/*
   *  Dummy soundcard

   *  Copyright (c) by 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/err.h>
  #include <linux/platform_device.h>

  #include <linux/jiffies.h>
  #include <linux/slab.h>
  #include <linux/time.h>
  #include <linux/wait.h>

  #include <linux/hrtimer.h>
  #include <linux/math64.h>

  #include <linux/module.h>

  #include <sound/core.h>
  #include <sound/control.h>

  #include <sound/tlv.h>

  #include <sound/pcm.h>
  #include <sound/rawmidi.h>

  #include <sound/info.h>

  #include <sound/initval.h>

  MODULE_AUTHOR("Jaroslav Kysela <perex@perex.cz>");

  MODULE_DESCRIPTION("Dummy soundcard (/dev/null)");
  MODULE_LICENSE("GPL");
  MODULE_SUPPORTED_DEVICE("{{ALSA,Dummy soundcard}}");
  
  #define MAX_PCM_DEVICES		4

  #define MAX_PCM_SUBSTREAMS	128

  #define MAX_MIDI_DEVICES	2

  /* defaults */

  #define MAX_BUFFER_SIZE		(64*1024)

  #define MIN_PERIOD_SIZE		64

  #define MAX_PERIOD_SIZE		MAX_BUFFER_SIZE

  #define USE_FORMATS 		(SNDRV_PCM_FMTBIT_U8 | SNDRV_PCM_FMTBIT_S16_LE)

  #define USE_RATE		SNDRV_PCM_RATE_CONTINUOUS | SNDRV_PCM_RATE_8000_48000
  #define USE_RATE_MIN		5500
  #define USE_RATE_MAX		48000

  #define USE_CHANNELS_MIN 	1

  #define USE_CHANNELS_MAX 	2

  #define USE_PERIODS_MIN 	1

  #define USE_PERIODS_MAX 	1024

  
  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 char *model[SNDRV_CARDS] = {[0 ... (SNDRV_CARDS - 1)] = NULL};

  static int pcm_devs[SNDRV_CARDS] = {[0 ... (SNDRV_CARDS - 1)] = 1};
  static int pcm_substreams[SNDRV_CARDS] = {[0 ... (SNDRV_CARDS - 1)] = 8};
  //static int midi_devs[SNDRV_CARDS] = {[0 ... (SNDRV_CARDS - 1)] = 2};

  #ifdef CONFIG_HIGH_RES_TIMERS

  static bool hrtimer = 1;

  #endif

  static bool fake_buffer = 1;

  
  module_param_array(index, int, NULL, 0444);
  MODULE_PARM_DESC(index, "Index value for dummy soundcard.");
  module_param_array(id, charp, NULL, 0444);
  MODULE_PARM_DESC(id, "ID string for dummy soundcard.");
  module_param_array(enable, bool, NULL, 0444);
  MODULE_PARM_DESC(enable, "Enable this dummy soundcard.");

  module_param_array(model, charp, NULL, 0444);
  MODULE_PARM_DESC(model, "Soundcard model.");

  module_param_array(pcm_devs, int, NULL, 0444);
  MODULE_PARM_DESC(pcm_devs, "PCM devices # (0-4) for dummy driver.");
  module_param_array(pcm_substreams, int, NULL, 0444);

  MODULE_PARM_DESC(pcm_substreams, "PCM substreams # (1-128) for dummy driver.");

  //module_param_array(midi_devs, int, NULL, 0444);
  //MODULE_PARM_DESC(midi_devs, "MIDI devices # (0-2) for dummy driver.");

  module_param(fake_buffer, bool, 0444);
  MODULE_PARM_DESC(fake_buffer, "Fake buffer allocations.");

  #ifdef CONFIG_HIGH_RES_TIMERS
  module_param(hrtimer, bool, 0644);
  MODULE_PARM_DESC(hrtimer, "Use hrtimer as the timer source.");
  #endif

  static struct platform_device *devices[SNDRV_CARDS];

  #define MIXER_ADDR_MASTER	0
  #define MIXER_ADDR_LINE		1
  #define MIXER_ADDR_MIC		2
  #define MIXER_ADDR_SYNTH	3
  #define MIXER_ADDR_CD		4
  #define MIXER_ADDR_LAST		4

  struct dummy_timer_ops {
  	int (*create)(struct snd_pcm_substream *);
  	void (*free)(struct snd_pcm_substream *);
  	int (*prepare)(struct snd_pcm_substream *);
  	int (*start)(struct snd_pcm_substream *);
  	int (*stop)(struct snd_pcm_substream *);
  	snd_pcm_uframes_t (*pointer)(struct snd_pcm_substream *);
  };

  struct dummy_model {
  	const char *name;
  	int (*playback_constraints)(struct snd_pcm_runtime *runtime);
  	int (*capture_constraints)(struct snd_pcm_runtime *runtime);
  	u64 formats;
  	size_t buffer_bytes_max;
  	size_t period_bytes_min;
  	size_t period_bytes_max;
  	unsigned int periods_min;
  	unsigned int periods_max;
  	unsigned int rates;
  	unsigned int rate_min;
  	unsigned int rate_max;
  	unsigned int channels_min;
  	unsigned int channels_max;
  };

  struct snd_dummy {
  	struct snd_card *card;

  	struct dummy_model *model;

  	struct snd_pcm *pcm;

  	struct snd_pcm_hardware pcm_hw;

  	spinlock_t mixer_lock;
  	int mixer_volume[MIXER_ADDR_LAST+1][2];
  	int capture_source[MIXER_ADDR_LAST+1][2];

  	int iobox;
  	struct snd_kcontrol *cd_volume_ctl;
  	struct snd_kcontrol *cd_switch_ctl;

  	const struct dummy_timer_ops *timer_ops;

  };

