ALSA: snd-aloop - fix locking issues (running flag updates)

[deliverable/linux.git] / sound / drivers / aloop.c

/*
 *  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/moduleparam.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 int 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;
};

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;

        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 |= (1 << substream->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 &= ~(1 << substream->stream);
                spin_unlock(&cable->lock);
                loopback_timer_stop(dpcm);
                if (substream->stream == SNDRV_PCM_STREAM_PLAYBACK)
                        loopback_active_notify(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;

        spin_lock(&cable->lock);        
        running = cable->running;
        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) {
                spin_unlock(&cable->lock);
                return running;
        }
                
        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) {
                spin_unlock(&cable->lock);
                return running;
        }
        /* 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);
        spin_unlock(&cable->lock);
        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),
        .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_malloc_pages(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_pages(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,
};

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,
};

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;

        snd_pcm_lib_preallocate_pages_for_all(pcm, SNDRV_DMA_TYPE_CONTINUOUS,
                        snd_dma_continuous_data(GFP_KERNEL),
                        0, 2 * 1024 * 1024);
        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\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);
        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\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)