/*
   *  Loopback soundcard
   *
   *  Original code:
   *  Copyright (c) by Jaroslav Kysela <perex@perex.cz>
   *
   *  More accurate positioning and full-duplex support:
   *  Copyright (c) Ahmet İnan <ainan at mathematik.uni-freiburg.de>
   *
   *  Major (almost complete) rewrite:
   *  Copyright (c) by Takashi Iwai <tiwai@suse.de>
   *
   *  A next major update in 2010 (separate timers for playback and capture):
   *  Copyright (c) Jaroslav Kysela <perex@perex.cz>
   *
   *   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/jiffies.h>
  #include <linux/slab.h>
  #include <linux/time.h>
  #include <linux/wait.h>

  #include <linux/module.h>

  #include <linux/platform_device.h>
  #include <sound/core.h>
  #include <sound/control.h>
  #include <sound/pcm.h>

  #include <sound/info.h>

  #include <sound/initval.h>
  
  MODULE_AUTHOR("Jaroslav Kysela <perex@perex.cz>");
  MODULE_DESCRIPTION("A loopback soundcard");
  MODULE_LICENSE("GPL");
  MODULE_SUPPORTED_DEVICE("{{ALSA,Loopback soundcard}}");
  
  #define MAX_PCM_SUBSTREAMS	8
  
  static int index[SNDRV_CARDS] = SNDRV_DEFAULT_IDX;	/* Index 0-MAX */
  static char *id[SNDRV_CARDS] = SNDRV_DEFAULT_STR;	/* ID for this card */

  static bool enable[SNDRV_CARDS] = {1, [1 ... (SNDRV_CARDS - 1)] = 0};

  static int pcm_substreams[SNDRV_CARDS] = {[0 ... (SNDRV_CARDS - 1)] = 8};
  static int pcm_notify[SNDRV_CARDS];
  
  module_param_array(index, int, NULL, 0444);
  MODULE_PARM_DESC(index, "Index value for loopback soundcard.");
  module_param_array(id, charp, NULL, 0444);
  MODULE_PARM_DESC(id, "ID string for loopback soundcard.");
  module_param_array(enable, bool, NULL, 0444);
  MODULE_PARM_DESC(enable, "Enable this loopback soundcard.");
  module_param_array(pcm_substreams, int, NULL, 0444);
  MODULE_PARM_DESC(pcm_substreams, "PCM substreams # (1-8) for loopback driver.");
  module_param_array(pcm_notify, int, NULL, 0444);
  MODULE_PARM_DESC(pcm_notify, "Break capture when PCM format/rate/channels changes.");
  
  #define NO_PITCH 100000
  
  struct loopback_pcm;
  
  struct loopback_cable {
  	spinlock_t lock;
  	struct loopback_pcm *streams[2];
  	struct snd_pcm_hardware hw;
  	/* flags */
  	unsigned int valid;
  	unsigned int running;

  	unsigned int pause;

  };
  
  struct loopback_setup {
  	unsigned int notify: 1;
  	unsigned int rate_shift;
  	unsigned int format;
  	unsigned int rate;
  	unsigned int channels;
  	struct snd_ctl_elem_id active_id;
  	struct snd_ctl_elem_id format_id;
  	struct snd_ctl_elem_id rate_id;
  	struct snd_ctl_elem_id channels_id;
  };
  
  struct loopback {
  	struct snd_card *card;
  	struct mutex cable_lock;
  	struct loopback_cable *cables[MAX_PCM_SUBSTREAMS][2];
  	struct snd_pcm *pcm[2];
  	struct loopback_setup setup[MAX_PCM_SUBSTREAMS][2];
  };
  
  struct loopback_pcm {
  	struct loopback *loopback;
  	struct snd_pcm_substream *substream;
  	struct loopback_cable *cable;
  	unsigned int pcm_buffer_size;
  	unsigned int buf_pos;	/* position in buffer */
  	unsigned int silent_size;
  	/* PCM parameters */
  	unsigned int pcm_period_size;
  	unsigned int pcm_bps;		/* bytes per second */
  	unsigned int pcm_salign;	/* bytes per sample * channels */
  	unsigned int pcm_rate_shift;	/* rate shift value */
  	/* flags */
  	unsigned int period_update_pending :1;
  	/* timer stuff */
  	unsigned int irq_pos;		/* fractional IRQ position */
  	unsigned int period_size_frac;
  	unsigned long last_jiffies;
  	struct timer_list timer;
  };
  
  static struct platform_device *devices[SNDRV_CARDS];
  
  static inline unsigned int byte_pos(struct loopback_pcm *dpcm, unsigned int x)
  {
  	if (dpcm->pcm_rate_shift == NO_PITCH) {
  		x /= HZ;
  	} else {
  		x = div_u64(NO_PITCH * (unsigned long long)x,
  			    HZ * (unsigned long long)dpcm->pcm_rate_shift);
  	}
  	return x - (x % dpcm->pcm_salign);
  }
  
  static inline unsigned int frac_pos(struct loopback_pcm *dpcm, unsigned int x)
  {
  	if (dpcm->pcm_rate_shift == NO_PITCH) {	/* no pitch */
  		return x * HZ;
  	} else {
  		x = div_u64(dpcm->pcm_rate_shift * (unsigned long long)x * HZ,
  			    NO_PITCH);
  	}
  	return x;
  }
  
  static inline struct loopback_setup *get_setup(struct loopback_pcm *dpcm)
  {
  	int device = dpcm->substream->pstr->pcm->device;
  	
  	if (dpcm->substream->stream == SNDRV_PCM_STREAM_PLAYBACK)
  		device ^= 1;
  	return &dpcm->loopback->setup[dpcm->substream->number][device];
  }
  
  static inline unsigned int get_notify(struct loopback_pcm *dpcm)
  {
  	return get_setup(dpcm)->notify;
  }
  
  static inline unsigned int get_rate_shift(struct loopback_pcm *dpcm)
  {
  	return get_setup(dpcm)->rate_shift;
  }
  
  static void loopback_timer_start(struct loopback_pcm *dpcm)
  {
  	unsigned long tick;
  	unsigned int rate_shift = get_rate_shift(dpcm);
  
  	if (rate_shift != dpcm->pcm_rate_shift) {
  		dpcm->pcm_rate_shift = rate_shift;
  		dpcm->period_size_frac = frac_pos(dpcm, dpcm->pcm_period_size);
  	}

  	if (dpcm->period_size_frac <= dpcm->irq_pos) {
  		dpcm->irq_pos %= dpcm->period_size_frac;
  		dpcm->period_update_pending = 1;
  	}

  	tick = dpcm->period_size_frac - dpcm->irq_pos;
  	tick = (tick + dpcm->pcm_bps - 1) / dpcm->pcm_bps;
  	dpcm->timer.expires = jiffies + tick;
  	add_timer(&dpcm->timer);
  }
  
  static inline void loopback_timer_stop(struct loopback_pcm *dpcm)
  {
  	del_timer(&dpcm->timer);

  	dpcm->timer.expires = 0;

