// SPDX-License-Identifier: GPL-2.0-or-later
/*
 *  Initialization routines
 *  Copyright (c) by Jaroslav Kysela <perex@perex.cz>
 */

#include <linux/init.h>
#include <linux/sched.h>
#include <linux/module.h>
#include <linux/device.h>
#include <linux/file.h>
#include <linux/slab.h>
#include <linux/time.h>
#include <linux/ctype.h>
#include <linux/pm.h>
#include <linux/debugfs.h>
#include <linux/completion.h>
#include <linux/interrupt.h>

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

/* monitor files for graceful shutdown (hotplug) */
struct snd_monitor_file {
        struct file *file;
        const struct file_operations *disconnected_f_op;
        struct list_head shutdown_list; /* still need to shutdown */
        struct list_head list;  /* link of monitor files */
};

static DEFINE_SPINLOCK(shutdown_lock);
static LIST_HEAD(shutdown_files);

static const struct file_operations snd_shutdown_f_ops;

/* locked for registering/using */
static DECLARE_BITMAP(snd_cards_lock, SNDRV_CARDS);
static struct snd_card *snd_cards[SNDRV_CARDS];

static DEFINE_MUTEX(snd_card_mutex);

static char *slots[SNDRV_CARDS];
module_param_array(slots, charp, NULL, 0444);
MODULE_PARM_DESC(slots, "Module names assigned to the slots.");

/* return non-zero if the given index is reserved for the given
 * module via slots option
 */
static int module_slot_match(struct module *module, int idx)
{
        int match = 1;
#ifdef MODULE
        const char *s1, *s2;

        if (!module || !*module->name || !slots[idx])
                return 0;

        s1 = module->name;
        s2 = slots[idx];
        if (*s2 == '!') {
                match = 0; /* negative match */
                s2++;
        }
        /* compare module name strings
         * hyphens are handled as equivalent with underscore
         */
        for (;;) {
                char c1 = *s1++;
                char c2 = *s2++;
                if (c1 == '-')
                        c1 = '_';
                if (c2 == '-')
                        c2 = '_';
                if (c1 != c2)
                        return !match;
                if (!c1)
                        break;
        }
#endif /* MODULE */
        return match;
}

#if IS_ENABLED(CONFIG_SND_MIXER_OSS)
int (*snd_mixer_oss_notify_callback)(struct snd_card *card, int free_flag);
EXPORT_SYMBOL(snd_mixer_oss_notify_callback);
#endif

static int check_empty_slot(struct module *module, int slot)
{
        return !slots[slot] || !*slots[slot];
}

/* return an empty slot number (>= 0) found in the given bitmask @mask.
 * @mask == -1 == 0xffffffff means: take any free slot up to 32
 * when no slot is available, return the original @mask as is.
 */
static int get_slot_from_bitmask(int mask, int (*check)(struct module *, int),
                                 struct module *module)
{
        int slot;

        for (slot = 0; slot < SNDRV_CARDS; slot++) {
                if (slot < 32 && !(mask & (1U << slot)))
                        continue;
                if (!test_bit(slot, snd_cards_lock)) {
                        if (check(module, slot))
                                return slot; /* found */
                }
        }
        return mask; /* unchanged */
}

/* the default release callback set in snd_device_initialize() below;
 * this is just NOP for now, as almost all jobs are already done in
 * dev_free callback of snd_device chain instead.
 */
static void default_release(struct device *dev)
{
}

/**
 * snd_device_initialize - Initialize struct device for sound devices
 * @dev: device to initialize
 * @card: card to assign, optional
 */
void snd_device_initialize(struct device *dev, struct snd_card *card)
{
        device_initialize(dev);
        if (card)
                dev->parent = &card->card_dev;
        dev->class = sound_class;
        dev->release = default_release;
}
EXPORT_SYMBOL_GPL(snd_device_initialize);

static int snd_card_init(struct snd_card *card, struct device *parent,
                         int idx, const char *xid, struct module *module,
                         size_t extra_size);
static int snd_card_do_free(struct snd_card *card);
static const struct attribute_group card_dev_attr_group;

static void release_card_device(struct device *dev)
{
        snd_card_do_free(dev_to_snd_card(dev));
}

