Quelle  usbusx2yaudio.c   Sprache: C

// SPDX-License-Identifier: GPL-2.0-or-later
/*
 *   US-X2Y AUDIO
 *   Copyright (c) 2002-2004 by Karsten Wiese
 *
 *   based on
 *
 *   (Tentative) USB Audio Driver for ALSA
 *
 *   Main and PCM part
 *
 *   Copyright (c) 2002 by Takashi Iwai <tiwai@suse.de>
 *
 *   Many codes borrowed from audio.c by
 *     Alan Cox (alan@lxorguk.ukuu.org.uk)
 *     Thomas Sailer (sailer@ife.ee.ethz.ch)
 */


#include <linux/interrupt.h>
#include <linux/slab.h>
#include <linux/usb.h>
#include <linux/moduleparam.h>
#include <sound/core.h>
#include <sound/info.h>
#include <sound/pcm.h>
#include <sound/pcm_params.h>
#include "usx2y.h"
#include "usbusx2y.h"

static int usx2y_urb_capt_retire(struct snd_usx2y_substream *subs)
{
 struct urb *urb = subs->completed_urb;
 struct snd_pcm_runtime *runtime = subs->pcm_substream->runtime;
 unsigned char *cp;
 int  i, len, lens = 0, hwptr_done = subs->hwptr_done;
 int  cnt, blen;
 struct usx2ydev *usx2y = subs->usx2y;

 for (i = 0; i < nr_of_packs(); i++) {
  cp = (unsigned char *)urb->transfer_buffer + urb->iso_frame_desc[i].offset;
  if (urb->iso_frame_desc[i].status) { /* active? hmm, skip this */
   dev_err(&usx2y->dev->dev,
    "%s: active frame status %i. Most probably some hardware problem.\n",
    __func__,
    urb->iso_frame_desc[i].status);
   return urb->iso_frame_desc[i].status;
  }
  len = urb->iso_frame_desc[i].actual_length / usx2y->stride;
  if (!len) {
   dev_dbg(&usx2y->dev->dev, "%s: 0 == len ERROR!\n", __func__);
   continue;
  }

  /* copy a data chunk */
  if ((hwptr_done + len) > runtime->buffer_size) {
   cnt = runtime->buffer_size - hwptr_done;
   blen = cnt * usx2y->stride;
   memcpy(runtime->dma_area + hwptr_done * usx2y->stride, cp, blen);
   memcpy(runtime->dma_area, cp + blen, len * usx2y->stride - blen);
  } else {
   memcpy(runtime->dma_area + hwptr_done * usx2y->stride, cp,
          len * usx2y->stride);
  }
  lens += len;
  hwptr_done += len;
  if (hwptr_done >= runtime->buffer_size)
   hwptr_done -= runtime->buffer_size;
 }

 subs->hwptr_done = hwptr_done;
 subs->transfer_done += lens;
 /* update the pointer, call callback if necessary */
 if (subs->transfer_done >= runtime->period_size) {
  subs->transfer_done -= runtime->period_size;
  snd_pcm_period_elapsed(subs->pcm_substream);
 }
 return 0;
}

/*
 * prepare urb for playback data pipe
 *
 * we copy the data directly from the pcm buffer.
 * the current position to be copied is held in hwptr field.
 * since a urb can handle only a single linear buffer, if the total
 * transferred area overflows the buffer boundary, we cannot send
 * it directly from the buffer.  thus the data is once copied to
 * a temporary buffer and urb points to that.
 */
static int usx2y_urb_play_prepare(struct snd_usx2y_substream *subs,
      struct urb *cap_urb,
      struct urb *urb)
{
 struct usx2ydev *usx2y = subs->usx2y;
 struct snd_pcm_runtime *runtime = subs->pcm_substream->runtime;
 int count, counts, pack, len;

