/*
   *   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/gfp.h>

  #include <linux/init.h>
  #include <linux/usb.h>
  #include <linux/usb/audio.h>
  
  #include <sound/core.h>
  #include <sound/pcm.h>
  
  #include "usbaudio.h"
  #include "helper.h"
  #include "card.h"
  #include "urb.h"
  #include "pcm.h"
  
  /*
   * 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;
  }
  
  /*
   * unlink active urbs.
   */
  static int deactivate_urbs(struct snd_usb_substream *subs, int force, int can_sleep)
  {
  	struct snd_usb_audio *chip = subs->stream->chip;
  	unsigned int i;
  	int async;
  
  	subs->running = 0;
  
  	if (!force && subs->stream->chip->shutdown) /* to be sure... */
  		return -EBADFD;
  
  	async = !can_sleep && chip->async_unlink;
  
  	if (!async && in_interrupt())
  		return 0;
  
  	for (i = 0; i < subs->nurbs; i++) {
  		if (test_bit(i, &subs->active_mask)) {
  			if (!test_and_set_bit(i, &subs->unlink_mask)) {
  				struct urb *u = subs->dataurb[i].urb;
  				if (async)
  					usb_unlink_urb(u);
  				else
  					usb_kill_urb(u);
  			}
  		}
  	}
  	if (subs->syncpipe) {
  		for (i = 0; i < SYNC_URBS; i++) {
  			if (test_bit(i+16, &subs->active_mask)) {
  				if (!test_and_set_bit(i+16, &subs->unlink_mask)) {
  					struct urb *u = subs->syncurb[i].urb;
  					if (async)
  						usb_unlink_urb(u);
  					else
  						usb_kill_urb(u);
  				}
  			}
  		}
  	}
  	return 0;
  }
  
  
  /*
   * release a urb data
   */
  static void release_urb_ctx(struct snd_urb_ctx *u)
  {
  	if (u->urb) {
  		if (u->buffer_size)

  			usb_free_coherent(u->subs->dev, u->buffer_size,

  					u->urb->transfer_buffer,
  					u->urb->transfer_dma);
  		usb_free_urb(u->urb);
  		u->urb = NULL;
  	}
  }
  
  /*
   *  wait until all urbs are processed.
   */
  static int wait_clear_urbs(struct snd_usb_substream *subs)
  {
  	unsigned long end_time = jiffies + msecs_to_jiffies(1000);
  	unsigned int i;
  	int alive;
  
  	do {
  		alive = 0;
  		for (i = 0; i < subs->nurbs; i++) {
  			if (test_bit(i, &subs->active_mask))
  				alive++;
  		}
  		if (subs->syncpipe) {
  			for (i = 0; i < SYNC_URBS; i++) {
  				if (test_bit(i + 16, &subs->active_mask))
  					alive++;
  			}
  		}
  		if (! alive)
  			break;
  		schedule_timeout_uninterruptible(1);
  	} while (time_before(jiffies, end_time));
  	if (alive)
  		snd_printk(KERN_ERR "timeout: still %d active urbs..
  ", alive);
  	return 0;
  }
  
  /*
   * release a substream
   */
  void snd_usb_release_substream_urbs(struct snd_usb_substream *subs, int force)
  {
  	int i;
  
  	/* stop urbs (to be sure) */
  	deactivate_urbs(subs, force, 1);
  	wait_clear_urbs(subs);
  
  	for (i = 0; i < MAX_URBS; i++)
  		release_urb_ctx(&subs->dataurb[i]);
  	for (i = 0; i < SYNC_URBS; i++)
  		release_urb_ctx(&subs->syncurb[i]);

  	usb_free_coherent(subs->dev, SYNC_URBS * 4,

  			subs->syncbuf, subs->sync_dma);
  	subs->syncbuf = NULL;
  	subs->nurbs = 0;
  }
  
  /*
   * complete callback from data urb
   */
  static void snd_complete_urb(struct urb *urb)
  {
  	struct snd_urb_ctx *ctx = urb->context;
  	struct snd_usb_substream *subs = ctx->subs;
  	struct snd_pcm_substream *substream = ctx->subs->pcm_substream;
  	int err = 0;
  
  	if ((subs->running && subs->ops.retire(subs, substream->runtime, urb)) ||
  	    !subs->running || /* can be stopped during retire callback */
  	    (err = subs->ops.prepare(subs, substream->runtime, urb)) < 0 ||
  	    (err = usb_submit_urb(urb, GFP_ATOMIC)) < 0) {
  		clear_bit(ctx->index, &subs->active_mask);
  		if (err < 0) {
  			snd_printd(KERN_ERR "cannot submit urb (err = %d)
  ", err);
  			snd_pcm_stop(substream, SNDRV_PCM_STATE_XRUN);
  		}
  	}
  }
  