  }
  
  #define CABLE_VALID_PLAYBACK	(1 << SNDRV_PCM_STREAM_PLAYBACK)
  #define CABLE_VALID_CAPTURE	(1 << SNDRV_PCM_STREAM_CAPTURE)
  #define CABLE_VALID_BOTH	(CABLE_VALID_PLAYBACK|CABLE_VALID_CAPTURE)
  
  static int loopback_check_format(struct loopback_cable *cable, int stream)
  {

  	struct snd_pcm_runtime *runtime, *cruntime;

  	struct loopback_setup *setup;
  	struct snd_card *card;
  	int check;
  
  	if (cable->valid != CABLE_VALID_BOTH) {
  		if (stream == SNDRV_PCM_STREAM_PLAYBACK)
  			goto __notify;
  		return 0;
  	}
  	runtime = cable->streams[SNDRV_PCM_STREAM_PLAYBACK]->
  							substream->runtime;

  	cruntime = cable->streams[SNDRV_PCM_STREAM_CAPTURE]->
  							substream->runtime;
  	check = runtime->format != cruntime->format ||
  		runtime->rate != cruntime->rate ||
  		runtime->channels != cruntime->channels;

  	if (!check)
  		return 0;
  	if (stream == SNDRV_PCM_STREAM_CAPTURE) {
  		return -EIO;
  	} else {
  		snd_pcm_stop(cable->streams[SNDRV_PCM_STREAM_CAPTURE]->
  					substream, SNDRV_PCM_STATE_DRAINING);
  	      __notify:
  		runtime = cable->streams[SNDRV_PCM_STREAM_PLAYBACK]->
  							substream->runtime;
  		setup = get_setup(cable->streams[SNDRV_PCM_STREAM_PLAYBACK]);
  		card = cable->streams[SNDRV_PCM_STREAM_PLAYBACK]->loopback->card;
  		if (setup->format != runtime->format) {
  			snd_ctl_notify(card, SNDRV_CTL_EVENT_MASK_VALUE,
  							&setup->format_id);
  			setup->format = runtime->format;
  		}
  		if (setup->rate != runtime->rate) {
  			snd_ctl_notify(card, SNDRV_CTL_EVENT_MASK_VALUE,
  							&setup->rate_id);
  			setup->rate = runtime->rate;
  		}
  		if (setup->channels != runtime->channels) {
  			snd_ctl_notify(card, SNDRV_CTL_EVENT_MASK_VALUE,
  							&setup->channels_id);
  			setup->channels = runtime->channels;
  		}
  	}
  	return 0;
  }
  
  static void loopback_active_notify(struct loopback_pcm *dpcm)
  {
  	snd_ctl_notify(dpcm->loopback->card,
  		       SNDRV_CTL_EVENT_MASK_VALUE,
  		       &get_setup(dpcm)->active_id);
  }
  
  static int loopback_trigger(struct snd_pcm_substream *substream, int cmd)
  {
  	struct snd_pcm_runtime *runtime = substream->runtime;
  	struct loopback_pcm *dpcm = runtime->private_data;
  	struct loopback_cable *cable = dpcm->cable;

  	int err, stream = 1 << substream->stream;

  
  	switch (cmd) {
  	case SNDRV_PCM_TRIGGER_START:
  		err = loopback_check_format(cable, substream->stream);
  		if (err < 0)
  			return err;
  		dpcm->last_jiffies = jiffies;
  		dpcm->pcm_rate_shift = 0;

  		spin_lock(&cable->lock);	

  		cable->running |= stream;
  		cable->pause &= ~stream;

  		spin_unlock(&cable->lock);
  		loopback_timer_start(dpcm);

  		if (substream->stream == SNDRV_PCM_STREAM_PLAYBACK)
  			loopback_active_notify(dpcm);
  		break;
  	case SNDRV_PCM_TRIGGER_STOP:

  		spin_lock(&cable->lock);	

  		cable->running &= ~stream;
  		cable->pause &= ~stream;

  		spin_unlock(&cable->lock);

  		loopback_timer_stop(dpcm);
  		if (substream->stream == SNDRV_PCM_STREAM_PLAYBACK)
  			loopback_active_notify(dpcm);
  		break;

  	case SNDRV_PCM_TRIGGER_PAUSE_PUSH:
  		spin_lock(&cable->lock);	
  		cable->pause |= stream;
  		spin_unlock(&cable->lock);
  		loopback_timer_stop(dpcm);
  		break;
  	case SNDRV_PCM_TRIGGER_PAUSE_RELEASE:
  		spin_lock(&cable->lock);
  		dpcm->last_jiffies = jiffies;
  		cable->pause &= ~stream;
  		spin_unlock(&cable->lock);
  		loopback_timer_start(dpcm);
  		break;

  	default:
  		return -EINVAL;
  	}
  	return 0;
  }

  static void params_change_substream(struct loopback_pcm *dpcm,
  				    struct snd_pcm_runtime *runtime)
  {
  	struct snd_pcm_runtime *dst_runtime;
  
  	if (dpcm == NULL || dpcm->substream == NULL)
  		return;
  	dst_runtime = dpcm->substream->runtime;
  	if (dst_runtime == NULL)
  		return;
  	dst_runtime->hw = dpcm->cable->hw;
  }
  
