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usb_stream.c

/*
 * Copyright (C) 2007, 2008 Karsten Wiese <fzu@wemgehoertderstaat.de>
 *
 * 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., 675 Mass Ave, Cambridge, MA 02139, USA.
 */

#include <linux/usb.h>

#include "usb_stream.h"


/*                             setup                                  */

static unsigned usb_stream_next_packet_size(struct usb_stream_kernel *sk)
{
      struct usb_stream *s = sk->s;
      sk->out_phase_peeked = (sk->out_phase & 0xffff) + sk->freqn;
      return (sk->out_phase_peeked >> 16) * s->cfg.frame_size;
}

static void playback_prep_freqn(struct usb_stream_kernel *sk, struct urb *urb)
{
      struct usb_stream *s = sk->s;
      unsigned l = 0;
      int pack;

      urb->iso_frame_desc[0].offset = 0;
      urb->iso_frame_desc[0].length =     usb_stream_next_packet_size(sk);
      sk->out_phase = sk->out_phase_peeked;
      urb->transfer_buffer_length = urb->iso_frame_desc[0].length;

      for (pack = 1; pack < sk->n_o_ps; pack++) {
            l = usb_stream_next_packet_size(sk);
            if (s->idle_outsize + urb->transfer_buffer_length + l >
                s->period_size)
                  goto check;

            sk->out_phase = sk->out_phase_peeked;
            urb->iso_frame_desc[pack].offset = urb->transfer_buffer_length;
            urb->iso_frame_desc[pack].length = l;
            urb->transfer_buffer_length += l;
      }
      snd_printdd(KERN_DEBUG "%i\n", urb->transfer_buffer_length);

check:
      urb->number_of_packets = pack;
      s->idle_outsize += urb->transfer_buffer_length - s->period_size;
      snd_printdd(KERN_DEBUG "idle=%i ul=%i ps=%i\n", s->idle_outsize,
                urb->transfer_buffer_length, s->period_size);
}

static void init_pipe_urbs(struct usb_stream_kernel *sk, unsigned use_packsize,
                     struct urb **urbs, char *transfer,
                     struct usb_device *dev, int pipe)
{
      int u, p;
      int maxpacket = use_packsize ?
            use_packsize : usb_maxpacket(dev, pipe, usb_pipeout(pipe));
      int transfer_length = maxpacket * sk->n_o_ps;

      for (u = 0; u < USB_STREAM_NURBS;
           ++u, transfer += transfer_length) {
            struct urb *urb = urbs[u];
            struct usb_iso_packet_descriptor *desc;
            urb->transfer_flags = URB_ISO_ASAP;
            urb->transfer_buffer = transfer;
            urb->dev = dev;
            urb->pipe = pipe;
            urb->number_of_packets = sk->n_o_ps;
            urb->context = sk;
            urb->interval = 1;
            if (usb_pipeout(pipe))
                  continue;

            urb->transfer_buffer_length = transfer_length;
            desc = urb->iso_frame_desc;
            desc->offset = 0;
            desc->length = maxpacket;
            for (p = 1; p < sk->n_o_ps; ++p) {
                  desc[p].offset = desc[p - 1].offset + maxpacket;
                  desc[p].length = maxpacket;
            }
      }
}

static void init_urbs(struct usb_stream_kernel *sk, unsigned use_packsize,
                  struct usb_device *dev, int in_pipe, int out_pipe)
{
      struct usb_stream *s = sk->s;
      char              *indata = (char *)s + sizeof(*s) +
                              sizeof(struct usb_stream_packet) *
                              s->inpackets;
      int               u;

      for (u = 0; u < USB_STREAM_NURBS; ++u) {
            sk->inurb[u] = usb_alloc_urb(sk->n_o_ps, GFP_KERNEL);
            sk->outurb[u] = usb_alloc_urb(sk->n_o_ps, GFP_KERNEL);
      }

      init_pipe_urbs(sk, use_packsize, sk->inurb, indata, dev, in_pipe);
      init_pipe_urbs(sk, use_packsize, sk->outurb, sk->write_page, dev,
                   out_pipe);
}