/**
 *  snd_card_new - create and initialize a soundcard structure
 *  @parent: the parent device object
 *  @idx: card index (address) [0 ... (SNDRV_CARDS-1)]
 *  @xid: card identification (ASCII string)
 *  @module: top level module for locking
 *  @extra_size: allocate this extra size after the main soundcard structure
 *  @card_ret: the pointer to store the created card instance
 *
 *  The function allocates snd_card instance via kzalloc with the given
 *  space for the driver to use freely.  The allocated struct is stored
 *  in the given card_ret pointer.
 *
 *  Return: Zero if successful or a negative error code.
 */
int snd_card_new(struct device *parent, int idx, const char *xid,
                    struct module *module, int extra_size,
                    struct snd_card **card_ret)
{
        struct snd_card *card;
        int err;

        if (snd_BUG_ON(!card_ret))
                return -EINVAL;
        *card_ret = NULL;

        if (extra_size < 0)
                extra_size = 0;
        card = kzalloc(sizeof(*card) + extra_size, GFP_KERNEL);
        if (!card)
                return -ENOMEM;

        err = snd_card_init(card, parent, idx, xid, module, extra_size);
        if (err < 0) {
                kfree(card);
                return err;
        }

        *card_ret = card;
        return 0;
}
EXPORT_SYMBOL(snd_card_new);

static void __snd_card_release(struct device *dev, void *data)
{
        snd_card_free(data);
}

/**
 * snd_devm_card_new - managed snd_card object creation
 * @parent: the parent device object
 * @idx: card index (address) [0 ... (SNDRV_CARDS-1)]
 * @xid: card identification (ASCII string)
 * @module: top level module for locking
 * @extra_size: allocate this extra size after the main soundcard structure
 * @card_ret: the pointer to store the created card instance
 *
 * This function works like snd_card_new() but manages the allocated resource
 * via devres, i.e. you don't need to free explicitly.
 *
 * When a snd_card object is created with this function and registered via
 * snd_card_register(), the very first devres action to call snd_card_free()
 * is added automatically.  In that way, the resource disconnection is assured
 * at first, then released in the expected order.
 */
int snd_devm_card_new(struct device *parent, int idx, const char *xid,
                      struct module *module, size_t extra_size,
                      struct snd_card **card_ret)
{
        struct snd_card *card;
        int err;

        *card_ret = NULL;
        card = devres_alloc(__snd_card_release, sizeof(*card) + extra_size,
                            GFP_KERNEL);
        if (!card)
                return -ENOMEM;
        card->managed = true;
        err = snd_card_init(card, parent, idx, xid, module, extra_size);
        if (err < 0) {
                devres_free(card);
                return err;
        }

        devres_add(parent, card);
        *card_ret = card;
        return 0;
}
EXPORT_SYMBOL_GPL(snd_devm_card_new);

static int snd_card_init(struct snd_card *card, struct device *parent,
                         int idx, const char *xid, struct module *module,
                         size_t extra_size)
{
        int err;
#ifdef CONFIG_SND_DEBUG
        char name[8];
#endif

        if (extra_size > 0)
                card->private_data = (char *)card + sizeof(struct snd_card);
        if (xid)
                strscpy(card->id, xid, sizeof(card->id));
        err = 0;
        mutex_lock(&snd_card_mutex);
        if (idx < 0) /* first check the matching module-name slot */
                idx = get_slot_from_bitmask(idx, module_slot_match, module);
        if (idx < 0) /* if not matched, assign an empty slot */
                idx = get_slot_from_bitmask(idx, check_empty_slot, module);
        if (idx < 0)
                err = -ENODEV;
        else if (idx < snd_ecards_limit) {
                if (test_bit(idx, snd_cards_lock))
                        err = -EBUSY;   /* invalid */
        } else if (idx >= SNDRV_CARDS)
                err = -ENODEV;
        if (err < 0) {
                mutex_unlock(&snd_card_mutex);
                dev_err(parent, "cannot find the slot for index %d (range 0-%i), error: %d\n",
                         idx, snd_ecards_limit - 1, err);
                return err;
        }
        set_bit(idx, snd_cards_lock);           /* lock it */
        if (idx >= snd_ecards_limit)
                snd_ecards_limit = idx + 1; /* increase the limit */
        mutex_unlock(&snd_card_mutex);
        card->dev = parent;
        card->number = idx;
#ifdef MODULE
        WARN_ON(!module);
        card->module = module;
#endif
        INIT_LIST_HEAD(&card->devices);
        init_rwsem(&card->controls_rwsem);
        rwlock_init(&card->ctl_files_rwlock);
        INIT_LIST_HEAD(&card->controls);
        INIT_LIST_HEAD(&card->ctl_files);
        spin_lock_init(&card->files_lock);
        INIT_LIST_HEAD(&card->files_list);
        mutex_init(&card->memory_mutex);
#ifdef CONFIG_PM
        init_waitqueue_head(&card->power_sleep);
        init_waitqueue_head(&card->power_ref_sleep);
        atomic_set(&card->power_ref, 0);
#endif
        init_waitqueue_head(&card->remove_sleep);
        card->sync_irq = -1;