 count = 0;
 for (pack = 0; pack <  nr_of_packs(); pack++) {
  /* calculate the size of a packet */
  counts = cap_urb->iso_frame_desc[pack].actual_length / usx2y->stride;
  count += counts;
  if (counts < 43 || counts > 50) {
   dev_err(&usx2y->dev->dev, "%s: should not be here with counts=%i\n",
    __func__, counts);
   return -EPIPE;
  }
  /* set up descriptor */
  urb->iso_frame_desc[pack].offset = pack ?
   urb->iso_frame_desc[pack - 1].offset +
   urb->iso_frame_desc[pack - 1].length :
   0;
  urb->iso_frame_desc[pack].length = cap_urb->iso_frame_desc[pack].actual_length;
 }
 if (atomic_read(&subs->state) >= STATE_PRERUNNING) {
  if (subs->hwptr + count > runtime->buffer_size) {
   /* err, the transferred area goes over buffer boundary.
 * copy the data to the temp buffer.
 */
   len = runtime->buffer_size - subs->hwptr;
   urb->transfer_buffer = subs->tmpbuf;
   memcpy(subs->tmpbuf, runtime->dma_area +
          subs->hwptr * usx2y->stride, len * usx2y->stride);
   memcpy(subs->tmpbuf + len * usx2y->stride,
          runtime->dma_area, (count - len) * usx2y->stride);
   subs->hwptr += count;
   subs->hwptr -= runtime->buffer_size;
  } else {
   /* set the buffer pointer */
   urb->transfer_buffer = runtime->dma_area + subs->hwptr * usx2y->stride;
   subs->hwptr += count;
   if (subs->hwptr >= runtime->buffer_size)
    subs->hwptr -= runtime->buffer_size;
  }
 } else {
  urb->transfer_buffer = subs->tmpbuf;
 }
 urb->transfer_buffer_length = count * usx2y->stride;
 return 0;
}

/*
 * process after playback data complete
 *
 * update the current position and call callback if a period is processed.
 */
static void usx2y_urb_play_retire(struct snd_usx2y_substream *subs, struct urb *urb)
{
 struct snd_pcm_runtime *runtime = subs->pcm_substream->runtime;
 int  len = urb->actual_length / subs->usx2y->stride;

 subs->transfer_done += len;
 subs->hwptr_done +=  len;
 if (subs->hwptr_done >= runtime->buffer_size)
  subs->hwptr_done -= runtime->buffer_size;
 if (subs->transfer_done >= runtime->period_size) {
  subs->transfer_done -= runtime->period_size;
  snd_pcm_period_elapsed(subs->pcm_substream);
 }
}

static int usx2y_urb_submit(struct snd_usx2y_substream *subs, struct urb *urb, int frame)
{
 int err;

 if (!urb)
  return -ENODEV;
 urb->start_frame = frame + NRURBS * nr_of_packs();  // let hcd do rollover sanity checks
 urb->hcpriv = NULL;
 urb->dev = subs->usx2y->dev; /* we need to set this at each time */
 err = usb_submit_urb(urb, GFP_ATOMIC);
 if (err < 0) {
  dev_err(&urb->dev->dev, "%s: usb_submit_urb() returned %i\n",
   __func__, err);
  return err;
 }
 return 0;
}

static int usx2y_usbframe_complete(struct snd_usx2y_substream *capsubs,
       struct snd_usx2y_substream *playbacksubs,
       int frame)
{
 int err, state;
 struct urb *urb = playbacksubs->completed_urb;

 state = atomic_read(&playbacksubs->state);
 if (urb) {
  if (state == STATE_RUNNING)
   usx2y_urb_play_retire(playbacksubs, urb);
  else if (state >= STATE_PRERUNNING)
   atomic_inc(&playbacksubs->state);
 } else {
  switch (state) {
  case STATE_STARTING1:
   urb = playbacksubs->urb[0];
   atomic_inc(&playbacksubs->state);
   break;
  case STATE_STARTING2:
   urb = playbacksubs->urb[1];
   atomic_inc(&playbacksubs->state);
   break;
  }
 }
 if (urb) {
  err = usx2y_urb_play_prepare(playbacksubs, capsubs->completed_urb, urb);
  if (err)
   return err;
  err = usx2y_urb_submit(playbacksubs, urb, frame);
  if (err)
   return err;
 }

 playbacksubs->completed_urb = NULL;

 state = atomic_read(&capsubs->state);
 if (state >= STATE_PREPARED) {
  if (state == STATE_RUNNING) {
   err = usx2y_urb_capt_retire(capsubs);
   if (err)
    return err;
  } else if (state >= STATE_PRERUNNING) {
   atomic_inc(&capsubs->state);
  }
  err = usx2y_urb_submit(capsubs, capsubs->completed_urb, frame);
  if (err)
   return err;
 }
 capsubs->completed_urb = NULL;
 return 0;
}

static void usx2y_clients_stop(struct usx2ydev *usx2y)
{
 struct snd_usx2y_substream *subs;
 struct urb *urb;
 int s, u;

