// SPDX-License-Identifier: GPL-2.0-or-later
/*
 *  Digital Audio (PCM) abstract layer
 *  Copyright (c) by Jaroslav Kysela <perex@perex.cz>
 */

#include <linux/init.h>
#include <linux/slab.h>
#include <linux/module.h>
#include <linux/time.h>
#include <linux/mutex.h>
#include <linux/device.h>
#include <linux/nospec.h>
#include <sound/core.h>
#include <sound/minors.h>
#include <sound/pcm.h>
#include <sound/timer.h>
#include <sound/control.h>
#include <sound/info.h>

#include "pcm_local.h"

MODULE_AUTHOR("Jaroslav Kysela <perex@perex.cz>, Abramo Bagnara <abramo@alsa-project.org>");
MODULE_DESCRIPTION("Midlevel PCM code for ALSA.");
MODULE_LICENSE("GPL");

static LIST_HEAD(snd_pcm_devices);
static DEFINE_MUTEX(register_mutex);
#if IS_ENABLED(CONFIG_SND_PCM_OSS)
static LIST_HEAD(snd_pcm_notify_list);
#endif

static int snd_pcm_free(struct snd_pcm *pcm);
static int snd_pcm_dev_free(struct snd_device *device);
static int snd_pcm_dev_register(struct snd_device *device);
static int snd_pcm_dev_disconnect(struct snd_device *device);

static struct snd_pcm *snd_pcm_get(struct snd_card *card, int device)
{
        struct snd_pcm *pcm;

        list_for_each_entry(pcm, &snd_pcm_devices, list) {
                if (pcm->card == card && pcm->device == device)
                        return pcm;
        }
        return NULL;
}

static int snd_pcm_next(struct snd_card *card, int device)
{
        struct snd_pcm *pcm;

        list_for_each_entry(pcm, &snd_pcm_devices, list) {
                if (pcm->card == card && pcm->device > device)
                        return pcm->device;
                else if (pcm->card->number > card->number)
                        return -1;
        }
        return -1;
}

static int snd_pcm_add(struct snd_pcm *newpcm)
{
        struct snd_pcm *pcm;

        if (newpcm->internal)
                return 0;

        list_for_each_entry(pcm, &snd_pcm_devices, list) {
                if (pcm->card == newpcm->card && pcm->device == newpcm->device)
                        return -EBUSY;
                if (pcm->card->number > newpcm->card->number ||
                                (pcm->card == newpcm->card &&
                                pcm->device > newpcm->device)) {
                        list_add(&newpcm->list, pcm->list.prev);
                        return 0;
                }
        }
        list_add_tail(&newpcm->list, &snd_pcm_devices);
        return 0;
}

static int snd_pcm_control_ioctl(struct snd_card *card,
                                 struct snd_ctl_file *control,
                                 unsigned int cmd, unsigned long arg)
{
        switch (cmd) {
        case SNDRV_CTL_IOCTL_PCM_NEXT_DEVICE:
                {
                        int device;

                        if (get_user(device, (int __user *)arg))
                                return -EFAULT;
                        scoped_guard(mutex, &register_mutex)
                                device = snd_pcm_next(card, device);
                        if (put_user(device, (int __user *)arg))
                                return -EFAULT;
                        return 0;
                }
        case SNDRV_CTL_IOCTL_PCM_INFO:
                {
                        struct snd_pcm_info __user *info;
                        unsigned int device, subdevice;
                        int stream;
                        struct snd_pcm *pcm;
                        struct snd_pcm_str *pstr;
                        struct snd_pcm_substream *substream;

                        info = (struct snd_pcm_info __user *)arg;
                        if (get_user(device, &info->device))
                                return -EFAULT;
                        if (get_user(stream, &info->stream))
                                return -EFAULT;
                        if (stream < 0 || stream > 1)
                                return -EINVAL;
                        stream = array_index_nospec(stream, 2);
                        if (get_user(subdevice, &info->subdevice))
                                return -EFAULT;
                        guard(mutex)(&register_mutex);
                        pcm = snd_pcm_get(card, device);
                        if (pcm == NULL)
                                return -ENXIO;
                        pstr = &pcm->streams[stream];
                        if (pstr->substream_count == 0)
                                return -ENOENT;
                        if (subdevice >= pstr->substream_count)
                                return -ENXIO;
                        for (substream = pstr->substream; substream;
                             substream = substream->next)
                                if (substream->number == (int)subdevice)
                                        break;
                        if (substream == NULL)
                                return -ENXIO;
                        guard(mutex)(&pcm->open_mutex);
                        return snd_pcm_info_user(substream, info);
                }
        case SNDRV_CTL_IOCTL_PCM_PREFER_SUBDEVICE:
                {
                        int val;
                        
                        if (get_user(val, (int __user *)arg))
                                return -EFAULT;
                        control->preferred_subdevice[SND_CTL_SUBDEV_PCM] = val;
                        return 0;
                }
        }
        return -ENOIOCTLCMD;
}