  static void params_change(struct snd_pcm_substream *substream)
  {
  	struct snd_pcm_runtime *runtime = substream->runtime;
  	struct loopback_pcm *dpcm = runtime->private_data;
  	struct loopback_cable *cable = dpcm->cable;
  
  	cable->hw.formats = (1ULL << runtime->format);
  	cable->hw.rate_min = runtime->rate;
  	cable->hw.rate_max = runtime->rate;
  	cable->hw.channels_min = runtime->channels;
  	cable->hw.channels_max = runtime->channels;
  	params_change_substream(cable->streams[SNDRV_PCM_STREAM_PLAYBACK],
  				runtime);
  	params_change_substream(cable->streams[SNDRV_PCM_STREAM_CAPTURE],
  				runtime);
  }

  static int loopback_prepare(struct snd_pcm_substream *substream)
  {
  	struct snd_pcm_runtime *runtime = substream->runtime;
  	struct loopback_pcm *dpcm = runtime->private_data;
  	struct loopback_cable *cable = dpcm->cable;

  	int bps, salign;

  
  	salign = (snd_pcm_format_width(runtime->format) *
  						runtime->channels) / 8;
  	bps = salign * runtime->rate;
  	if (bps <= 0 || salign <= 0)
  		return -EINVAL;
  
  	dpcm->buf_pos = 0;
  	dpcm->pcm_buffer_size = frames_to_bytes(runtime, runtime->buffer_size);
  	if (substream->stream == SNDRV_PCM_STREAM_CAPTURE) {
  		/* clear capture buffer */
  		dpcm->silent_size = dpcm->pcm_buffer_size;
  		snd_pcm_format_set_silence(runtime->format, runtime->dma_area,
  					   runtime->buffer_size * runtime->channels);
  	}
  
  	dpcm->irq_pos = 0;
  	dpcm->period_update_pending = 0;
  	dpcm->pcm_bps = bps;
  	dpcm->pcm_salign = salign;
  	dpcm->pcm_period_size = frames_to_bytes(runtime, runtime->period_size);
  
  	mutex_lock(&dpcm->loopback->cable_lock);

  	if (!(cable->valid & ~(1 << substream->stream)) ||
              (get_setup(dpcm)->notify &&
  	     substream->stream == SNDRV_PCM_STREAM_PLAYBACK))
  		params_change(substream);

  	cable->valid |= 1 << substream->stream;
  	mutex_unlock(&dpcm->loopback->cable_lock);
  
  	return 0;
  }
  
  static void clear_capture_buf(struct loopback_pcm *dpcm, unsigned int bytes)
  {
  	struct snd_pcm_runtime *runtime = dpcm->substream->runtime;
  	char *dst = runtime->dma_area;
  	unsigned int dst_off = dpcm->buf_pos;
  
  	if (dpcm->silent_size >= dpcm->pcm_buffer_size)
  		return;
  	if (dpcm->silent_size + bytes > dpcm->pcm_buffer_size)
  		bytes = dpcm->pcm_buffer_size - dpcm->silent_size;
  
  	for (;;) {
  		unsigned int size = bytes;
  		if (dst_off + size > dpcm->pcm_buffer_size)
  			size = dpcm->pcm_buffer_size - dst_off;
  		snd_pcm_format_set_silence(runtime->format, dst + dst_off,
  					   bytes_to_frames(runtime, size) *
  					   	runtime->channels);
  		dpcm->silent_size += size;
  		bytes -= size;
  		if (!bytes)
  			break;
  		dst_off = 0;
  	}
  }
  
  static void copy_play_buf(struct loopback_pcm *play,
  			  struct loopback_pcm *capt,
  			  unsigned int bytes)
  {
  	struct snd_pcm_runtime *runtime = play->substream->runtime;

  	char *src = runtime->dma_area;

  	char *dst = capt->substream->runtime->dma_area;
  	unsigned int src_off = play->buf_pos;
  	unsigned int dst_off = capt->buf_pos;
  	unsigned int clear_bytes = 0;
  
  	/* check if playback is draining, trim the capture copy size
  	 * when our pointer is at the end of playback ring buffer */
  	if (runtime->status->state == SNDRV_PCM_STATE_DRAINING &&
  	    snd_pcm_playback_hw_avail(runtime) < runtime->buffer_size) { 
  	    	snd_pcm_uframes_t appl_ptr, appl_ptr1, diff;
  		appl_ptr = appl_ptr1 = runtime->control->appl_ptr;
  		appl_ptr1 -= appl_ptr1 % runtime->buffer_size;
  		appl_ptr1 += play->buf_pos / play->pcm_salign;
  		if (appl_ptr < appl_ptr1)
  			appl_ptr1 -= runtime->buffer_size;
  		diff = (appl_ptr - appl_ptr1) * play->pcm_salign;
  		if (diff < bytes) {
  			clear_bytes = bytes - diff;
  			bytes = diff;
  		}
  	}
  
  	for (;;) {
  		unsigned int size = bytes;
  		if (src_off + size > play->pcm_buffer_size)
  			size = play->pcm_buffer_size - src_off;
  		if (dst_off + size > capt->pcm_buffer_size)
  			size = capt->pcm_buffer_size - dst_off;
  		memcpy(dst + dst_off, src + src_off, size);
  		capt->silent_size = 0;
  		bytes -= size;
  		if (!bytes)
  			break;
  		src_off = (src_off + size) % play->pcm_buffer_size;
  		dst_off = (dst_off + size) % capt->pcm_buffer_size;
  	}

  	if (clear_bytes > 0) {

  		clear_capture_buf(capt, clear_bytes);

  		capt->silent_size = 0;
  	}

  }
  
  #define BYTEPOS_UPDATE_POSONLY	0
  #define BYTEPOS_UPDATE_CLEAR	1
  #define BYTEPOS_UPDATE_COPY	2
  
  static void loopback_bytepos_update(struct loopback_pcm *dpcm,
  				    unsigned int delta,
  				    unsigned int cmd)
  {
  	unsigned int count;
  	unsigned long last_pos;
  
  	last_pos = byte_pos(dpcm, dpcm->irq_pos);
  	dpcm->irq_pos += delta * dpcm->pcm_bps;
  	count = byte_pos(dpcm, dpcm->irq_pos) - last_pos;
  	if (!count)
  		return;
  	if (cmd == BYTEPOS_UPDATE_CLEAR)
  		clear_capture_buf(dpcm, count);
  	else if (cmd == BYTEPOS_UPDATE_COPY)
  		copy_play_buf(dpcm->cable->streams[SNDRV_PCM_STREAM_PLAYBACK],
  			      dpcm->cable->streams[SNDRV_PCM_STREAM_CAPTURE],
  			      count);
  	dpcm->buf_pos += count;
  	dpcm->buf_pos %= dpcm->pcm_buffer_size;
  	if (dpcm->irq_pos >= dpcm->period_size_frac) {
  		dpcm->irq_pos %= dpcm->period_size_frac;
  		dpcm->period_update_pending = 1;
  	}
  }

  static unsigned int loopback_pos_update(struct loopback_cable *cable)