 for (s = 0; s < 4; s++) {
  subs = usx2y->subs[s];
  if (subs) {
   dev_dbg(&usx2y->dev->dev, "%s: %i %p state=%i\n",
    __func__, s, subs, atomic_read(&subs->state));
   atomic_set(&subs->state, STATE_STOPPED);
  }
 }
 for (s = 0; s < 4; s++) {
  subs = usx2y->subs[s];
  if (subs) {
   if (atomic_read(&subs->state) >= STATE_PRERUNNING)
    snd_pcm_stop_xrun(subs->pcm_substream);
   for (u = 0; u < NRURBS; u++) {
    urb = subs->urb[u];
    if (urb)
     dev_dbg(&usx2y->dev->dev,
      "%s: %i status=%i start_frame=%i\n",
      __func__, u, urb->status, urb->start_frame);
   }
  }
 }
 usx2y->prepare_subs = NULL;
 wake_up(&usx2y->prepare_wait_queue);
}

static void usx2y_error_urb_status(struct usx2ydev *usx2y,
       struct snd_usx2y_substream *subs, struct urb *urb)
{
 dev_err(&usx2y->dev->dev, "%s: ep=%i stalled with status=%i\n",
  __func__, subs->endpoint, urb->status);
 urb->status = 0;
 usx2y_clients_stop(usx2y);
}

static void i_usx2y_urb_complete(struct urb *urb)
{
 struct snd_usx2y_substream *subs = urb->context;
 struct usx2ydev *usx2y = subs->usx2y;
 struct snd_usx2y_substream *capsubs, *playbacksubs;

 if (unlikely(atomic_read(&subs->state) < STATE_PREPARED)) {
  dev_dbg(&usx2y->dev->dev,
   "%s: hcd_frame=%i ep=%i%s status=%i start_frame=%i\n",
   __func__,
   usb_get_current_frame_number(usx2y->dev),
   subs->endpoint, usb_pipein(urb->pipe) ? "in" : "out",
   urb->status, urb->start_frame);
  return;
 }
 if (unlikely(urb->status)) {
  usx2y_error_urb_status(usx2y, subs, urb);
  return;
 }

 subs->completed_urb = urb;

 capsubs = usx2y->subs[SNDRV_PCM_STREAM_CAPTURE];
 playbacksubs = usx2y->subs[SNDRV_PCM_STREAM_PLAYBACK];

 if (capsubs->completed_urb &&
     atomic_read(&capsubs->state) >= STATE_PREPARED &&
     (playbacksubs->completed_urb ||
      atomic_read(&playbacksubs->state) < STATE_PREPARED)) {
  if (!usx2y_usbframe_complete(capsubs, playbacksubs, urb->start_frame)) {
   usx2y->wait_iso_frame += nr_of_packs();
  } else {
   usx2y_clients_stop(usx2y);
  }
 }
}

static void usx2y_urbs_set_complete(struct usx2ydev *usx2y,
        void (*complete)(struct urb *))
{
 struct snd_usx2y_substream *subs;
 struct urb *urb;
 int s, u;

 for (s = 0; s < 4; s++) {
  subs = usx2y->subs[s];
  if (subs) {
   for (u = 0; u < NRURBS; u++) {
    urb = subs->urb[u];
    if (urb)
     urb->complete = complete;
   }
  }
 }
}

static void usx2y_subs_startup_finish(struct usx2ydev *usx2y)
{
 usx2y_urbs_set_complete(usx2y, i_usx2y_urb_complete);
 usx2y->prepare_subs = NULL;
}

static void i_usx2y_subs_startup(struct urb *urb)
{
 struct snd_usx2y_substream *subs = urb->context;
 struct usx2ydev *usx2y = subs->usx2y;
 struct snd_usx2y_substream *prepare_subs = usx2y->prepare_subs;

 if (prepare_subs) {
  if (urb->start_frame == prepare_subs->urb[0]->start_frame) {
   usx2y_subs_startup_finish(usx2y);
   atomic_inc(&prepare_subs->state);
   wake_up(&usx2y->prepare_wait_queue);
  }
 }

 i_usx2y_urb_complete(urb);
}

static void usx2y_subs_prepare(struct snd_usx2y_substream *subs)
{
 dev_dbg(&subs->usx2y->dev->dev,
  "%s(%p) ep=%i urb0=%p urb1=%p\n",
  __func__, subs, subs->endpoint, subs->urb[0], subs->urb[1]);
 /* reset the pointer */
 subs->hwptr = 0;
 subs->hwptr_done = 0;
 subs->transfer_done = 0;
}

static void usx2y_urb_release(struct urb **urb, int free_tb)
{
 if (*urb) {
  usb_kill_urb(*urb);
  if (free_tb)
   kfree((*urb)->transfer_buffer);
  usb_free_urb(*urb);
  *urb = NULL;
 }
}

