/*
   *   This program is free software; you can redistribute it and/or modify
   *   it under the terms of the GNU General Public License as published by
   *   the Free Software Foundation; either version 2 of the License, or
   *   (at your option) any later version.
   *
   *   This program is distributed in the hope that it will be useful,
   *   but WITHOUT ANY WARRANTY; without even the implied warranty of
   *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   *   GNU General Public License for more details.
   *
   *   You should have received a copy of the GNU General Public License
   *   along with this program; if not, write to the Free Software
   *   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307 USA
   */
  
  #include <linux/init.h>

  #include <linux/slab.h>

  #include <linux/bitrev.h>

  #include <linux/ratelimit.h>

  #include <linux/usb.h>
  #include <linux/usb/audio.h>

  #include <linux/usb/audio-v2.h>

  
  #include <sound/core.h>
  #include <sound/pcm.h>
  #include <sound/pcm_params.h>
  
  #include "usbaudio.h"
  #include "card.h"
  #include "quirks.h"
  #include "debug.h"

  #include "endpoint.h"

  #include "helper.h"
  #include "pcm.h"

  #include "clock.h"

  #include "power.h"

  #define SUBSTREAM_FLAG_DATA_EP_STARTED	0
  #define SUBSTREAM_FLAG_SYNC_EP_STARTED	1

  /* return the estimated delay based on USB frame counters */
  snd_pcm_uframes_t snd_usb_pcm_delay(struct snd_usb_substream *subs,
  				    unsigned int rate)
  {
  	int current_frame_number;
  	int frame_diff;
  	int est_delay;

  	if (!subs->last_delay)
  		return 0; /* short path */

  	current_frame_number = usb_get_current_frame_number(subs->dev);
  	/*
  	 * HCD implementations use different widths, use lower 8 bits.
  	 * The delay will be managed up to 256ms, which is more than
  	 * enough
  	 */
  	frame_diff = (current_frame_number - subs->last_frame_number) & 0xff;
  
  	/* Approximation based on number of samples per USB frame (ms),
  	   some truncation for 44.1 but the estimate is good enough */

  	est_delay =  frame_diff * rate / 1000;
  	if (subs->direction == SNDRV_PCM_STREAM_PLAYBACK)
  		est_delay = subs->last_delay - est_delay;
  	else
  		est_delay = subs->last_delay + est_delay;

  	if (est_delay < 0)
  		est_delay = 0;
  	return est_delay;
  }

  /*
   * return the current pcm pointer.  just based on the hwptr_done value.
   */
  static snd_pcm_uframes_t snd_usb_pcm_pointer(struct snd_pcm_substream *substream)
  {
  	struct snd_usb_substream *subs;
  	unsigned int hwptr_done;
  
  	subs = (struct snd_usb_substream *)substream->runtime->private_data;

  	if (atomic_read(&subs->stream->chip->shutdown))

  		return SNDRV_PCM_POS_XRUN;

  	spin_lock(&subs->lock);
  	hwptr_done = subs->hwptr_done;

  	substream->runtime->delay = snd_usb_pcm_delay(subs,

  						substream->runtime->rate);

  	spin_unlock(&subs->lock);
  	return hwptr_done / (substream->runtime->frame_bits >> 3);
  }
  
  /*
   * find a matching audio format
   */

  static struct audioformat *find_format(struct snd_usb_substream *subs)

  {

  	struct audioformat *fp;

  	struct audioformat *found = NULL;
  	int cur_attr = 0, attr;

  	list_for_each_entry(fp, &subs->fmt_list, list) {

  		if (!(fp->formats & pcm_format_to_bits(subs->pcm_format)))

  			continue;

  		if (fp->channels != subs->channels)

  			continue;

  		if (subs->cur_rate < fp->rate_min ||
  		    subs->cur_rate > fp->rate_max)

  			continue;
  		if (! (fp->rates & SNDRV_PCM_RATE_CONTINUOUS)) {
  			unsigned int i;
  			for (i = 0; i < fp->nr_rates; i++)

  				if (fp->rate_table[i] == subs->cur_rate)

  					break;
  			if (i >= fp->nr_rates)
  				continue;
  		}
  		attr = fp->ep_attr & USB_ENDPOINT_SYNCTYPE;
  		if (! found) {
  			found = fp;
  			cur_attr = attr;
  			continue;
  		}
  		/* avoid async out and adaptive in if the other method
  		 * supports the same format.
  		 * this is a workaround for the case like
  		 * M-audio audiophile USB.
  		 */
  		if (attr != cur_attr) {
  			if ((attr == USB_ENDPOINT_SYNC_ASYNC &&
  			     subs->direction == SNDRV_PCM_STREAM_PLAYBACK) ||
  			    (attr == USB_ENDPOINT_SYNC_ADAPTIVE &&
  			     subs->direction == SNDRV_PCM_STREAM_CAPTURE))
  				continue;
  			if ((cur_attr == USB_ENDPOINT_SYNC_ASYNC &&
  			     subs->direction == SNDRV_PCM_STREAM_PLAYBACK) ||
  			    (cur_attr == USB_ENDPOINT_SYNC_ADAPTIVE &&
  			     subs->direction == SNDRV_PCM_STREAM_CAPTURE)) {
  				found = fp;
  				cur_attr = attr;
  				continue;
  			}
  		}
  		/* find the format with the largest max. packet size */
  		if (fp->maxpacksize > found->maxpacksize) {
  			found = fp;
  			cur_attr = attr;
  		}
  	}
  	return found;
  }

  static int init_pitch_v1(struct snd_usb_audio *chip, int iface,
  			 struct usb_host_interface *alts,
  			 struct audioformat *fmt)
  {
  	struct usb_device *dev = chip->dev;
  	unsigned int ep;
  	unsigned char data[1];
  	int err;

  	if (get_iface_desc(alts)->bNumEndpoints < 1)
  		return -EINVAL;

  	ep = get_endpoint(alts, 0)->bEndpointAddress;

  	data[0] = 1;
  	if ((err = snd_usb_ctl_msg(dev, usb_sndctrlpipe(dev, 0), UAC_SET_CUR,
  				   USB_TYPE_CLASS|USB_RECIP_ENDPOINT|USB_DIR_OUT,
  				   UAC_EP_CS_ATTR_PITCH_CONTROL << 8, ep,

  				   data, sizeof(data))) < 0) {

  		usb_audio_err(chip, "%d:%d: cannot set enable PITCH
  ",
  			      iface, ep);

  		return err;
  	}
  
  	return 0;
  }

  static int init_pitch_v2(struct snd_usb_audio *chip, int iface,
  			 struct usb_host_interface *alts,
  			 struct audioformat *fmt)
  {
  	struct usb_device *dev = chip->dev;
  	unsigned char data[1];

  	int err;

  	data[0] = 1;
  	if ((err = snd_usb_ctl_msg(dev, usb_sndctrlpipe(dev, 0), UAC2_CS_CUR,
  				   USB_TYPE_CLASS | USB_RECIP_ENDPOINT | USB_DIR_OUT,
  				   UAC2_EP_CS_PITCH << 8, 0,

  				   data, sizeof(data))) < 0) {

  		usb_audio_err(chip, "%d:%d: cannot set enable PITCH (v2)
  ",
  			      iface, fmt->altsetting);

  		return err;
  	}
  
  	return 0;
  }

  /*

   * initialize the pitch control and sample rate

   */

  int snd_usb_init_pitch(struct snd_usb_audio *chip, int iface,

  		       struct usb_host_interface *alts,
  		       struct audioformat *fmt)
  {

  	/* if endpoint doesn't have pitch control, bail out */
  	if (!(fmt->attributes & UAC_EP_CS_ATTR_PITCH_CONTROL))
  		return 0;

  	switch (fmt->protocol) {

  	case UAC_VERSION_1:

  	default:

  		return init_pitch_v1(chip, iface, alts, fmt);
  
  	case UAC_VERSION_2:

  		return init_pitch_v2(chip, iface, alts, fmt);