        device_initialize(&card->card_dev);
        card->card_dev.parent = parent;
        card->card_dev.class = sound_class;
        card->card_dev.release = release_card_device;
        card->card_dev.groups = card->dev_groups;
        card->dev_groups[0] = &card_dev_attr_group;
        err = kobject_set_name(&card->card_dev.kobj, "card%d", idx);
        if (err < 0)
                goto __error;

        snprintf(card->irq_descr, sizeof(card->irq_descr), "%s:%s",
                 dev_driver_string(card->dev), dev_name(&card->card_dev));

        /* the control interface cannot be accessed from the user space until */
        /* snd_cards_bitmask and snd_cards are set with snd_card_register */
        err = snd_ctl_create(card);
        if (err < 0) {
                dev_err(parent, "unable to register control minors\n");
                goto __error;
        }
        err = snd_info_card_create(card);
        if (err < 0) {
                dev_err(parent, "unable to create card info\n");
                goto __error_ctl;
        }

#ifdef CONFIG_SND_DEBUG
        sprintf(name, "card%d", idx);
        card->debugfs_root = debugfs_create_dir(name, sound_debugfs_root);
#endif
        return 0;

      __error_ctl:
        snd_device_free_all(card);
      __error:
        put_device(&card->card_dev);
        return err;
}

/**
 * snd_card_ref - Get the card object from the index
 * @idx: the card index
 *
 * Returns a card object corresponding to the given index or NULL if not found.
 * Release the object via snd_card_unref().
 */
struct snd_card *snd_card_ref(int idx)
{
        struct snd_card *card;

        mutex_lock(&snd_card_mutex);
        card = snd_cards[idx];
        if (card)
                get_device(&card->card_dev);
        mutex_unlock(&snd_card_mutex);
        return card;
}
EXPORT_SYMBOL_GPL(snd_card_ref);

/* return non-zero if a card is already locked */
int snd_card_locked(int card)
{
        int locked;

        mutex_lock(&snd_card_mutex);
        locked = test_bit(card, snd_cards_lock);
        mutex_unlock(&snd_card_mutex);
        return locked;
}

static loff_t snd_disconnect_llseek(struct file *file, loff_t offset, int orig)
{
        return -ENODEV;
}

static ssize_t snd_disconnect_read(struct file *file, char __user *buf,
                                   size_t count, loff_t *offset)
{
        return -ENODEV;
}

static ssize_t snd_disconnect_write(struct file *file, const char __user *buf,
                                    size_t count, loff_t *offset)
{
        return -ENODEV;
}

static int snd_disconnect_release(struct inode *inode, struct file *file)
{
        struct snd_monitor_file *df = NULL, *_df;

        spin_lock(&shutdown_lock);
        list_for_each_entry(_df, &shutdown_files, shutdown_list) {
                if (_df->file == file) {
                        df = _df;
                        list_del_init(&df->shutdown_list);
                        break;
                }
        }
        spin_unlock(&shutdown_lock);

        if (likely(df)) {
                if ((file->f_flags & FASYNC) && df->disconnected_f_op->fasync)
                        df->disconnected_f_op->fasync(-1, file, 0);
                return df->disconnected_f_op->release(inode, file);
        }

        panic("%s(%p, %p) failed!", __func__, inode, file);
}

static __poll_t snd_disconnect_poll(struct file * file, poll_table * wait)
{
        return EPOLLERR | EPOLLNVAL;
}

static long snd_disconnect_ioctl(struct file *file,
                                 unsigned int cmd, unsigned long arg)
{
        return -ENODEV;
}

static int snd_disconnect_mmap(struct file *file, struct vm_area_struct *vma)
{
        return -ENODEV;
}

static int snd_disconnect_fasync(int fd, struct file *file, int on)
{
        return -ENODEV;
}

static const struct file_operations snd_shutdown_f_ops =
{
        .owner =        THIS_MODULE,
        .llseek =       snd_disconnect_llseek,
        .read =         snd_disconnect_read,
        .write =        snd_disconnect_write,
        .release =      snd_disconnect_release,
        .poll =         snd_disconnect_poll,
        .unlocked_ioctl = snd_disconnect_ioctl,
#ifdef CONFIG_COMPAT
        .compat_ioctl = snd_disconnect_ioctl,
#endif
        .mmap =         snd_disconnect_mmap,
        .fasync =       snd_disconnect_fasync
};