/*
 * release a substreams urbs
 */
static void usx2y_urbs_release(struct snd_usx2y_substream *subs)
{
 int i;

 dev_dbg(&subs->usx2y->dev->dev, "%s %i\n", __func__, subs->endpoint);
 for (i = 0; i < NRURBS; i++)
  usx2y_urb_release(subs->urb + i,
      subs != subs->usx2y->subs[SNDRV_PCM_STREAM_PLAYBACK]);

 kfree(subs->tmpbuf);
 subs->tmpbuf = NULL;
}

/*
 * initialize a substream's urbs
 */
static int usx2y_urbs_allocate(struct snd_usx2y_substream *subs)
{
 int i;
 unsigned int pipe;
 int is_playback = subs == subs->usx2y->subs[SNDRV_PCM_STREAM_PLAYBACK];
 struct usb_device *dev = subs->usx2y->dev;
 struct urb **purb;

 pipe = is_playback ? usb_sndisocpipe(dev, subs->endpoint) :
   usb_rcvisocpipe(dev, subs->endpoint);
 subs->maxpacksize = usb_maxpacket(dev, pipe);
 if (!subs->maxpacksize)
  return -EINVAL;

 if (is_playback && !subs->tmpbuf) { /* allocate a temporary buffer for playback */
  subs->tmpbuf = kcalloc(nr_of_packs(), subs->maxpacksize, GFP_KERNEL);
  if (!subs->tmpbuf)
   return -ENOMEM;
 }
 /* allocate and initialize data urbs */
 for (i = 0; i < NRURBS; i++) {
  purb = subs->urb + i;
  if (*purb) {
   usb_kill_urb(*purb);
   continue;
  }
  *purb = usb_alloc_urb(nr_of_packs(), GFP_KERNEL);
  if (!*purb) {
   usx2y_urbs_release(subs);
   return -ENOMEM;
  }
  if (!is_playback && !(*purb)->transfer_buffer) {
   /* allocate a capture buffer per urb */
   (*purb)->transfer_buffer =
    kmalloc_array(subs->maxpacksize,
           nr_of_packs(), GFP_KERNEL);
   if (!(*purb)->transfer_buffer) {
    usx2y_urbs_release(subs);
    return -ENOMEM;
   }
  }
  (*purb)->dev = dev;
  (*purb)->pipe = pipe;
  (*purb)->number_of_packets = nr_of_packs();
  (*purb)->context = subs;
  (*purb)->interval = 1;
  (*purb)->complete = i_usx2y_subs_startup;
 }
 return 0;
}

static void usx2y_subs_startup(struct snd_usx2y_substream *subs)
{
 struct usx2ydev *usx2y = subs->usx2y;

 usx2y->prepare_subs = subs;
 subs->urb[0]->start_frame = -1;
 wmb();
 usx2y_urbs_set_complete(usx2y, i_usx2y_subs_startup);
}

static int usx2y_urbs_start(struct snd_usx2y_substream *subs)
{
 int i, err;
 struct usx2ydev *usx2y = subs->usx2y;
 struct urb *urb;
 unsigned long pack;

 err = usx2y_urbs_allocate(subs);
 if (err < 0)
  return err;
 subs->completed_urb = NULL;
 for (i = 0; i < 4; i++) {
  struct snd_usx2y_substream *subs = usx2y->subs[i];

  if (subs && atomic_read(&subs->state) >= STATE_PREPARED)
   goto start;
 }

 start:
 usx2y_subs_startup(subs);
 for (i = 0; i < NRURBS; i++) {
  urb = subs->urb[i];
  if (usb_pipein(urb->pipe)) {
   if (!i)
    atomic_set(&subs->state, STATE_STARTING3);
   urb->dev = usx2y->dev;
   for (pack = 0; pack < nr_of_packs(); pack++) {
    urb->iso_frame_desc[pack].offset = subs->maxpacksize * pack;
    urb->iso_frame_desc[pack].length = subs->maxpacksize;
   }
   urb->transfer_buffer_length = subs->maxpacksize * nr_of_packs();
   err = usb_submit_urb(urb, GFP_ATOMIC);
   if (err < 0) {
    dev_err(&urb->dev->dev, "%s: cannot submit datapipe for urb %d, err = %d\n",
     __func__, i, err);
    err = -EPIPE;
    goto cleanup;
   } else {
    if (!i)
     usx2y->wait_iso_frame = urb->start_frame;
   }
   urb->transfer_flags = 0;
  } else {
   atomic_set(&subs->state, STATE_STARTING1);
   break;
  }
 }
 err = 0;
 wait_event(usx2y->prepare_wait_queue, !usx2y->prepare_subs);
 if (atomic_read(&subs->state) != STATE_PREPARED)
  err = -EPIPE;

 cleanup:
 if (err) {
  usx2y_subs_startup_finish(usx2y);
  usx2y_clients_stop(usx2y); // something is completely wrong > stop everything
 }
 return err;
}