/*
 * 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 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 rate)
{
      return ((rate << 10) + 62) / 125;
}

void usb_stream_free(struct usb_stream_kernel *sk)
{
      struct usb_stream *s;
      unsigned u;

      for (u = 0; u < USB_STREAM_NURBS; ++u) {
            usb_free_urb(sk->inurb[u]);
            sk->inurb[u] = NULL;
            usb_free_urb(sk->outurb[u]);
            sk->outurb[u] = NULL;
      }

      s = sk->s;
      if (!s)
            return;

      free_pages((unsigned long)sk->write_page, get_order(s->write_size));
      sk->write_page = NULL;
      free_pages((unsigned long)s, get_order(s->read_size));
      sk->s = NULL;
}

struct usb_stream *usb_stream_new(struct usb_stream_kernel *sk,
                          struct usb_device *dev,
                          unsigned in_endpoint, unsigned out_endpoint,
                          unsigned sample_rate, unsigned use_packsize,
                          unsigned period_frames, unsigned frame_size)
{
      int packets, max_packsize;
      int in_pipe, out_pipe;
      int read_size = sizeof(struct usb_stream);
      int write_size;
      int usb_frames = dev->speed == USB_SPEED_HIGH ? 8000 : 1000;
      int pg;

      in_pipe = usb_rcvisocpipe(dev, in_endpoint);
      out_pipe = usb_sndisocpipe(dev, out_endpoint);

      max_packsize = use_packsize ?
            use_packsize : usb_maxpacket(dev, in_pipe, 0);

      /*
            t_period = period_frames / sample_rate
            iso_packs = t_period / t_iso_frame
                  = (period_frames / sample_rate) * (1 / t_iso_frame)
      */

      packets = period_frames * usb_frames / sample_rate + 1;

      if (dev->speed == USB_SPEED_HIGH)
            packets = (packets + 7) & ~7;

      read_size += packets * USB_STREAM_URBDEPTH *
            (max_packsize + sizeof(struct usb_stream_packet));

      max_packsize = usb_maxpacket(dev, out_pipe, 1);
      write_size = max_packsize * packets * USB_STREAM_URBDEPTH;

      if (read_size >= 256*PAGE_SIZE || write_size >= 256*PAGE_SIZE) {
            snd_printk(KERN_WARNING "a size exceeds 128*PAGE_SIZE\n");
            goto out;
      }

      pg = get_order(read_size);
      sk->s = (void *) __get_free_pages(GFP_KERNEL|__GFP_COMP|__GFP_ZERO, pg);
      if (!sk->s) {
            snd_printk(KERN_WARNING "couldn't __get_free_pages()\n");
            goto out;
      }
      sk->s->cfg.version = USB_STREAM_INTERFACE_VERSION;

      sk->s->read_size = read_size;

      sk->s->cfg.sample_rate = sample_rate;
      sk->s->cfg.frame_size = frame_size;
      sk->n_o_ps = packets;
      sk->s->inpackets = packets * USB_STREAM_URBDEPTH;
      sk->s->cfg.period_frames = period_frames;
      sk->s->period_size = frame_size * period_frames;

      sk->s->write_size = write_size;
      pg = get_order(write_size);

      sk->write_page =
            (void *)__get_free_pages(GFP_KERNEL|__GFP_COMP|__GFP_ZERO, pg);
      if (!sk->write_page) {
            snd_printk(KERN_WARNING "couldn't __get_free_pages()\n");
            usb_stream_free(sk);
            return NULL;
      }

      /* calculate the frequency in 16.16 format */
      if (dev->speed == USB_SPEED_FULL)
            sk->freqn = get_usb_full_speed_rate(sample_rate);
      else
            sk->freqn = get_usb_high_speed_rate(sample_rate);

      init_urbs(sk, use_packsize, dev, in_pipe, out_pipe);
      sk->s->state = usb_stream_stopped;
out:
      return sk->s;
}