  {
  	struct loopback_pcm *dpcm_play =
  			cable->streams[SNDRV_PCM_STREAM_PLAYBACK];
  	struct loopback_pcm *dpcm_capt =
  			cable->streams[SNDRV_PCM_STREAM_CAPTURE];
  	unsigned long delta_play = 0, delta_capt = 0;

  	unsigned int running;

  	unsigned long flags;

  	spin_lock_irqsave(&cable->lock, flags);

  	running = cable->running ^ cable->pause;

  	if (running & (1 << SNDRV_PCM_STREAM_PLAYBACK)) {

  		delta_play = jiffies - dpcm_play->last_jiffies;
  		dpcm_play->last_jiffies += delta_play;
  	}

  	if (running & (1 << SNDRV_PCM_STREAM_CAPTURE)) {

  		delta_capt = jiffies - dpcm_capt->last_jiffies;
  		dpcm_capt->last_jiffies += delta_capt;
  	}

  	if (delta_play == 0 && delta_capt == 0)
  		goto unlock;

  		
  	if (delta_play > delta_capt) {
  		loopback_bytepos_update(dpcm_play, delta_play - delta_capt,
  					BYTEPOS_UPDATE_POSONLY);
  		delta_play = delta_capt;
  	} else if (delta_play < delta_capt) {
  		loopback_bytepos_update(dpcm_capt, delta_capt - delta_play,
  					BYTEPOS_UPDATE_CLEAR);
  		delta_capt = delta_play;
  	}

  	if (delta_play == 0 && delta_capt == 0)
  		goto unlock;

  	/* note delta_capt == delta_play at this moment */
  	loopback_bytepos_update(dpcm_capt, delta_capt, BYTEPOS_UPDATE_COPY);
  	loopback_bytepos_update(dpcm_play, delta_play, BYTEPOS_UPDATE_POSONLY);

   unlock:
  	spin_unlock_irqrestore(&cable->lock, flags);

  	return running;

  }
  
  static void loopback_timer_function(unsigned long data)
  {
  	struct loopback_pcm *dpcm = (struct loopback_pcm *)data;

  	unsigned int running;

  	running = loopback_pos_update(dpcm->cable);
  	if (running & (1 << dpcm->substream->stream)) {

  		loopback_timer_start(dpcm);

  		if (dpcm->period_update_pending) {
  			dpcm->period_update_pending = 0;

  			snd_pcm_period_elapsed(dpcm->substream);

  		}

  	}
  }
  
  static snd_pcm_uframes_t loopback_pointer(struct snd_pcm_substream *substream)
  {
  	struct snd_pcm_runtime *runtime = substream->runtime;
  	struct loopback_pcm *dpcm = runtime->private_data;
  
  	loopback_pos_update(dpcm->cable);
  	return bytes_to_frames(runtime, dpcm->buf_pos);
  }
  
  static struct snd_pcm_hardware loopback_pcm_hardware =
  {
  	.info =		(SNDRV_PCM_INFO_INTERLEAVED | SNDRV_PCM_INFO_MMAP |

  			 SNDRV_PCM_INFO_MMAP_VALID | SNDRV_PCM_INFO_PAUSE),

  	.formats =	(SNDRV_PCM_FMTBIT_S16_LE | SNDRV_PCM_FMTBIT_S16_BE |
  			 SNDRV_PCM_FMTBIT_S32_LE | SNDRV_PCM_FMTBIT_S32_BE |
  			 SNDRV_PCM_FMTBIT_FLOAT_LE | SNDRV_PCM_FMTBIT_FLOAT_BE),
  	.rates =	SNDRV_PCM_RATE_CONTINUOUS | SNDRV_PCM_RATE_8000_192000,
  	.rate_min =		8000,
  	.rate_max =		192000,
  	.channels_min =		1,
  	.channels_max =		32,
  	.buffer_bytes_max =	2 * 1024 * 1024,
  	.period_bytes_min =	64,

  	/* note check overflow in frac_pos() using pcm_rate_shift before
  	   changing period_bytes_max value */
  	.period_bytes_max =	1024 * 1024,

  	.periods_min =		1,
  	.periods_max =		1024,
  	.fifo_size =		0,
  };
  
  static void loopback_runtime_free(struct snd_pcm_runtime *runtime)
  {
  	struct loopback_pcm *dpcm = runtime->private_data;
  	kfree(dpcm);
  }
  
  static int loopback_hw_params(struct snd_pcm_substream *substream,
  			      struct snd_pcm_hw_params *params)
  {

  	return snd_pcm_lib_alloc_vmalloc_buffer(substream,
  						params_buffer_bytes(params));

  }
  
  static int loopback_hw_free(struct snd_pcm_substream *substream)
  {
  	struct snd_pcm_runtime *runtime = substream->runtime;
  	struct loopback_pcm *dpcm = runtime->private_data;
  	struct loopback_cable *cable = dpcm->cable;
  
  	mutex_lock(&dpcm->loopback->cable_lock);
  	cable->valid &= ~(1 << substream->stream);
  	mutex_unlock(&dpcm->loopback->cable_lock);

  	return snd_pcm_lib_free_vmalloc_buffer(substream);