  /*

   * card models
   */
  
  static int emu10k1_playback_constraints(struct snd_pcm_runtime *runtime)
  {
  	int err;
  	err = snd_pcm_hw_constraint_integer(runtime, SNDRV_PCM_HW_PARAM_PERIODS);
  	if (err < 0)
  		return err;
  	err = snd_pcm_hw_constraint_minmax(runtime, SNDRV_PCM_HW_PARAM_BUFFER_BYTES, 256, UINT_MAX);
  	if (err < 0)
  		return err;
  	return 0;
  }
  
  struct dummy_model model_emu10k1 = {
  	.name = "emu10k1",
  	.playback_constraints = emu10k1_playback_constraints,
  	.buffer_bytes_max = 128 * 1024,
  };
  
  struct dummy_model model_rme9652 = {
  	.name = "rme9652",
  	.buffer_bytes_max = 26 * 64 * 1024,
  	.formats = SNDRV_PCM_FMTBIT_S32_LE,
  	.channels_min = 26,
  	.channels_max = 26,
  	.periods_min = 2,
  	.periods_max = 2,
  };
  
  struct dummy_model model_ice1712 = {
  	.name = "ice1712",
  	.buffer_bytes_max = 256 * 1024,
  	.formats = SNDRV_PCM_FMTBIT_S32_LE,
  	.channels_min = 10,
  	.channels_max = 10,
  	.periods_min = 1,
  	.periods_max = 1024,
  };
  
  struct dummy_model model_uda1341 = {
  	.name = "uda1341",
  	.buffer_bytes_max = 16380,
  	.formats = SNDRV_PCM_FMTBIT_S16_LE,
  	.channels_min = 2,
  	.channels_max = 2,
  	.periods_min = 2,
  	.periods_max = 255,
  };
  
  struct dummy_model model_ac97 = {
  	.name = "ac97",
  	.formats = SNDRV_PCM_FMTBIT_S16_LE,
  	.channels_min = 2,
  	.channels_max = 2,
  	.rates = SNDRV_PCM_RATE_48000,
  	.rate_min = 48000,
  	.rate_max = 48000,
  };
  
  struct dummy_model model_ca0106 = {
  	.name = "ca0106",
  	.formats = SNDRV_PCM_FMTBIT_S16_LE,
  	.buffer_bytes_max = ((65536-64)*8),
  	.period_bytes_max = (65536-64),
  	.periods_min = 2,
  	.periods_max = 8,
  	.channels_min = 2,
  	.channels_max = 2,
  	.rates = SNDRV_PCM_RATE_48000|SNDRV_PCM_RATE_96000|SNDRV_PCM_RATE_192000,
  	.rate_min = 48000,
  	.rate_max = 192000,
  };
  
  struct dummy_model *dummy_models[] = {
  	&model_emu10k1,
  	&model_rme9652,
  	&model_ice1712,
  	&model_uda1341,
  	&model_ac97,
  	&model_ca0106,
  	NULL
  };
  
  /*

   * system timer interface
   */
  
  struct dummy_systimer_pcm {

  	spinlock_t lock;
  	struct timer_list timer;

  	unsigned long base_time;
  	unsigned int frac_pos;	/* fractional sample position (based HZ) */

  	unsigned int frac_period_rest;

  	unsigned int frac_buffer_size;	/* buffer_size * HZ */
  	unsigned int frac_period_size;	/* period_size * HZ */
  	unsigned int rate;

  	int elapsed;

  	struct snd_pcm_substream *substream;
  };

  static void dummy_systimer_rearm(struct dummy_systimer_pcm *dpcm)
  {

  	dpcm->timer.expires = jiffies +

  		(dpcm->frac_period_rest + dpcm->rate - 1) / dpcm->rate;

  	add_timer(&dpcm->timer);
  }
  
  static void dummy_systimer_update(struct dummy_systimer_pcm *dpcm)
  {
  	unsigned long delta;
  
  	delta = jiffies - dpcm->base_time;
  	if (!delta)
  		return;

  	dpcm->base_time += delta;
  	delta *= dpcm->rate;
  	dpcm->frac_pos += delta;

  	while (dpcm->frac_pos >= dpcm->frac_buffer_size)
  		dpcm->frac_pos -= dpcm->frac_buffer_size;

  	while (dpcm->frac_period_rest <= delta) {
  		dpcm->elapsed++;
  		dpcm->frac_period_rest += dpcm->frac_period_size;
  	}
  	dpcm->frac_period_rest -= delta;

  }

  static int dummy_systimer_start(struct snd_pcm_substream *substream)

  {

  	struct dummy_systimer_pcm *dpcm = substream->runtime->private_data;
  	spin_lock(&dpcm->lock);

  	dpcm->base_time = jiffies;
  	dummy_systimer_rearm(dpcm);

  	spin_unlock(&dpcm->lock);
  	return 0;

  }

  static int dummy_systimer_stop(struct snd_pcm_substream *substream)

  {

  	struct dummy_systimer_pcm *dpcm = substream->runtime->private_data;

  	spin_lock(&dpcm->lock);

  	del_timer(&dpcm->timer);

  	spin_unlock(&dpcm->lock);

  	return 0;

  }

  static int dummy_systimer_prepare(struct snd_pcm_substream *substream)

  {

  	struct snd_pcm_runtime *runtime = substream->runtime;

  	struct dummy_systimer_pcm *dpcm = runtime->private_data;

  	dpcm->frac_pos = 0;
  	dpcm->rate = runtime->rate;
  	dpcm->frac_buffer_size = runtime->buffer_size * HZ;
  	dpcm->frac_period_size = runtime->period_size * HZ;

  	dpcm->frac_period_rest = dpcm->frac_period_size;
  	dpcm->elapsed = 0;

  	return 0;
  }

  static void dummy_systimer_callback(unsigned long data)