/*                             start                                  */

static bool balance_check(struct usb_stream_kernel *sk, struct urb *urb)
{
      bool r;
      if (unlikely(urb->status)) {
            if (urb->status != -ESHUTDOWN && urb->status != -ENOENT)
                  snd_printk(KERN_WARNING "status=%i\n", urb->status);
            sk->iso_frame_balance = 0x7FFFFFFF;
            return false;
      }
      r = sk->iso_frame_balance == 0;
      if (!r)
            sk->i_urb = urb;
      return r;
}

static bool balance_playback(struct usb_stream_kernel *sk, struct urb *urb)
{
      sk->iso_frame_balance += urb->number_of_packets;
      return balance_check(sk, urb);
}

static bool balance_capture(struct usb_stream_kernel *sk, struct urb *urb)
{
      sk->iso_frame_balance -= urb->number_of_packets;
      return balance_check(sk, urb);
}

static void subs_set_complete(struct urb **urbs, void (*complete)(struct urb *))
{
      int u;

      for (u = 0; u < USB_STREAM_NURBS; u++) {
            struct urb *urb = urbs[u];
            urb->complete = complete;
      }
}

int usb_stream_prepare_playback(struct usb_stream_kernel *sk, struct urb *inurb)
{
      struct usb_stream *s = sk->s;
      struct urb *io;
      struct usb_iso_packet_descriptor *id, *od;
      int p, l = 0;

      io = sk->idle_outurb;
      od = io->iso_frame_desc;
      io->transfer_buffer_length = 0;

      for (p = 0; s->sync_packet < 0; ++p, ++s->sync_packet) {
            struct urb *ii = sk->completed_inurb;
            id = ii->iso_frame_desc +
                  ii->number_of_packets + s->sync_packet;
            l = id->actual_length;

            od[p].length = l;
            od[p].offset = io->transfer_buffer_length;
            io->transfer_buffer_length += l;
      }

      for (;
           s->sync_packet < inurb->number_of_packets && p < sk->n_o_ps;
           ++p, ++s->sync_packet) {
            l = inurb->iso_frame_desc[s->sync_packet].actual_length;

            if (s->idle_outsize + io->transfer_buffer_length + l >
                s->period_size)
                  goto check_ok;

            od[p].length = l;
            od[p].offset = io->transfer_buffer_length;
            io->transfer_buffer_length += l;
      }

check_ok:
      s->sync_packet -= inurb->number_of_packets;
      if (s->sync_packet < -2 || s->sync_packet > 0) {
            snd_printk(KERN_WARNING "invalid sync_packet = %i;"
                     " p=%i nop=%i %i %x %x %x > %x\n",
                     s->sync_packet, p, inurb->number_of_packets,
                     s->idle_outsize + io->transfer_buffer_length + l,
                     s->idle_outsize, io->transfer_buffer_length,  l,
                     s->period_size);
            return -1;
      }
      if (io->transfer_buffer_length % s->cfg.frame_size) {
            snd_printk(KERN_WARNING"invalid outsize = %i\n",
                     io->transfer_buffer_length);
            return -1;
      }
      s->idle_outsize += io->transfer_buffer_length - s->period_size;
      io->number_of_packets = p;
      if (s->idle_outsize > 0) {
            snd_printk(KERN_WARNING "idle=%i\n", s->idle_outsize);
            return -1;
      }
      return 0;
}

static void prepare_inurb(int number_of_packets, struct urb *iu)
{
      struct usb_iso_packet_descriptor *id;
      int p;

      iu->number_of_packets = number_of_packets;
      id = iu->iso_frame_desc;
      id->offset = 0;
      for (p = 0; p < iu->number_of_packets - 1; ++p)
            id[p + 1].offset = id[p].offset + id[p].length;

      iu->transfer_buffer_length =
            id[0].length * iu->number_of_packets;
}

static int submit_urbs(struct usb_stream_kernel *sk,
                   struct urb *inurb, struct urb *outurb)
{
      int err;
      prepare_inurb(sk->idle_outurb->number_of_packets, sk->idle_inurb);
      err = usb_submit_urb(sk->idle_inurb, GFP_ATOMIC);
      if (err < 0) {
            snd_printk(KERN_ERR "%i\n", err);
            return err;
      }
      sk->idle_inurb = sk->completed_inurb;
      sk->completed_inurb = inurb;
      err = usb_submit_urb(sk->idle_outurb, GFP_ATOMIC);
      if (err < 0) {
            snd_printk(KERN_ERR "%i\n", err);
            return err;
      }
      sk->idle_outurb = sk->completed_outurb;
      sk->completed_outurb = outurb;
      return 0;
}

