Adding upstream version 4.19.249.upstream/4.19.249

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1292 insertions, 0 deletions

diff --git a/sound/drivers/aloop.c b/sound/drivers/aloop.c
new file mode 100644
index 000000000..3c65e52b0
--- /dev/null
+++ b/sound/drivers/aloop.c
@@ -0,0 +1,1292 @@
+/*
+ *  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/pcm_params.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 int last_drift;
+	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;
+}
+
+/* call in cable->lock */
+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;
+	mod_timer(&dpcm->timer, jiffies + tick);
+}
+
+/* call in cable->lock */
+static inline void loopback_timer_stop(struct loopback_pcm *dpcm)
+{
+	del_timer(&dpcm->timer);
+	dpcm->timer.expires = 0;
+}
+
+static inline void loopback_timer_stop_sync(struct loopback_pcm *dpcm)
+{
+	del_timer_sync(&dpcm->timer);
+}
+
+#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;
+		dpcm->last_drift = 0;
+		spin_lock(&cable->lock);	
+		cable->running |= stream;
+		cable->pause &= ~stream;
+		loopback_timer_start(dpcm);
+		spin_unlock(&cable->lock);
+		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;
+		loopback_timer_stop(dpcm);
+		spin_unlock(&cable->lock);
+		if (substream->stream == SNDRV_PCM_STREAM_PLAYBACK)
+			loopback_active_notify(dpcm);
+		break;
+	case SNDRV_PCM_TRIGGER_PAUSE_PUSH:
+	case SNDRV_PCM_TRIGGER_SUSPEND:
+		spin_lock(&cable->lock);	
+		cable->pause |= stream;
+		loopback_timer_stop(dpcm);
+		spin_unlock(&cable->lock);
+		if (substream->stream == SNDRV_PCM_STREAM_PLAYBACK)
+			loopback_active_notify(dpcm);
+		break;
+	case SNDRV_PCM_TRIGGER_PAUSE_RELEASE:
+	case SNDRV_PCM_TRIGGER_RESUME:
+		spin_lock(&cable->lock);
+		dpcm->last_jiffies = jiffies;
+		cable->pause &= ~stream;
+		loopback_timer_start(dpcm);
+		spin_unlock(&cable->lock);
+		if (substream->stream == SNDRV_PCM_STREAM_PLAYBACK)
+			loopback_active_notify(dpcm);
+		break;
+	default:
+		return -EINVAL;
+	}
+	return 0;
+}
+
+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 = pcm_format_to_bits(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;
+}
+
+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;
+
+	loopback_timer_stop_sync(dpcm);
+
+	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;
+	}
+}
+
+static inline unsigned int bytepos_delta(struct loopback_pcm *dpcm,
+					 unsigned int jiffies_delta)
+{
+	unsigned long last_pos;
+	unsigned int delta;
+
+	last_pos = byte_pos(dpcm, dpcm->irq_pos);
+	dpcm->irq_pos += jiffies_delta * dpcm->pcm_bps;
+	delta = byte_pos(dpcm, dpcm->irq_pos) - last_pos;
+	if (delta >= dpcm->last_drift)
+		delta -= dpcm->last_drift;
+	dpcm->last_drift = 0;
+	if (dpcm->irq_pos >= dpcm->period_size_frac) {
+		dpcm->irq_pos %= dpcm->period_size_frac;
+		dpcm->period_update_pending = 1;
+	}
+	return delta;
+}
+
+static inline void bytepos_finish(struct loopback_pcm *dpcm,
+				  unsigned int delta)
+{
+	dpcm->buf_pos += delta;
+	dpcm->buf_pos %= dpcm->pcm_buffer_size;
+}
+
+/* call in cable->lock */
+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, count1, count2;
+
+	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) {
+		count1 = bytepos_delta(dpcm_play, delta_play - delta_capt);
+		bytepos_finish(dpcm_play, count1);
+		delta_play = delta_capt;
+	} else if (delta_play < delta_capt) {
+		count1 = bytepos_delta(dpcm_capt, delta_capt - delta_play);
+		clear_capture_buf(dpcm_capt, count1);
+		bytepos_finish(dpcm_capt, count1);
+		delta_capt = delta_play;
+	}
+
+	if (delta_play == 0 && delta_capt == 0)
+		goto unlock;
+
+	/* note delta_capt == delta_play at this moment */
+	count1 = bytepos_delta(dpcm_play, delta_play);
+	count2 = bytepos_delta(dpcm_capt, delta_capt);
+	if (count1 < count2) {
+		dpcm_capt->last_drift = count2 - count1;
+		count1 = count2;
+	} else if (count1 > count2) {
+		dpcm_play->last_drift = count1 - count2;
+	}
+	copy_play_buf(dpcm_play, dpcm_capt, count1);
+	bytepos_finish(dpcm_play, count1);
+	bytepos_finish(dpcm_capt, count1);
+ unlock:
+	return running;
+}
+
+static void loopback_timer_function(struct timer_list *t)
+{
+	struct loopback_pcm *dpcm = from_timer(dpcm, t, timer);
+	unsigned long flags;
+
+	spin_lock_irqsave(&dpcm->cable->lock, flags);
+	if (loopback_pos_update(dpcm->cable) & (1 << dpcm->substream->stream)) {
+		loopback_timer_start(dpcm);