  }
  
  static unsigned int get_cable_index(struct snd_pcm_substream *substream)
  {
  	if (!substream->pcm->device)
  		return substream->stream;
  	else
  		return !substream->stream;
  }

  static int rule_format(struct snd_pcm_hw_params *params,
  		       struct snd_pcm_hw_rule *rule)
  {
  
  	struct snd_pcm_hardware *hw = rule->private;
  	struct snd_mask *maskp = hw_param_mask(params, rule->var);
  
  	maskp->bits[0] &= (u_int32_t)hw->formats;
  	maskp->bits[1] &= (u_int32_t)(hw->formats >> 32);
  	memset(maskp->bits + 2, 0, (SNDRV_MASK_MAX-64) / 8); /* clear rest */
  	if (! maskp->bits[0] && ! maskp->bits[1])
  		return -EINVAL;
  	return 0;
  }
  
  static int rule_rate(struct snd_pcm_hw_params *params,
  		     struct snd_pcm_hw_rule *rule)
  {
  	struct snd_pcm_hardware *hw = rule->private;
  	struct snd_interval t;
  
          t.min = hw->rate_min;
          t.max = hw->rate_max;
          t.openmin = t.openmax = 0;
          t.integer = 0;
  	return snd_interval_refine(hw_param_interval(params, rule->var), &t);
  }
  
  static int rule_channels(struct snd_pcm_hw_params *params,
  			 struct snd_pcm_hw_rule *rule)
  {
  	struct snd_pcm_hardware *hw = rule->private;
  	struct snd_interval t;
  
          t.min = hw->channels_min;
          t.max = hw->channels_max;
          t.openmin = t.openmax = 0;
          t.integer = 0;
  	return snd_interval_refine(hw_param_interval(params, rule->var), &t);
  }

  static int loopback_open(struct snd_pcm_substream *substream)
  {
  	struct snd_pcm_runtime *runtime = substream->runtime;
  	struct loopback *loopback = substream->private_data;
  	struct loopback_pcm *dpcm;
  	struct loopback_cable *cable;
  	int err = 0;
  	int dev = get_cable_index(substream);
  
  	mutex_lock(&loopback->cable_lock);
  	dpcm = kzalloc(sizeof(*dpcm), GFP_KERNEL);
  	if (!dpcm) {
  		err = -ENOMEM;
  		goto unlock;
  	}
  	dpcm->loopback = loopback;
  	dpcm->substream = substream;
  	setup_timer(&dpcm->timer, loopback_timer_function,
  		    (unsigned long)dpcm);
  
  	cable = loopback->cables[substream->number][dev];
  	if (!cable) {
  		cable = kzalloc(sizeof(*cable), GFP_KERNEL);
  		if (!cable) {
  			kfree(dpcm);
  			err = -ENOMEM;
  			goto unlock;
  		}
  		spin_lock_init(&cable->lock);
  		cable->hw = loopback_pcm_hardware;
  		loopback->cables[substream->number][dev] = cable;
  	}
  	dpcm->cable = cable;
  	cable->streams[substream->stream] = dpcm;
  
  	snd_pcm_hw_constraint_integer(runtime, SNDRV_PCM_HW_PARAM_PERIODS);

  	/* use dynamic rules based on actual runtime->hw values */
  	/* note that the default rules created in the PCM midlevel code */
  	/* are cached -> they do not reflect the actual state */
  	err = snd_pcm_hw_rule_add(runtime, 0,
  				  SNDRV_PCM_HW_PARAM_FORMAT,
  				  rule_format, &runtime->hw,
  				  SNDRV_PCM_HW_PARAM_FORMAT, -1);
  	if (err < 0)
  		goto unlock;
  	err = snd_pcm_hw_rule_add(runtime, 0,
  				  SNDRV_PCM_HW_PARAM_RATE,
  				  rule_rate, &runtime->hw,
  				  SNDRV_PCM_HW_PARAM_RATE, -1);
  	if (err < 0)
  		goto unlock;
  	err = snd_pcm_hw_rule_add(runtime, 0,
  				  SNDRV_PCM_HW_PARAM_CHANNELS,
  				  rule_channels, &runtime->hw,
  				  SNDRV_PCM_HW_PARAM_CHANNELS, -1);
  	if (err < 0)
  		goto unlock;

  	runtime->private_data = dpcm;
  	runtime->private_free = loopback_runtime_free;

  	if (get_notify(dpcm))

  		runtime->hw = loopback_pcm_hardware;

  	else

  		runtime->hw = cable->hw;

   unlock:
  	mutex_unlock(&loopback->cable_lock);
  	return err;
  }
  
  static int loopback_close(struct snd_pcm_substream *substream)
  {
  	struct loopback *loopback = substream->private_data;
  	struct loopback_pcm *dpcm = substream->runtime->private_data;
  	struct loopback_cable *cable;
  	int dev = get_cable_index(substream);
  
  	loopback_timer_stop(dpcm);
  	mutex_lock(&loopback->cable_lock);
  	cable = loopback->cables[substream->number][dev];
  	if (cable->streams[!substream->stream]) {
  		/* other stream is still alive */
  		cable->streams[substream->stream] = NULL;
  	} else {
  		/* free the cable */
  		loopback->cables[substream->number][dev] = NULL;
  		kfree(cable);
  	}
  	mutex_unlock(&loopback->cable_lock);
  	return 0;
  }
  
  static struct snd_pcm_ops loopback_playback_ops = {
  	.open =		loopback_open,
  	.close =	loopback_close,
  	.ioctl =	snd_pcm_lib_ioctl,
  	.hw_params =	loopback_hw_params,
  	.hw_free =	loopback_hw_free,
  	.prepare =	loopback_prepare,
  	.trigger =	loopback_trigger,
  	.pointer =	loopback_pointer,

  	.page =		snd_pcm_lib_get_vmalloc_page,
  	.mmap =		snd_pcm_lib_mmap_vmalloc,

  };
  
  static struct snd_pcm_ops loopback_capture_ops = {
  	.open =		loopback_open,
  	.close =	loopback_close,
  	.ioctl =	snd_pcm_lib_ioctl,
  	.hw_params =	loopback_hw_params,
  	.hw_free =	loopback_hw_free,
  	.prepare =	loopback_prepare,
  	.trigger =	loopback_trigger,
  	.pointer =	loopback_pointer,