#ifdef DEBUG_LOOP_BACK
/*
  This loop_back() shows how to read/write the period data.
 */
static void loop_back(struct usb_stream *s)
{
      char *i, *o;
      int il, ol, l, p;
      struct urb *iu;
      struct usb_iso_packet_descriptor *id;

      o = s->playback1st_to;
      ol = s->playback1st_size;
      l = 0;

      if (s->insplit_pack >= 0) {
            iu = sk->idle_inurb;
            id = iu->iso_frame_desc;
            p = s->insplit_pack;
      } else
            goto second;
loop:
      for (; p < iu->number_of_packets && l < s->period_size; ++p) {
            i = iu->transfer_buffer + id[p].offset;
            il = id[p].actual_length;
            if (l + il > s->period_size)
                  il = s->period_size - l;
            if (il <= ol) {
                  memcpy(o, i, il);
                  o += il;
                  ol -= il;
            } else {
                  memcpy(o, i, ol);
                  singen_6pack(o, ol);
                  o = s->playback_to;
                  memcpy(o, i + ol, il - ol);
                  o += il - ol;
                  ol = s->period_size - s->playback1st_size;
            }
            l += il;
      }
      if (iu == sk->completed_inurb) {
            if (l != s->period_size)
                  printk(KERN_DEBUG"%s:%i %i\n", __func__, __LINE__,
                         l/(int)s->cfg.frame_size);

            return;
      }
second:
      iu = sk->completed_inurb;
      id = iu->iso_frame_desc;
      p = 0;
      goto loop;

}
#else
static void loop_back(struct usb_stream *s)
{
}
#endif

static void stream_idle(struct usb_stream_kernel *sk,
                  struct urb *inurb, struct urb *outurb)
{
      struct usb_stream *s = sk->s;
      int l, p;
      int insize = s->idle_insize;
      int urb_size = 0;

      s->inpacket_split = s->next_inpacket_split;
      s->inpacket_split_at = s->next_inpacket_split_at;
      s->next_inpacket_split = -1;
      s->next_inpacket_split_at = 0;

      for (p = 0; p < inurb->number_of_packets; ++p) {
            struct usb_iso_packet_descriptor *id = inurb->iso_frame_desc;
            l = id[p].actual_length;
            if (unlikely(l == 0 || id[p].status)) {
                  snd_printk(KERN_WARNING "underrun, status=%u\n",
                           id[p].status);
                  goto err_out;
            }
            s->inpacket_head++;
            s->inpacket_head %= s->inpackets;
            if (s->inpacket_split == -1)
                  s->inpacket_split = s->inpacket_head;

            s->inpacket[s->inpacket_head].offset =
                  id[p].offset + (inurb->transfer_buffer - (void *)s);
            s->inpacket[s->inpacket_head].length = l;
            if (insize + l > s->period_size &&
                s->next_inpacket_split == -1) {
                  s->next_inpacket_split = s->inpacket_head;
                  s->next_inpacket_split_at = s->period_size - insize;
            }
            insize += l;
            urb_size += l;
      }
      s->idle_insize += urb_size - s->period_size;
      if (s->idle_insize < 0) {
            snd_printk(KERN_WARNING "%i\n",
                     (s->idle_insize)/(int)s->cfg.frame_size);
            goto err_out;
      }
      s->insize_done += urb_size;

      l = s->idle_outsize;
      s->outpacket[0].offset = (sk->idle_outurb->transfer_buffer -
                          sk->write_page) - l;

      if (usb_stream_prepare_playback(sk, inurb) < 0)
            goto err_out;

      s->outpacket[0].length = sk->idle_outurb->transfer_buffer_length + l;
      s->outpacket[1].offset = sk->completed_outurb->transfer_buffer -
            sk->write_page;

      if (submit_urbs(sk, inurb, outurb) < 0)
            goto err_out;

      loop_back(s);
      s->periods_done++;
      wake_up_all(&sk->sleep);
      return;
err_out:
      s->state = usb_stream_xrun;
      wake_up_all(&sk->sleep);
}

static void i_capture_idle(struct urb *urb)
{
      struct usb_stream_kernel *sk = urb->context;
      if (balance_capture(sk, urb))
            stream_idle(sk, urb, sk->i_urb);
}