/*
 * return the current pcm pointer.  just return the hwptr_done value.
 */
static snd_pcm_uframes_t snd_usx2y_pcm_pointer(struct snd_pcm_substream *substream)
{
 struct snd_usx2y_substream *subs = substream->runtime->private_data;

 return subs->hwptr_done;
}

/*
 * start/stop substream
 */
static int snd_usx2y_pcm_trigger(struct snd_pcm_substream *substream, int cmd)
{
 struct snd_usx2y_substream *subs = substream->runtime->private_data;

 switch (cmd) {
 case SNDRV_PCM_TRIGGER_START:
  dev_dbg(&subs->usx2y->dev->dev, "%s(START)\n", __func__);
  if (atomic_read(&subs->state) == STATE_PREPARED &&
      atomic_read(&subs->usx2y->subs[SNDRV_PCM_STREAM_CAPTURE]->state) >= STATE_PREPARED) {
   atomic_set(&subs->state, STATE_PRERUNNING);
  } else {
   return -EPIPE;
  }
  break;
 case SNDRV_PCM_TRIGGER_STOP:
  dev_dbg(&subs->usx2y->dev->dev, "%s(STOP)\n", __func__);
  if (atomic_read(&subs->state) >= STATE_PRERUNNING)
   atomic_set(&subs->state, STATE_PREPARED);
  break;
 default:
  return -EINVAL;
 }
 return 0;
}

/*
 * allocate a buffer, setup samplerate
 *
 * 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.
 */
struct s_c2 {
 char c1, c2;
};

static const struct s_c2 setrate_44100[] = {
 { 0x14, 0x08}, // this line sets 44100, well actually a little less
 { 0x18, 0x40}, // only tascam / frontier design knows the further lines .......
 { 0x18, 0x42},
 { 0x18, 0x45},
 { 0x18, 0x46},
 { 0x18, 0x48},
 { 0x18, 0x4A},
 { 0x18, 0x4C},
 { 0x18, 0x4E},
 { 0x18, 0x50},
 { 0x18, 0x52},
 { 0x18, 0x54},
 { 0x18, 0x56},
 { 0x18, 0x58},
 { 0x18, 0x5A},
 { 0x18, 0x5C},
 { 0x18, 0x5E},
 { 0x18, 0x60},
 { 0x18, 0x62},
 { 0x18, 0x64},
 { 0x18, 0x66},
 { 0x18, 0x68},
 { 0x18, 0x6A},
 { 0x18, 0x6C},
 { 0x18, 0x6E},
 { 0x18, 0x70},
 { 0x18, 0x72},
 { 0x18, 0x74},
 { 0x18, 0x76},
 { 0x18, 0x78},
 { 0x18, 0x7A},
 { 0x18, 0x7C},
 { 0x18, 0x7E}
};

static const struct s_c2 setrate_48000[] = {
 { 0x14, 0x09}, // this line sets 48000, well actually a little less
 { 0x18, 0x40}, // only tascam / frontier design knows the further lines .......
 { 0x18, 0x42},
 { 0x18, 0x45},
 { 0x18, 0x46},
 { 0x18, 0x48},
 { 0x18, 0x4A},
 { 0x18, 0x4C},
 { 0x18, 0x4E},
 { 0x18, 0x50},
 { 0x18, 0x52},
 { 0x18, 0x54},
 { 0x18, 0x56},
 { 0x18, 0x58},
 { 0x18, 0x5A},
 { 0x18, 0x5C},
 { 0x18, 0x5E},
 { 0x18, 0x60},
 { 0x18, 0x62},
 { 0x18, 0x64},
 { 0x18, 0x66},
 { 0x18, 0x68},
 { 0x18, 0x6A},
 { 0x18, 0x6C},
 { 0x18, 0x6E},
 { 0x18, 0x70},
 { 0x18, 0x73},
 { 0x18, 0x74},
 { 0x18, 0x76},
 { 0x18, 0x78},
 { 0x18, 0x7A},
 { 0x18, 0x7C},
 { 0x18, 0x7E}
};