  
  /*
   * complete callback from sync urb
   */
  static void snd_complete_sync_urb(struct urb *urb)
  {
  	struct snd_urb_ctx *ctx = urb->context;
  	struct snd_usb_substream *subs = ctx->subs;
  	struct snd_pcm_substream *substream = ctx->subs->pcm_substream;
  	int err = 0;
  
  	if ((subs->running && subs->ops.retire_sync(subs, substream->runtime, urb)) ||
  	    !subs->running || /* can be stopped during retire callback */
  	    (err = subs->ops.prepare_sync(subs, substream->runtime, urb)) < 0 ||
  	    (err = usb_submit_urb(urb, GFP_ATOMIC)) < 0) {
  		clear_bit(ctx->index + 16, &subs->active_mask);
  		if (err < 0) {
  			snd_printd(KERN_ERR "cannot submit sync urb (err = %d)
  ", err);
  			snd_pcm_stop(substream, SNDRV_PCM_STATE_XRUN);
  		}
  	}
  }
  
  
  /*
   * initialize a substream for plaback/capture
   */
  int snd_usb_init_substream_urbs(struct snd_usb_substream *subs,
  				unsigned int period_bytes,
  				unsigned int rate,
  				unsigned int frame_bits)
  {
  	unsigned int maxsize, i;
  	int is_playback = subs->direction == SNDRV_PCM_STREAM_PLAYBACK;
  	unsigned int urb_packs, total_packs, packs_per_ms;
  	struct snd_usb_audio *chip = subs->stream->chip;
  
  	/* calculate the frequency in 16.16 format */
  	if (snd_usb_get_speed(subs->dev) == USB_SPEED_FULL)
  		subs->freqn = get_usb_full_speed_rate(rate);
  	else
  		subs->freqn = get_usb_high_speed_rate(rate);
  	subs->freqm = subs->freqn;

  	subs->freqshift = INT_MIN;

  	/* calculate max. frequency */
  	if (subs->maxpacksize) {
  		/* whatever fits into a max. size packet */
  		maxsize = subs->maxpacksize;
  		subs->freqmax = (maxsize / (frame_bits >> 3))
  				<< (16 - subs->datainterval);
  	} else {
  		/* no max. packet size: just take 25% higher than nominal */
  		subs->freqmax = subs->freqn + (subs->freqn >> 2);
  		maxsize = ((subs->freqmax + 0xffff) * (frame_bits >> 3))
  				>> (16 - subs->datainterval);
  	}
  	subs->phase = 0;
  
  	if (subs->fill_max)
  		subs->curpacksize = subs->maxpacksize;
  	else
  		subs->curpacksize = maxsize;

  	if (snd_usb_get_speed(subs->dev) != USB_SPEED_FULL)

  		packs_per_ms = 8 >> subs->datainterval;
  	else
  		packs_per_ms = 1;
  
  	if (is_playback) {
  		urb_packs = max(chip->nrpacks, 1);
  		urb_packs = min(urb_packs, (unsigned int)MAX_PACKS);
  	} else
  		urb_packs = 1;
  	urb_packs *= packs_per_ms;
  	if (subs->syncpipe)
  		urb_packs = min(urb_packs, 1U << subs->syncinterval);
  