  {

  	struct dummy_systimer_pcm *dpcm = (struct dummy_systimer_pcm *)data;

  	unsigned long flags;

  	int elapsed = 0;

  	spin_lock_irqsave(&dpcm->lock, flags);

  	dummy_systimer_update(dpcm);
  	dummy_systimer_rearm(dpcm);

  	elapsed = dpcm->elapsed;
  	dpcm->elapsed = 0;

  	spin_unlock_irqrestore(&dpcm->lock, flags);

  	if (elapsed)
  		snd_pcm_period_elapsed(dpcm->substream);

  }

  static snd_pcm_uframes_t
  dummy_systimer_pointer(struct snd_pcm_substream *substream)

  {

  	struct dummy_systimer_pcm *dpcm = substream->runtime->private_data;

  	snd_pcm_uframes_t pos;

  	spin_lock(&dpcm->lock);
  	dummy_systimer_update(dpcm);

  	pos = dpcm->frac_pos / HZ;

  	spin_unlock(&dpcm->lock);

  	return pos;

  }

  static int dummy_systimer_create(struct snd_pcm_substream *substream)

  {

  	struct dummy_systimer_pcm *dpcm;
  
  	dpcm = kzalloc(sizeof(*dpcm), GFP_KERNEL);
  	if (!dpcm)
  		return -ENOMEM;
  	substream->runtime->private_data = dpcm;
  	init_timer(&dpcm->timer);
  	dpcm->timer.data = (unsigned long) dpcm;
  	dpcm->timer.function = dummy_systimer_callback;
  	spin_lock_init(&dpcm->lock);
  	dpcm->substream = substream;
  	return 0;
  }
  
  static void dummy_systimer_free(struct snd_pcm_substream *substream)
  {
  	kfree(substream->runtime->private_data);
  }
  
  static struct dummy_timer_ops dummy_systimer_ops = {
  	.create =	dummy_systimer_create,
  	.free =		dummy_systimer_free,
  	.prepare =	dummy_systimer_prepare,
  	.start =	dummy_systimer_start,
  	.stop =		dummy_systimer_stop,
  	.pointer =	dummy_systimer_pointer,

  };

  #ifdef CONFIG_HIGH_RES_TIMERS
  /*
   * hrtimer interface
   */
  
  struct dummy_hrtimer_pcm {
  	ktime_t base_time;
  	ktime_t period_time;
  	atomic_t running;
  	struct hrtimer timer;
  	struct tasklet_struct tasklet;
  	struct snd_pcm_substream *substream;
  };
  
  static void dummy_hrtimer_pcm_elapsed(unsigned long priv)
  {
  	struct dummy_hrtimer_pcm *dpcm = (struct dummy_hrtimer_pcm *)priv;
  	if (atomic_read(&dpcm->running))
  		snd_pcm_period_elapsed(dpcm->substream);
  }
  
  static enum hrtimer_restart dummy_hrtimer_callback(struct hrtimer *timer)
  {
  	struct dummy_hrtimer_pcm *dpcm;
  
  	dpcm = container_of(timer, struct dummy_hrtimer_pcm, timer);
  	if (!atomic_read(&dpcm->running))
  		return HRTIMER_NORESTART;
  	tasklet_schedule(&dpcm->tasklet);
  	hrtimer_forward_now(timer, dpcm->period_time);
  	return HRTIMER_RESTART;
  }
  
  static int dummy_hrtimer_start(struct snd_pcm_substream *substream)
  {
  	struct dummy_hrtimer_pcm *dpcm = substream->runtime->private_data;
  
  	dpcm->base_time = hrtimer_cb_get_time(&dpcm->timer);
  	hrtimer_start(&dpcm->timer, dpcm->period_time, HRTIMER_MODE_REL);
  	atomic_set(&dpcm->running, 1);
  	return 0;
  }
  
  static int dummy_hrtimer_stop(struct snd_pcm_substream *substream)
  {
  	struct dummy_hrtimer_pcm *dpcm = substream->runtime->private_data;
  
  	atomic_set(&dpcm->running, 0);
  	hrtimer_cancel(&dpcm->timer);
  	return 0;
  }
  
  static inline void dummy_hrtimer_sync(struct dummy_hrtimer_pcm *dpcm)
  {
  	tasklet_kill(&dpcm->tasklet);
  }
  
  static snd_pcm_uframes_t
  dummy_hrtimer_pointer(struct snd_pcm_substream *substream)
  {
  	struct snd_pcm_runtime *runtime = substream->runtime;
  	struct dummy_hrtimer_pcm *dpcm = runtime->private_data;
  	u64 delta;
  	u32 pos;
  
  	delta = ktime_us_delta(hrtimer_cb_get_time(&dpcm->timer),
  			       dpcm->base_time);
  	delta = div_u64(delta * runtime->rate + 999999, 1000000);
  	div_u64_rem(delta, runtime->buffer_size, &pos);
  	return pos;
  }
  
  static int dummy_hrtimer_prepare(struct snd_pcm_substream *substream)

  {

  	struct snd_pcm_runtime *runtime = substream->runtime;
  	struct dummy_hrtimer_pcm *dpcm = runtime->private_data;
  	unsigned int period, rate;
  	long sec;
  	unsigned long nsecs;
  
  	dummy_hrtimer_sync(dpcm);
  	period = runtime->period_size;
  	rate = runtime->rate;
  	sec = period / rate;
  	period %= rate;
  	nsecs = div_u64((u64)period * 1000000000UL + rate - 1, rate);
  	dpcm->period_time = ktime_set(sec, nsecs);
  
  	return 0;
  }
  
  static int dummy_hrtimer_create(struct snd_pcm_substream *substream)
  {
  	struct dummy_hrtimer_pcm *dpcm;
  