/**
 *  snd_card_disconnect - disconnect all APIs from the file-operations (user space)
 *  @card: soundcard structure
 *
 *  Disconnects all APIs from the file-operations (user space).
 *
 *  Return: Zero, otherwise a negative error code.
 *
 *  Note: The current implementation replaces all active file->f_op with special
 *        dummy file operations (they do nothing except release).
 */
int snd_card_disconnect(struct snd_card *card)
{
        struct snd_monitor_file *mfile;

        if (!card)
                return -EINVAL;

        spin_lock(&card->files_lock);
        if (card->shutdown) {
                spin_unlock(&card->files_lock);
                return 0;
        }
        card->shutdown = 1;

        /* replace file->f_op with special dummy operations */
        list_for_each_entry(mfile, &card->files_list, list) {
                /* it's critical part, use endless loop */
                /* we have no room to fail */
                mfile->disconnected_f_op = mfile->file->f_op;

                spin_lock(&shutdown_lock);
                list_add(&mfile->shutdown_list, &shutdown_files);
                spin_unlock(&shutdown_lock);

                mfile->file->f_op = &snd_shutdown_f_ops;
                fops_get(mfile->file->f_op);
        }
        spin_unlock(&card->files_lock); 

        /* notify all connected devices about disconnection */
        /* at this point, they cannot respond to any calls except release() */

#if IS_ENABLED(CONFIG_SND_MIXER_OSS)
        if (snd_mixer_oss_notify_callback)
                snd_mixer_oss_notify_callback(card, SND_MIXER_OSS_NOTIFY_DISCONNECT);
#endif

        /* notify all devices that we are disconnected */
        snd_device_disconnect_all(card);

        if (card->sync_irq > 0)
                synchronize_irq(card->sync_irq);

        snd_info_card_disconnect(card);
        if (card->registered) {
                device_del(&card->card_dev);
                card->registered = false;
        }

        /* disable fops (user space) operations for ALSA API */
        mutex_lock(&snd_card_mutex);
        snd_cards[card->number] = NULL;
        clear_bit(card->number, snd_cards_lock);
        mutex_unlock(&snd_card_mutex);

#ifdef CONFIG_PM
        wake_up(&card->power_sleep);
        snd_power_sync_ref(card);
#endif
        return 0;       
}
EXPORT_SYMBOL(snd_card_disconnect);

/**
 * snd_card_disconnect_sync - disconnect card and wait until files get closed
 * @card: card object to disconnect
 *
 * This calls snd_card_disconnect() for disconnecting all belonging components
 * and waits until all pending files get closed.
 * It assures that all accesses from user-space finished so that the driver
 * can release its resources gracefully.
 */
void snd_card_disconnect_sync(struct snd_card *card)
{
        int err;

        err = snd_card_disconnect(card);
        if (err < 0) {
                dev_err(card->dev,
                        "snd_card_disconnect error (%d), skipping sync\n",
                        err);
                return;
        }

        spin_lock_irq(&card->files_lock);
        wait_event_lock_irq(card->remove_sleep,
                            list_empty(&card->files_list),
                            card->files_lock);
        spin_unlock_irq(&card->files_lock);
}
EXPORT_SYMBOL_GPL(snd_card_disconnect_sync);

static int snd_card_do_free(struct snd_card *card)
{
        card->releasing = true;
#if IS_ENABLED(CONFIG_SND_MIXER_OSS)
        if (snd_mixer_oss_notify_callback)
                snd_mixer_oss_notify_callback(card, SND_MIXER_OSS_NOTIFY_FREE);
#endif
        snd_device_free_all(card);
        if (card->private_free)
                card->private_free(card);
        if (snd_info_card_free(card) < 0) {
                dev_warn(card->dev, "unable to free card info\n");
                /* Not fatal error */
        }
#ifdef CONFIG_SND_DEBUG
        debugfs_remove(card->debugfs_root);
        card->debugfs_root = NULL;
#endif
        if (card->release_completion)
                complete(card->release_completion);
        if (!card->managed)
                kfree(card);
        return 0;
}