  	/* decide how many packets to be used */
  	if (is_playback) {
  		unsigned int minsize, maxpacks;
  		/* determine how small a packet can be */
  		minsize = (subs->freqn >> (16 - subs->datainterval))
  			  * (frame_bits >> 3);
  		/* with sync from device, assume it can be 12% lower */
  		if (subs->syncpipe)
  			minsize -= minsize >> 3;
  		minsize = max(minsize, 1u);
  		total_packs = (period_bytes + minsize - 1) / minsize;
  		/* we need at least two URBs for queueing */
  		if (total_packs < 2) {
  			total_packs = 2;
  		} else {
  			/* and we don't want too long a queue either */
  			maxpacks = max(MAX_QUEUE * packs_per_ms, urb_packs * 2);
  			total_packs = min(total_packs, maxpacks);
  		}
  	} else {
  		while (urb_packs > 1 && urb_packs * maxsize >= period_bytes)
  			urb_packs >>= 1;
  		total_packs = MAX_URBS * urb_packs;
  	}
  	subs->nurbs = (total_packs + urb_packs - 1) / urb_packs;
  	if (subs->nurbs > MAX_URBS) {
  		/* too much... */
  		subs->nurbs = MAX_URBS;
  		total_packs = MAX_URBS * urb_packs;
  	} else if (subs->nurbs < 2) {
  		/* too little - we need at least two packets
  		 * to ensure contiguous playback/capture
  		 */
  		subs->nurbs = 2;
  	}
  
  	/* allocate and initialize data urbs */
  	for (i = 0; i < subs->nurbs; i++) {
  		struct snd_urb_ctx *u = &subs->dataurb[i];
  		u->index = i;
  		u->subs = subs;
  		u->packets = (i + 1) * total_packs / subs->nurbs
  			- i * total_packs / subs->nurbs;
  		u->buffer_size = maxsize * u->packets;
  		if (subs->fmt_type == UAC_FORMAT_TYPE_II)
  			u->packets++; /* for transfer delimiter */
  		u->urb = usb_alloc_urb(u->packets, GFP_KERNEL);
  		if (!u->urb)
  			goto out_of_memory;
  		u->urb->transfer_buffer =

  			usb_alloc_coherent(subs->dev, u->buffer_size,
  					   GFP_KERNEL, &u->urb->transfer_dma);

  		if (!u->urb->transfer_buffer)
  			goto out_of_memory;
  		u->urb->pipe = subs->datapipe;
  		u->urb->transfer_flags = URB_ISO_ASAP | URB_NO_TRANSFER_DMA_MAP;
  		u->urb->interval = 1 << subs->datainterval;
  		u->urb->context = u;
  		u->urb->complete = snd_complete_urb;
  	}
  
  	if (subs->syncpipe) {
  		/* allocate and initialize sync urbs */

  		subs->syncbuf = usb_alloc_coherent(subs->dev, SYNC_URBS * 4,

  						 GFP_KERNEL, &subs->sync_dma);
  		if (!subs->syncbuf)
  			goto out_of_memory;
  		for (i = 0; i < SYNC_URBS; i++) {
  			struct snd_urb_ctx *u = &subs->syncurb[i];
  			u->index = i;
  			u->subs = subs;
  			u->packets = 1;
  			u->urb = usb_alloc_urb(1, GFP_KERNEL);
  			if (!u->urb)
  				goto out_of_memory;
  			u->urb->transfer_buffer = subs->syncbuf + i * 4;
  			u->urb->transfer_dma = subs->sync_dma + i * 4;
  			u->urb->transfer_buffer_length = 4;
  			u->urb->pipe = subs->syncpipe;
  			u->urb->transfer_flags = URB_ISO_ASAP |
  						 URB_NO_TRANSFER_DMA_MAP;
  			u->urb->number_of_packets = 1;
  			u->urb->interval = 1 << subs->syncinterval;
  			u->urb->context = u;
  			u->urb->complete = snd_complete_sync_urb;
  		}
  	}
  	return 0;
  
  out_of_memory:
  	snd_usb_release_substream_urbs(subs, 0);
  	return -ENOMEM;
  }
  
  /*
   * prepare urb for full speed capture sync pipe
   *
   * fill the length and offset of each urb descriptor.
   * the fixed 10.14 frequency is passed through the pipe.
   */
  static int prepare_capture_sync_urb(struct snd_usb_substream *subs,
  				    struct snd_pcm_runtime *runtime,
  				    struct urb *urb)
  {
  	unsigned char *cp = urb->transfer_buffer;
  	struct snd_urb_ctx *ctx = urb->context;
  
  	urb->dev = ctx->subs->dev; /* we need to set this at each time */
  	urb->iso_frame_desc[0].length = 3;
  	urb->iso_frame_desc[0].offset = 0;
  	cp[0] = subs->freqn >> 2;
  	cp[1] = subs->freqn >> 10;
  	cp[2] = subs->freqn >> 18;
  	return 0;
  }
  