+		if (dpcm->period_update_pending) {
+			dpcm->period_update_pending = 0;
+			spin_unlock_irqrestore(&dpcm->cable->lock, flags);
+			/* need to unlock before calling below */
+			snd_pcm_period_elapsed(dpcm->substream);
+			return;
+		}
+	}
+	spin_unlock_irqrestore(&dpcm->cable->lock, flags);
+}
+
+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;
+	snd_pcm_uframes_t pos;
+
+	spin_lock(&dpcm->cable->lock);
+	loopback_pos_update(dpcm->cable);
+	pos = dpcm->buf_pos;
+	spin_unlock(&dpcm->cable->lock);
+	return bytes_to_frames(runtime, pos);
+}
+
+static const 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 |
+			 SNDRV_PCM_INFO_RESUME),
+	.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 loopback_pcm *dpcm = rule->private;
+	struct loopback_cable *cable = dpcm->cable;
+	struct snd_mask m;
+
+	snd_mask_none(&m);
+	mutex_lock(&dpcm->loopback->cable_lock);
+	m.bits[0] = (u_int32_t)cable->hw.formats;
+	m.bits[1] = (u_int32_t)(cable->hw.formats >> 32);
+	mutex_unlock(&dpcm->loopback->cable_lock);
+	return snd_mask_refine(hw_param_mask(params, rule->var), &m);
+}
+
+static int rule_rate(struct snd_pcm_hw_params *params,
+		     struct snd_pcm_hw_rule *rule)
+{
+	struct loopback_pcm *dpcm = rule->private;
+	struct loopback_cable *cable = dpcm->cable;
+	struct snd_interval t;
+
+	mutex_lock(&dpcm->loopback->cable_lock);
+	t.min = cable->hw.rate_min;
+	t.max = cable->hw.rate_max;
+	mutex_unlock(&dpcm->loopback->cable_lock);
+        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 loopback_pcm *dpcm = rule->private;
+	struct loopback_cable *cable = dpcm->cable;
+	struct snd_interval t;
+
+	mutex_lock(&dpcm->loopback->cable_lock);
+	t.min = cable->hw.channels_min;
+	t.max = cable->hw.channels_max;
+	mutex_unlock(&dpcm->loopback->cable_lock);
+        t.openmin = t.openmax = 0;
+        t.integer = 0;
+	return snd_interval_refine(hw_param_interval(params, rule->var), &t);
+}
+
+static void free_cable(struct snd_pcm_substream *substream)
+{
+	struct loopback *loopback = substream->private_data;
+	int dev = get_cable_index(substream);
+	struct loopback_cable *cable;
+
+	cable = loopback->cables[substream->number][dev];
+	if (!cable)
+		return;
+	if (cable->streams[!substream->stream]) {
+		/* other stream is still alive */
+		spin_lock_irq(&cable->lock);
+		cable->streams[substream->stream] = NULL;
+		spin_unlock_irq(&cable->lock);
+	} else {
+		/* free the cable */
+		loopback->cables[substream->number][dev] = NULL;
+		kfree(cable);
+	}
+}
+
+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 = NULL;
+	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;
+	timer_setup(&dpcm->timer, loopback_timer_function, 0);
+
+	cable = loopback->cables[substream->number][dev];
+	if (!cable) {
+		cable = kzalloc(sizeof(*cable), GFP_KERNEL);
+		if (!cable) {
+			err = -ENOMEM;
+			goto unlock;
+		}
+		spin_lock_init(&cable->lock);
+		cable->hw = loopback_pcm_hardware;
+		loopback->cables[substream->number][dev] = cable;
+	}
+	dpcm->cable = cable;
+
+	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, dpcm,
+				  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, dpcm,
+				  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, dpcm,
+				  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;
+
+	spin_lock_irq(&cable->lock);
+	cable->streams[substream->stream] = dpcm;
+	spin_unlock_irq(&cable->lock);
+
+ unlock:
+	if (err < 0) {
+		free_cable(substream);
+		kfree(dpcm);
+	}
+	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;
+
+	loopback_timer_stop_sync(dpcm);
+	mutex_lock(&loopback->cable_lock);
+	free_cable(substream);
+	mutex_unlock(&loopback->cable_lock);
+	return 0;
+}
+
+static const struct snd_pcm_ops loopback_pcm_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,
+};
+
+static int 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_pcm_ops);
+	snd_pcm_set_ops(pcm, SNDRV_PCM_STREAM_CAPTURE, &loopback_pcm_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);
+	
+	mutex_lock(&loopback->cable_lock);
+	ucontrol->value.integer.value[0] =
+		loopback->setup[kcontrol->id.subdevice]
+			       [kcontrol->id.device].rate_shift;
+	mutex_unlock(&loopback->cable_lock);
+	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);
+	
+	mutex_lock(&loopback->cable_lock);
+	ucontrol->value.integer.value[0] =
+		loopback->setup[kcontrol->id.subdevice]