#define FORMAT(v) [SNDRV_PCM_FORMAT_##v] = #v

static const char * const snd_pcm_format_names[] = {
        FORMAT(S8),
        FORMAT(U8),
        FORMAT(S16_LE),
        FORMAT(S16_BE),
        FORMAT(U16_LE),
        FORMAT(U16_BE),
        FORMAT(S24_LE),
        FORMAT(S24_BE),
        FORMAT(U24_LE),
        FORMAT(U24_BE),
        FORMAT(S32_LE),
        FORMAT(S32_BE),
        FORMAT(U32_LE),
        FORMAT(U32_BE),
        FORMAT(FLOAT_LE),
        FORMAT(FLOAT_BE),
        FORMAT(FLOAT64_LE),
        FORMAT(FLOAT64_BE),
        FORMAT(IEC958_SUBFRAME_LE),
        FORMAT(IEC958_SUBFRAME_BE),
        FORMAT(MU_LAW),
        FORMAT(A_LAW),
        FORMAT(IMA_ADPCM),
        FORMAT(MPEG),
        FORMAT(GSM),
        FORMAT(SPECIAL),
        FORMAT(S24_3LE),
        FORMAT(S24_3BE),
        FORMAT(U24_3LE),
        FORMAT(U24_3BE),
        FORMAT(S20_3LE),
        FORMAT(S20_3BE),
        FORMAT(U20_3LE),
        FORMAT(U20_3BE),
        FORMAT(S18_3LE),
        FORMAT(S18_3BE),
        FORMAT(U18_3LE),
        FORMAT(U18_3BE),
        FORMAT(G723_24),
        FORMAT(G723_24_1B),
        FORMAT(G723_40),
        FORMAT(G723_40_1B),
        FORMAT(DSD_U8),
        FORMAT(DSD_U16_LE),
        FORMAT(DSD_U32_LE),
        FORMAT(DSD_U16_BE),
        FORMAT(DSD_U32_BE),
        FORMAT(S20_LE),
        FORMAT(S20_BE),
        FORMAT(U20_LE),
        FORMAT(U20_BE),
};

/**
 * snd_pcm_format_name - Return a name string for the given PCM format
 * @format: PCM format
 *
 * Return: the format name string
 */
const char *snd_pcm_format_name(snd_pcm_format_t format)
{
        unsigned int format_num = (__force unsigned int)format;

        if (format_num >= ARRAY_SIZE(snd_pcm_format_names) || !snd_pcm_format_names[format_num])
                return "Unknown";
        return snd_pcm_format_names[format_num];
}
EXPORT_SYMBOL_GPL(snd_pcm_format_name);

#ifdef CONFIG_SND_VERBOSE_PROCFS

#define STATE(v) [SNDRV_PCM_STATE_##v] = #v
#define STREAM(v) [SNDRV_PCM_STREAM_##v] = #v
#define READY(v) [SNDRV_PCM_READY_##v] = #v
#define XRUN(v) [SNDRV_PCM_XRUN_##v] = #v
#define SILENCE(v) [SNDRV_PCM_SILENCE_##v] = #v
#define TSTAMP(v) [SNDRV_PCM_TSTAMP_##v] = #v
#define ACCESS(v) [SNDRV_PCM_ACCESS_##v] = #v
#define START(v) [SNDRV_PCM_START_##v] = #v
#define SUBFORMAT(v) [SNDRV_PCM_SUBFORMAT_##v] = #v 

static const char * const snd_pcm_stream_names[] = {
        STREAM(PLAYBACK),
        STREAM(CAPTURE),
};

static const char * const snd_pcm_state_names[] = {
        STATE(OPEN),
        STATE(SETUP),
        STATE(PREPARED),
        STATE(RUNNING),
        STATE(XRUN),
        STATE(DRAINING),
        STATE(PAUSED),
        STATE(SUSPENDED),
        STATE(DISCONNECTED),
};

static const char * const snd_pcm_access_names[] = {
        ACCESS(MMAP_INTERLEAVED), 
        ACCESS(MMAP_NONINTERLEAVED),
        ACCESS(MMAP_COMPLEX),
        ACCESS(RW_INTERLEAVED),
        ACCESS(RW_NONINTERLEAVED),
};

static const char * const snd_pcm_subformat_names[] = {
        SUBFORMAT(STD), 
        SUBFORMAT(MSBITS_MAX),
        SUBFORMAT(MSBITS_20),
        SUBFORMAT(MSBITS_24),
};

static const char * const snd_pcm_tstamp_mode_names[] = {
        TSTAMP(NONE),
        TSTAMP(ENABLE),
};

static const char *snd_pcm_stream_name(int stream)
{
        return snd_pcm_stream_names[stream];
}

static const char *snd_pcm_access_name(snd_pcm_access_t access)
{
        return snd_pcm_access_names[(__force int)access];
}

static const char *snd_pcm_subformat_name(snd_pcm_subformat_t subformat)
{
        return snd_pcm_subformat_names[(__force int)subformat];
}

static const char *snd_pcm_tstamp_mode_name(int mode)
{
        return snd_pcm_tstamp_mode_names[mode];
}

static const char *snd_pcm_state_name(snd_pcm_state_t state)
{
        return snd_pcm_state_names[(__force int)state];
}

#if IS_ENABLED(CONFIG_SND_PCM_OSS)
#include <linux/soundcard.h>

static const char *snd_pcm_oss_format_name(int format)
{
        switch (format) {
        case AFMT_MU_LAW:
                return "MU_LAW";
        case AFMT_A_LAW:
                return "A_LAW";
        case AFMT_IMA_ADPCM:
                return "IMA_ADPCM";
        case AFMT_U8:
                return "U8";
        case AFMT_S16_LE:
                return "S16_LE";
        case AFMT_S16_BE:
                return "S16_BE";
        case AFMT_S8:
                return "S8";
        case AFMT_U16_LE:
                return "U16_LE";
        case AFMT_U16_BE:
                return "U16_BE";
        case AFMT_MPEG:
                return "MPEG";
        default:
                return "unknown";
        }
}
#endif

static void snd_pcm_proc_info_read(struct snd_pcm_substream *substream,
                                   struct snd_info_buffer *buffer)
{
        int err;

        if (! substream)
                return;