  	dpcm = kzalloc(sizeof(*dpcm), GFP_KERNEL);
  	if (!dpcm)
  		return -ENOMEM;
  	substream->runtime->private_data = dpcm;
  	hrtimer_init(&dpcm->timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
  	dpcm->timer.function = dummy_hrtimer_callback;
  	dpcm->substream = substream;
  	atomic_set(&dpcm->running, 0);
  	tasklet_init(&dpcm->tasklet, dummy_hrtimer_pcm_elapsed,
  		     (unsigned long)dpcm);
  	return 0;
  }
  
  static void dummy_hrtimer_free(struct snd_pcm_substream *substream)
  {
  	struct dummy_hrtimer_pcm *dpcm = substream->runtime->private_data;
  	dummy_hrtimer_sync(dpcm);
  	kfree(dpcm);
  }
  
  static struct dummy_timer_ops dummy_hrtimer_ops = {
  	.create =	dummy_hrtimer_create,
  	.free =		dummy_hrtimer_free,
  	.prepare =	dummy_hrtimer_prepare,
  	.start =	dummy_hrtimer_start,
  	.stop =		dummy_hrtimer_stop,
  	.pointer =	dummy_hrtimer_pointer,
  };
  
  #endif /* CONFIG_HIGH_RES_TIMERS */
  
  /*
   * PCM interface
   */
  
  static int dummy_pcm_trigger(struct snd_pcm_substream *substream, int cmd)
  {
  	struct snd_dummy *dummy = snd_pcm_substream_chip(substream);
  
  	switch (cmd) {
  	case SNDRV_PCM_TRIGGER_START:
  	case SNDRV_PCM_TRIGGER_RESUME:
  		return dummy->timer_ops->start(substream);
  	case SNDRV_PCM_TRIGGER_STOP:
  	case SNDRV_PCM_TRIGGER_SUSPEND:
  		return dummy->timer_ops->stop(substream);
  	}
  	return -EINVAL;
  }
  
  static int dummy_pcm_prepare(struct snd_pcm_substream *substream)
  {

  	struct snd_dummy *dummy = snd_pcm_substream_chip(substream);

  	return dummy->timer_ops->prepare(substream);
  }
  
  static snd_pcm_uframes_t dummy_pcm_pointer(struct snd_pcm_substream *substream)
  {
  	struct snd_dummy *dummy = snd_pcm_substream_chip(substream);
  
  	return dummy->timer_ops->pointer(substream);
  }
  
  static struct snd_pcm_hardware dummy_pcm_hardware = {
  	.info =			(SNDRV_PCM_INFO_MMAP |
  				 SNDRV_PCM_INFO_INTERLEAVED |
  				 SNDRV_PCM_INFO_RESUME |
  				 SNDRV_PCM_INFO_MMAP_VALID),

  	.formats =		USE_FORMATS,
  	.rates =		USE_RATE,
  	.rate_min =		USE_RATE_MIN,
  	.rate_max =		USE_RATE_MAX,
  	.channels_min =		USE_CHANNELS_MIN,
  	.channels_max =		USE_CHANNELS_MAX,
  	.buffer_bytes_max =	MAX_BUFFER_SIZE,

  	.period_bytes_min =	MIN_PERIOD_SIZE,

  	.period_bytes_max =	MAX_PERIOD_SIZE,

  	.periods_min =		USE_PERIODS_MIN,
  	.periods_max =		USE_PERIODS_MAX,
  	.fifo_size =		0,
  };

  static int dummy_pcm_hw_params(struct snd_pcm_substream *substream,
  			       struct snd_pcm_hw_params *hw_params)

  {

  	if (fake_buffer) {
  		/* runtime->dma_bytes has to be set manually to allow mmap */
  		substream->runtime->dma_bytes = params_buffer_bytes(hw_params);
  		return 0;
  	}

  	return snd_pcm_lib_malloc_pages(substream,
  					params_buffer_bytes(hw_params));

  }

  static int dummy_pcm_hw_free(struct snd_pcm_substream *substream)

  {

  	if (fake_buffer)
  		return 0;

  	return snd_pcm_lib_free_pages(substream);
  }

  static int dummy_pcm_open(struct snd_pcm_substream *substream)

  {

  	struct snd_dummy *dummy = snd_pcm_substream_chip(substream);

  	struct dummy_model *model = dummy->model;

  	struct snd_pcm_runtime *runtime = substream->runtime;

  	int err;

  	dummy->timer_ops = &dummy_systimer_ops;
  #ifdef CONFIG_HIGH_RES_TIMERS
  	if (hrtimer)
  		dummy->timer_ops = &dummy_hrtimer_ops;
  #endif
  
  	err = dummy->timer_ops->create(substream);

  	if (err < 0)

  		return err;

  	runtime->hw = dummy->pcm_hw;

  	if (substream->pcm->device & 1) {

  		runtime->hw.info &= ~SNDRV_PCM_INFO_INTERLEAVED;
  		runtime->hw.info |= SNDRV_PCM_INFO_NONINTERLEAVED;
  	}
  	if (substream->pcm->device & 2)

  		runtime->hw.info &= ~(SNDRV_PCM_INFO_MMAP |
  				      SNDRV_PCM_INFO_MMAP_VALID);

  	if (model == NULL)
  		return 0;
  
  	if (substream->stream == SNDRV_PCM_STREAM_PLAYBACK) {
  		if (model->playback_constraints)
  			err = model->playback_constraints(substream->runtime);
  	} else {
  		if (model->capture_constraints)
  			err = model->capture_constraints(substream->runtime);
  	}

  	if (err < 0) {
  		dummy->timer_ops->free(substream);

  		return err;

  	}

  	return 0;
  }

  static int dummy_pcm_close(struct snd_pcm_substream *substream)