#define NOOF_SETRATE_URBS ARRAY_SIZE(setrate_48000)

static void i_usx2y_04int(struct urb *urb)
{
 struct usx2ydev *usx2y = urb->context;

 if (urb->status)
  dev_err(&urb->dev->dev, "%s() urb->status=%i\n",
   __func__, urb->status);
 if (!--usx2y->us04->len)
  wake_up(&usx2y->in04_wait_queue);
}

static int usx2y_rate_set(struct usx2ydev *usx2y, int rate)
{
 int err = 0, i;
 struct snd_usx2y_urb_seq *us = NULL;
 int *usbdata = NULL;
 const struct s_c2 *ra = rate == 48000 ? setrate_48000 : setrate_44100;
 struct urb *urb;

 if (usx2y->rate != rate) {
  us = kzalloc(struct_size(us, urb, NOOF_SETRATE_URBS),
        GFP_KERNEL);
  if (!us) {
   err = -ENOMEM;
   goto cleanup;
  }
  us->len = NOOF_SETRATE_URBS;
  usbdata = kmalloc_array(NOOF_SETRATE_URBS, sizeof(int),
     GFP_KERNEL);
  if (!usbdata) {
   err = -ENOMEM;
   goto cleanup;
  }
  for (i = 0; i < NOOF_SETRATE_URBS; ++i) {
   us->urb[i] = usb_alloc_urb(0, GFP_KERNEL);
   if (!us->urb[i]) {
    err = -ENOMEM;
    goto cleanup;
   }
   ((char *)(usbdata + i))[0] = ra[i].c1;
   ((char *)(usbdata + i))[1] = ra[i].c2;
   usb_fill_bulk_urb(us->urb[i], usx2y->dev, usb_sndbulkpipe(usx2y->dev, 4),
       usbdata + i, 2, i_usx2y_04int, usx2y);
  }
  err = usb_urb_ep_type_check(us->urb[0]);
  if (err < 0)
   goto cleanup;
  us->submitted = 0;
  usx2y->us04 = us;
  wait_event_timeout(usx2y->in04_wait_queue, !us->len, HZ);
  usx2y->us04 = NULL;
  if (us->len)
   err = -ENODEV;
 cleanup:
  if (us) {
   us->submitted = 2*NOOF_SETRATE_URBS;
   for (i = 0; i < NOOF_SETRATE_URBS; ++i) {
    urb = us->urb[i];
    if (!urb)
     continue;
    if (urb->status) {
     if (!err)
      err = -ENODEV;
     usb_kill_urb(urb);
    }
    usb_free_urb(urb);
   }
   usx2y->us04 = NULL;
   kfree(usbdata);
   kfree(us);
   if (!err)
    usx2y->rate = rate;
  }
 }

 return err;
}

static int usx2y_format_set(struct usx2ydev *usx2y, snd_pcm_format_t format)
{
 int alternate, err;
 struct list_head *p;

 if (format == SNDRV_PCM_FORMAT_S24_3LE) {
  alternate = 2;
  usx2y->stride = 6;
 } else {
  alternate = 1;
  usx2y->stride = 4;
 }
 list_for_each(p, &usx2y->midi_list) {
  snd_usbmidi_input_stop(p);
 }
 usb_kill_urb(usx2y->in04_urb);
 err = usb_set_interface(usx2y->dev, 0, alternate);
 if (err) {
  dev_err(&usx2y->dev->dev, "%s: usb_set_interface error\n",
   __func__);
  return err;
 }
 usx2y->in04_urb->dev = usx2y->dev;
 err = usb_submit_urb(usx2y->in04_urb, GFP_KERNEL);
 list_for_each(p, &usx2y->midi_list) {
  snd_usbmidi_input_start(p);
 }
 usx2y->format = format;
 usx2y->rate = 0;
 return err;
}


static int snd_usx2y_pcm_hw_params(struct snd_pcm_substream *substream,
       struct snd_pcm_hw_params *hw_params)
{
 int   err = 0;
 unsigned int  rate = params_rate(hw_params);
 snd_pcm_format_t format = params_format(hw_params);
 struct snd_card *card = substream->pstr->pcm->card;
 struct usx2ydev *dev = usx2y(card);
 struct snd_usx2y_substream *subs;
 struct snd_pcm_substream *test_substream;
 int i;

 mutex_lock(&usx2y(card)->pcm_mutex);
 dev_dbg(&dev->dev->dev, "%s(%p, %p)\n", __func__, substream, hw_params);
 /* all pcm substreams off one usx2y have to operate at the same
 * rate & format
 */
 for (i = 0; i < dev->pcm_devs * 2; i++) {
  subs = dev->subs[i];
  if (!subs)
   continue;
  test_substream = subs->pcm_substream;
  if (!test_substream || test_substream == substream ||
      !test_substream->runtime)
   continue;
  if ((test_substream->runtime->format &&
       test_substream->runtime->format != format) ||
      (test_substream->runtime->rate &&
       test_substream->runtime->rate != rate)) {
   err = -EINVAL;
   goto error;
  }
 }

 error:
 mutex_unlock(&usx2y(card)->pcm_mutex);
 return err;
}

/*
 * free the buffer
 */
static int snd_usx2y_pcm_hw_free(struct snd_pcm_substream *substream)
{
 struct snd_pcm_runtime *runtime = substream->runtime;
 struct snd_usx2y_substream *subs = runtime->private_data;
 struct snd_usx2y_substream *cap_subs, *playback_subs;