  	}

  }

  static int start_endpoints(struct snd_usb_substream *subs)

  {
  	int err;
  
  	if (!subs->data_endpoint)
  		return -EINVAL;
  
  	if (!test_and_set_bit(SUBSTREAM_FLAG_DATA_EP_STARTED, &subs->flags)) {
  		struct snd_usb_endpoint *ep = subs->data_endpoint;

  		dev_dbg(&subs->dev->dev, "Starting data EP @%p
  ", ep);

  
  		ep->data_subs = subs;

  		err = snd_usb_endpoint_start(ep);

  		if (err < 0) {
  			clear_bit(SUBSTREAM_FLAG_DATA_EP_STARTED, &subs->flags);
  			return err;
  		}
  	}
  
  	if (subs->sync_endpoint &&
  	    !test_and_set_bit(SUBSTREAM_FLAG_SYNC_EP_STARTED, &subs->flags)) {
  		struct snd_usb_endpoint *ep = subs->sync_endpoint;

  		if (subs->data_endpoint->iface != subs->sync_endpoint->iface ||

  		    subs->data_endpoint->altsetting != subs->sync_endpoint->altsetting) {

  			err = usb_set_interface(subs->dev,
  						subs->sync_endpoint->iface,

  						subs->sync_endpoint->altsetting);

  			if (err < 0) {

  				clear_bit(SUBSTREAM_FLAG_SYNC_EP_STARTED, &subs->flags);

  				dev_err(&subs->dev->dev,
  					   "%d:%d: cannot set interface (%d)
  ",

  					   subs->sync_endpoint->iface,

  					   subs->sync_endpoint->altsetting, err);

  				return -EIO;
  			}
  		}

  		dev_dbg(&subs->dev->dev, "Starting sync EP @%p
  ", ep);

  
  		ep->sync_slave = subs->data_endpoint;

  		err = snd_usb_endpoint_start(ep);

  		if (err < 0) {
  			clear_bit(SUBSTREAM_FLAG_SYNC_EP_STARTED, &subs->flags);
  			return err;
  		}
  	}
  
  	return 0;
  }

  static void stop_endpoints(struct snd_usb_substream *subs, bool wait)

  {
  	if (test_and_clear_bit(SUBSTREAM_FLAG_SYNC_EP_STARTED, &subs->flags))

  		snd_usb_endpoint_stop(subs->sync_endpoint);

  
  	if (test_and_clear_bit(SUBSTREAM_FLAG_DATA_EP_STARTED, &subs->flags))

  		snd_usb_endpoint_stop(subs->data_endpoint);
  
  	if (wait) {
  		snd_usb_endpoint_sync_pending_stop(subs->sync_endpoint);
  		snd_usb_endpoint_sync_pending_stop(subs->data_endpoint);
  	}

  }

  static int search_roland_implicit_fb(struct usb_device *dev, int ifnum,
  				     unsigned int altsetting,
  				     struct usb_host_interface **alts,
  				     unsigned int *ep)
  {
  	struct usb_interface *iface;
  	struct usb_interface_descriptor *altsd;
  	struct usb_endpoint_descriptor *epd;
  
  	iface = usb_ifnum_to_if(dev, ifnum);
  	if (!iface || iface->num_altsetting < altsetting + 1)
  		return -ENOENT;
  	*alts = &iface->altsetting[altsetting];
  	altsd = get_iface_desc(*alts);
  	if (altsd->bAlternateSetting != altsetting ||
  	    altsd->bInterfaceClass != USB_CLASS_VENDOR_SPEC ||
  	    (altsd->bInterfaceSubClass != 2 &&
  	     altsd->bInterfaceProtocol != 2   ) ||
  	    altsd->bNumEndpoints < 1)
  		return -ENOENT;
  	epd = get_endpoint(*alts, 0);
  	if (!usb_endpoint_is_isoc_in(epd) ||
  	    (epd->bmAttributes & USB_ENDPOINT_USAGE_MASK) !=
  					USB_ENDPOINT_USAGE_IMPLICIT_FB)
  		return -ENOENT;
  	*ep = epd->bEndpointAddress;
  	return 0;
  }

  static int set_sync_ep_implicit_fb_quirk(struct snd_usb_substream *subs,
  					 struct usb_device *dev,
  					 struct usb_interface_descriptor *altsd,
  					 unsigned int attr)

  {

  	struct usb_host_interface *alts;

  	struct usb_interface *iface;

  	unsigned int ep;

  	/* Implicit feedback sync EPs consumers are always playback EPs */
  	if (subs->direction != SNDRV_PCM_STREAM_PLAYBACK)
  		return 0;

  	switch (subs->stream->chip->usb_id) {

  	case USB_ID(0x0763, 0x2030): /* M-Audio Fast Track C400 */

  	case USB_ID(0x0763, 0x2031): /* M-Audio Fast Track C600 */

  		ep = 0x81;
  		iface = usb_ifnum_to_if(dev, 3);

  		if (!iface || iface->num_altsetting == 0)
  			return -EINVAL;

  		alts = &iface->altsetting[1];
  		goto add_sync_ep;

  		break;

  	case USB_ID(0x0763, 0x2080): /* M-Audio FastTrack Ultra */
  	case USB_ID(0x0763, 0x2081):

  		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 (attr == USB_ENDPOINT_SYNC_ASYNC &&

  	    altsd->bInterfaceClass == USB_CLASS_VENDOR_SPEC &&
  	    altsd->bInterfaceProtocol == 2 &&
  	    altsd->bNumEndpoints == 1 &&
  	    USB_ID_VENDOR(subs->stream->chip->usb_id) == 0x0582 /* Roland */ &&
  	    search_roland_implicit_fb(dev, altsd->bInterfaceNumber + 1,
  				      altsd->bAlternateSetting,
  				      &alts, &ep) >= 0) {

  		goto add_sync_ep;
  	}

  	/* No quirk */
  	return 0;
  
  add_sync_ep:
  	subs->sync_endpoint = snd_usb_add_endpoint(subs->stream->chip,
  						   alts, ep, !subs->direction,

  						   SND_USB_ENDPOINT_TYPE_DATA);

  	if (!subs->sync_endpoint)
  		return -EINVAL;
  
  	subs->data_endpoint->sync_master = subs->sync_endpoint;
  
  	return 0;
  }
  
  static int set_sync_endpoint(struct snd_usb_substream *subs,
  			     struct audioformat *fmt,
  			     struct usb_device *dev,
  			     struct usb_host_interface *alts,
  			     struct usb_interface_descriptor *altsd)
  {
  	int is_playback = subs->direction == SNDRV_PCM_STREAM_PLAYBACK;
  	unsigned int ep, attr;

  	bool implicit_fb;

  	int err;
  
  	/* we need a sync pipe in async OUT or adaptive IN mode */
  	/* check the number of EP, since some devices have broken
  	 * descriptors which fool us.  if it has only one EP,
  	 * 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))) {
  
  		/*
  		 * In these modes the notion of sync_endpoint is irrelevant.
  		 * Reset pointers to avoid using stale data from previously
  		 * used settings, e.g. when configuration and endpoints were
  		 * changed
  		 */
  
  		subs->sync_endpoint = NULL;
  		subs->data_endpoint->sync_master = NULL;
  	}

  	err = set_sync_ep_implicit_fb_quirk(subs, dev, altsd, attr);
  	if (err < 0)
  		return err;

  	if (altsd->bNumEndpoints < 2)
  		return 0;

  	if ((is_playback && (attr == USB_ENDPOINT_SYNC_SYNC ||
  			     attr == USB_ENDPOINT_SYNC_ADAPTIVE)) ||