        struct snd_pcm_info *info __free(kfree) =
                kmalloc_obj(*info);
        if (!info)
                return;

        err = snd_pcm_info(substream, info);
        if (err < 0) {
                snd_iprintf(buffer, "error %d\n", err);
                return;
        }
        snd_iprintf(buffer, "card: %d\n", info->card);
        snd_iprintf(buffer, "device: %d\n", info->device);
        snd_iprintf(buffer, "subdevice: %d\n", info->subdevice);
        snd_iprintf(buffer, "stream: %s\n", snd_pcm_stream_name(info->stream));
        snd_iprintf(buffer, "id: %s\n", info->id);
        snd_iprintf(buffer, "name: %s\n", info->name);
        snd_iprintf(buffer, "subname: %s\n", info->subname);
        snd_iprintf(buffer, "class: %d\n", info->dev_class);
        snd_iprintf(buffer, "subclass: %d\n", info->dev_subclass);
        snd_iprintf(buffer, "subdevices_count: %d\n", info->subdevices_count);
        snd_iprintf(buffer, "subdevices_avail: %d\n", info->subdevices_avail);
}

static void snd_pcm_stream_proc_info_read(struct snd_info_entry *entry,
                                          struct snd_info_buffer *buffer)
{
        snd_pcm_proc_info_read(((struct snd_pcm_str *)entry->private_data)->substream,
                               buffer);
}

static void snd_pcm_substream_proc_info_read(struct snd_info_entry *entry,
                                             struct snd_info_buffer *buffer)
{
        snd_pcm_proc_info_read(entry->private_data, buffer);
}

static void snd_pcm_substream_proc_hw_params_read(struct snd_info_entry *entry,
                                                  struct snd_info_buffer *buffer)
{
        struct snd_pcm_substream *substream = entry->private_data;
        struct snd_pcm_runtime *runtime;

        guard(mutex)(&substream->pcm->open_mutex);
        runtime = substream->runtime;
        if (!runtime) {
                snd_iprintf(buffer, "closed\n");
                return;
        }
        if (runtime->state == SNDRV_PCM_STATE_OPEN) {
                snd_iprintf(buffer, "no setup\n");
                return;
        }
        snd_iprintf(buffer, "access: %s\n", snd_pcm_access_name(runtime->access));
        snd_iprintf(buffer, "format: %s\n", snd_pcm_format_name(runtime->format));
        snd_iprintf(buffer, "subformat: %s\n", snd_pcm_subformat_name(runtime->subformat));
        snd_iprintf(buffer, "channels: %u\n", runtime->channels);       
        snd_iprintf(buffer, "rate: %u (%u/%u)\n", runtime->rate, runtime->rate_num, runtime->rate_den); 
        snd_iprintf(buffer, "period_size: %lu\n", runtime->period_size);        
        snd_iprintf(buffer, "buffer_size: %lu\n", runtime->buffer_size);        
#if IS_ENABLED(CONFIG_SND_PCM_OSS)
        if (substream->oss.oss) {
                snd_iprintf(buffer, "OSS format: %s\n", snd_pcm_oss_format_name(runtime->oss.format));
                snd_iprintf(buffer, "OSS channels: %u\n", runtime->oss.channels);       
                snd_iprintf(buffer, "OSS rate: %u\n", runtime->oss.rate);
                snd_iprintf(buffer, "OSS period bytes: %lu\n", (unsigned long)runtime->oss.period_bytes);
                snd_iprintf(buffer, "OSS periods: %u\n", runtime->oss.periods);
                snd_iprintf(buffer, "OSS period frames: %lu\n", (unsigned long)runtime->oss.period_frames);
        }
#endif
}

static void snd_pcm_substream_proc_sw_params_read(struct snd_info_entry *entry,
                                                  struct snd_info_buffer *buffer)
{
        struct snd_pcm_substream *substream = entry->private_data;
        struct snd_pcm_runtime *runtime;

        guard(mutex)(&substream->pcm->open_mutex);
        runtime = substream->runtime;
        if (!runtime) {
                snd_iprintf(buffer, "closed\n");
                return;
        }
        if (runtime->state == SNDRV_PCM_STATE_OPEN) {
                snd_iprintf(buffer, "no setup\n");
                return;
        }
        snd_iprintf(buffer, "tstamp_mode: %s\n", snd_pcm_tstamp_mode_name(runtime->tstamp_mode));
        snd_iprintf(buffer, "period_step: %u\n", runtime->period_step);
        snd_iprintf(buffer, "avail_min: %lu\n", runtime->control->avail_min);
        snd_iprintf(buffer, "start_threshold: %lu\n", runtime->start_threshold);
        snd_iprintf(buffer, "stop_threshold: %lu\n", runtime->stop_threshold);
        snd_iprintf(buffer, "silence_threshold: %lu\n", runtime->silence_threshold);
        snd_iprintf(buffer, "silence_size: %lu\n", runtime->silence_size);
        snd_iprintf(buffer, "boundary: %lu\n", runtime->boundary);
}

static void snd_pcm_substream_proc_status_read(struct snd_info_entry *entry,
                                               struct snd_info_buffer *buffer)
{
        struct snd_pcm_substream *substream = entry->private_data;
        struct snd_pcm_runtime *runtime;
        struct snd_pcm_status64 status;
        int err;