static void i_playback_idle(struct urb *urb)
{
      struct usb_stream_kernel *sk = urb->context;
      if (balance_playback(sk, urb))
            stream_idle(sk, sk->i_urb, urb);
}

static void stream_start(struct usb_stream_kernel *sk,
                   struct urb *inurb, struct urb *outurb)
{
      struct usb_stream *s = sk->s;
      if (s->state >= usb_stream_sync1) {
            int l, p, max_diff, max_diff_0;
            int urb_size = 0;
            unsigned frames_per_packet, min_frames = 0;
            frames_per_packet = (s->period_size - s->idle_insize);
            frames_per_packet <<= 8;
            frames_per_packet /=
                  s->cfg.frame_size * inurb->number_of_packets;
            frames_per_packet++;

            max_diff_0 = s->cfg.frame_size;
            if (s->cfg.period_frames >= 256)
                  max_diff_0 <<= 1;
            if (s->cfg.period_frames >= 1024)
                  max_diff_0 <<= 1;
            max_diff = max_diff_0;
            for (p = 0; p < inurb->number_of_packets; ++p) {
                  int diff;
                  l = inurb->iso_frame_desc[p].actual_length;
                  urb_size += l;

                  min_frames += frames_per_packet;
                  diff = urb_size -
                        (min_frames >> 8) * s->cfg.frame_size;
                  if (diff < max_diff) {
                        snd_printdd(KERN_DEBUG "%i %i %i %i\n",
                                  s->insize_done,
                                  urb_size / (int)s->cfg.frame_size,
                                  inurb->number_of_packets, diff);
                        max_diff = diff;
                  }
            }
            s->idle_insize -= max_diff - max_diff_0;
            s->idle_insize += urb_size - s->period_size;
            if (s->idle_insize < 0) {
                  snd_printk("%i %i %i\n",
                           s->idle_insize, urb_size, s->period_size);
                  return;
            } else if (s->idle_insize == 0) {
                  s->next_inpacket_split =
                        (s->inpacket_head + 1) % s->inpackets;
                  s->next_inpacket_split_at = 0;
            } else {
                  unsigned split = s->inpacket_head;
                  l = s->idle_insize;
                  while (l > s->inpacket[split].length) {
                        l -= s->inpacket[split].length;
                        if (split == 0)
                              split = s->inpackets - 1;
                        else
                              split--;
                  }
                  s->next_inpacket_split = split;
                  s->next_inpacket_split_at =
                        s->inpacket[split].length - l;
            }

            s->insize_done += urb_size;

            if (usb_stream_prepare_playback(sk, inurb) < 0)
                  return;

      } else
            playback_prep_freqn(sk, sk->idle_outurb);

      if (submit_urbs(sk, inurb, outurb) < 0)
            return;

      if (s->state == usb_stream_sync1 && s->insize_done > 360000) {
            /* just guesswork                            ^^^^^^ */
            s->state = usb_stream_ready;
            subs_set_complete(sk->inurb, i_capture_idle);
            subs_set_complete(sk->outurb, i_playback_idle);
      }
}

static void i_capture_start(struct urb *urb)
{
      struct usb_iso_packet_descriptor *id = urb->iso_frame_desc;
      struct usb_stream_kernel *sk = urb->context;
      struct usb_stream *s = sk->s;
      int p;
      int empty = 0;

      if (urb->status) {
            snd_printk(KERN_WARNING "status=%i\n", urb->status);
            return;
      }

      for (p = 0; p < urb->number_of_packets; ++p) {
            int l = id[p].actual_length;
            if (l < s->cfg.frame_size) {
                  ++empty;
                  if (s->state >= usb_stream_sync0) {
                        snd_printk(KERN_WARNING "%i\n", l);
                        return;
                  }
            }
            s->inpacket_head++;
            s->inpacket_head %= s->inpackets;
            s->inpacket[s->inpacket_head].offset =
                  id[p].offset + (urb->transfer_buffer - (void *)s);
            s->inpacket[s->inpacket_head].length = l;
      }
#ifdef SHOW_EMPTY
      if (empty) {
            printk(KERN_DEBUG"%s:%i: %i", __func__, __LINE__,
                   urb->iso_frame_desc[0].actual_length);
            for (pack = 1; pack < urb->number_of_packets; ++pack) {
                  int l = urb->iso_frame_desc[pack].actual_length;
                  printk(" %i", l);
            }
            printk("\n");
      }
#endif
      if (!empty && s->state < usb_stream_sync1)
            ++s->state;