  	    (!is_playback && attr != USB_ENDPOINT_SYNC_ADAPTIVE))
  		return 0;

  	/*
  	 * In case of illegal SYNC_NONE for OUT endpoint, we keep going to see
  	 * if we don't find a sync endpoint, as on M-Audio Transit. In case of
  	 * error fall back to SYNC mode and don't create sync endpoint
  	 */

  	/* 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) != USB_ENDPOINT_XFER_ISOC ||
  	    (get_endpoint(alts, 1)->bLength >= USB_DT_ENDPOINT_AUDIO_SIZE &&

  	     get_endpoint(alts, 1)->bSynchAddress != 0)) {

  		dev_err(&dev->dev,
  			"%d:%d : invalid sync pipe. bmAttributes %02x, bLength %d, bSynchAddress %02x
  ",
  			   fmt->iface, fmt->altsetting,

  			   get_endpoint(alts, 1)->bmAttributes,
  			   get_endpoint(alts, 1)->bLength,
  			   get_endpoint(alts, 1)->bSynchAddress);

  		if (is_playback && attr == USB_ENDPOINT_SYNC_NONE)
  			return 0;

  		return -EINVAL;
  	}
  	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)))) {

  		dev_err(&dev->dev,
  			"%d:%d : invalid sync pipe. is_playback %d, ep %02x, bSynchAddress %02x
  ",
  			   fmt->iface, fmt->altsetting,

  			   is_playback, ep, get_endpoint(alts, 0)->bSynchAddress);

  		if (is_playback && attr == USB_ENDPOINT_SYNC_NONE)
  			return 0;

  		return -EINVAL;

  	}

  	implicit_fb = (get_endpoint(alts, 1)->bmAttributes & USB_ENDPOINT_USAGE_MASK)
  			== USB_ENDPOINT_USAGE_IMPLICIT_FB;
  
  	subs->sync_endpoint = snd_usb_add_endpoint(subs->stream->chip,
  						   alts, ep, !subs->direction,
  						   implicit_fb ?
  							SND_USB_ENDPOINT_TYPE_DATA :
  							SND_USB_ENDPOINT_TYPE_SYNC);

  	if (!subs->sync_endpoint) {
  		if (is_playback && attr == USB_ENDPOINT_SYNC_NONE)
  			return 0;

  		return -EINVAL;

  	}

  
  	subs->data_endpoint->sync_master = subs->sync_endpoint;

  	return 0;
  }
  
  /*
   * find a matching format and set up the interface
   */
  static int set_format(struct snd_usb_substream *subs, struct audioformat *fmt)
  {
  	struct usb_device *dev = subs->dev;
  	struct usb_host_interface *alts;
  	struct usb_interface_descriptor *altsd;
  	struct usb_interface *iface;
  	int err;
  
  	iface = usb_ifnum_to_if(dev, fmt->iface);
  	if (WARN_ON(!iface))
  		return -EINVAL;
  	alts = &iface->altsetting[fmt->altset_idx];
  	altsd = get_iface_desc(alts);
  	if (WARN_ON(altsd->bAlternateSetting != fmt->altsetting))
  		return -EINVAL;
  
  	if (fmt == subs->cur_audiofmt)
  		return 0;
  
  	/* close the old interface */
  	if (subs->interface >= 0 && subs->interface != fmt->iface) {
  		err = usb_set_interface(subs->dev, subs->interface, 0);
  		if (err < 0) {

  			dev_err(&dev->dev,
  				"%d:%d: return to setting 0 failed (%d)
  ",
  				fmt->iface, fmt->altsetting, err);

  			return -EIO;
  		}
  		subs->interface = -1;
  		subs->altset_idx = 0;
  	}
  
  	/* set interface */
  	if (subs->interface != fmt->iface ||
  	    subs->altset_idx != fmt->altset_idx) {

  
  		err = snd_usb_select_mode_quirk(subs, fmt);
  		if (err < 0)
  			return -EIO;

  		err = usb_set_interface(dev, fmt->iface, fmt->altsetting);
  		if (err < 0) {

  			dev_err(&dev->dev,
  				"%d:%d: usb_set_interface failed (%d)
  ",
  				fmt->iface, fmt->altsetting, err);

  			return -EIO;
  		}

  		dev_dbg(&dev->dev, "setting usb interface %d:%d
  ",
  			fmt->iface, fmt->altsetting);

  		subs->interface = fmt->iface;
  		subs->altset_idx = fmt->altset_idx;
  
  		snd_usb_set_interface_quirk(dev);
  	}
  
  	subs->data_endpoint = snd_usb_add_endpoint(subs->stream->chip,
  						   alts, fmt->endpoint, subs->direction,
  						   SND_USB_ENDPOINT_TYPE_DATA);
  
  	if (!subs->data_endpoint)
  		return -EINVAL;
  
  	err = set_sync_endpoint(subs, fmt, dev, alts, altsd);
  	if (err < 0)
  		return err;

  	err = snd_usb_init_pitch(subs->stream->chip, fmt->iface, alts, fmt);
  	if (err < 0)

  		return err;
  
  	subs->cur_audiofmt = fmt;
  
  	snd_usb_set_format_quirk(subs, fmt);

  	return 0;
  }
  
  /*

   * Return the score of matching two audioformats.
   * Veto the audioformat if:
   * - It has no channels for some reason.
   * - Requested PCM format is not supported.
   * - Requested sample rate is not supported.
   */

  static int match_endpoint_audioformats(struct snd_usb_substream *subs,
  				       struct audioformat *fp,
  				       struct audioformat *match, int rate,
  				       snd_pcm_format_t pcm_format)

  {
  	int i;
  	int score = 0;
  
  	if (fp->channels < 1) {

  		dev_dbg(&subs->dev->dev,
  			"%s: (fmt @%p) no channels
  ", __func__, fp);

  		return 0;
  	}

  	if (!(fp->formats & pcm_format_to_bits(pcm_format))) {

  		dev_dbg(&subs->dev->dev,
  			"%s: (fmt @%p) no match for format %d
  ", __func__,

  			fp, pcm_format);
  		return 0;
  	}
  
  	for (i = 0; i < fp->nr_rates; i++) {
  		if (fp->rate_table[i] == rate) {
  			score++;
  			break;
  		}
  	}
  	if (!score) {

  		dev_dbg(&subs->dev->dev,
  			"%s: (fmt @%p) no match for rate %d
  ", __func__,

  			fp, rate);
  		return 0;
  	}
  
  	if (fp->channels == match->channels)
  		score++;

  	dev_dbg(&subs->dev->dev,
  		"%s: (fmt @%p) score %d
  ", __func__, fp, score);

  
  	return score;
  }
  
  /*
   * Configure the sync ep using the rate and pcm format of the data ep.
   */
  static int configure_sync_endpoint(struct snd_usb_substream *subs)
  {
  	int ret;
  	struct audioformat *fp;
  	struct audioformat *sync_fp = NULL;
  	int cur_score = 0;
  	int sync_period_bytes = subs->period_bytes;
  	struct snd_usb_substream *sync_subs =
  		&subs->stream->substream[subs->direction ^ 1];

  	if (subs->sync_endpoint->type != SND_USB_ENDPOINT_TYPE_DATA ||
  	    !subs->stream)
  		return snd_usb_endpoint_set_params(subs->sync_endpoint,
  						   subs->pcm_format,
  						   subs->channels,
  						   subs->period_bytes,