 mutex_lock(&subs->usx2y->pcm_mutex);
 dev_dbg(&subs->usx2y->dev->dev, "%s(%p)\n", __func__, substream);

 if (substream->stream == SNDRV_PCM_STREAM_PLAYBACK) {
  cap_subs = subs->usx2y->subs[SNDRV_PCM_STREAM_CAPTURE];
  atomic_set(&subs->state, STATE_STOPPED);
  usx2y_urbs_release(subs);
  if (!cap_subs->pcm_substream ||
      !cap_subs->pcm_substream->runtime ||
      cap_subs->pcm_substream->runtime->state < SNDRV_PCM_STATE_PREPARED) {
   atomic_set(&cap_subs->state, STATE_STOPPED);
   usx2y_urbs_release(cap_subs);
  }
 } else {
  playback_subs = subs->usx2y->subs[SNDRV_PCM_STREAM_PLAYBACK];
  if (atomic_read(&playback_subs->state) < STATE_PREPARED) {
   atomic_set(&subs->state, STATE_STOPPED);
   usx2y_urbs_release(subs);
  }
 }
 mutex_unlock(&subs->usx2y->pcm_mutex);
 return 0;
}

/*
 * prepare callback
 *
 * set format and initialize urbs
 */
static int snd_usx2y_pcm_prepare(struct snd_pcm_substream *substream)
{
 struct snd_pcm_runtime *runtime = substream->runtime;
 struct snd_usx2y_substream *subs = runtime->private_data;
 struct usx2ydev *usx2y = subs->usx2y;
 struct snd_usx2y_substream *capsubs = subs->usx2y->subs[SNDRV_PCM_STREAM_CAPTURE];
 int err = 0;

 dev_dbg(&usx2y->dev->dev, "%s(%p)\n", __func__, substream);

 mutex_lock(&usx2y->pcm_mutex);
 usx2y_subs_prepare(subs);
 // Start hardware streams
 // SyncStream first....
 if (atomic_read(&capsubs->state) < STATE_PREPARED) {
  if (usx2y->format != runtime->format) {
   err = usx2y_format_set(usx2y, runtime->format);
   if (err < 0)
    goto up_prepare_mutex;
  }
  if (usx2y->rate != runtime->rate) {
   err = usx2y_rate_set(usx2y, runtime->rate);
   if (err < 0)
    goto up_prepare_mutex;
  }
  dev_dbg(&usx2y->dev->dev, "%s: starting capture pipe for %s\n",
   __func__, subs == capsubs ? "self" : "playpipe");
  err = usx2y_urbs_start(capsubs);
  if (err < 0)
   goto up_prepare_mutex;
 }

 if (subs != capsubs && atomic_read(&subs->state) < STATE_PREPARED)
  err = usx2y_urbs_start(subs);

 up_prepare_mutex:
 mutex_unlock(&usx2y->pcm_mutex);
 return err;
}

static const struct snd_pcm_hardware snd_usx2y_2c = {
 .info =   (SNDRV_PCM_INFO_MMAP | SNDRV_PCM_INFO_INTERLEAVED |
     SNDRV_PCM_INFO_BLOCK_TRANSFER |
     SNDRV_PCM_INFO_MMAP_VALID |
     SNDRV_PCM_INFO_BATCH),
 .formats =                 SNDRV_PCM_FMTBIT_S16_LE | SNDRV_PCM_FMTBIT_S24_3LE,
 .rates =                   SNDRV_PCM_RATE_44100 | SNDRV_PCM_RATE_48000,
 .rate_min =                44100,
 .rate_max =                48000,
 .channels_min =            2,
 .channels_max =            2,
 .buffer_bytes_max = (2*128*1024),
 .period_bytes_min = 64,
 .period_bytes_max = (128*1024),
 .periods_min =  2,
 .periods_max =  1024,
 .fifo_size =              0
};

static int snd_usx2y_pcm_open(struct snd_pcm_substream *substream)
{
 struct snd_usx2y_substream *subs =
  ((struct snd_usx2y_substream **)
   snd_pcm_substream_chip(substream))[substream->stream];
 struct snd_pcm_runtime *runtime = substream->runtime;

 if (subs->usx2y->chip_status & USX2Y_STAT_CHIP_MMAP_PCM_URBS)
  return -EBUSY;

 runtime->hw = snd_usx2y_2c;
 runtime->private_data = subs;
 subs->pcm_substream = substream;
 snd_pcm_hw_constraint_minmax(runtime, SNDRV_PCM_HW_PARAM_PERIOD_TIME, 1000, 200000);
 return 0;
}