  {

  	struct snd_dummy *dummy = snd_pcm_substream_chip(substream);
  	dummy->timer_ops->free(substream);

  	return 0;
  }

  /*
   * dummy buffer handling
   */
  
  static void *dummy_page[2];
  
  static void free_fake_buffer(void)
  {
  	if (fake_buffer) {
  		int i;
  		for (i = 0; i < 2; i++)
  			if (dummy_page[i]) {
  				free_page((unsigned long)dummy_page[i]);
  				dummy_page[i] = NULL;
  			}
  	}
  }
  
  static int alloc_fake_buffer(void)
  {
  	int i;
  
  	if (!fake_buffer)
  		return 0;
  	for (i = 0; i < 2; i++) {
  		dummy_page[i] = (void *)get_zeroed_page(GFP_KERNEL);
  		if (!dummy_page[i]) {
  			free_fake_buffer();
  			return -ENOMEM;
  		}
  	}
  	return 0;
  }
  
  static int dummy_pcm_copy(struct snd_pcm_substream *substream,
  			  int channel, snd_pcm_uframes_t pos,
  			  void __user *dst, snd_pcm_uframes_t count)
  {
  	return 0; /* do nothing */
  }
  
  static int dummy_pcm_silence(struct snd_pcm_substream *substream,
  			     int channel, snd_pcm_uframes_t pos,
  			     snd_pcm_uframes_t count)
  {
  	return 0; /* do nothing */
  }
  
  static struct page *dummy_pcm_page(struct snd_pcm_substream *substream,
  				   unsigned long offset)
  {
  	return virt_to_page(dummy_page[substream->stream]); /* the same page */
  }

  static struct snd_pcm_ops dummy_pcm_ops = {
  	.open =		dummy_pcm_open,
  	.close =	dummy_pcm_close,
  	.ioctl =	snd_pcm_lib_ioctl,
  	.hw_params =	dummy_pcm_hw_params,
  	.hw_free =	dummy_pcm_hw_free,
  	.prepare =	dummy_pcm_prepare,
  	.trigger =	dummy_pcm_trigger,
  	.pointer =	dummy_pcm_pointer,

  };

  static struct snd_pcm_ops dummy_pcm_ops_no_buf = {
  	.open =		dummy_pcm_open,
  	.close =	dummy_pcm_close,
  	.ioctl =	snd_pcm_lib_ioctl,
  	.hw_params =	dummy_pcm_hw_params,
  	.hw_free =	dummy_pcm_hw_free,
  	.prepare =	dummy_pcm_prepare,
  	.trigger =	dummy_pcm_trigger,
  	.pointer =	dummy_pcm_pointer,
  	.copy =		dummy_pcm_copy,
  	.silence =	dummy_pcm_silence,
  	.page =		dummy_pcm_page,
  };

  static int snd_card_dummy_pcm(struct snd_dummy *dummy, int device,
  			      int substreams)

  {

  	struct snd_pcm *pcm;

  	struct snd_pcm_ops *ops;

  	int err;

  	err = snd_pcm_new(dummy->card, "Dummy PCM", device,
  			       substreams, substreams, &pcm);
  	if (err < 0)

  		return err;

  	dummy->pcm = pcm;

  	if (fake_buffer)
  		ops = &dummy_pcm_ops_no_buf;
  	else
  		ops = &dummy_pcm_ops;
  	snd_pcm_set_ops(pcm, SNDRV_PCM_STREAM_PLAYBACK, ops);
  	snd_pcm_set_ops(pcm, SNDRV_PCM_STREAM_CAPTURE, ops);

  	pcm->private_data = dummy;
  	pcm->info_flags = 0;
  	strcpy(pcm->name, "Dummy PCM");

  	if (!fake_buffer) {
  		snd_pcm_lib_preallocate_pages_for_all(pcm,
  			SNDRV_DMA_TYPE_CONTINUOUS,
  			snd_dma_continuous_data(GFP_KERNEL),
  			0, 64*1024);
  	}

  	return 0;
  }

  /*
   * mixer interface
   */

  #define DUMMY_VOLUME(xname, xindex, addr) \

  { .iface = SNDRV_CTL_ELEM_IFACE_MIXER, \
    .access = SNDRV_CTL_ELEM_ACCESS_READWRITE | SNDRV_CTL_ELEM_ACCESS_TLV_READ, \
    .name = xname, .index = xindex, \

    .info = snd_dummy_volume_info, \
    .get = snd_dummy_volume_get, .put = snd_dummy_volume_put, \

    .private_value = addr, \
    .tlv = { .p = db_scale_dummy } }

  static int snd_dummy_volume_info(struct snd_kcontrol *kcontrol,
  				 struct snd_ctl_elem_info *uinfo)

  {
  	uinfo->type = SNDRV_CTL_ELEM_TYPE_INTEGER;
  	uinfo->count = 2;
  	uinfo->value.integer.min = -50;
  	uinfo->value.integer.max = 100;
  	return 0;
  }
   

  static int snd_dummy_volume_get(struct snd_kcontrol *kcontrol,
  				struct snd_ctl_elem_value *ucontrol)

  {

  	struct snd_dummy *dummy = snd_kcontrol_chip(kcontrol);

  	int addr = kcontrol->private_value;

  	spin_lock_irq(&dummy->mixer_lock);

  	ucontrol->value.integer.value[0] = dummy->mixer_volume[addr][0];
  	ucontrol->value.integer.value[1] = dummy->mixer_volume[addr][1];

  	spin_unlock_irq(&dummy->mixer_lock);

  	return 0;
  }

  static int snd_dummy_volume_put(struct snd_kcontrol *kcontrol,
  				struct snd_ctl_elem_value *ucontrol)

  {

  	struct snd_dummy *dummy = snd_kcontrol_chip(kcontrol);

  	int change, addr = kcontrol->private_value;
  	int left, right;
  
  	left = ucontrol->value.integer.value[0];
  	if (left < -50)
  		left = -50;
  	if (left > 100)
  		left = 100;
  	right = ucontrol->value.integer.value[1];
  	if (right < -50)
  		right = -50;
  	if (right > 100)
  		right = 100;

  	spin_lock_irq(&dummy->mixer_lock);

  	change = dummy->mixer_volume[addr][0] != left ||
  	         dummy->mixer_volume[addr][1] != right;
  	dummy->mixer_volume[addr][0] = left;
  	dummy->mixer_volume[addr][1] = right;

  	spin_unlock_irq(&dummy->mixer_lock);

  	return change;
  }

  static const DECLARE_TLV_DB_SCALE(db_scale_dummy, -4500, 30, 0);