  						   0, 0,

  						   subs->cur_rate,
  						   subs->cur_audiofmt,
  						   NULL);

  	/* Try to find the best matching audioformat. */
  	list_for_each_entry(fp, &sync_subs->fmt_list, list) {

  		int score = match_endpoint_audioformats(subs,
  							fp, subs->cur_audiofmt,

  			subs->cur_rate, subs->pcm_format);
  
  		if (score > cur_score) {
  			sync_fp = fp;
  			cur_score = score;
  		}
  	}
  
  	if (unlikely(sync_fp == NULL)) {

  		dev_err(&subs->dev->dev,
  			"%s: no valid audioformat for sync ep %x found
  ",

  			__func__, sync_subs->ep_num);
  		return -EINVAL;
  	}
  
  	/*
  	 * Recalculate the period bytes if channel number differ between
  	 * data and sync ep audioformat.
  	 */
  	if (sync_fp->channels != subs->channels) {
  		sync_period_bytes = (subs->period_bytes / subs->channels) *
  			sync_fp->channels;

  		dev_dbg(&subs->dev->dev,
  			"%s: adjusted sync ep period bytes (%d -> %d)
  ",

  			__func__, subs->period_bytes, sync_period_bytes);
  	}
  
  	ret = snd_usb_endpoint_set_params(subs->sync_endpoint,
  					  subs->pcm_format,
  					  sync_fp->channels,
  					  sync_period_bytes,

  					  0, 0,

  					  subs->cur_rate,
  					  sync_fp,
  					  NULL);
  
  	return ret;
  }
  
  /*

   * configure endpoint params
   *
   * called  during initial setup and upon resume
   */
  static int configure_endpoint(struct snd_usb_substream *subs)
  {
  	int ret;

  	/* format changed */

  	stop_endpoints(subs, true);

  	ret = snd_usb_endpoint_set_params(subs->data_endpoint,
  					  subs->pcm_format,
  					  subs->channels,
  					  subs->period_bytes,

  					  subs->period_frames,
  					  subs->buffer_periods,

  					  subs->cur_rate,
  					  subs->cur_audiofmt,
  					  subs->sync_endpoint);
  	if (ret < 0)

  		return ret;

  
  	if (subs->sync_endpoint)

  		ret = configure_sync_endpoint(subs);

  	return ret;
  }
  
  /*

   * hw_params callback
   *
   * allocate a buffer and set the given audio format.
   *
   * so far we use a physically linear buffer although packetize transfer
   * doesn't need a continuous area.
   * if sg buffer is supported on the later version of alsa, we'll follow
   * that.
   */
  static int snd_usb_hw_params(struct snd_pcm_substream *substream,
  			     struct snd_pcm_hw_params *hw_params)
  {
  	struct snd_usb_substream *subs = substream->runtime->private_data;
  	struct audioformat *fmt;

  	int ret;

  
  	ret = snd_pcm_lib_alloc_vmalloc_buffer(substream,
  					       params_buffer_bytes(hw_params));
  	if (ret < 0)

  		return ret;

  	subs->pcm_format = params_format(hw_params);
  	subs->period_bytes = params_period_bytes(hw_params);

  	subs->period_frames = params_period_size(hw_params);
  	subs->buffer_periods = params_periods(hw_params);

  	subs->channels = params_channels(hw_params);
  	subs->cur_rate = params_rate(hw_params);
  
  	fmt = find_format(subs);

  	if (!fmt) {

  		dev_dbg(&subs->dev->dev,
  			"cannot set format: format = %#x, rate = %d, channels = %d
  ",

  			   subs->pcm_format, subs->cur_rate, subs->channels);

  		return -EINVAL;

  	}

  	ret = snd_usb_lock_shutdown(subs->stream->chip);
  	if (ret < 0)

  		return ret;

  	ret = set_format(subs, fmt);
  	snd_usb_unlock_shutdown(subs->stream->chip);

  	if (ret < 0)

  		return ret;

  	subs->interface = fmt->iface;
  	subs->altset_idx = fmt->altset_idx;

  	subs->need_setup_ep = true;

  	return 0;

  }
  
  /*
   * hw_free callback
   *
   * reset the audio format and release the buffer
   */
  static int snd_usb_hw_free(struct snd_pcm_substream *substream)
  {
  	struct snd_usb_substream *subs = substream->runtime->private_data;
  
  	subs->cur_audiofmt = NULL;
  	subs->cur_rate = 0;
  	subs->period_bytes = 0;

  	if (!snd_usb_lock_shutdown(subs->stream->chip)) {

  		stop_endpoints(subs, true);

  		snd_usb_endpoint_deactivate(subs->sync_endpoint);
  		snd_usb_endpoint_deactivate(subs->data_endpoint);

  		snd_usb_unlock_shutdown(subs->stream->chip);

  	}

  	return snd_pcm_lib_free_vmalloc_buffer(substream);
  }
  
  /*
   * prepare callback
   *
   * only a few subtle things...
   */
  static int snd_usb_pcm_prepare(struct snd_pcm_substream *substream)
  {
  	struct snd_pcm_runtime *runtime = substream->runtime;
  	struct snd_usb_substream *subs = runtime->private_data;

  	struct usb_host_interface *alts;
  	struct usb_interface *iface;
  	int ret;

  
  	if (! subs->cur_audiofmt) {

  		dev_err(&subs->dev->dev, "no format is specified!
  ");

  		return -ENXIO;
  	}

  	ret = snd_usb_lock_shutdown(subs->stream->chip);
  	if (ret < 0)
  		return ret;

  	if (snd_BUG_ON(!subs->data_endpoint)) {
  		ret = -EIO;
  		goto unlock;
  	}

  	snd_usb_endpoint_sync_pending_stop(subs->sync_endpoint);
  	snd_usb_endpoint_sync_pending_stop(subs->data_endpoint);

  	ret = set_format(subs, subs->cur_audiofmt);
  	if (ret < 0)

  		goto unlock;

  
  	iface = usb_ifnum_to_if(subs->dev, subs->cur_audiofmt->iface);
  	alts = &iface->altsetting[subs->cur_audiofmt->altset_idx];
  	ret = snd_usb_init_sample_rate(subs->stream->chip,
  				       subs->cur_audiofmt->iface,
  				       alts,
  				       subs->cur_audiofmt,
  				       subs->cur_rate);
  	if (ret < 0)

  		goto unlock;

  	if (subs->need_setup_ep) {
  		ret = configure_endpoint(subs);
  		if (ret < 0)

  			goto unlock;

  		subs->need_setup_ep = false;
  	}

  	/* some unit conversions in runtime */

  	subs->data_endpoint->maxframesize =
  		bytes_to_frames(runtime, subs->data_endpoint->maxpacksize);
  	subs->data_endpoint->curframesize =
  		bytes_to_frames(runtime, subs->data_endpoint->curpacksize);

  
  	/* reset the pointer */
  	subs->hwptr_done = 0;
  	subs->transfer_done = 0;

  	subs->last_delay = 0;
  	subs->last_frame_number = 0;

  	runtime->delay = 0;

  	/* 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)

  		ret = start_endpoints(subs);

   unlock:

  	snd_usb_unlock_shutdown(subs->stream->chip);

  	return ret;