        guard(mutex)(&substream->pcm->open_mutex);
        runtime = substream->runtime;
        if (!runtime) {
                snd_iprintf(buffer, "closed\n");
                return;
        }
        memset(&status, 0, sizeof(status));
        err = snd_pcm_status64(substream, &status);
        if (err < 0) {
                snd_iprintf(buffer, "error %d\n", err);
                return;
        }
        snd_iprintf(buffer, "state: %s\n", snd_pcm_state_name(status.state));
        snd_iprintf(buffer, "owner_pid   : %d\n", pid_vnr(substream->pid));
        snd_iprintf(buffer, "trigger_time: %lld.%09lld\n",
                status.trigger_tstamp_sec, status.trigger_tstamp_nsec);
        snd_iprintf(buffer, "tstamp      : %lld.%09lld\n",
                status.tstamp_sec, status.tstamp_nsec);
        snd_iprintf(buffer, "delay       : %ld\n", status.delay);
        snd_iprintf(buffer, "avail       : %ld\n", status.avail);
        snd_iprintf(buffer, "avail_max   : %ld\n", status.avail_max);
        snd_iprintf(buffer, "-----\n");
        snd_iprintf(buffer, "hw_ptr      : %ld\n", runtime->status->hw_ptr);
        snd_iprintf(buffer, "appl_ptr    : %ld\n", runtime->control->appl_ptr);
#ifdef CONFIG_SND_PCM_XRUN_DEBUG
        snd_iprintf(buffer, "xrun_counter: %d\n", substream->xrun_counter);
#endif
}

#ifdef CONFIG_SND_PCM_XRUN_DEBUG
static void snd_pcm_xrun_injection_write(struct snd_info_entry *entry,
                                         struct snd_info_buffer *buffer)
{
        struct snd_pcm_substream *substream = entry->private_data;

        snd_pcm_stop_xrun(substream);
}

static void snd_pcm_xrun_debug_read(struct snd_info_entry *entry,
                                    struct snd_info_buffer *buffer)
{
        struct snd_pcm_str *pstr = entry->private_data;
        snd_iprintf(buffer, "%d\n", pstr->xrun_debug);
}

static void snd_pcm_xrun_debug_write(struct snd_info_entry *entry,
                                     struct snd_info_buffer *buffer)
{
        struct snd_pcm_str *pstr = entry->private_data;
        char line[64];
        if (!snd_info_get_line(buffer, line, sizeof(line)))
                pstr->xrun_debug = simple_strtoul(line, NULL, 10);
}
#endif

static int snd_pcm_stream_proc_init(struct snd_pcm_str *pstr)
{
        struct snd_pcm *pcm = pstr->pcm;
        struct snd_info_entry *entry;
        char name[16];

        sprintf(name, "pcm%i%c", pcm->device, 
                pstr->stream == SNDRV_PCM_STREAM_PLAYBACK ? 'p' : 'c');
        entry = snd_info_create_card_entry(pcm->card, name,
                                           pcm->card->proc_root);
        if (!entry)
                return -ENOMEM;
        entry->mode = S_IFDIR | 0555;
        pstr->proc_root = entry;
        entry = snd_info_create_card_entry(pcm->card, "info", pstr->proc_root);
        if (entry)
                snd_info_set_text_ops(entry, pstr, snd_pcm_stream_proc_info_read);
#ifdef CONFIG_SND_PCM_XRUN_DEBUG
        entry = snd_info_create_card_entry(pcm->card, "xrun_debug",
                                           pstr->proc_root);
        if (entry) {
                snd_info_set_text_ops(entry, pstr, snd_pcm_xrun_debug_read);
                entry->c.text.write = snd_pcm_xrun_debug_write;
                entry->mode |= 0200;
        }
#endif
        return 0;
}

static int snd_pcm_stream_proc_done(struct snd_pcm_str *pstr)
{
        snd_info_free_entry(pstr->proc_root);
        pstr->proc_root = NULL;
        return 0;
}

static struct snd_info_entry *
create_substream_info_entry(struct snd_pcm_substream *substream,
                            const char *name,
                            void (*read)(struct snd_info_entry *,
                                         struct snd_info_buffer *))
{
        struct snd_info_entry *entry;

        entry = snd_info_create_card_entry(substream->pcm->card, name,
                                           substream->proc_root);
        if (entry)
                snd_info_set_text_ops(entry, substream, read);
        return entry;
}

static int snd_pcm_substream_proc_init(struct snd_pcm_substream *substream)
{
        struct snd_info_entry *entry;
        struct snd_card *card;
        char name[16];

        card = substream->pcm->card;

        sprintf(name, "sub%i", substream->number);
        entry = snd_info_create_card_entry(card, name,
                                           substream->pstr->proc_root);
        if (!entry)
                return -ENOMEM;
        entry->mode = S_IFDIR | 0555;
        substream->proc_root = entry;

        create_substream_info_entry(substream, "info",
                                    snd_pcm_substream_proc_info_read);
        create_substream_info_entry(substream, "hw_params",
                                    snd_pcm_substream_proc_hw_params_read);
        create_substream_info_entry(substream, "sw_params",
                                    snd_pcm_substream_proc_sw_params_read);
        create_substream_info_entry(substream, "status",
                                    snd_pcm_substream_proc_status_read);

#ifdef CONFIG_SND_PCM_XRUN_DEBUG
        entry = create_substream_info_entry(substream, "xrun_injection", NULL);
        if (entry) {
                entry->c.text.write = snd_pcm_xrun_injection_write;
                entry->mode = S_IFREG | 0200;
        }
#endif /* CONFIG_SND_PCM_XRUN_DEBUG */

        return 0;
}

#else /* !CONFIG_SND_VERBOSE_PROCFS */
static inline int snd_pcm_stream_proc_init(struct snd_pcm_str *pstr) { return 0; }
static inline int snd_pcm_stream_proc_done(struct snd_pcm_str *pstr) { return 0; }
static inline int snd_pcm_substream_proc_init(struct snd_pcm_substream *substream) { return 0; }
#endif /* CONFIG_SND_VERBOSE_PROCFS */

static const struct attribute_group *pcm_dev_attr_groups[];