  #define DUMMY_CAPSRC(xname, xindex, addr) \
  { .iface = SNDRV_CTL_ELEM_IFACE_MIXER, .name = xname, .index = xindex, \
    .info = snd_dummy_capsrc_info, \
    .get = snd_dummy_capsrc_get, .put = snd_dummy_capsrc_put, \
    .private_value = addr }

  #define snd_dummy_capsrc_info	snd_ctl_boolean_stereo_info

  static int snd_dummy_capsrc_get(struct snd_kcontrol *kcontrol,
  				struct snd_ctl_elem_value *ucontrol)

  {

  	struct snd_dummy *dummy = snd_kcontrol_chip(kcontrol);

  	int addr = kcontrol->private_value;

  	spin_lock_irq(&dummy->mixer_lock);

  	ucontrol->value.integer.value[0] = dummy->capture_source[addr][0];
  	ucontrol->value.integer.value[1] = dummy->capture_source[addr][1];

  	spin_unlock_irq(&dummy->mixer_lock);

  	return 0;
  }

  static int snd_dummy_capsrc_put(struct snd_kcontrol *kcontrol, struct snd_ctl_elem_value *ucontrol)

  {

  	struct snd_dummy *dummy = snd_kcontrol_chip(kcontrol);

  	int change, addr = kcontrol->private_value;
  	int left, right;
  
  	left = ucontrol->value.integer.value[0] & 1;
  	right = ucontrol->value.integer.value[1] & 1;

  	spin_lock_irq(&dummy->mixer_lock);

  	change = dummy->capture_source[addr][0] != left &&
  	         dummy->capture_source[addr][1] != right;
  	dummy->capture_source[addr][0] = left;
  	dummy->capture_source[addr][1] = right;

  	spin_unlock_irq(&dummy->mixer_lock);

  	return change;
  }

  static int snd_dummy_iobox_info(struct snd_kcontrol *kcontrol,
  				struct snd_ctl_elem_info *info)
  {
  	const char *const names[] = { "None", "CD Player" };
  
  	return snd_ctl_enum_info(info, 1, 2, names);
  }
  
  static int snd_dummy_iobox_get(struct snd_kcontrol *kcontrol,
  			       struct snd_ctl_elem_value *value)
  {
  	struct snd_dummy *dummy = snd_kcontrol_chip(kcontrol);
  
  	value->value.enumerated.item[0] = dummy->iobox;
  	return 0;
  }
  
  static int snd_dummy_iobox_put(struct snd_kcontrol *kcontrol,
  			       struct snd_ctl_elem_value *value)
  {
  	struct snd_dummy *dummy = snd_kcontrol_chip(kcontrol);
  	int changed;
  
  	if (value->value.enumerated.item[0] > 1)
  		return -EINVAL;
  
  	changed = value->value.enumerated.item[0] != dummy->iobox;
  	if (changed) {
  		dummy->iobox = value->value.enumerated.item[0];
  
  		if (dummy->iobox) {
  			dummy->cd_volume_ctl->vd[0].access &=
  				~SNDRV_CTL_ELEM_ACCESS_INACTIVE;
  			dummy->cd_switch_ctl->vd[0].access &=
  				~SNDRV_CTL_ELEM_ACCESS_INACTIVE;
  		} else {
  			dummy->cd_volume_ctl->vd[0].access |=
  				SNDRV_CTL_ELEM_ACCESS_INACTIVE;
  			dummy->cd_switch_ctl->vd[0].access |=
  				SNDRV_CTL_ELEM_ACCESS_INACTIVE;
  		}
  
  		snd_ctl_notify(dummy->card, SNDRV_CTL_EVENT_MASK_INFO,
  			       &dummy->cd_volume_ctl->id);
  		snd_ctl_notify(dummy->card, SNDRV_CTL_EVENT_MASK_INFO,
  			       &dummy->cd_switch_ctl->id);
  	}
  
  	return changed;
  }

  static struct snd_kcontrol_new snd_dummy_controls[] = {

  DUMMY_VOLUME("Master Volume", 0, MIXER_ADDR_MASTER),
  DUMMY_CAPSRC("Master Capture Switch", 0, MIXER_ADDR_MASTER),
  DUMMY_VOLUME("Synth Volume", 0, MIXER_ADDR_SYNTH),

  DUMMY_CAPSRC("Synth Capture Switch", 0, MIXER_ADDR_SYNTH),

  DUMMY_VOLUME("Line Volume", 0, MIXER_ADDR_LINE),

  DUMMY_CAPSRC("Line Capture Switch", 0, MIXER_ADDR_LINE),

  DUMMY_VOLUME("Mic Volume", 0, MIXER_ADDR_MIC),

  DUMMY_CAPSRC("Mic Capture Switch", 0, MIXER_ADDR_MIC),

  DUMMY_VOLUME("CD Volume", 0, MIXER_ADDR_CD),

  DUMMY_CAPSRC("CD Capture Switch", 0, MIXER_ADDR_CD),
  {
  	.iface = SNDRV_CTL_ELEM_IFACE_MIXER,
  	.name  = "External I/O Box",
  	.info  = snd_dummy_iobox_info,
  	.get   = snd_dummy_iobox_get,
  	.put   = snd_dummy_iobox_put,
  },

  };

  static int snd_card_dummy_new_mixer(struct snd_dummy *dummy)