+			       [kcontrol->id.device].notify;
+	mutex_unlock(&loopback->cable_lock);
+	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;
+	mutex_lock(&loopback->cable_lock);
+	if (val != loopback->setup[kcontrol->id.subdevice]
+				[kcontrol->id.device].notify) {
+		loopback->setup[kcontrol->id.subdevice]
+			[kcontrol->id.device].notify = val;
+		change = 1;
+	}
+	mutex_unlock(&loopback->cable_lock);
+	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;
+
+	unsigned int val = 0;
+
+	mutex_lock(&loopback->cable_lock);
+	cable = loopback->cables[kcontrol->id.subdevice][kcontrol->id.device ^ 1];
+	if (cable != NULL) {
+		unsigned int running = cable->running ^ cable->pause;
+
+		val = (running & (1 << SNDRV_PCM_STREAM_PLAYBACK)) ? 1 : 0;
+	}
+	mutex_unlock(&loopback->cable_lock);
+	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);
+	
+	mutex_lock(&loopback->cable_lock);
+	ucontrol->value.integer.value[0] =
+		loopback->setup[kcontrol->id.subdevice]
+			       [kcontrol->id.device].rate;
+	mutex_unlock(&loopback->cable_lock);
+	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);
+	
+	mutex_lock(&loopback->cable_lock);
+	ucontrol->value.integer.value[0] =
+		loopback->setup[kcontrol->id.subdevice]
+			       [kcontrol->id.device].channels;
+	mutex_unlock(&loopback->cable_lock);
+	return 0;
+}
+
+static struct snd_kcontrol_new loopback_controls[]  = {
+{
+	.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 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;
+
+				/* Add the control before copying the id so that
+				 * the numid field of the id is set in the copy.
+				 */
+				err = snd_ctl_add(card, kctl);
+				if (err < 0)
+					return err;
+
+				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;
+				}
+			}
+		}
+	}
+	return 0;
+}
+
+static void print_dpcm_info(struct snd_info_buffer *buffer,
+			    struct loopback_pcm *dpcm,
+			    const char *id)
+{
+	snd_iprintf(buffer, "  %s\n", id);
+	if (dpcm == NULL) {
+		snd_iprintf(buffer, "    inactive\n");
+		return;
+	}
+	snd_iprintf(buffer, "    buffer_size:\t%u\n", dpcm->pcm_buffer_size);
+	snd_iprintf(buffer, "    buffer_pos:\t\t%u\n", dpcm->buf_pos);
+	snd_iprintf(buffer, "    silent_size:\t%u\n", dpcm->silent_size);
+	snd_iprintf(buffer, "    period_size:\t%u\n", dpcm->pcm_period_size);
+	snd_iprintf(buffer, "    bytes_per_sec:\t%u\n", dpcm->pcm_bps);
+	snd_iprintf(buffer, "    sample_align:\t%u\n", dpcm->pcm_salign);
+	snd_iprintf(buffer, "    rate_shift:\t\t%u\n", dpcm->pcm_rate_shift);
+	snd_iprintf(buffer, "    update_pending:\t%u\n",
+						dpcm->period_update_pending);
+	snd_iprintf(buffer, "    irq_pos:\t\t%u\n", dpcm->irq_pos);
+	snd_iprintf(buffer, "    period_frac:\t%u\n", dpcm->period_size_frac);
+	snd_iprintf(buffer, "    last_jiffies:\t%lu (%lu)\n",
+					dpcm->last_jiffies, jiffies);
+	snd_iprintf(buffer, "    timer_expires:\t%lu\n", 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:\n", num, sub);
+	if (cable == NULL) {
+		snd_iprintf(buffer, "  inactive\n");
+		return;
+	}
+	snd_iprintf(buffer, "  valid: %u\n", cable->valid);
+	snd_iprintf(buffer, "  running: %u\n", cable->running);
+	snd_iprintf(buffer, "  pause: %u\n", 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 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;
+}
+
+static int loopback_probe(struct platform_device *devptr)
+{
+	struct snd_card *card;
+	struct loopback *loopback;
+	int dev = devptr->id;
+	int err;
+
+	err = snd_card_new(&devptr->dev, 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 loopback_remove(struct platform_device *devptr)
+{
+	snd_card_free(platform_get_drvdata(devptr));
+	return 0;
+}
+
+#ifdef CONFIG_PM_SLEEP
+static int loopback_suspend(struct device *pdev)
+{
+	struct snd_card *card = dev_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 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(loopback_pm, loopback_suspend, loopback_resume);
+#define LOOPBACK_PM_OPS	&loopback_pm
+#else
+#define LOOPBACK_PM_OPS	NULL
+#endif
+
+#define SND_LOOPBACK_DRIVER	"snd_aloop"
+
+static struct platform_driver loopback_driver = {
+	.probe		= loopback_probe,
+	.remove		= loopback_remove,
+	.driver		= {
+		.name	= SND_LOOPBACK_DRIVER,
+		.pm	= LOOPBACK_PM_OPS,
+	},
+};
+
+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\n");
+#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)