static int snd_usx2y_pcm_close(struct snd_pcm_substream *substream)
{
 struct snd_pcm_runtime *runtime = substream->runtime;
 struct snd_usx2y_substream *subs = runtime->private_data;

 subs->pcm_substream = NULL;

 return 0;
}

static const struct snd_pcm_ops snd_usx2y_pcm_ops = {
 .open =  snd_usx2y_pcm_open,
 .close = snd_usx2y_pcm_close,
 .hw_params = snd_usx2y_pcm_hw_params,
 .hw_free = snd_usx2y_pcm_hw_free,
 .prepare = snd_usx2y_pcm_prepare,
 .trigger = snd_usx2y_pcm_trigger,
 .pointer = snd_usx2y_pcm_pointer,
};

/*
 * free a usb stream instance
 */
static void usx2y_audio_stream_free(struct snd_usx2y_substream **usx2y_substream)
{
 int stream;

 for_each_pcm_streams(stream) {
  kfree(usx2y_substream[stream]);
  usx2y_substream[stream] = NULL;
 }
}

static void snd_usx2y_pcm_private_free(struct snd_pcm *pcm)
{
 struct snd_usx2y_substream **usx2y_stream = pcm->private_data;

 if (usx2y_stream)
  usx2y_audio_stream_free(usx2y_stream);
}

static int usx2y_audio_stream_new(struct snd_card *card, int playback_endpoint, int capture_endpoint)
{
 struct snd_pcm *pcm;
 int err, i;
 struct snd_usx2y_substream **usx2y_substream =
  usx2y(card)->subs + 2 * usx2y(card)->pcm_devs;

 for (i = playback_endpoint ? SNDRV_PCM_STREAM_PLAYBACK : SNDRV_PCM_STREAM_CAPTURE;
      i <= SNDRV_PCM_STREAM_CAPTURE; ++i) {
  usx2y_substream[i] = kzalloc(sizeof(struct snd_usx2y_substream), GFP_KERNEL);
  if (!usx2y_substream[i])
   return -ENOMEM;

  usx2y_substream[i]->usx2y = usx2y(card);
 }

 if (playback_endpoint)
  usx2y_substream[SNDRV_PCM_STREAM_PLAYBACK]->endpoint = playback_endpoint;
 usx2y_substream[SNDRV_PCM_STREAM_CAPTURE]->endpoint = capture_endpoint;

 err = snd_pcm_new(card, NAME_ALLCAPS" Audio", usx2y(card)->pcm_devs,
     playback_endpoint ? 1 : 0, 1,
     &pcm);
 if (err < 0) {
  usx2y_audio_stream_free(usx2y_substream);
  return err;
 }

 if (playback_endpoint)
  snd_pcm_set_ops(pcm, SNDRV_PCM_STREAM_PLAYBACK, &snd_usx2y_pcm_ops);
 snd_pcm_set_ops(pcm, SNDRV_PCM_STREAM_CAPTURE, &snd_usx2y_pcm_ops);

 pcm->private_data = usx2y_substream;
 pcm->private_free = snd_usx2y_pcm_private_free;
 pcm->info_flags = 0;

 sprintf(pcm->name, NAME_ALLCAPS" Audio #%d", usx2y(card)->pcm_devs);

 if (playback_endpoint) {
  snd_pcm_set_managed_buffer(pcm->streams[SNDRV_PCM_STREAM_PLAYBACK].substream,
        SNDRV_DMA_TYPE_CONTINUOUS,
        NULL,
        64*1024, 128*1024);
 }

 snd_pcm_set_managed_buffer(pcm->streams[SNDRV_PCM_STREAM_CAPTURE].substream,
       SNDRV_DMA_TYPE_CONTINUOUS,
       NULL,
       64*1024, 128*1024);
 usx2y(card)->pcm_devs++;

 return 0;
}

/*
 * create a chip instance and set its names.
 */
int usx2y_audio_create(struct snd_card *card)
{
 int err;

 err = usx2y_audio_stream_new(card, 0xA, 0x8);
 if (err < 0)
  return err;
 if (le16_to_cpu(usx2y(card)->dev->descriptor.idProduct) == USB_ID_US428) {
  err = usx2y_audio_stream_new(card, 0, 0xA);
  if (err < 0)
   return err;
 }
 if (le16_to_cpu(usx2y(card)->dev->descriptor.idProduct) != USB_ID_US122)
  err = usx2y_rate_set(usx2y(card), 44100); // Lets us428 recognize output-volume settings, disturbs us122.
 return err;
}