  }
  
  static struct snd_pcm_hardware snd_usb_hardware =
  {
  	.info =			SNDRV_PCM_INFO_MMAP |
  				SNDRV_PCM_INFO_MMAP_VALID |
  				SNDRV_PCM_INFO_BATCH |
  				SNDRV_PCM_INFO_INTERLEAVED |
  				SNDRV_PCM_INFO_BLOCK_TRANSFER |
  				SNDRV_PCM_INFO_PAUSE,
  	.buffer_bytes_max =	1024 * 1024,
  	.period_bytes_min =	64,
  	.period_bytes_max =	512 * 1024,
  	.periods_min =		2,
  	.periods_max =		1024,
  };
  
  static int hw_check_valid_format(struct snd_usb_substream *subs,
  				 struct snd_pcm_hw_params *params,
  				 struct audioformat *fp)
  {
  	struct snd_interval *it = hw_param_interval(params, SNDRV_PCM_HW_PARAM_RATE);
  	struct snd_interval *ct = hw_param_interval(params, SNDRV_PCM_HW_PARAM_CHANNELS);
  	struct snd_mask *fmts = hw_param_mask(params, SNDRV_PCM_HW_PARAM_FORMAT);
  	struct snd_interval *pt = hw_param_interval(params, SNDRV_PCM_HW_PARAM_PERIOD_TIME);

  	struct snd_mask check_fmts;

  	unsigned int ptime;
  
  	/* check the format */

  	snd_mask_none(&check_fmts);
  	check_fmts.bits[0] = (u32)fp->formats;
  	check_fmts.bits[1] = (u32)(fp->formats >> 32);
  	snd_mask_intersect(&check_fmts, fmts);
  	if (snd_mask_empty(&check_fmts)) {

  		hwc_debug("   > check: no supported format %d
  ", fp->format);
  		return 0;
  	}
  	/* check the channels */
  	if (fp->channels < ct->min || fp->channels > ct->max) {
  		hwc_debug("   > check: no valid channels %d (%d/%d)
  ", fp->channels, ct->min, ct->max);
  		return 0;
  	}
  	/* check the rate is within the range */
  	if (fp->rate_min > it->max || (fp->rate_min == it->max && it->openmax)) {
  		hwc_debug("   > check: rate_min %d > max %d
  ", fp->rate_min, it->max);
  		return 0;
  	}
  	if (fp->rate_max < it->min || (fp->rate_max == it->min && it->openmin)) {
  		hwc_debug("   > check: rate_max %d < min %d
  ", fp->rate_max, it->min);
  		return 0;
  	}
  	/* check whether the period time is >= the data packet interval */

  	if (subs->speed != USB_SPEED_FULL) {

  		ptime = 125 * (1 << fp->datainterval);
  		if (ptime > pt->max || (ptime == pt->max && pt->openmax)) {
  			hwc_debug("   > check: ptime %u > max %u
  ", ptime, pt->max);
  			return 0;
  		}
  	}
  	return 1;
  }
  
  static int hw_rule_rate(struct snd_pcm_hw_params *params,
  			struct snd_pcm_hw_rule *rule)
  {
  	struct snd_usb_substream *subs = rule->private;

  	struct audioformat *fp;

  	struct snd_interval *it = hw_param_interval(params, SNDRV_PCM_HW_PARAM_RATE);
  	unsigned int rmin, rmax;
  	int changed;
  
  	hwc_debug("hw_rule_rate: (%d,%d)
  ", it->min, it->max);
  	changed = 0;
  	rmin = rmax = 0;

  	list_for_each_entry(fp, &subs->fmt_list, list) {

  		if (!hw_check_valid_format(subs, params, fp))
  			continue;
  		if (changed++) {
  			if (rmin > fp->rate_min)
  				rmin = fp->rate_min;
  			if (rmax < fp->rate_max)
  				rmax = fp->rate_max;
  		} else {
  			rmin = fp->rate_min;
  			rmax = fp->rate_max;
  		}
  	}
  
  	if (!changed) {
  		hwc_debug("  --> get empty
  ");
  		it->empty = 1;
  		return -EINVAL;
  	}
  
  	changed = 0;
  	if (it->min < rmin) {
  		it->min = rmin;
  		it->openmin = 0;
  		changed = 1;
  	}
  	if (it->max > rmax) {
  		it->max = rmax;
  		it->openmax = 0;
  		changed = 1;
  	}
  	if (snd_interval_checkempty(it)) {
  		it->empty = 1;
  		return -EINVAL;
  	}
  	hwc_debug("  --> (%d, %d) (changed = %d)
  ", it->min, it->max, changed);
  	return changed;
  }
  
  
  static int hw_rule_channels(struct snd_pcm_hw_params *params,
  			    struct snd_pcm_hw_rule *rule)
  {
  	struct snd_usb_substream *subs = rule->private;

  	struct audioformat *fp;

  	struct snd_interval *it = hw_param_interval(params, SNDRV_PCM_HW_PARAM_CHANNELS);
  	unsigned int rmin, rmax;
  	int changed;
  
  	hwc_debug("hw_rule_channels: (%d,%d)
  ", it->min, it->max);
  	changed = 0;
  	rmin = rmax = 0;

  	list_for_each_entry(fp, &subs->fmt_list, list) {

  		if (!hw_check_valid_format(subs, params, fp))
  			continue;
  		if (changed++) {
  			if (rmin > fp->channels)
  				rmin = fp->channels;
  			if (rmax < fp->channels)
  				rmax = fp->channels;
  		} else {
  			rmin = fp->channels;
  			rmax = fp->channels;
  		}
  	}
  
  	if (!changed) {
  		hwc_debug("  --> get empty
  ");
  		it->empty = 1;
  		return -EINVAL;
  	}
  
  	changed = 0;
  	if (it->min < rmin) {
  		it->min = rmin;
  		it->openmin = 0;
  		changed = 1;
  	}
  	if (it->max > rmax) {
  		it->max = rmax;
  		it->openmax = 0;
  		changed = 1;
  	}
  	if (snd_interval_checkempty(it)) {
  		it->empty = 1;
  		return -EINVAL;
  	}
  	hwc_debug("  --> (%d, %d) (changed = %d)
  ", it->min, it->max, changed);
  	return changed;
  }
  
  static int hw_rule_format(struct snd_pcm_hw_params *params,
  			  struct snd_pcm_hw_rule *rule)
  {
  	struct snd_usb_substream *subs = rule->private;

  	struct audioformat *fp;

  	struct snd_mask *fmt = hw_param_mask(params, SNDRV_PCM_HW_PARAM_FORMAT);
  	u64 fbits;
  	u32 oldbits[2];
  	int changed;
  
  	hwc_debug("hw_rule_format: %x:%x
  ", fmt->bits[0], fmt->bits[1]);
  	fbits = 0;

  	list_for_each_entry(fp, &subs->fmt_list, list) {

  		if (!hw_check_valid_format(subs, params, fp))
  			continue;

  		fbits |= fp->formats;