/*
 * PM callbacks: we need to deal only with suspend here, as the resume is
 * triggered either from user-space or the driver's resume callback
 */
static int do_pcm_suspend(struct device *dev)
{
        struct snd_pcm_str *pstr = dev_get_drvdata(dev);

        if (!pstr->pcm->no_device_suspend)
                snd_pcm_suspend_all(pstr->pcm);
        return 0;
}

static const struct dev_pm_ops pcm_dev_pm_ops = {
        SYSTEM_SLEEP_PM_OPS(do_pcm_suspend, NULL)
};

/* device type for PCM -- basically only for passing PM callbacks */
static const struct device_type pcm_dev_type = {
        .name = "pcm",
        .pm = &pcm_dev_pm_ops,
};

/**
 * snd_pcm_new_stream - create a new PCM stream
 * @pcm: the pcm instance
 * @stream: the stream direction, SNDRV_PCM_STREAM_XXX
 * @substream_count: the number of substreams
 *
 * Creates a new stream for the pcm.
 * The corresponding stream on the pcm must have been empty before
 * calling this, i.e. zero must be given to the argument of
 * snd_pcm_new().
 *
 * Return: Zero if successful, or a negative error code on failure.
 */
int snd_pcm_new_stream(struct snd_pcm *pcm, int stream, int substream_count)
{
        int idx, err;
        struct snd_pcm_str *pstr = &pcm->streams[stream];
        struct snd_pcm_substream *substream, *prev;

#if IS_ENABLED(CONFIG_SND_PCM_OSS)
        mutex_init(&pstr->oss.setup_mutex);
#endif
        pstr->stream = stream;
        pstr->pcm = pcm;
        pstr->substream_count = substream_count;
        if (!substream_count)
                return 0;

        err = snd_device_alloc(&pstr->dev, pcm->card);
        if (err < 0)
                return err;
        dev_set_name(pstr->dev, "pcmC%iD%i%c", pcm->card->number, pcm->device,
                     stream == SNDRV_PCM_STREAM_PLAYBACK ? 'p' : 'c');
        pstr->dev->groups = pcm_dev_attr_groups;
        pstr->dev->type = &pcm_dev_type;
        dev_set_drvdata(pstr->dev, pstr);

        if (!pcm->internal) {
                err = snd_pcm_stream_proc_init(pstr);
                if (err < 0) {
                        pcm_err(pcm, "Error in snd_pcm_stream_proc_init\n");
                        return err;
                }
        }
        prev = NULL;
        for (idx = 0, prev = NULL; idx < substream_count; idx++) {
                substream = kzalloc_obj(*substream);
                if (!substream)
                        return -ENOMEM;
                substream->pcm = pcm;
                substream->pstr = pstr;
                substream->number = idx;
                substream->stream = stream;
                sprintf(substream->name, "subdevice #%i", idx);
                substream->buffer_bytes_max = UINT_MAX;
                if (prev == NULL)
                        pstr->substream = substream;
                else
                        prev->next = substream;

                if (!pcm->internal) {
                        err = snd_pcm_substream_proc_init(substream);
                        if (err < 0) {
                                pcm_err(pcm,
                                        "Error in snd_pcm_stream_proc_init\n");
                                if (prev == NULL)
                                        pstr->substream = NULL;
                                else
                                        prev->next = NULL;
                                kfree(substream);
                                return err;
                        }
                }
                substream->group = &substream->self_group;
                snd_pcm_group_init(&substream->self_group);
                list_add_tail(&substream->link_list, &substream->self_group.substreams);
                atomic_set(&substream->mmap_count, 0);
                prev = substream;
        }
        return 0;
}                               
EXPORT_SYMBOL(snd_pcm_new_stream);

static int _snd_pcm_new(struct snd_card *card, const char *id, int device,
                int playback_count, int capture_count, bool internal,
                struct snd_pcm **rpcm)
{
        struct snd_pcm *pcm;
        int err;
        static const struct snd_device_ops ops = {
                .dev_free = snd_pcm_dev_free,
                .dev_register = snd_pcm_dev_register,
                .dev_disconnect = snd_pcm_dev_disconnect,
        };
        static const struct snd_device_ops internal_ops = {
                .dev_free = snd_pcm_dev_free,
        };

        if (snd_BUG_ON(!card))
                return -ENXIO;
        if (rpcm)
                *rpcm = NULL;
        pcm = kzalloc_obj(*pcm);
        if (!pcm)
                return -ENOMEM;
        pcm->card = card;
        pcm->device = device;
        pcm->internal = internal;
        mutex_init(&pcm->open_mutex);
        init_waitqueue_head(&pcm->open_wait);
        INIT_LIST_HEAD(&pcm->list);
        if (id)
                strscpy(pcm->id, id, sizeof(pcm->id));

        err = snd_pcm_new_stream(pcm, SNDRV_PCM_STREAM_PLAYBACK,
                                 playback_count);
        if (err < 0)
                goto free_pcm;

        err = snd_pcm_new_stream(pcm, SNDRV_PCM_STREAM_CAPTURE, capture_count);
        if (err < 0)
                goto free_pcm;

        err = snd_device_new(card, SNDRV_DEV_PCM, pcm,
                             internal ? &internal_ops : &ops);
        if (err < 0)
                goto free_pcm;

        if (rpcm)
                *rpcm = pcm;
        return 0;

free_pcm:
        snd_pcm_free(pcm);
        return err;
}

/**
 * snd_pcm_new - create a new PCM instance
 * @card: the card instance
 * @id: the id string
 * @device: the device index (zero based)
 * @playback_count: the number of substreams for playback
 * @capture_count: the number of substreams for capture
 * @rpcm: the pointer to store the new pcm instance
 *
 * Creates a new PCM instance.
 *
 * The pcm operators have to be set afterwards to the new instance
 * via snd_pcm_set_ops().
 *
 * Return: Zero if successful, or a negative error code on failure.
 */
int snd_pcm_new(struct snd_card *card, const char *id, int device,
                int playback_count, int capture_count, struct snd_pcm **rpcm)
{
        return _snd_pcm_new(card, id, device, playback_count, capture_count,
                        false, rpcm);
}
EXPORT_SYMBOL(snd_pcm_new);