  {

  	struct snd_card *card = dummy->card;

  	struct snd_kcontrol *kcontrol;

  	unsigned int idx;
  	int err;

  	spin_lock_init(&dummy->mixer_lock);
  	strcpy(card->mixername, "Dummy Mixer");

  	dummy->iobox = 1;

  
  	for (idx = 0; idx < ARRAY_SIZE(snd_dummy_controls); idx++) {

  		kcontrol = snd_ctl_new1(&snd_dummy_controls[idx], dummy);
  		err = snd_ctl_add(card, kcontrol);

  		if (err < 0)

  			return err;

  		if (!strcmp(kcontrol->id.name, "CD Volume"))
  			dummy->cd_volume_ctl = kcontrol;
  		else if (!strcmp(kcontrol->id.name, "CD Capture Switch"))
  			dummy->cd_switch_ctl = kcontrol;

  	}
  	return 0;
  }

  #if defined(CONFIG_SND_DEBUG) && defined(CONFIG_PROC_FS)
  /*
   * proc interface
   */

  static void print_formats(struct snd_dummy *dummy,
  			  struct snd_info_buffer *buffer)

  {
  	int i;
  
  	for (i = 0; i < SNDRV_PCM_FORMAT_LAST; i++) {

  		if (dummy->pcm_hw.formats & (1ULL << i))

  			snd_iprintf(buffer, " %s", snd_pcm_format_name(i));
  	}
  }

  static void print_rates(struct snd_dummy *dummy,
  			struct snd_info_buffer *buffer)

  {
  	static int rates[] = {
  		5512, 8000, 11025, 16000, 22050, 32000, 44100, 48000,
  		64000, 88200, 96000, 176400, 192000,
  	};
  	int i;

  	if (dummy->pcm_hw.rates & SNDRV_PCM_RATE_CONTINUOUS)

  		snd_iprintf(buffer, " continuous");

  	if (dummy->pcm_hw.rates & SNDRV_PCM_RATE_KNOT)

  		snd_iprintf(buffer, " knot");
  	for (i = 0; i < ARRAY_SIZE(rates); i++)

  		if (dummy->pcm_hw.rates & (1 << i))

  			snd_iprintf(buffer, " %d", rates[i]);
  }

  #define get_dummy_int_ptr(dummy, ofs) \
  	(unsigned int *)((char *)&((dummy)->pcm_hw) + (ofs))
  #define get_dummy_ll_ptr(dummy, ofs) \
  	(unsigned long long *)((char *)&((dummy)->pcm_hw) + (ofs))

  
  struct dummy_hw_field {
  	const char *name;
  	const char *format;
  	unsigned int offset;
  	unsigned int size;
  };
  #define FIELD_ENTRY(item, fmt) {		   \
  	.name = #item,				   \
  	.format = fmt,				   \
  	.offset = offsetof(struct snd_pcm_hardware, item), \
  	.size = sizeof(dummy_pcm_hardware.item) }
  
  static struct dummy_hw_field fields[] = {
  	FIELD_ENTRY(formats, "%#llx"),
  	FIELD_ENTRY(rates, "%#x"),
  	FIELD_ENTRY(rate_min, "%d"),
  	FIELD_ENTRY(rate_max, "%d"),
  	FIELD_ENTRY(channels_min, "%d"),
  	FIELD_ENTRY(channels_max, "%d"),
  	FIELD_ENTRY(buffer_bytes_max, "%ld"),
  	FIELD_ENTRY(period_bytes_min, "%ld"),
  	FIELD_ENTRY(period_bytes_max, "%ld"),
  	FIELD_ENTRY(periods_min, "%d"),
  	FIELD_ENTRY(periods_max, "%d"),
  };
  
  static void dummy_proc_read(struct snd_info_entry *entry,
  			    struct snd_info_buffer *buffer)
  {

  	struct snd_dummy *dummy = entry->private_data;

  	int i;
  
  	for (i = 0; i < ARRAY_SIZE(fields); i++) {
  		snd_iprintf(buffer, "%s ", fields[i].name);
  		if (fields[i].size == sizeof(int))
  			snd_iprintf(buffer, fields[i].format,

  				*get_dummy_int_ptr(dummy, fields[i].offset));

  		else
  			snd_iprintf(buffer, fields[i].format,

  				*get_dummy_ll_ptr(dummy, fields[i].offset));

  		if (!strcmp(fields[i].name, "formats"))

  			print_formats(dummy, buffer);

  		else if (!strcmp(fields[i].name, "rates"))

  			print_rates(dummy, buffer);

  		snd_iprintf(buffer, "
  ");
  	}
  }
  
  static void dummy_proc_write(struct snd_info_entry *entry,
  			     struct snd_info_buffer *buffer)
  {

  	struct snd_dummy *dummy = entry->private_data;

  	char line[64];
  
  	while (!snd_info_get_line(buffer, line, sizeof(line))) {
  		char item[20];
  		const char *ptr;
  		unsigned long long val;
  		int i;
  
  		ptr = snd_info_get_str(item, line, sizeof(item));
  		for (i = 0; i < ARRAY_SIZE(fields); i++) {
  			if (!strcmp(item, fields[i].name))
  				break;
  		}
  		if (i >= ARRAY_SIZE(fields))
  			continue;
  		snd_info_get_str(item, ptr, sizeof(item));

  		if (kstrtoull(item, 0, &val))

  			continue;
  		if (fields[i].size == sizeof(int))

  			*get_dummy_int_ptr(dummy, fields[i].offset) = val;

  		else

  			*get_dummy_ll_ptr(dummy, fields[i].offset) = val;

  	}
  }

  static void dummy_proc_init(struct snd_dummy *chip)

  {
  	struct snd_info_entry *entry;
  
  	if (!snd_card_proc_new(chip->card, "dummy_pcm", &entry)) {
  		snd_info_set_text_ops(entry, chip, dummy_proc_read);
  		entry->c.text.write = dummy_proc_write;
  		entry->mode |= S_IWUSR;

  		entry->private_data = chip;