  	}
  
  	oldbits[0] = fmt->bits[0];
  	oldbits[1] = fmt->bits[1];
  	fmt->bits[0] &= (u32)fbits;
  	fmt->bits[1] &= (u32)(fbits >> 32);
  	if (!fmt->bits[0] && !fmt->bits[1]) {
  		hwc_debug("  --> get empty
  ");
  		return -EINVAL;
  	}
  	changed = (oldbits[0] != fmt->bits[0] || oldbits[1] != fmt->bits[1]);
  	hwc_debug("  --> %x:%x (changed = %d)
  ", fmt->bits[0], fmt->bits[1], changed);
  	return changed;
  }
  
  static int hw_rule_period_time(struct snd_pcm_hw_params *params,
  			       struct snd_pcm_hw_rule *rule)
  {
  	struct snd_usb_substream *subs = rule->private;
  	struct audioformat *fp;
  	struct snd_interval *it;
  	unsigned char min_datainterval;
  	unsigned int pmin;
  	int changed;
  
  	it = hw_param_interval(params, SNDRV_PCM_HW_PARAM_PERIOD_TIME);
  	hwc_debug("hw_rule_period_time: (%u,%u)
  ", it->min, it->max);
  	min_datainterval = 0xff;
  	list_for_each_entry(fp, &subs->fmt_list, list) {
  		if (!hw_check_valid_format(subs, params, fp))
  			continue;
  		min_datainterval = min(min_datainterval, fp->datainterval);
  	}
  	if (min_datainterval == 0xff) {

  		hwc_debug("  --> get empty
  ");

  		it->empty = 1;
  		return -EINVAL;
  	}
  	pmin = 125 * (1 << min_datainterval);
  	changed = 0;
  	if (it->min < pmin) {
  		it->min = pmin;
  		it->openmin = 0;
  		changed = 1;
  	}
  	if (snd_interval_checkempty(it)) {
  		it->empty = 1;
  		return -EINVAL;
  	}
  	hwc_debug("  --> (%u,%u) (changed = %d)
  ", it->min, it->max, changed);
  	return changed;
  }
  
  /*
   *  If the device supports unusual bit rates, does the request meet these?
   */
  static int snd_usb_pcm_check_knot(struct snd_pcm_runtime *runtime,
  				  struct snd_usb_substream *subs)
  {
  	struct audioformat *fp;

  	int *rate_list;

  	int count = 0, needs_knot = 0;
  	int err;

  	kfree(subs->rate_list.list);
  	subs->rate_list.list = NULL;

  	list_for_each_entry(fp, &subs->fmt_list, list) {
  		if (fp->rates & SNDRV_PCM_RATE_CONTINUOUS)
  			return 0;
  		count += fp->nr_rates;
  		if (fp->rates & SNDRV_PCM_RATE_KNOT)
  			needs_knot = 1;
  	}
  	if (!needs_knot)
  		return 0;

  	subs->rate_list.list = rate_list =
  		kmalloc(sizeof(int) * count, GFP_KERNEL);

  	if (!subs->rate_list.list)
  		return -ENOMEM;
  	subs->rate_list.count = count;

  	subs->rate_list.mask = 0;
  	count = 0;
  	list_for_each_entry(fp, &subs->fmt_list, list) {
  		int i;
  		for (i = 0; i < fp->nr_rates; i++)

  			rate_list[count++] = fp->rate_table[i];

  	}
  	err = snd_pcm_hw_constraint_list(runtime, 0, SNDRV_PCM_HW_PARAM_RATE,
  					 &subs->rate_list);
  	if (err < 0)
  		return err;
  
  	return 0;
  }
  
  
  /*
   * set up the runtime hardware information.
   */
  
  static int setup_hw_info(struct snd_pcm_runtime *runtime, struct snd_usb_substream *subs)
  {

  	struct audioformat *fp;

  	unsigned int pt, ptmin;
  	int param_period_time_if_needed;
  	int err;
  
  	runtime->hw.formats = subs->formats;
  
  	runtime->hw.rate_min = 0x7fffffff;
  	runtime->hw.rate_max = 0;
  	runtime->hw.channels_min = 256;
  	runtime->hw.channels_max = 0;
  	runtime->hw.rates = 0;
  	ptmin = UINT_MAX;
  	/* check min/max rates and channels */

  	list_for_each_entry(fp, &subs->fmt_list, list) {

  		runtime->hw.rates |= fp->rates;
  		if (runtime->hw.rate_min > fp->rate_min)
  			runtime->hw.rate_min = fp->rate_min;
  		if (runtime->hw.rate_max < fp->rate_max)
  			runtime->hw.rate_max = fp->rate_max;
  		if (runtime->hw.channels_min > fp->channels)
  			runtime->hw.channels_min = fp->channels;
  		if (runtime->hw.channels_max < fp->channels)
  			runtime->hw.channels_max = fp->channels;
  		if (fp->fmt_type == UAC_FORMAT_TYPE_II && fp->frame_size > 0) {
  			/* FIXME: there might be more than one audio formats... */
  			runtime->hw.period_bytes_min = runtime->hw.period_bytes_max =
  				fp->frame_size;
  		}
  		pt = 125 * (1 << fp->datainterval);
  		ptmin = min(ptmin, pt);
  	}

  	err = snd_usb_autoresume(subs->stream->chip);
  	if (err < 0)
  		return err;

  
  	param_period_time_if_needed = SNDRV_PCM_HW_PARAM_PERIOD_TIME;

  	if (subs->speed == USB_SPEED_FULL)

  		/* full speed devices have fixed data packet interval */
  		ptmin = 1000;
  	if (ptmin == 1000)
  		/* if period time doesn't go below 1 ms, no rules needed */
  		param_period_time_if_needed = -1;
  	snd_pcm_hw_constraint_minmax(runtime, SNDRV_PCM_HW_PARAM_PERIOD_TIME,
  				     ptmin, UINT_MAX);
  
  	if ((err = snd_pcm_hw_rule_add(runtime, 0, SNDRV_PCM_HW_PARAM_RATE,
  				       hw_rule_rate, subs,
  				       SNDRV_PCM_HW_PARAM_FORMAT,
  				       SNDRV_PCM_HW_PARAM_CHANNELS,
  				       param_period_time_if_needed,
  				       -1)) < 0)

  		goto rep_err;

  	if ((err = snd_pcm_hw_rule_add(runtime, 0, SNDRV_PCM_HW_PARAM_CHANNELS,
  				       hw_rule_channels, subs,
  				       SNDRV_PCM_HW_PARAM_FORMAT,
  				       SNDRV_PCM_HW_PARAM_RATE,
  				       param_period_time_if_needed,
  				       -1)) < 0)

  		goto rep_err;

  	if ((err = snd_pcm_hw_rule_add(runtime, 0, SNDRV_PCM_HW_PARAM_FORMAT,
  				       hw_rule_format, subs,
  				       SNDRV_PCM_HW_PARAM_RATE,
  				       SNDRV_PCM_HW_PARAM_CHANNELS,
  				       param_period_time_if_needed,
  				       -1)) < 0)

  		goto rep_err;

  	if (param_period_time_if_needed >= 0) {
  		err = snd_pcm_hw_rule_add(runtime, 0,
  					  SNDRV_PCM_HW_PARAM_PERIOD_TIME,
  					  hw_rule_period_time, subs,
  					  SNDRV_PCM_HW_PARAM_FORMAT,
  					  SNDRV_PCM_HW_PARAM_CHANNELS,
  					  SNDRV_PCM_HW_PARAM_RATE,
  					  -1);
  		if (err < 0)

  			goto rep_err;

  	}
  	if ((err = snd_usb_pcm_check_knot(runtime, subs)) < 0)

  		goto rep_err;

  	return 0;

  
  rep_err:
  	snd_usb_autosuspend(subs->stream->chip);
  	return err;

  }
  
  static int snd_usb_pcm_open(struct snd_pcm_substream *substream, int direction)
  {
  	struct snd_usb_stream *as = snd_pcm_substream_chip(substream);
  	struct snd_pcm_runtime *runtime = substream->runtime;
  	struct snd_usb_substream *subs = &as->substream[direction];
  
  	subs->interface = -1;

  	subs->altset_idx = 0;

  	runtime->hw = snd_usb_hardware;
  	runtime->private_data = subs;
  	subs->pcm_substream = substream;

  	/* runtime PM is also done there */

  
  	/* initialize DSD/DOP context */
  	subs->dsd_dop.byte_idx = 0;
  	subs->dsd_dop.channel = 0;
  	subs->dsd_dop.marker = 1;

  	return setup_hw_info(runtime, subs);