  	.page =		snd_pcm_lib_get_vmalloc_page,
  	.mmap =		snd_pcm_lib_mmap_vmalloc,

  };
  
  static int __devinit loopback_pcm_new(struct loopback *loopback,
  				      int device, int substreams)
  {
  	struct snd_pcm *pcm;
  	int err;
  
  	err = snd_pcm_new(loopback->card, "Loopback PCM", device,
  			  substreams, substreams, &pcm);
  	if (err < 0)
  		return err;
  	snd_pcm_set_ops(pcm, SNDRV_PCM_STREAM_PLAYBACK, &loopback_playback_ops);
  	snd_pcm_set_ops(pcm, SNDRV_PCM_STREAM_CAPTURE, &loopback_capture_ops);
  
  	pcm->private_data = loopback;
  	pcm->info_flags = 0;
  	strcpy(pcm->name, "Loopback PCM");
  
  	loopback->pcm[device] = pcm;

  	return 0;
  }
  
  static int loopback_rate_shift_info(struct snd_kcontrol *kcontrol,   
  				    struct snd_ctl_elem_info *uinfo) 
  {
  	uinfo->type = SNDRV_CTL_ELEM_TYPE_INTEGER;
  	uinfo->count = 1;
  	uinfo->value.integer.min = 80000;
  	uinfo->value.integer.max = 120000;
  	uinfo->value.integer.step = 1;
  	return 0;
  }                                  
  
  static int loopback_rate_shift_get(struct snd_kcontrol *kcontrol,
  				   struct snd_ctl_elem_value *ucontrol)
  {
  	struct loopback *loopback = snd_kcontrol_chip(kcontrol);
  	
  	ucontrol->value.integer.value[0] =
  		loopback->setup[kcontrol->id.subdevice]
  			       [kcontrol->id.device].rate_shift;
  	return 0;
  }
  
  static int loopback_rate_shift_put(struct snd_kcontrol *kcontrol,
  				   struct snd_ctl_elem_value *ucontrol)
  {
  	struct loopback *loopback = snd_kcontrol_chip(kcontrol);
  	unsigned int val;
  	int change = 0;
  
  	val = ucontrol->value.integer.value[0];
  	if (val < 80000)
  		val = 80000;
  	if (val > 120000)
  		val = 120000;	
  	mutex_lock(&loopback->cable_lock);
  	if (val != loopback->setup[kcontrol->id.subdevice]
  				  [kcontrol->id.device].rate_shift) {
  		loopback->setup[kcontrol->id.subdevice]
  			       [kcontrol->id.device].rate_shift = val;
  		change = 1;
  	}
  	mutex_unlock(&loopback->cable_lock);
  	return change;
  }
  
  static int loopback_notify_get(struct snd_kcontrol *kcontrol,
  			       struct snd_ctl_elem_value *ucontrol)
  {
  	struct loopback *loopback = snd_kcontrol_chip(kcontrol);
  	
  	ucontrol->value.integer.value[0] =
  		loopback->setup[kcontrol->id.subdevice]
  			       [kcontrol->id.device].notify;
  	return 0;
  }
  
  static int loopback_notify_put(struct snd_kcontrol *kcontrol,
  			       struct snd_ctl_elem_value *ucontrol)
  {
  	struct loopback *loopback = snd_kcontrol_chip(kcontrol);
  	unsigned int val;
  	int change = 0;
  
  	val = ucontrol->value.integer.value[0] ? 1 : 0;
  	if (val != loopback->setup[kcontrol->id.subdevice]
  				[kcontrol->id.device].notify) {
  		loopback->setup[kcontrol->id.subdevice]
  			[kcontrol->id.device].notify = val;
  		change = 1;
  	}
  	return change;
  }
  
  static int loopback_active_get(struct snd_kcontrol *kcontrol,
  			       struct snd_ctl_elem_value *ucontrol)
  {
  	struct loopback *loopback = snd_kcontrol_chip(kcontrol);
  	struct loopback_cable *cable = loopback->cables

  			[kcontrol->id.subdevice][kcontrol->id.device ^ 1];

  	unsigned int val = 0;
  
  	if (cable != NULL)
  		val = (cable->running & (1 << SNDRV_PCM_STREAM_PLAYBACK)) ?
  									1 : 0;
  	ucontrol->value.integer.value[0] = val;
  	return 0;
  }
  
  static int loopback_format_info(struct snd_kcontrol *kcontrol,   
  				struct snd_ctl_elem_info *uinfo) 
  {
  	uinfo->type = SNDRV_CTL_ELEM_TYPE_INTEGER;
  	uinfo->count = 1;
  	uinfo->value.integer.min = 0;
  	uinfo->value.integer.max = SNDRV_PCM_FORMAT_LAST;
  	uinfo->value.integer.step = 1;
  	return 0;
  }                                  
  
  static int loopback_format_get(struct snd_kcontrol *kcontrol,
  			       struct snd_ctl_elem_value *ucontrol)
  {
  	struct loopback *loopback = snd_kcontrol_chip(kcontrol);
  	
  	ucontrol->value.integer.value[0] =
  		loopback->setup[kcontrol->id.subdevice]
  			       [kcontrol->id.device].format;
  	return 0;
  }
  
  static int loopback_rate_info(struct snd_kcontrol *kcontrol,   
  			      struct snd_ctl_elem_info *uinfo) 
  {
  	uinfo->type = SNDRV_CTL_ELEM_TYPE_INTEGER;
  	uinfo->count = 1;
  	uinfo->value.integer.min = 0;
  	uinfo->value.integer.max = 192000;
  	uinfo->value.integer.step = 1;
  	return 0;
  }                                  
  
  static int loopback_rate_get(struct snd_kcontrol *kcontrol,
  			     struct snd_ctl_elem_value *ucontrol)
  {
  	struct loopback *loopback = snd_kcontrol_chip(kcontrol);
  	
  	ucontrol->value.integer.value[0] =
  		loopback->setup[kcontrol->id.subdevice]
  			       [kcontrol->id.device].rate;
  	return 0;
  }
  
  static int loopback_channels_info(struct snd_kcontrol *kcontrol,   
  				  struct snd_ctl_elem_info *uinfo) 
  {
  	uinfo->type = SNDRV_CTL_ELEM_TYPE_INTEGER;
  	uinfo->count = 1;
  	uinfo->value.integer.min = 1;
  	uinfo->value.integer.max = 1024;
  	uinfo->value.integer.step = 1;
  	return 0;
  }                                  
  
  static int loopback_channels_get(struct snd_kcontrol *kcontrol,
  				 struct snd_ctl_elem_value *ucontrol)
  {
  	struct loopback *loopback = snd_kcontrol_chip(kcontrol);
  	
  	ucontrol->value.integer.value[0] =
  		loopback->setup[kcontrol->id.subdevice]