  /*
   * prepare urb for high speed capture sync pipe
   *
   * fill the length and offset of each urb descriptor.
   * the fixed 12.13 frequency is passed as 16.16 through the pipe.
   */
  static int prepare_capture_sync_urb_hs(struct snd_usb_substream *subs,
  				       struct snd_pcm_runtime *runtime,
  				       struct urb *urb)
  {
  	unsigned char *cp = urb->transfer_buffer;
  	struct snd_urb_ctx *ctx = urb->context;
  
  	urb->dev = ctx->subs->dev; /* we need to set this at each time */
  	urb->iso_frame_desc[0].length = 4;
  	urb->iso_frame_desc[0].offset = 0;
  	cp[0] = subs->freqn;
  	cp[1] = subs->freqn >> 8;
  	cp[2] = subs->freqn >> 16;
  	cp[3] = subs->freqn >> 24;
  	return 0;
  }
  
  /*
   * process after capture sync complete
   * - nothing to do
   */
  static int retire_capture_sync_urb(struct snd_usb_substream *subs,
  				   struct snd_pcm_runtime *runtime,
  				   struct urb *urb)
  {
  	return 0;
  }
  
  /*
   * prepare urb for capture data pipe
   *
   * fill the offset and length of each descriptor.
   *
   * we use a temporary buffer to write the captured data.
   * since the length of written data is determined by host, we cannot
   * write onto the pcm buffer directly...  the data is thus copied
   * later at complete callback to the global buffer.
   */
  static int prepare_capture_urb(struct snd_usb_substream *subs,
  			       struct snd_pcm_runtime *runtime,
  			       struct urb *urb)
  {
  	int i, offs;
  	struct snd_urb_ctx *ctx = urb->context;
  
  	offs = 0;
  	urb->dev = ctx->subs->dev; /* we need to set this at each time */
  	for (i = 0; i < ctx->packets; i++) {
  		urb->iso_frame_desc[i].offset = offs;
  		urb->iso_frame_desc[i].length = subs->curpacksize;
  		offs += subs->curpacksize;
  	}
  	urb->transfer_buffer_length = offs;
  	urb->number_of_packets = ctx->packets;
  	return 0;
  }
  
  /*
   * process after capture complete
   *
   * copy the data from each desctiptor to the pcm buffer, and
   * update the current position.
   */
  static int retire_capture_urb(struct snd_usb_substream *subs,
  			      struct snd_pcm_runtime *runtime,
  			      struct urb *urb)
  {
  	unsigned long flags;
  	unsigned char *cp;
  	int i;
  	unsigned int stride, frames, bytes, oldptr;
  	int period_elapsed = 0;
  
  	stride = runtime->frame_bits >> 3;
  
  	for (i = 0; i < urb->number_of_packets; i++) {
  		cp = (unsigned char *)urb->transfer_buffer + urb->iso_frame_desc[i].offset;
  		if (urb->iso_frame_desc[i].status) {
  			snd_printd(KERN_ERR "frame %d active: %d
  ", i, urb->iso_frame_desc[i].status);
  			// continue;
  		}
  		bytes = urb->iso_frame_desc[i].actual_length;
  		frames = bytes / stride;
  		if (!subs->txfr_quirk)
  			bytes = frames * stride;
  		if (bytes % (runtime->sample_bits >> 3) != 0) {
  #ifdef CONFIG_SND_DEBUG_VERBOSE
  			int oldbytes = bytes;
  #endif
  			bytes = frames * stride;
  			snd_printdd(KERN_ERR "Corrected urb data len. %d->%d
  ",
  							oldbytes, bytes);
  		}
  		/* update the current pointer */
  		spin_lock_irqsave(&subs->lock, flags);
  		oldptr = subs->hwptr_done;
  		subs->hwptr_done += bytes;
  		if (subs->hwptr_done >= runtime->buffer_size * stride)
  			subs->hwptr_done -= runtime->buffer_size * stride;
  		frames = (bytes + (oldptr % stride)) / stride;
  		subs->transfer_done += frames;
  		if (subs->transfer_done >= runtime->period_size) {
  			subs->transfer_done -= runtime->period_size;
  			period_elapsed = 1;
  		}
  		spin_unlock_irqrestore(&subs->lock, flags);
  		/* copy a data chunk */
  		if (oldptr + bytes > runtime->buffer_size * stride) {
  			unsigned int bytes1 =
  					runtime->buffer_size * stride - oldptr;
  			memcpy(runtime->dma_area + oldptr, cp, bytes1);
  			memcpy(runtime->dma_area, cp + bytes1, bytes - bytes1);
  		} else {
  			memcpy(runtime->dma_area + oldptr, cp, bytes);
  		}
  	}
  	if (period_elapsed)
  		snd_pcm_period_elapsed(subs->pcm_substream);
  	return 0;
  }
  