  }
  
  static int snd_usb_pcm_close(struct snd_pcm_substream *substream, int direction)
  {
  	struct snd_usb_stream *as = snd_pcm_substream_chip(substream);
  	struct snd_usb_substream *subs = &as->substream[direction];

  	stop_endpoints(subs, true);

  	if (subs->interface >= 0 &&
  	    !snd_usb_lock_shutdown(subs->stream->chip)) {

  		usb_set_interface(subs->dev, subs->interface, 0);
  		subs->interface = -1;

  		snd_usb_unlock_shutdown(subs->stream->chip);

  	}

  	subs->pcm_substream = NULL;

  	snd_usb_autosuspend(subs->stream->chip);

  	return 0;

  }
  
  /* 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 void retire_capture_urb(struct snd_usb_substream *subs,
  			       struct urb *urb)
  {
  	struct snd_pcm_runtime *runtime = subs->pcm_substream->runtime;
  	unsigned int stride, frames, bytes, oldptr;
  	int i, period_elapsed = 0;
  	unsigned long flags;
  	unsigned char *cp;

  	int current_frame_number;
  
  	/* read frame number here, update pointer in critical section */
  	current_frame_number = usb_get_current_frame_number(subs->dev);

  
  	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 + subs->pkt_offset_adj;

  		if (urb->iso_frame_desc[i].status && printk_ratelimit()) {

  			dev_dbg(&subs->dev->dev, "frame %d active: %d
  ",
  				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) {

  			int oldbytes = bytes;

  			bytes = frames * stride;

  			dev_warn(&subs->dev->dev,
  				 "Corrected urb data len. %d->%d
  ",

  							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;
  		}

  		/* capture delay is by construction limited to one URB,
  		 * reset delays here
  		 */
  		runtime->delay = subs->last_delay = 0;
  
  		/* realign last_frame_number */
  		subs->last_frame_number = current_frame_number;
  		subs->last_frame_number &= 0xFF; /* keep 8 LSBs */

  		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);
  }

  static inline void fill_playback_urb_dsd_dop(struct snd_usb_substream *subs,
  					     struct urb *urb, unsigned int bytes)
  {
  	struct snd_pcm_runtime *runtime = subs->pcm_substream->runtime;
  	unsigned int stride = runtime->frame_bits >> 3;
  	unsigned int dst_idx = 0;
  	unsigned int src_idx = subs->hwptr_done;
  	unsigned int wrap = runtime->buffer_size * stride;
  	u8 *dst = urb->transfer_buffer;
  	u8 *src = runtime->dma_area;
  	u8 marker[] = { 0x05, 0xfa };
  
  	/*
  	 * The DSP DOP format defines a way to transport DSD samples over
  	 * normal PCM data endpoints. It requires stuffing of marker bytes
  	 * (0x05 and 0xfa, alternating per sample frame), and then expects
  	 * 2 additional bytes of actual payload. The whole frame is stored
  	 * LSB.
  	 *
  	 * Hence, for a stereo transport, the buffer layout looks like this,
  	 * where L refers to left channel samples and R to right.
  	 *
  	 *   L1 L2 0x05   R1 R2 0x05   L3 L4 0xfa  R3 R4 0xfa
  	 *   L5 L6 0x05   R5 R6 0x05   L7 L8 0xfa  R7 R8 0xfa
  	 *   .....
  	 *
  	 */
  
  	while (bytes--) {
  		if (++subs->dsd_dop.byte_idx == 3) {
  			/* frame boundary? */
  			dst[dst_idx++] = marker[subs->dsd_dop.marker];
  			src_idx += 2;
  			subs->dsd_dop.byte_idx = 0;
  
  			if (++subs->dsd_dop.channel % runtime->channels == 0) {
  				/* alternate the marker */
  				subs->dsd_dop.marker++;
  				subs->dsd_dop.marker %= ARRAY_SIZE(marker);
  				subs->dsd_dop.channel = 0;
  			}
  		} else {
  			/* stuff the DSD payload */
  			int idx = (src_idx + subs->dsd_dop.byte_idx - 1) % wrap;

  
  			if (subs->cur_audiofmt->dsd_bitrev)
  				dst[dst_idx++] = bitrev8(src[idx]);
  			else
  				dst[dst_idx++] = src[idx];

  			subs->hwptr_done++;
  		}
  	}

  	if (subs->hwptr_done >= runtime->buffer_size * stride)
  		subs->hwptr_done -= runtime->buffer_size * stride;

  }

  static void copy_to_urb(struct snd_usb_substream *subs, struct urb *urb,
  			int offset, int stride, unsigned int bytes)

  {
  	struct snd_pcm_runtime *runtime = subs->pcm_substream->runtime;
  
  	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 + offset,

  		       runtime->dma_area + subs->hwptr_done, bytes1);

  		memcpy(urb->transfer_buffer + offset + bytes1,

  		       runtime->dma_area, bytes - bytes1);
  	} else {

  		memcpy(urb->transfer_buffer + offset,

  		       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;

  }

  static unsigned int copy_to_urb_quirk(struct snd_usb_substream *subs,
  				      struct urb *urb, int stride,
  				      unsigned int bytes)
  {
  	__le32 packet_length;
  	int i;
  
  	/* Put __le32 length descriptor at start of each packet. */
  	for (i = 0; i < urb->number_of_packets; i++) {
  		unsigned int length = urb->iso_frame_desc[i].length;
  		unsigned int offset = urb->iso_frame_desc[i].offset;
  
  		packet_length = cpu_to_le32(length);
  		offset += i * sizeof(packet_length);
  		urb->iso_frame_desc[i].offset = offset;
  		urb->iso_frame_desc[i].length += sizeof(packet_length);
  		memcpy(urb->transfer_buffer + offset,
  		       &packet_length, sizeof(packet_length));
  		copy_to_urb(subs, urb, offset + sizeof(packet_length),
  			    stride, length);
  	}
  	/* Adjust transfer size accordingly. */
  	bytes += urb->number_of_packets * sizeof(packet_length);
  	return bytes;
  }

  static void prepare_playback_urb(struct snd_usb_substream *subs,
  				 struct urb *urb)
  {
  	struct snd_pcm_runtime *runtime = subs->pcm_substream->runtime;

  	struct snd_usb_endpoint *ep = subs->data_endpoint;

  	struct snd_urb_ctx *ctx = urb->context;
  	unsigned int counts, frames, bytes;
  	int i, stride, period_elapsed = 0;
  	unsigned long flags;
  
  	stride = runtime->frame_bits >> 3;
  
  	frames = 0;
  	urb->number_of_packets = 0;
  	spin_lock_irqsave(&subs->lock, flags);

  	subs->frame_limit += ep->max_urb_frames;

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

  		if (ctx->packet_size[i])
  			counts = ctx->packet_size[i];
  		else
  			counts = snd_usb_endpoint_next_packet_size(ep);

  		/* set up descriptor */

  		urb->iso_frame_desc[i].offset = frames * ep->stride;
  		urb->iso_frame_desc[i].length = counts * ep->stride;

  		frames += counts;
  		urb->number_of_packets++;
  		subs->transfer_done += counts;
  		if (subs->transfer_done >= runtime->period_size) {
  			subs->transfer_done -= runtime->period_size;

  			subs->frame_limit = 0;

  			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 * ep->stride;

  					subs->transfer_done = 0;
  				}
  				i++;
  				if (i < ctx->packets) {
  					/* add a transfer delimiter */
  					urb->iso_frame_desc[i].offset =

  						frames * ep->stride;

  					urb->iso_frame_desc[i].length = 0;
  					urb->number_of_packets++;
  				}
  				break;
  			}
  		}