  			       [kcontrol->id.device].channels;

  	return 0;
  }
  
  static struct snd_kcontrol_new loopback_controls[]  __devinitdata = {
  {
  	.iface =        SNDRV_CTL_ELEM_IFACE_PCM,
  	.name =         "PCM Rate Shift 100000",
  	.info =         loopback_rate_shift_info,
  	.get =          loopback_rate_shift_get,
  	.put =          loopback_rate_shift_put,
  },
  {
  	.iface =        SNDRV_CTL_ELEM_IFACE_PCM,
  	.name =         "PCM Notify",
  	.info =         snd_ctl_boolean_mono_info,
  	.get =          loopback_notify_get,
  	.put =          loopback_notify_put,
  },
  #define ACTIVE_IDX 2
  {
  	.access =	SNDRV_CTL_ELEM_ACCESS_READ,
  	.iface =        SNDRV_CTL_ELEM_IFACE_PCM,
  	.name =         "PCM Slave Active",
  	.info =         snd_ctl_boolean_mono_info,
  	.get =          loopback_active_get,
  },
  #define FORMAT_IDX 3
  {
  	.access =	SNDRV_CTL_ELEM_ACCESS_READ,
  	.iface =        SNDRV_CTL_ELEM_IFACE_PCM,
  	.name =         "PCM Slave Format",
  	.info =         loopback_format_info,
  	.get =          loopback_format_get
  },
  #define RATE_IDX 4
  {
  	.access =	SNDRV_CTL_ELEM_ACCESS_READ,
  	.iface =        SNDRV_CTL_ELEM_IFACE_PCM,
  	.name =         "PCM Slave Rate",
  	.info =         loopback_rate_info,
  	.get =          loopback_rate_get
  },
  #define CHANNELS_IDX 5
  {
  	.access =	SNDRV_CTL_ELEM_ACCESS_READ,
  	.iface =        SNDRV_CTL_ELEM_IFACE_PCM,
  	.name =         "PCM Slave Channels",
  	.info =         loopback_channels_info,
  	.get =          loopback_channels_get
  }
  };
  
  static int __devinit loopback_mixer_new(struct loopback *loopback, int notify)
  {
  	struct snd_card *card = loopback->card;
  	struct snd_pcm *pcm;
  	struct snd_kcontrol *kctl;
  	struct loopback_setup *setup;
  	int err, dev, substr, substr_count, idx;
  
  	strcpy(card->mixername, "Loopback Mixer");
  	for (dev = 0; dev < 2; dev++) {
  		pcm = loopback->pcm[dev];
  		substr_count =
  		    pcm->streams[SNDRV_PCM_STREAM_CAPTURE].substream_count;
  		for (substr = 0; substr < substr_count; substr++) {
  			setup = &loopback->setup[substr][dev];
  			setup->notify = notify;
  			setup->rate_shift = NO_PITCH;
  			setup->format = SNDRV_PCM_FORMAT_S16_LE;
  			setup->rate = 48000;
  			setup->channels = 2;
  			for (idx = 0; idx < ARRAY_SIZE(loopback_controls);
  									idx++) {
  				kctl = snd_ctl_new1(&loopback_controls[idx],
  						    loopback);
  				if (!kctl)
  					return -ENOMEM;
  				kctl->id.device = dev;
  				kctl->id.subdevice = substr;
  				switch (idx) {
  				case ACTIVE_IDX:
  					setup->active_id = kctl->id;
  					break;
  				case FORMAT_IDX:
  					setup->format_id = kctl->id;
  					break;
  				case RATE_IDX:
  					setup->rate_id = kctl->id;
  					break;
  				case CHANNELS_IDX:
  					setup->channels_id = kctl->id;
  					break;
  				default:
  					break;
  				}
  				err = snd_ctl_add(card, kctl);
  				if (err < 0)
  					return err;
  			}
  		}
  	}
  	return 0;
  }

  #ifdef CONFIG_PROC_FS
  
  static void print_dpcm_info(struct snd_info_buffer *buffer,
  			    struct loopback_pcm *dpcm,
  			    const char *id)
  {
  	snd_iprintf(buffer, "  %s
  ", id);
  	if (dpcm == NULL) {
  		snd_iprintf(buffer, "    inactive
  ");
  		return;
  	}
  	snd_iprintf(buffer, "    buffer_size:\t%u
  ", dpcm->pcm_buffer_size);
  	snd_iprintf(buffer, "    buffer_pos:\t\t%u
  ", dpcm->buf_pos);
  	snd_iprintf(buffer, "    silent_size:\t%u
  ", dpcm->silent_size);
  	snd_iprintf(buffer, "    period_size:\t%u
  ", dpcm->pcm_period_size);
  	snd_iprintf(buffer, "    bytes_per_sec:\t%u
  ", dpcm->pcm_bps);
  	snd_iprintf(buffer, "    sample_align:\t%u
  ", dpcm->pcm_salign);
  	snd_iprintf(buffer, "    rate_shift:\t\t%u
  ", dpcm->pcm_rate_shift);
  	snd_iprintf(buffer, "    update_pending:\t%u
  ",
  						dpcm->period_update_pending);
  	snd_iprintf(buffer, "    irq_pos:\t\t%u
  ", dpcm->irq_pos);
  	snd_iprintf(buffer, "    period_frac:\t%u
  ", dpcm->period_size_frac);
  	snd_iprintf(buffer, "    last_jiffies:\t%lu (%lu)
  ",
  					dpcm->last_jiffies, jiffies);
  	snd_iprintf(buffer, "    timer_expires:\t%lu
  ", dpcm->timer.expires);
  }
  
  static void print_substream_info(struct snd_info_buffer *buffer,
  				 struct loopback *loopback,
  				 int sub,
  				 int num)
  {
  	struct loopback_cable *cable = loopback->cables[sub][num];
  