  /*
   * Process after capture complete when paused.  Nothing to do.
   */
  static int retire_paused_capture_urb(struct snd_usb_substream *subs,
  				     struct snd_pcm_runtime *runtime,
  				     struct urb *urb)
  {
  	return 0;
  }
  
  
  /*

   * prepare urb for playback sync pipe

   *
   * set up the offset and length to receive the current frequency.
   */

  static int prepare_playback_sync_urb(struct snd_usb_substream *subs,
  				     struct snd_pcm_runtime *runtime,
  				     struct urb *urb)
  {
  	struct snd_urb_ctx *ctx = urb->context;
  
  	urb->dev = ctx->subs->dev; /* we need to set this at each time */

  	urb->iso_frame_desc[0].length = min(4u, ctx->subs->syncmaxsize);

  	urb->iso_frame_desc[0].offset = 0;
  	return 0;
  }
  
  /*

   * process after playback sync complete

   *

   * Full speed devices report feedback values in 10.14 format as samples per
   * frame, high speed devices in 16.16 format as samples per microframe.
   * Because the Audio Class 1 spec was written before USB 2.0, many high speed
   * devices use a wrong interpretation, some others use an entirely different
   * format.  Therefore, we cannot predict what format any particular device uses
   * and must detect it automatically.

   */
  static int retire_playback_sync_urb(struct snd_usb_substream *subs,
  				    struct snd_pcm_runtime *runtime,
  				    struct urb *urb)
  {
  	unsigned int f;

  	int shift;

  	unsigned long flags;

  	if (urb->iso_frame_desc[0].status != 0 ||
  	    urb->iso_frame_desc[0].actual_length < 3)
  		return 0;

  	f = le32_to_cpup(urb->transfer_buffer);
  	if (urb->iso_frame_desc[0].actual_length == 3)
  		f &= 0x00ffffff;
  	else
  		f &= 0x0fffffff;
  	if (f == 0)
  		return 0;

  	if (unlikely(subs->freqshift == INT_MIN)) {
  		/*
  		 * The first time we see a feedback value, determine its format
  		 * by shifting it left or right until it matches the nominal
  		 * frequency value.  This assumes that the feedback does not
  		 * differ from the nominal value more than +50% or -25%.
  		 */
  		shift = 0;
  		while (f < subs->freqn - subs->freqn / 4) {
  			f <<= 1;
  			shift++;
  		}
  		while (f > subs->freqn + subs->freqn / 2) {
  			f >>= 1;
  			shift--;

  		}

  		subs->freqshift = shift;

  	}

  	else if (subs->freqshift >= 0)
  		f <<= subs->freqshift;
  	else
  		f >>= -subs->freqshift;

  	if (likely(f >= subs->freqn - subs->freqn / 8 && f <= subs->freqmax)) {
  		/*
  		 * If the frequency looks valid, set it.
  		 * This value is referred to in prepare_playback_urb().
  		 */
  		spin_lock_irqsave(&subs->lock, flags);
  		subs->freqm = f;
  		spin_unlock_irqrestore(&subs->lock, flags);
  	} else {
  		/*
  		 * Out of range; maybe the shift value is wrong.
  		 * Reset it so that we autodetect again the next time.
  		 */
  		subs->freqshift = INT_MIN;