  	}
  }
  #else
  #define dummy_proc_init(x)
  #endif /* CONFIG_SND_DEBUG && CONFIG_PROC_FS */

  static int snd_dummy_probe(struct platform_device *devptr)

  {

  	struct snd_card *card;
  	struct snd_dummy *dummy;

  	struct dummy_model *m = NULL, **mdl;

  	int idx, err;

  	int dev = devptr->id;

  	err = snd_card_new(&devptr->dev, index[dev], id[dev], THIS_MODULE,
  			   sizeof(struct snd_dummy), &card);

  	if (err < 0)
  		return err;

  	dummy = card->private_data;

  	dummy->card = card;

  	for (mdl = dummy_models; *mdl && model[dev]; mdl++) {
  		if (strcmp(model[dev], (*mdl)->name) == 0) {
  			printk(KERN_INFO
  				"snd-dummy: Using model '%s' for card %i
  ",
  				(*mdl)->name, card->number);
  			m = dummy->model = *mdl;
  			break;
  		}
  	}

  	for (idx = 0; idx < MAX_PCM_DEVICES && idx < pcm_devs[dev]; idx++) {
  		if (pcm_substreams[dev] < 1)
  			pcm_substreams[dev] = 1;
  		if (pcm_substreams[dev] > MAX_PCM_SUBSTREAMS)
  			pcm_substreams[dev] = MAX_PCM_SUBSTREAMS;

  		err = snd_card_dummy_pcm(dummy, idx, pcm_substreams[dev]);
  		if (err < 0)

  			goto __nodev;
  	}

  
  	dummy->pcm_hw = dummy_pcm_hardware;
  	if (m) {
  		if (m->formats)
  			dummy->pcm_hw.formats = m->formats;
  		if (m->buffer_bytes_max)
  			dummy->pcm_hw.buffer_bytes_max = m->buffer_bytes_max;
  		if (m->period_bytes_min)
  			dummy->pcm_hw.period_bytes_min = m->period_bytes_min;
  		if (m->period_bytes_max)
  			dummy->pcm_hw.period_bytes_max = m->period_bytes_max;
  		if (m->periods_min)
  			dummy->pcm_hw.periods_min = m->periods_min;
  		if (m->periods_max)
  			dummy->pcm_hw.periods_max = m->periods_max;
  		if (m->rates)
  			dummy->pcm_hw.rates = m->rates;
  		if (m->rate_min)
  			dummy->pcm_hw.rate_min = m->rate_min;
  		if (m->rate_max)
  			dummy->pcm_hw.rate_max = m->rate_max;
  		if (m->channels_min)
  			dummy->pcm_hw.channels_min = m->channels_min;
  		if (m->channels_max)
  			dummy->pcm_hw.channels_max = m->channels_max;
  	}

  	err = snd_card_dummy_new_mixer(dummy);
  	if (err < 0)

  		goto __nodev;
  	strcpy(card->driver, "Dummy");
  	strcpy(card->shortname, "Dummy");
  	sprintf(card->longname, "Dummy %i", dev + 1);

  	dummy_proc_init(dummy);

  	err = snd_card_register(card);
  	if (err == 0) {

  		platform_set_drvdata(devptr, card);

  		return 0;
  	}
        __nodev:
  	snd_card_free(card);
  	return err;
  }

  static int snd_dummy_remove(struct platform_device *devptr)

  {
  	snd_card_free(platform_get_drvdata(devptr));

  	return 0;
  }

  #ifdef CONFIG_PM_SLEEP

  static int snd_dummy_suspend(struct device *pdev)

  {

  	struct snd_card *card = dev_get_drvdata(pdev);

  	struct snd_dummy *dummy = card->private_data;

  	snd_power_change_state(card, SNDRV_CTL_POWER_D3hot);
  	snd_pcm_suspend_all(dummy->pcm);
  	return 0;
  }
  	

  static int snd_dummy_resume(struct device *pdev)

  {

  	struct snd_card *card = dev_get_drvdata(pdev);

  
  	snd_power_change_state(card, SNDRV_CTL_POWER_D0);
  	return 0;
  }

  
  static SIMPLE_DEV_PM_OPS(snd_dummy_pm, snd_dummy_suspend, snd_dummy_resume);
  #define SND_DUMMY_PM_OPS	&snd_dummy_pm
  #else
  #define SND_DUMMY_PM_OPS	NULL

  #endif
  
  #define SND_DUMMY_DRIVER	"snd_dummy"
  
  static struct platform_driver snd_dummy_driver = {
  	.probe		= snd_dummy_probe,

  	.remove		= snd_dummy_remove,

  	.driver		= {

  		.name	= SND_DUMMY_DRIVER,
  		.owner	= THIS_MODULE,

  		.pm	= SND_DUMMY_PM_OPS,

  	},
  };

  static void snd_dummy_unregister_all(void)

  {
  	int i;
  
  	for (i = 0; i < ARRAY_SIZE(devices); ++i)
  		platform_device_unregister(devices[i]);
  	platform_driver_unregister(&snd_dummy_driver);

  	free_fake_buffer();

  }

  static int __init alsa_card_dummy_init(void)
  {
  	int i, cards, err;

  	err = platform_driver_register(&snd_dummy_driver);
  	if (err < 0)

  		return err;

  	err = alloc_fake_buffer();
  	if (err < 0) {
  		platform_driver_unregister(&snd_dummy_driver);
  		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_DUMMY_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 "Dummy soundcard not found or device busy
  ");
  #endif

  		snd_dummy_unregister_all();
  		return -ENODEV;

  	}
  	return 0;
  }
  
  static void __exit alsa_card_dummy_exit(void)
  {

  	snd_dummy_unregister_all();

  }
  
  module_init(alsa_card_dummy_init)
  module_exit(alsa_card_dummy_exit)