms and smaller than a period */
  		urb_packs = min(max_packs_per_urb, urb_packs);
  		while (urb_packs > 1 && urb_packs * maxsize >= period_bytes)
  			urb_packs >>= 1;
  		ret = ret && (ep->nurbs == MAX_URBS);
  
  	/*
  	 * Playback endpoints without implicit sync are adjusted so that
  	 * a period fits as evenly as possible in the smallest number of
  	 * URBs.  The total number of URBs is adjusted to the size of the
  	 * ALSA buffer, subject to the MAX_URBS and MAX_QUEUE limits.
  	 */
  	} else {
  		/* 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);
  
  		/* how many packets will contain an entire ALSA period? */
  		max_packs_per_period = DIV_ROUND_UP(period_bytes, minsize);
  
  		/* how many URBs will contain a period? */
  		urbs_per_period = DIV_ROUND_UP(max_packs_per_period,
  				max_packs_per_urb);
  		/* how many packets are needed in each URB? */
  		urb_packs = DIV_ROUND_UP(max_packs_per_period, urbs_per_period);
  
  		/* limit the number of frames in a single URB */
  		ret = ret && (ep->max_urb_frames ==
  			DIV_ROUND_UP(frames_per_period, urbs_per_period));
  
  		/* try to use enough URBs to contain an entire ALSA buffer */
  		max_urbs = min((unsigned) MAX_URBS,
  				MAX_QUEUE * packs_per_ms / urb_packs);
  		ret = ret && (ep->nurbs == min(max_urbs,
  				urbs_per_period * periods_per_buffer));
  	}
  
  	ret = ret && (ep->datainterval == fmt->datainterval);
  	ret = ret && (ep->maxpacksize == fmt->maxpacksize);
  	ret = ret &&
  		(ep->fill_max == !!(fmt->attributes & UAC_EP_CS_ATTR_FILL_MAX));
  
  	return ret;
  }
  
  /*

   * configure a data endpoint
   */

  static int data_ep_set_params(struct snd_usb_endpoint *ep,

  			      snd_pcm_format_t pcm_format,
  			      unsigned int channels,
  			      unsigned int period_bytes,

  			      unsigned int frames_per_period,
  			      unsigned int periods_per_buffer,

  			      struct audioformat *fmt,
  			      struct snd_usb_endpoint *sync_ep)
  {

  	unsigned int maxsize, minsize, packs_per_ms, max_packs_per_urb;
  	unsigned int max_packs_per_period, urbs_per_period, urb_packs;
  	unsigned int max_urbs, i;

  	int frame_bits = snd_pcm_format_physical_width(pcm_format) * channels;

  	int tx_length_quirk = (ep->chip->tx_length_quirk &&
  			       usb_pipeout(ep->pipe));

  	if (pcm_format == SNDRV_PCM_FORMAT_DSD_U16_LE && fmt->dsd_dop) {
  		/*
  		 * When operating in DSD DOP mode, the size of a sample frame
  		 * in hardware differs from the actual physical format width
  		 * because we need to make room for the DOP markers.
  		 */
  		frame_bits += channels << 3;
  	}

  	ep->datainterval = fmt->datainterval;
  	ep->stride = frame_bits >> 3;

  
  	switch (pcm_format) {
  	case SNDRV_PCM_FORMAT_U8:
  		ep->silence_value = 0x80;
  		break;
  	case SNDRV_PCM_FORMAT_DSD_U8:
  	case SNDRV_PCM_FORMAT_DSD_U16_LE:
  	case SNDRV_PCM_FORMAT_DSD_U32_LE:
  	case SNDRV_PCM_FORMAT_DSD_U16_BE:
  	case SNDRV_PCM_FORMAT_DSD_U32_BE:
  		ep->silence_value = 0x69;
  		break;
  	default:
  		ep->silence_value = 0;
  	}

  	/* assume max. frequency is 50% higher than nominal */
  	ep->freqmax = ep->freqn + (ep->freqn >> 1);