/**
 * snd_pcm_new_internal - create a new internal PCM instance
 * @card: the card instance
 * @id: the id string
 * @device: the device index (zero based - shared with normal PCMs)
 * @playback_count: the number of substreams for playback
 * @capture_count: the number of substreams for capture
 * @rpcm: the pointer to store the new pcm instance
 *
 * Creates a new internal PCM instance with no userspace device or procfs
 * entries. This is used by ASoC Back End PCMs in order to create a PCM that
 * will only be used internally by kernel drivers. i.e. it cannot be opened
 * by userspace. It provides existing ASoC components drivers with a substream
 * and access to any private data.
 *
 * The pcm operators have to be set afterwards to the new instance
 * via snd_pcm_set_ops().
 *
 * Return: Zero if successful, or a negative error code on failure.
 */
int snd_pcm_new_internal(struct snd_card *card, const char *id, int device,
        int playback_count, int capture_count,
        struct snd_pcm **rpcm)
{
        return _snd_pcm_new(card, id, device, playback_count, capture_count,
                        true, rpcm);
}
EXPORT_SYMBOL(snd_pcm_new_internal);

static void free_chmap(struct snd_pcm_str *pstr)
{
        if (pstr->chmap_kctl) {
                struct snd_card *card = pstr->pcm->card;

                snd_ctl_remove(card, pstr->chmap_kctl);
                pstr->chmap_kctl = NULL;
        }
}

static void snd_pcm_free_stream(struct snd_pcm_str * pstr)
{
        struct snd_pcm_substream *substream, *substream_next;
#if IS_ENABLED(CONFIG_SND_PCM_OSS)
        struct snd_pcm_oss_setup *setup, *setupn;
#endif

        /* free all proc files under the stream */
        snd_pcm_stream_proc_done(pstr);

        substream = pstr->substream;
        while (substream) {
                substream_next = substream->next;
                snd_pcm_timer_done(substream);
                kfree(substream);
                substream = substream_next;
        }
#if IS_ENABLED(CONFIG_SND_PCM_OSS)
        for (setup = pstr->oss.setup_list; setup; setup = setupn) {
                setupn = setup->next;
                kfree(setup->task_name);
                kfree(setup);
        }
#endif
        free_chmap(pstr);
        if (pstr->substream_count)
                put_device(pstr->dev);
}

#if IS_ENABLED(CONFIG_SND_PCM_OSS)
#define pcm_call_notify(pcm, call)                                      \
        do {                                                            \
                struct snd_pcm_notify *_notify;                         \
                list_for_each_entry(_notify, &snd_pcm_notify_list, list) \
                        _notify->call(pcm);                             \
        } while (0)
#else
#define pcm_call_notify(pcm, call) do {} while (0)
#endif

static int snd_pcm_free(struct snd_pcm *pcm)
{
        if (!pcm)
                return 0;
        if (!pcm->internal)
                pcm_call_notify(pcm, n_unregister);
        if (pcm->private_free)
                pcm->private_free(pcm);
        snd_pcm_lib_preallocate_free_for_all(pcm);
        snd_pcm_free_stream(&pcm->streams[SNDRV_PCM_STREAM_PLAYBACK]);
        snd_pcm_free_stream(&pcm->streams[SNDRV_PCM_STREAM_CAPTURE]);
        kfree(pcm);
        return 0;
}

static int snd_pcm_dev_free(struct snd_device *device)
{
        struct snd_pcm *pcm = device->device_data;
        return snd_pcm_free(pcm);
}

int snd_pcm_attach_substream(struct snd_pcm *pcm, int stream,
                             struct file *file,
                             struct snd_pcm_substream **rsubstream)
{
        struct snd_pcm_str * pstr;
        struct snd_pcm_substream *substream;
        struct snd_pcm_runtime *runtime;
        struct snd_card *card;
        int prefer_subdevice;
        size_t size;

        if (snd_BUG_ON(!pcm || !rsubstream))
                return -ENXIO;
        if (snd_BUG_ON(stream != SNDRV_PCM_STREAM_PLAYBACK &&
                       stream != SNDRV_PCM_STREAM_CAPTURE))
                return -EINVAL;
        *rsubstream = NULL;
        pstr = &pcm->streams[stream];
        if (pstr->substream == NULL || pstr->substream_count == 0)
                return -ENODEV;

        card = pcm->card;
        prefer_subdevice = snd_ctl_get_preferred_subdevice(card, SND_CTL_SUBDEV_PCM);

        if (pcm->info_flags & SNDRV_PCM_INFO_HALF_DUPLEX) {
                int opposite = !stream;

                for (substream = pcm->streams[opposite].substream; substream;
                     substream = substream->next) {
                        if (SUBSTREAM_BUSY(substream))
                                return -EAGAIN;
                }
        }