      if (balance_capture(sk, urb))
            stream_start(sk, urb, sk->i_urb);
}

static void i_playback_start(struct urb *urb)
{
      struct usb_stream_kernel *sk = urb->context;
      if (balance_playback(sk, urb))
            stream_start(sk, sk->i_urb, urb);
}

int usb_stream_start(struct usb_stream_kernel *sk)
{
      struct usb_stream *s = sk->s;
      int frame = 0, iters = 0;
      int u, err;
      int try = 0;

      if (s->state != usb_stream_stopped)
            return -EAGAIN;

      subs_set_complete(sk->inurb, i_capture_start);
      subs_set_complete(sk->outurb, i_playback_start);
      memset(sk->write_page, 0, s->write_size);
dotry:
      s->insize_done = 0;
      s->idle_insize = 0;
      s->idle_outsize = 0;
      s->sync_packet = -1;
      s->inpacket_head = -1;
      sk->iso_frame_balance = 0;
      ++try;
      for (u = 0; u < 2; u++) {
            struct urb *inurb = sk->inurb[u];
            struct urb *outurb = sk->outurb[u];
            playback_prep_freqn(sk, outurb);
            inurb->number_of_packets = outurb->number_of_packets;
            inurb->transfer_buffer_length =
                  inurb->number_of_packets *
                  inurb->iso_frame_desc[0].length;
            preempt_disable();
            if (u == 0) {
                  int now;
                  struct usb_device *dev = inurb->dev;
                  frame = usb_get_current_frame_number(dev);
                  do {
                        now = usb_get_current_frame_number(dev);
                        ++iters;
                  } while (now > -1 && now == frame);
            }
            err = usb_submit_urb(inurb, GFP_ATOMIC);
            if (err < 0) {
                  preempt_enable();
                  snd_printk(KERN_ERR"usb_submit_urb(sk->inurb[%i])"
                           " returned %i\n", u, err);
                  return err;
            }
            err = usb_submit_urb(outurb, GFP_ATOMIC);
            if (err < 0) {
                  preempt_enable();
                  snd_printk(KERN_ERR"usb_submit_urb(sk->outurb[%i])"
                           " returned %i\n", u, err);
                  return err;
            }
            preempt_enable();
            if (inurb->start_frame != outurb->start_frame) {
                  snd_printd(KERN_DEBUG
                           "u[%i] start_frames differ in:%u out:%u\n",
                           u, inurb->start_frame, outurb->start_frame);
                  goto check_retry;
            }
      }
      snd_printdd(KERN_DEBUG "%i %i\n", frame, iters);
      try = 0;
check_retry:
      if (try) {
            usb_stream_stop(sk);
            if (try < 5) {
                  msleep(1500);
                  snd_printd(KERN_DEBUG "goto dotry;\n");
                  goto dotry;
            }
            snd_printk(KERN_WARNING"couldn't start"
                     " all urbs on the same start_frame.\n");
            return -EFAULT;
      }

      sk->idle_inurb = sk->inurb[USB_STREAM_NURBS - 2];
      sk->idle_outurb = sk->outurb[USB_STREAM_NURBS - 2];
      sk->completed_inurb = sk->inurb[USB_STREAM_NURBS - 1];
      sk->completed_outurb = sk->outurb[USB_STREAM_NURBS - 1];

/* wait, check */
      {
            int wait_ms = 3000;
            while (s->state != usb_stream_ready && wait_ms > 0) {
                  snd_printdd(KERN_DEBUG "%i\n", s->state);
                  msleep(200);
                  wait_ms -= 200;
            }
      }

      return s->state == usb_stream_ready ? 0 : -EFAULT;
}


/*                             stop                                   */

void usb_stream_stop(struct usb_stream_kernel *sk)
{
      int u;
      if (!sk->s)
            return;
      for (u = 0; u < USB_STREAM_NURBS; ++u) {
            usb_kill_urb(sk->inurb[u]);
            usb_kill_urb(sk->outurb[u]);
      }
      sk->s->state = usb_stream_stopped;
      msleep(400);
}

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