  	/* Round up freqmax to nearest integer in order to calculate maximum
  	 * packet size, which must represent a whole number of frames.
  	 * This is accomplished by adding 0x0.ffff before converting the
  	 * Q16.16 format into integer.
  	 * In order to accurately calculate the maximum packet size when
  	 * the data interval is more than 1 (i.e. ep->datainterval > 0),
  	 * multiply by the data interval prior to rounding. For instance,
  	 * a freqmax of 41 kHz will result in a max packet size of 6 (5.125)
  	 * frames with a data interval of 1, but 11 (10.25) frames with a
  	 * data interval of 2.
  	 * (ep->freqmax << ep->datainterval overflows at 8.192 MHz for the
  	 * maximum datainterval value of 3, at USB full speed, higher for
  	 * USB high speed, noting that ep->freqmax is in units of
  	 * frames per packet in Q16.16 format.)
  	 */
  	maxsize = (((ep->freqmax << ep->datainterval) + 0xffff) >> 16) *
  			 (frame_bits >> 3);

  	if (tx_length_quirk)
  		maxsize += sizeof(__le32); /* Space for length descriptor */

  	/* but wMaxPacketSize might reduce this */
  	if (ep->maxpacksize && ep->maxpacksize < maxsize) {

  		/* whatever fits into a max. size packet */

  		unsigned int data_maxsize = maxsize = ep->maxpacksize;
  
  		if (tx_length_quirk)
  			/* Need to remove the length descriptor to calc freq */
  			data_maxsize -= sizeof(__le32);
  		ep->freqmax = (data_maxsize / (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;

  		max_packs_per_urb = MAX_PACKS_HS;

  	} else {

  		packs_per_ms = 1;
  		max_packs_per_urb = MAX_PACKS;

  	}

  	if (sync_ep && !snd_usb_endpoint_implicit_feedback_sink(ep))

  		max_packs_per_urb = min(max_packs_per_urb,
  					1U << sync_ep->syncinterval);
  	max_packs_per_urb = max(1u, max_packs_per_urb >> ep->datainterval);
  
  	/*
  	 * Capture endpoints need to use small URBs because there's no way
  	 * to tell in advance where the next period will end, and we don't
  	 * want the next URB to complete much after the period ends.
  	 *
  	 * Playback endpoints with implicit sync much use the same parameters
  	 * as their corresponding capture endpoint.
  	 */
  	if (usb_pipein(ep->pipe) ||
  			snd_usb_endpoint_implicit_feedback_sink(ep)) {

  		urb_packs = packs_per_ms;
  		/*
  		 * Wireless devices can poll at a max rate of once per 4ms.
  		 * For dataintervals less than 5, increase the packet count to
  		 * allow the host controller to use bursting to fill in the
  		 * gaps.
  		 */
  		if (snd_usb_get_speed(ep->chip->dev) == USB_SPEED_WIRELESS) {
  			int interval = ep->datainterval;
  			while (interval < 5) {
  				urb_packs <<= 1;
  				++interval;
  			}
  		}

  		/* make capture URBs <= 1 ms and smaller than a period */

  		urb_packs = min(max_packs_per_urb, urb_packs);

  		while (urb_packs > 1 && urb_packs * maxsize >= period_bytes)
  			urb_packs >>= 1;
  		ep->nurbs = MAX_URBS;

  	/*
  	 * Playback endpoints without implicit sync are adjusted so that
  	 * a period fits as evenly as possible in the smallest number of
  	 * URBs.  The total number of URBs is adjusted to the size of the
  	 * ALSA buffer, subject to the MAX_URBS and MAX_QUEUE limits.
  	 */
  	} else {

  		/* 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);

  		/* how many packets will contain an entire ALSA period? */
  		max_packs_per_period = DIV_ROUND_UP(period_bytes, minsize);
  
  		/* how many URBs will contain a period? */
  		urbs_per_period = DIV_ROUND_UP(max_packs_per_period,
  				max_packs_per_urb);
  		/* how many packets are needed in each URB? */
  		urb_packs = DIV_ROUND_UP(max_packs_per_period, urbs_per_period);
  
  		/* limit the number of frames in a single URB */
  		ep->max_urb_frames = DIV_ROUND_UP(frames_per_period,
  					urbs_per_period);
  