  		/* finish at the period boundary or after enough frames */
  		if ((period_elapsed ||
  				subs->transfer_done >= subs->frame_limit) &&
  		    !snd_usb_endpoint_implicit_feedback_sink(ep))

  			break;
  	}

  	bytes = frames * ep->stride;

  
  	if (unlikely(subs->pcm_format == SNDRV_PCM_FORMAT_DSD_U16_LE &&
  		     subs->cur_audiofmt->dsd_dop)) {
  		fill_playback_urb_dsd_dop(subs, urb, bytes);

  	} else if (unlikely(subs->pcm_format == SNDRV_PCM_FORMAT_DSD_U8 &&
  			   subs->cur_audiofmt->dsd_bitrev)) {
  		/* bit-reverse the bytes */
  		u8 *buf = urb->transfer_buffer;
  		for (i = 0; i < bytes; i++) {
  			int idx = (subs->hwptr_done + i)
  				% (runtime->buffer_size * stride);
  			buf[i] = bitrev8(runtime->dma_area[idx]);
  		}
  
  		subs->hwptr_done += bytes;

  		if (subs->hwptr_done >= runtime->buffer_size * stride)
  			subs->hwptr_done -= runtime->buffer_size * stride;

  	} else {

  		/* usual PCM */

  		if (!subs->tx_length_quirk)
  			copy_to_urb(subs, urb, 0, stride, bytes);
  		else
  			bytes = copy_to_urb_quirk(subs, urb, stride, bytes);
  			/* bytes is now amount of outgoing data */

  	}

  	/* 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 */

  	if (subs->trigger_tstamp_pending_update) {
  		/* this is the first actual URB submitted,
  		 * update trigger timestamp to reflect actual start time
  		 */
  		snd_pcm_gettime(runtime, &runtime->trigger_tstamp);
  		subs->trigger_tstamp_pending_update = false;
  	}

  	spin_unlock_irqrestore(&subs->lock, flags);
  	urb->transfer_buffer_length = bytes;
  	if (period_elapsed)
  		snd_pcm_period_elapsed(subs->pcm_substream);
  }
  
  /*
   * process after playback data complete
   * - decrease the delay count again
   */
  static void retire_playback_urb(struct snd_usb_substream *subs,
  			       struct urb *urb)
  {
  	unsigned long flags;
  	struct snd_pcm_runtime *runtime = subs->pcm_substream->runtime;

  	struct snd_usb_endpoint *ep = subs->data_endpoint;
  	int processed = urb->transfer_buffer_length / ep->stride;

  	int est_delay;

  	/* ignore the delay accounting when procssed=0 is given, i.e.
  	 * silent payloads are procssed before handling the actual data
  	 */
  	if (!processed)
  		return;

  	spin_lock_irqsave(&subs->lock, flags);

  	if (!subs->last_delay)
  		goto out; /* short path */

  	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)
  		dev_dbg_ratelimited(&subs->dev->dev,

  			"delay: estimated %d, actual %d
  ",

  			est_delay, subs->last_delay);

  	if (!subs->running) {
  		/* update last_frame_number for delay counting here since
  		 * prepare_playback_urb won't be called during pause
  		 */
  		subs->last_frame_number =
  			usb_get_current_frame_number(subs->dev) & 0xff;
  	}
  
   out:

  	spin_unlock_irqrestore(&subs->lock, flags);

  }
  
  static int snd_usb_playback_open(struct snd_pcm_substream *substream)
  {
  	return snd_usb_pcm_open(substream, SNDRV_PCM_STREAM_PLAYBACK);
  }
  
  static int snd_usb_playback_close(struct snd_pcm_substream *substream)
  {
  	return snd_usb_pcm_close(substream, SNDRV_PCM_STREAM_PLAYBACK);
  }
  
  static int snd_usb_capture_open(struct snd_pcm_substream *substream)
  {
  	return snd_usb_pcm_open(substream, SNDRV_PCM_STREAM_CAPTURE);
  }
  
  static int snd_usb_capture_close(struct snd_pcm_substream *substream)
  {
  	return snd_usb_pcm_close(substream, SNDRV_PCM_STREAM_CAPTURE);
  }

  static 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:

  		subs->trigger_tstamp_pending_update = true;

  	case SNDRV_PCM_TRIGGER_PAUSE_RELEASE:
  		subs->data_endpoint->prepare_data_urb = prepare_playback_urb;
  		subs->data_endpoint->retire_data_urb = retire_playback_urb;

  		subs->running = 1;

  		return 0;
  	case SNDRV_PCM_TRIGGER_STOP:

  		stop_endpoints(subs, false);

  		subs->running = 0;

  		return 0;
  	case SNDRV_PCM_TRIGGER_PAUSE_PUSH:
  		subs->data_endpoint->prepare_data_urb = NULL;

  		/* keep retire_data_urb for delay calculation */
  		subs->data_endpoint->retire_data_urb = retire_playback_urb;

  		subs->running = 0;

  		return 0;
  	}
  
  	return -EINVAL;
  }

  static int snd_usb_substream_capture_trigger(struct snd_pcm_substream *substream,
  					     int cmd)

  {
  	int err;
  	struct snd_usb_substream *subs = substream->runtime->private_data;
  
  	switch (cmd) {
  	case SNDRV_PCM_TRIGGER_START:

  		err = start_endpoints(subs);

  		if (err < 0)
  			return err;
  
  		subs->data_endpoint->retire_data_urb = retire_capture_urb;

  		subs->running = 1;

  		return 0;
  	case SNDRV_PCM_TRIGGER_STOP:

  		stop_endpoints(subs, false);

  		subs->running = 0;

  		return 0;
  	case SNDRV_PCM_TRIGGER_PAUSE_PUSH:
  		subs->data_endpoint->retire_data_urb = NULL;

  		subs->running = 0;

  		return 0;
  	case SNDRV_PCM_TRIGGER_PAUSE_RELEASE:
  		subs->data_endpoint->retire_data_urb = retire_capture_urb;

  		subs->running = 1;

  		return 0;
  	}
  
  	return -EINVAL;
  }

  static struct snd_pcm_ops snd_usb_playback_ops = {
  	.open =		snd_usb_playback_open,
  	.close =	snd_usb_playback_close,
  	.ioctl =	snd_pcm_lib_ioctl,
  	.hw_params =	snd_usb_hw_params,
  	.hw_free =	snd_usb_hw_free,
  	.prepare =	snd_usb_pcm_prepare,
  	.trigger =	snd_usb_substream_playback_trigger,
  	.pointer =	snd_usb_pcm_pointer,
  	.page =		snd_pcm_lib_get_vmalloc_page,
  	.mmap =		snd_pcm_lib_mmap_vmalloc,
  };
  
  static struct snd_pcm_ops snd_usb_capture_ops = {
  	.open =		snd_usb_capture_open,
  	.close =	snd_usb_capture_close,
  	.ioctl =	snd_pcm_lib_ioctl,
  	.hw_params =	snd_usb_hw_params,
  	.hw_free =	snd_usb_hw_free,
  	.prepare =	snd_usb_pcm_prepare,
  	.trigger =	snd_usb_substream_capture_trigger,
  	.pointer =	snd_usb_pcm_pointer,
  	.page =		snd_pcm_lib_get_vmalloc_page,
  	.mmap =		snd_pcm_lib_mmap_vmalloc,
  };
  
  void snd_usb_set_pcm_ops(struct snd_pcm *pcm, int stream)
  {
  	snd_pcm_set_ops(pcm, stream,
  			stream == SNDRV_PCM_STREAM_PLAYBACK ?
  			&snd_usb_playback_ops : &snd_usb_capture_ops);
  }