        if (file->f_flags & O_APPEND) {
                if (prefer_subdevice < 0) {
                        if (pstr->substream_count > 1)
                                return -EINVAL; /* must be unique */
                        substream = pstr->substream;
                } else {
                        for (substream = pstr->substream; substream;
                             substream = substream->next)
                                if (substream->number == prefer_subdevice)
                                        break;
                }
                if (! substream)
                        return -ENODEV;
                if (! SUBSTREAM_BUSY(substream))
                        return -EBADFD;
                substream->ref_count++;
                *rsubstream = substream;
                return 0;
        }

        for (substream = pstr->substream; substream; substream = substream->next) {
                if (!SUBSTREAM_BUSY(substream) &&
                    (prefer_subdevice == -1 ||
                     substream->number == prefer_subdevice))
                        break;
        }
        if (substream == NULL)
                return -EAGAIN;

        runtime = kzalloc_obj(*runtime);
        if (runtime == NULL)
                return -ENOMEM;

        size = PAGE_ALIGN(sizeof(struct snd_pcm_mmap_status));
        runtime->status = alloc_pages_exact(size, GFP_KERNEL);
        if (runtime->status == NULL) {
                kfree(runtime);
                return -ENOMEM;
        }
        memset(runtime->status, 0, size);

        size = PAGE_ALIGN(sizeof(struct snd_pcm_mmap_control));
        runtime->control = alloc_pages_exact(size, GFP_KERNEL);
        if (runtime->control == NULL) {
                free_pages_exact(runtime->status,
                               PAGE_ALIGN(sizeof(struct snd_pcm_mmap_status)));
                kfree(runtime);
                return -ENOMEM;
        }
        memset(runtime->control, 0, size);

        init_waitqueue_head(&runtime->sleep);
        init_waitqueue_head(&runtime->tsleep);

        __snd_pcm_set_state(runtime, SNDRV_PCM_STATE_OPEN);
        mutex_init(&runtime->buffer_mutex);
        atomic_set(&runtime->buffer_accessing, 0);

        substream->runtime = runtime;
        substream->private_data = pcm->private_data;
        substream->ref_count = 1;
        substream->f_flags = file->f_flags;
        substream->pid = get_pid(task_pid(current));
        pstr->substream_opened++;
        *rsubstream = substream;
#ifdef CONFIG_SND_PCM_XRUN_DEBUG
        substream->xrun_counter = 0;
#endif /* CONFIG_SND_PCM_XRUN_DEBUG */
        return 0;
}

void snd_pcm_detach_substream(struct snd_pcm_substream *substream)
{
        struct snd_pcm_runtime *runtime;

        if (PCM_RUNTIME_CHECK(substream))
                return;
        runtime = substream->runtime;
        if (runtime->private_free != NULL)
                runtime->private_free(runtime);
        free_pages_exact(runtime->status,
                       PAGE_ALIGN(sizeof(struct snd_pcm_mmap_status)));
        free_pages_exact(runtime->control,
                       PAGE_ALIGN(sizeof(struct snd_pcm_mmap_control)));
        kfree(runtime->hw_constraints.rules);
        /* Avoid concurrent access to runtime via PCM timer interface */
        if (substream->timer) {
                scoped_guard(spinlock_irq, &substream->timer->lock)
                        substream->runtime = NULL;
        } else {
                substream->runtime = NULL;
        }
        mutex_destroy(&runtime->buffer_mutex);
        snd_fasync_free(runtime->fasync);
        kfree(runtime);
        put_pid(substream->pid);
        substream->pid = NULL;
        substream->pstr->substream_opened--;
}

static ssize_t pcm_class_show(struct device *dev,
                              struct device_attribute *attr, char *buf)
{
        struct snd_pcm_str *pstr = dev_get_drvdata(dev);
        struct snd_pcm *pcm = pstr->pcm;
        const char *str;
        static const char *strs[SNDRV_PCM_CLASS_LAST + 1] = {
                [SNDRV_PCM_CLASS_GENERIC] = "generic",
                [SNDRV_PCM_CLASS_MULTI] = "multi",
                [SNDRV_PCM_CLASS_MODEM] = "modem",
                [SNDRV_PCM_CLASS_DIGITIZER] = "digitizer",
        };

        if (pcm->dev_class > SNDRV_PCM_CLASS_LAST)
                str = "none";
        else
                str = strs[pcm->dev_class];
        return sysfs_emit(buf, "%s\n", str);
}

static DEVICE_ATTR_RO(pcm_class);
static struct attribute *pcm_dev_attrs[] = {
        &dev_attr_pcm_class.attr,
        NULL
};

static const struct attribute_group pcm_dev_attr_group = {
        .attrs  = pcm_dev_attrs,
};

static const struct attribute_group *pcm_dev_attr_groups[] = {
        &pcm_dev_attr_group,
        NULL
};

static int snd_pcm_dev_register(struct snd_device *device)
{
        int cidx, err;
        struct snd_pcm_substream *substream;
        struct snd_pcm *pcm;

        if (snd_BUG_ON(!device || !device->device_data))
                return -ENXIO;
        pcm = device->device_data;

        guard(mutex)(&register_mutex);
        err = snd_pcm_add(pcm);
        if (err)
                return err;
        for (cidx = 0; cidx < 2; cidx++) {
                int devtype = -1;
                if (pcm->streams[cidx].substream == NULL)
                        continue;
                switch (cidx) {
                case SNDRV_PCM_STREAM_PLAYBACK:
                        devtype = SNDRV_DEVICE_TYPE_PCM_PLAYBACK;
                        break;
                case SNDRV_PCM_STREAM_CAPTURE:
                        devtype = SNDRV_DEVICE_TYPE_PCM_CAPTURE;
                        break;
                }
                /* register pcm */
                err = snd_register_device(devtype, pcm->card, pcm->device,
                                          &snd_pcm_f_ops[cidx], pcm,
                                          pcm->streams[cidx].dev);
                if (err < 0) {
                        list_del_init(&pcm->list);
                        return err;
                }