  		/* try to use enough URBs to contain an entire ALSA buffer */
  		max_urbs = min((unsigned) MAX_URBS,
  				MAX_QUEUE * packs_per_ms / urb_packs);
  		ep->nurbs = min(max_urbs, urbs_per_period * periods_per_buffer);

  	}
  
  	/* 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 = urb_packs;

  		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_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;
  }

  /*
   * configure a sync endpoint
   */

  static int sync_ep_set_params(struct snd_usb_endpoint *ep)

  {
  	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_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;
  }

  /**

   * snd_usb_endpoint_set_params: configure an snd_usb_endpoint

   *

   * @ep: the snd_usb_endpoint to configure

   * @pcm_format: the audio fomat.
   * @channels: the number of audio channels.
   * @period_bytes: the number of bytes in one alsa period.

   * @period_frames: the number of frames in one alsa period.
   * @buffer_periods: the number of periods in one alsa buffer.

   * @rate: the frame rate.

   * @fmt: the USB audio format information
   * @sync_ep: the sync endpoint to use, if any

   *

   * Determine the number of URBs to be used on this endpoint.

   * An endpoint must be configured before it can be started.
   * An endpoint that is already running can not be reconfigured.
   */

  int snd_usb_endpoint_set_params(struct snd_usb_endpoint *ep,

  				snd_pcm_format_t pcm_format,
  				unsigned int channels,
  				unsigned int period_bytes,

  				unsigned int period_frames,
  				unsigned int buffer_periods,

  				unsigned int rate,

  				struct audioformat *fmt,
  				struct snd_usb_endpoint *sync_ep)
  {
  	int err;
  
  	if (ep->use_count != 0) {

  		bool check = ep->is_implicit_feedback &&
  			check_ep_params(ep, pcm_format,
  					     channels, period_bytes,
  					     period_frames, buffer_periods,
  					     fmt, sync_ep);
  
  		if (!check) {
  			usb_audio_warn(ep->chip,
  				"Unable to change format on ep #%x: already in use
  ",
  				ep->ep_num);
  			return -EBUSY;
  		}
  
  		usb_audio_dbg(ep->chip,
  			      "Ep #%x already in use as implicit feedback but format not changed
  ",
  			      ep->ep_num);
  		return 0;

  	}
  
  	/* 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(rate);

  		ep->pps = 1000 >> ep->datainterval;

  	} else {

  		ep->freqn = get_usb_high_speed_rate(rate);

  		ep->pps = 8000 >> ep->datainterval;

  	}

  	ep->sample_rem = rate % ep->pps;
  	ep->packsize[0] = rate / ep->pps;
  	ep->packsize[1] = (rate + (ep->pps - 1)) / ep->pps;

  
  	/* 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, pcm_format, channels,

  					 period_bytes, period_frames,
  					 buffer_periods, fmt, sync_ep);

  		break;
  	case  SND_USB_ENDPOINT_TYPE_SYNC:

  		err = sync_ep_set_params(ep);

  		break;
  	default:
  		err = -EINVAL;
  	}

  	usb_audio_dbg(ep->chip,
  		"Setting params for ep #%x (type %d, %d urbs), ret=%d
  ",
  		ep->ep_num, ep->type, ep->nurbs, err);

  
  	return err;
  }

  /**
   * snd_usb_endpoint_start: start an snd_usb_endpoint
   *

   * @ep: the endpoint to start

   *
   * A call to this function will increment the use count of the endpoint.

   * In case it is not already running, the URBs for this endpoint will be

   * submitted. Otherwise, this function does nothing.
   *
   * Must be balanced to calls of snd_usb_endpoint_stop().
   *
   * Returns an error if the URB submission failed, 0 in all other cases.
   */

  int snd_usb_endpoint_start(struct snd_usb_endpoint *ep)

  {
  	int err;
  	unsigned int i;

  	if (atomic_read(&ep->chip->shutdown))

  		return -EBADFD;
  
  	/* already running? */
  	if (++ep->use_count != 1)
  		return 0;

  	/* just to be sure */

  	deactivate_urbs(ep, false);

  	ep->active_mask = 0;
  	ep->unlink_mask = 0;
  	ep->phase = 0;

  	ep->sample_accum = 0;

  	snd_usb_endpoint_start_quirk(ep);

  	/*
  	 * 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 return and queue the playback urbs
  	 * from that context.