  	}
  
  	return 0;
  }
  
  /* determine the number of frames in the next packet */
  static int snd_usb_audio_next_packet_size(struct snd_usb_substream *subs)
  {
  	if (subs->fill_max)
  		return subs->maxframesize;
  	else {
  		subs->phase = (subs->phase & 0xffff)
  			+ (subs->freqm << subs->datainterval);
  		return min(subs->phase >> 16, subs->maxframesize);
  	}
  }
  
  /*
   * Prepare urb for streaming before playback starts or when paused.
   *
   * We don't have any data, so we send silence.
   */
  static int prepare_nodata_playback_urb(struct snd_usb_substream *subs,
  				       struct snd_pcm_runtime *runtime,
  				       struct urb *urb)
  {
  	unsigned int i, offs, counts;
  	struct snd_urb_ctx *ctx = urb->context;
  	int stride = runtime->frame_bits >> 3;
  
  	offs = 0;
  	urb->dev = ctx->subs->dev;
  	for (i = 0; i < ctx->packets; ++i) {
  		counts = snd_usb_audio_next_packet_size(subs);
  		urb->iso_frame_desc[i].offset = offs * stride;
  		urb->iso_frame_desc[i].length = counts * stride;
  		offs += counts;
  	}
  	urb->number_of_packets = ctx->packets;
  	urb->transfer_buffer_length = offs * stride;
  	memset(urb->transfer_buffer,

  	       runtime->format == SNDRV_PCM_FORMAT_U8 ? 0x80 : 0,

  	       offs * stride);
  	return 0;
  }
  
  /*
   * prepare urb for playback data pipe
   *
   * Since a URB can handle only a single linear buffer, we must use double
   * buffering when the data to be transferred overflows the buffer boundary.
   * To avoid inconsistencies when updating hwptr_done, we use double buffering
   * for all URBs.
   */
  static int prepare_playback_urb(struct snd_usb_substream *subs,
  				struct snd_pcm_runtime *runtime,
  				struct urb *urb)
  {
  	int i, stride;
  	unsigned int counts, frames, bytes;
  	unsigned long flags;
  	int period_elapsed = 0;
  	struct snd_urb_ctx *ctx = urb->context;
  
  	stride = runtime->frame_bits >> 3;
  
  	frames = 0;
  	urb->dev = ctx->subs->dev; /* we need to set this at each time */
  	urb->number_of_packets = 0;
  	spin_lock_irqsave(&subs->lock, flags);
  	for (i = 0; i < ctx->packets; i++) {
  		counts = snd_usb_audio_next_packet_size(subs);
  		/* set up descriptor */
  		urb->iso_frame_desc[i].offset = frames * stride;
  		urb->iso_frame_desc[i].length = counts * stride;
  		frames += counts;
  		urb->number_of_packets++;
  		subs->transfer_done += counts;
  		if (subs->transfer_done >= runtime->period_size) {
  			subs->transfer_done -= runtime->period_size;
  			period_elapsed = 1;
  			if (subs->fmt_type == UAC_FORMAT_TYPE_II) {
  				if (subs->transfer_done > 0) {
  					/* FIXME: fill-max mode is not
  					 * supported yet */
  					frames -= subs->transfer_done;
  					counts -= subs->transfer_done;
  					urb->iso_frame_desc[i].length =
  						counts * stride;
  					subs->transfer_done = 0;
  				}
  				i++;
  				if (i < ctx->packets) {
  					/* add a transfer delimiter */
  					urb->iso_frame_desc[i].offset =
  						frames * stride;
  					urb->iso_frame_desc[i].length = 0;
  					urb->number_of_packets++;
  				}
  				break;
  			}
  		}
  		if (period_elapsed) /* finish at the period boundary */
  			break;
  	}
  	bytes = frames * stride;
  	if (subs->hwptr_done + bytes > runtime->buffer_size * stride) {
  		/* err, the transferred area goes over buffer boundary. */
  		unsigned int bytes1 =
  			runtime->buffer_size * stride - subs->hwptr_done;
  		memcpy(urb->transfer_buffer,
  		       runtime->dma_area + subs->hwptr_done, bytes1);
  		memcpy(urb->transfer_buffer + bytes1,
  		       runtime->dma_area, bytes - bytes1);
  	} else {
  		memcpy(urb->transfer_buffer,
  		       runtime->dma_area + subs->hwptr_done, bytes);
  	}
  	subs->hwptr_done += bytes;
  	if (subs->hwptr_done >= runtime->buffer_size * stride)
  		subs->hwptr_done -= runtime->buffer_size * stride;
  	runtime->delay += frames;
  	spin_unlock_irqrestore(&subs->lock, flags);
  	urb->transfer_buffer_length = bytes;
  	if (period_elapsed)
  		snd_pcm_period_elapsed(subs->pcm_substream);
  	return 0;
  }
  