                for (substream = pcm->streams[cidx].substream; substream; substream = substream->next)
                        snd_pcm_timer_init(substream);
        }

        pcm_call_notify(pcm, n_register);
        return err;
}

static int snd_pcm_dev_disconnect(struct snd_device *device)
{
        struct snd_pcm *pcm = device->device_data;
        struct snd_pcm_substream *substream;
        int cidx;

        guard(mutex)(&register_mutex);
        guard(mutex)(&pcm->open_mutex);
        wake_up(&pcm->open_wait);
        list_del_init(&pcm->list);

        for_each_pcm_substream(pcm, cidx, substream) {
                snd_pcm_stream_lock_irq(substream);
                if (substream->runtime) {
                        if (snd_pcm_running(substream))
                                snd_pcm_stop(substream, SNDRV_PCM_STATE_DISCONNECTED);
                        /* to be sure, set the state unconditionally */
                        __snd_pcm_set_state(substream->runtime,
                                            SNDRV_PCM_STATE_DISCONNECTED);
                        wake_up(&substream->runtime->sleep);
                        wake_up(&substream->runtime->tsleep);
                }
                snd_pcm_stream_unlock_irq(substream);
        }

        for_each_pcm_substream(pcm, cidx, substream)
                snd_pcm_sync_stop(substream, false);

        pcm_call_notify(pcm, n_disconnect);
        for (cidx = 0; cidx < 2; cidx++) {
                if (pcm->streams[cidx].dev)
                        snd_unregister_device(pcm->streams[cidx].dev);
                free_chmap(&pcm->streams[cidx]);
        }
        return 0;
}

#if IS_ENABLED(CONFIG_SND_PCM_OSS)
/**
 * snd_pcm_notify - Add/remove the notify list
 * @notify: PCM notify list
 * @nfree: 0 = register, 1 = unregister
 *
 * This adds the given notifier to the global list so that the callback is
 * called for each registered PCM devices.  This exists only for PCM OSS
 * emulation, so far.
 *
 * Return: zero if successful, or a negative error code
 */
int snd_pcm_notify(struct snd_pcm_notify *notify, int nfree)
{
        struct snd_pcm *pcm;

        if (snd_BUG_ON(!notify ||
                       !notify->n_register ||
                       !notify->n_unregister ||
                       !notify->n_disconnect))
                return -EINVAL;
        guard(mutex)(&register_mutex);
        if (nfree) {
                list_del(&notify->list);
                list_for_each_entry(pcm, &snd_pcm_devices, list)
                        notify->n_unregister(pcm);
        } else {
                list_add_tail(&notify->list, &snd_pcm_notify_list);
                list_for_each_entry(pcm, &snd_pcm_devices, list)
                        notify->n_register(pcm);
        }
        return 0;
}
EXPORT_SYMBOL(snd_pcm_notify);
#endif /* CONFIG_SND_PCM_OSS */

#ifdef CONFIG_SND_PROC_FS
/*
 *  Info interface
 */

static void snd_pcm_proc_read(struct snd_info_entry *entry,
                              struct snd_info_buffer *buffer)
{
        struct snd_pcm *pcm;

        guard(mutex)(&register_mutex);
        list_for_each_entry(pcm, &snd_pcm_devices, list) {
                snd_iprintf(buffer, "%02i-%02i: %s : %s",
                            pcm->card->number, pcm->device, pcm->id, pcm->name);
                if (pcm->streams[SNDRV_PCM_STREAM_PLAYBACK].substream)
                        snd_iprintf(buffer, " : playback %i",
                                    pcm->streams[SNDRV_PCM_STREAM_PLAYBACK].substream_count);
                if (pcm->streams[SNDRV_PCM_STREAM_CAPTURE].substream)
                        snd_iprintf(buffer, " : capture %i",
                                    pcm->streams[SNDRV_PCM_STREAM_CAPTURE].substream_count);
                snd_iprintf(buffer, "\n");
        }
}

static struct snd_info_entry *snd_pcm_proc_entry;

static void snd_pcm_proc_init(void)
{
        struct snd_info_entry *entry;

        entry = snd_info_create_module_entry(THIS_MODULE, "pcm", NULL);
        if (entry) {
                snd_info_set_text_ops(entry, NULL, snd_pcm_proc_read);
                if (snd_info_register(entry) < 0) {
                        snd_info_free_entry(entry);
                        entry = NULL;
                }
        }
        snd_pcm_proc_entry = entry;
}

static void snd_pcm_proc_done(void)
{
        snd_info_free_entry(snd_pcm_proc_entry);
}

#else /* !CONFIG_SND_PROC_FS */
#define snd_pcm_proc_init()
#define snd_pcm_proc_done()
#endif /* CONFIG_SND_PROC_FS */


/*
 *  ENTRY functions
 */

static int __init alsa_pcm_init(void)
{
        snd_ctl_register_ioctl(snd_pcm_control_ioctl);
        snd_ctl_register_ioctl_compat(snd_pcm_control_ioctl);
        snd_pcm_proc_init();
        return 0;
}

static void __exit alsa_pcm_exit(void)
{
        snd_ctl_unregister_ioctl(snd_pcm_control_ioctl);
        snd_ctl_unregister_ioctl_compat(snd_pcm_control_ioctl);
        snd_pcm_proc_done();
}

module_init(alsa_pcm_init)
module_exit(alsa_pcm_exit)