  	 */
  
  	set_bit(EP_FLAG_RUNNING, &ep->flags);

  	if (snd_usb_endpoint_implicit_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(ep, urb->context);
  		} else {
  			prepare_inbound_urb(ep, urb->context);
  		}
  
  		err = usb_submit_urb(urb, GFP_ATOMIC);
  		if (err < 0) {

  			usb_audio_err(ep->chip,
  				"cannot submit urb %d, error %d: %s
  ",
  				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, false);

  	return -EPIPE;
  }

  /**
   * snd_usb_endpoint_stop: stop an snd_usb_endpoint
   *
   * @ep: the endpoint to stop (may be NULL)
   *
   * A call to this function will decrement the use count of the endpoint.
   * In case the last user has requested the endpoint stop, the URBs will

   * actually be deactivated.

   *
   * Must be balanced to calls of snd_usb_endpoint_start().

   *
   * The caller needs to synchronize the pending stop operation via
   * snd_usb_endpoint_sync_pending_stop().

   */

  void snd_usb_endpoint_stop(struct snd_usb_endpoint *ep)

  {
  	if (!ep)
  		return;
  
  	if (snd_BUG_ON(ep->use_count == 0))
  		return;

  	if (--ep->use_count == 0) {

  		deactivate_urbs(ep, false);

  		set_bit(EP_FLAG_STOPPING, &ep->flags);

  	}
  }

  /**

   * snd_usb_endpoint_deactivate: deactivate an snd_usb_endpoint
   *
   * @ep: the endpoint to deactivate
   *

   * If the endpoint is not currently in use, this functions will
   * deactivate its associated URBs.

   *
   * In case of any active users, this functions does nothing.

   */

  void snd_usb_endpoint_deactivate(struct snd_usb_endpoint *ep)

  {
  	if (!ep)

  		return;

  
  	if (ep->use_count != 0)

  		return;

  	deactivate_urbs(ep, true);
  	wait_clear_urbs(ep);

  }

  /**

   * snd_usb_endpoint_release: Tear down an snd_usb_endpoint
   *
   * @ep: the endpoint to release
   *
   * This function does not care for the endpoint's use count but will tear
   * down all the streaming URBs immediately.
   */
  void snd_usb_endpoint_release(struct snd_usb_endpoint *ep)
  {
  	release_urbs(ep, 1);
  }
  
  /**

   * snd_usb_endpoint_free: Free the resources of an snd_usb_endpoint

   *

   * @ep: the endpoint to free

   *

   * This free all resources of the given ep.

   */

  void snd_usb_endpoint_free(struct snd_usb_endpoint *ep)

  {

  	kfree(ep);
  }

  /**
   * snd_usb_handle_sync_urb: parse an USB sync packet
   *
   * @ep: the endpoint to handle the packet
   * @sender: the sending endpoint
   * @urb: the received packet
   *
   * This function is called from the context of an endpoint that received
   * the packet and is used to let another endpoint object handle the payload.

   */
  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);

  	/*
  	 * In case the endpoint is operating in implicit feedback mode, prepare

  	 * a new outbound URB that has the same layout as the received packet
  	 * and add it to the list of pending urbs. queue_pending_output_urbs()
  	 * will take care of them later.

  	 */

  	if (snd_usb_endpoint_implicit_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 bytes per stride as the
  		 * IN packet we just received. Since the actual size is scaled
  		 * by the stride, use the sender stride to calculate the length
  		 * in case the number of channels differ between the implicitly
  		 * fed-back endpoint and the synchronizing endpoint.

  		 */
  
  		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 / sender->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;
  	}

  	/*
  	 * 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.
  	 */

  
  	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(sender->tenor_fb_quirk)) {

  		/*

  		 * Devices based on Tenor 8802 chipsets (TEAC UD-H01
  		 * and others) sometimes change the feedback value

  		 * by +/- 0x1.0000.
  		 */
  		if (f < ep->freqn - 0x8000)

  			f += 0xf000;

  		else if (f > ep->freqn + 0x8000)

  			f -= 0xf000;

  	} else 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;
  	}
  }