  	snd_iprintf(buffer, "Cable %i substream %i:
  ", num, sub);
  	if (cable == NULL) {
  		snd_iprintf(buffer, "  inactive
  ");
  		return;
  	}
  	snd_iprintf(buffer, "  valid: %u
  ", cable->valid);
  	snd_iprintf(buffer, "  running: %u
  ", cable->running);

  	snd_iprintf(buffer, "  pause: %u
  ", cable->pause);

  	print_dpcm_info(buffer, cable->streams[0], "Playback");
  	print_dpcm_info(buffer, cable->streams[1], "Capture");
  }
  
  static void print_cable_info(struct snd_info_entry *entry,
  			     struct snd_info_buffer *buffer)
  {
  	struct loopback *loopback = entry->private_data;
  	int sub, num;
  
  	mutex_lock(&loopback->cable_lock);
  	num = entry->name[strlen(entry->name)-1];
  	num = num == '0' ? 0 : 1;
  	for (sub = 0; sub < MAX_PCM_SUBSTREAMS; sub++)
  		print_substream_info(buffer, loopback, sub, num);
  	mutex_unlock(&loopback->cable_lock);
  }
  
  static int __devinit loopback_proc_new(struct loopback *loopback, int cidx)
  {
  	char name[32];
  	struct snd_info_entry *entry;
  	int err;
  
  	snprintf(name, sizeof(name), "cable#%d", cidx);
  	err = snd_card_proc_new(loopback->card, name, &entry);
  	if (err < 0)
  		return err;
  
  	snd_info_set_text_ops(entry, loopback, print_cable_info);
  	return 0;
  }
  
  #else /* !CONFIG_PROC_FS */
  
  #define loopback_proc_new(loopback, cidx) do { } while (0)
  
  #endif

  static int __devinit loopback_probe(struct platform_device *devptr)
  {
  	struct snd_card *card;
  	struct loopback *loopback;
  	int dev = devptr->id;
  	int err;
  
  	err = snd_card_create(index[dev], id[dev], THIS_MODULE,
  			      sizeof(struct loopback), &card);
  	if (err < 0)
  		return err;
  	loopback = card->private_data;
  
  	if (pcm_substreams[dev] < 1)
  		pcm_substreams[dev] = 1;
  	if (pcm_substreams[dev] > MAX_PCM_SUBSTREAMS)
  		pcm_substreams[dev] = MAX_PCM_SUBSTREAMS;
  	
  	loopback->card = card;
  	mutex_init(&loopback->cable_lock);
  
  	err = loopback_pcm_new(loopback, 0, pcm_substreams[dev]);
  	if (err < 0)
  		goto __nodev;
  	err = loopback_pcm_new(loopback, 1, pcm_substreams[dev]);
  	if (err < 0)
  		goto __nodev;
  	err = loopback_mixer_new(loopback, pcm_notify[dev] ? 1 : 0);
  	if (err < 0)
  		goto __nodev;

  	loopback_proc_new(loopback, 0);
  	loopback_proc_new(loopback, 1);

  	strcpy(card->driver, "Loopback");
  	strcpy(card->shortname, "Loopback");
  	sprintf(card->longname, "Loopback %i", dev + 1);
  	err = snd_card_register(card);
  	if (!err) {
  		platform_set_drvdata(devptr, card);
  		return 0;
  	}
        __nodev:
  	snd_card_free(card);
  	return err;
  }
  
  static int __devexit loopback_remove(struct platform_device *devptr)
  {
  	snd_card_free(platform_get_drvdata(devptr));
  	platform_set_drvdata(devptr, NULL);
  	return 0;
  }
  
  #ifdef CONFIG_PM
  static int loopback_suspend(struct platform_device *pdev,
  				pm_message_t state)
  {
  	struct snd_card *card = platform_get_drvdata(pdev);
  	struct loopback *loopback = card->private_data;
  
  	snd_power_change_state(card, SNDRV_CTL_POWER_D3hot);
  
  	snd_pcm_suspend_all(loopback->pcm[0]);
  	snd_pcm_suspend_all(loopback->pcm[1]);
  	return 0;
  }
  	
  static int loopback_resume(struct platform_device *pdev)
  {
  	struct snd_card *card = platform_get_drvdata(pdev);
  
  	snd_power_change_state(card, SNDRV_CTL_POWER_D0);
  	return 0;
  }
  #endif
  
  #define SND_LOOPBACK_DRIVER	"snd_aloop"
  
  static struct platform_driver loopback_driver = {
  	.probe		= loopback_probe,
  	.remove		= __devexit_p(loopback_remove),
  #ifdef CONFIG_PM
  	.suspend	= loopback_suspend,
  	.resume		= loopback_resume,
  #endif
  	.driver		= {
  		.name	= SND_LOOPBACK_DRIVER
  	},
  };
  
  static void loopback_unregister_all(void)
  {
  	int i;
  
  	for (i = 0; i < ARRAY_SIZE(devices); ++i)
  		platform_device_unregister(devices[i]);
  	platform_driver_unregister(&loopback_driver);
  }
  
  static int __init alsa_card_loopback_init(void)
  {
  	int i, err, cards;
  
  	err = platform_driver_register(&loopback_driver);
  	if (err < 0)
  		return err;
  
  
  	cards = 0;
  	for (i = 0; i < SNDRV_CARDS; i++) {
  		struct platform_device *device;
  		if (!enable[i])
  			continue;
  		device = platform_device_register_simple(SND_LOOPBACK_DRIVER,
  							 i, NULL, 0);
  		if (IS_ERR(device))
  			continue;
  		if (!platform_get_drvdata(device)) {
  			platform_device_unregister(device);
  			continue;
  		}
  		devices[i] = device;
  		cards++;
  	}
  	if (!cards) {
  #ifdef MODULE
  		printk(KERN_ERR "aloop: No loopback enabled
  ");
  #endif
  		loopback_unregister_all();
  		return -ENODEV;
  	}
  	return 0;
  }
  
  static void __exit alsa_card_loopback_exit(void)
  {
  	loopback_unregister_all();
  }
  
  module_init(alsa_card_loopback_init)
  module_exit(alsa_card_loopback_exit)