  /*
   * process after playback data complete
   * - decrease the delay count again
   */
  static int retire_playback_urb(struct snd_usb_substream *subs,
  			       struct snd_pcm_runtime *runtime,
  			       struct urb *urb)
  {
  	unsigned long flags;
  	int stride = runtime->frame_bits >> 3;
  	int processed = urb->transfer_buffer_length / stride;
  
  	spin_lock_irqsave(&subs->lock, flags);
  	if (processed > runtime->delay)
  		runtime->delay = 0;
  	else
  		runtime->delay -= processed;
  	spin_unlock_irqrestore(&subs->lock, flags);
  	return 0;
  }
  
  static const char *usb_error_string(int err)
  {
  	switch (err) {
  	case -ENODEV:
  		return "no device";
  	case -ENOENT:
  		return "endpoint not enabled";
  	case -EPIPE:
  		return "endpoint stalled";
  	case -ENOSPC:
  		return "not enough bandwidth";
  	case -ESHUTDOWN:
  		return "device disabled";
  	case -EHOSTUNREACH:
  		return "device suspended";
  	case -EINVAL:
  	case -EAGAIN:
  	case -EFBIG:
  	case -EMSGSIZE:
  		return "internal error";
  	default:
  		return "unknown error";
  	}
  }
  
  /*
   * set up and start data/sync urbs
   */
  static int start_urbs(struct snd_usb_substream *subs, struct snd_pcm_runtime *runtime)
  {
  	unsigned int i;
  	int err;
  
  	if (subs->stream->chip->shutdown)
  		return -EBADFD;
  
  	for (i = 0; i < subs->nurbs; i++) {
  		if (snd_BUG_ON(!subs->dataurb[i].urb))
  			return -EINVAL;
  		if (subs->ops.prepare(subs, runtime, subs->dataurb[i].urb) < 0) {
  			snd_printk(KERN_ERR "cannot prepare datapipe for urb %d
  ", i);
  			goto __error;
  		}
  	}
  	if (subs->syncpipe) {
  		for (i = 0; i < SYNC_URBS; i++) {
  			if (snd_BUG_ON(!subs->syncurb[i].urb))
  				return -EINVAL;
  			if (subs->ops.prepare_sync(subs, runtime, subs->syncurb[i].urb) < 0) {
  				snd_printk(KERN_ERR "cannot prepare syncpipe for urb %d
  ", i);
  				goto __error;
  			}
  		}
  	}
  
  	subs->active_mask = 0;
  	subs->unlink_mask = 0;
  	subs->running = 1;
  	for (i = 0; i < subs->nurbs; i++) {
  		err = usb_submit_urb(subs->dataurb[i].urb, GFP_ATOMIC);
  		if (err < 0) {
  			snd_printk(KERN_ERR "cannot submit datapipe "
  				   "for urb %d, error %d: %s
  ",
  				   i, err, usb_error_string(err));
  			goto __error;
  		}
  		set_bit(i, &subs->active_mask);
  	}
  	if (subs->syncpipe) {
  		for (i = 0; i < SYNC_URBS; i++) {
  			err = usb_submit_urb(subs->syncurb[i].urb, GFP_ATOMIC);
  			if (err < 0) {
  				snd_printk(KERN_ERR "cannot submit syncpipe "
  					   "for urb %d, error %d: %s
  ",
  					   i, err, usb_error_string(err));
  				goto __error;
  			}
  			set_bit(i + 16, &subs->active_mask);
  		}
  	}
  	return 0;
  
   __error:
  	// snd_pcm_stop(subs->pcm_substream, SNDRV_PCM_STATE_XRUN);
  	deactivate_urbs(subs, 0, 0);
  	return -EPIPE;
  }
  
  
  /*
   */
  static struct snd_urb_ops audio_urb_ops[2] = {
  	{
  		.prepare =	prepare_nodata_playback_urb,
  		.retire =	retire_playback_urb,
  		.prepare_sync =	prepare_playback_sync_urb,
  		.retire_sync =	retire_playback_sync_urb,
  	},
  	{
  		.prepare =	prepare_capture_urb,
  		.retire =	retire_capture_urb,
  		.prepare_sync =	prepare_capture_sync_urb,
  		.retire_sync =	retire_capture_sync_urb,
  	},
  };

  /*
   * initialize the substream instance.
   */
  
  void snd_usb_init_substream(struct snd_usb_stream *as,
  			    int stream, struct audioformat *fp)
  {
  	struct snd_usb_substream *subs = &as->substream[stream];
  
  	INIT_LIST_HEAD(&subs->fmt_list);
  	spin_lock_init(&subs->lock);
  
  	subs->stream = as;
  	subs->direction = stream;
  	subs->dev = as->chip->dev;
  	subs->txfr_quirk = as->chip->txfr_quirk;

  	subs->ops = audio_urb_ops[stream];
  	if (snd_usb_get_speed(subs->dev) >= USB_SPEED_HIGH)
  		subs->ops.prepare_sync = prepare_capture_sync_urb_hs;

  
  	snd_usb_set_pcm_ops(as->pcm, stream);
  
  	list_add_tail(&fp->list, &subs->fmt_list);

  	subs->formats |= fp->formats;

  	subs->endpoint = fp->endpoint;
  	subs->num_formats++;
  	subs->fmt_type = fp->fmt_type;
  }
  
  int snd_usb_substream_playback_trigger(struct snd_pcm_substream *substream, int cmd)
  {
  	struct snd_usb_substream *subs = substream->runtime->private_data;
  
  	switch (cmd) {
  	case SNDRV_PCM_TRIGGER_START:
  	case SNDRV_PCM_TRIGGER_PAUSE_RELEASE:
  		subs->ops.prepare = prepare_playback_urb;
  		return 0;
  	case SNDRV_PCM_TRIGGER_STOP:
  		return deactivate_urbs(subs, 0, 0);
  	case SNDRV_PCM_TRIGGER_PAUSE_PUSH:
  		subs->ops.prepare = prepare_nodata_playback_urb;
  		return 0;
  	}
  
  	return -EINVAL;
  }
  
  int snd_usb_substream_capture_trigger(struct snd_pcm_substream *substream, int cmd)
  {
  	struct snd_usb_substream *subs = substream->runtime->private_data;
  
  	switch (cmd) {
  	case SNDRV_PCM_TRIGGER_START:
  		subs->ops.retire = retire_capture_urb;
  		return start_urbs(subs, substream->runtime);
  	case SNDRV_PCM_TRIGGER_STOP:
  		return deactivate_urbs(subs, 0, 0);
  	case SNDRV_PCM_TRIGGER_PAUSE_PUSH:
  		subs->ops.retire = retire_paused_capture_urb;
  		return 0;
  	case SNDRV_PCM_TRIGGER_PAUSE_RELEASE:
  		subs->ops.retire = retire_capture_urb;
  		return 0;
  	}
  
  	return -EINVAL;
  }
  
  int snd_usb_substream_prepare(struct snd_usb_substream *subs,
  			      struct snd_pcm_runtime *runtime)
  {
  	/* clear urbs (to be sure) */
  	deactivate_urbs(subs, 0, 1);
  	wait_clear_urbs(subs);
  
  	/* for playback, submit the URBs now; otherwise, the first hwptr_done
  	 * updates for all URBs would happen at the same time when starting */
  	if (subs->direction == SNDRV_PCM_STREAM_PLAYBACK) {
  		subs->ops.prepare = prepare_nodata_playback_urb;
  		return start_urbs(subs, runtime);
  	}
  
  	return 0;
  }