/**
 * snd_card_free_when_closed - Disconnect the card, free it later eventually
 * @card: soundcard structure
 *
 * Unlike snd_card_free(), this function doesn't try to release the card
 * resource immediately, but tries to disconnect at first.  When the card
 * is still in use, the function returns before freeing the resources.
 * The card resources will be freed when the refcount gets to zero.
 */
int snd_card_free_when_closed(struct snd_card *card)
{
        int ret = snd_card_disconnect(card);
        if (ret)
                return ret;
        put_device(&card->card_dev);
        return 0;
}
EXPORT_SYMBOL(snd_card_free_when_closed);

/**
 * snd_card_free - frees given soundcard structure
 * @card: soundcard structure
 *
 * This function releases the soundcard structure and the all assigned
 * devices automatically.  That is, you don't have to release the devices
 * by yourself.
 *
 * This function waits until the all resources are properly released.
 *
 * Return: Zero. Frees all associated devices and frees the control
 * interface associated to given soundcard.
 */
int snd_card_free(struct snd_card *card)
{
        DECLARE_COMPLETION_ONSTACK(released);
        int ret;

        /* The call of snd_card_free() is allowed from various code paths;
         * a manual call from the driver and the call via devres_free, and
         * we need to avoid double-free. Moreover, the release via devres
         * may call snd_card_free() twice due to its nature, we need to have
         * the check here at the beginning.
         */
        if (card->releasing)
                return 0;

        card->release_completion = &released;
        ret = snd_card_free_when_closed(card);
        if (ret)
                return ret;
        /* wait, until all devices are ready for the free operation */
        wait_for_completion(&released);

        return 0;
}
EXPORT_SYMBOL(snd_card_free);

/* retrieve the last word of shortname or longname */
static const char *retrieve_id_from_card_name(const char *name)
{
        const char *spos = name;

        while (*name) {
                if (isspace(*name) && isalnum(name[1]))
                        spos = name + 1;
                name++;
        }
        return spos;
}

/* return true if the given id string doesn't conflict any other card ids */
static bool card_id_ok(struct snd_card *card, const char *id)
{
        int i;
        if (!snd_info_check_reserved_words(id))
                return false;
        for (i = 0; i < snd_ecards_limit; i++) {
                if (snd_cards[i] && snd_cards[i] != card &&
                    !strcmp(snd_cards[i]->id, id))
                        return false;
        }
        return true;
}

/* copy to card->id only with valid letters from nid */
static void copy_valid_id_string(struct snd_card *card, const char *src,
                                 const char *nid)
{
        char *id = card->id;

        while (*nid && !isalnum(*nid))
                nid++;
        if (isdigit(*nid))
                *id++ = isalpha(*src) ? *src : 'D';
        while (*nid && (size_t)(id - card->id) < sizeof(card->id) - 1) {
                if (isalnum(*nid))
                        *id++ = *nid;
                nid++;
        }
        *id = 0;
}

/* Set card->id from the given string
 * If the string conflicts with other ids, add a suffix to make it unique.
 */
static void snd_card_set_id_no_lock(struct snd_card *card, const char *src,
                                    const char *nid)
{
        int len, loops;
        bool is_default = false;
        char *id;
        
        copy_valid_id_string(card, src, nid);
        id = card->id;

 again:
        /* use "Default" for obviously invalid strings
         * ("card" conflicts with proc directories)
         */
        if (!*id || !strncmp(id, "card", 4)) {
                strcpy(id, "Default");
                is_default = true;
        }

        len = strlen(id);
        for (loops = 0; loops < SNDRV_CARDS; loops++) {
                char *spos;
                char sfxstr[5]; /* "_012" */
                int sfxlen;

                if (card_id_ok(card, id))
                        return; /* OK */

                /* Add _XYZ suffix */
                sprintf(sfxstr, "_%X", loops + 1);
                sfxlen = strlen(sfxstr);
                if (len + sfxlen >= sizeof(card->id))
                        spos = id + sizeof(card->id) - sfxlen - 1;
                else
                        spos = id + len;
                strcpy(spos, sfxstr);
        }
        /* fallback to the default id */
        if (!is_default) {
                *id = 0;
                goto again;
        }
        /* last resort... */
        dev_err(card->dev, "unable to set card id (%s)\n", id);
        if (card->proc_root->name)
                strscpy(card->id, card->proc_root->name, sizeof(card->id));
}

/**
 *  snd_card_set_id - set card identification name
 *  @card: soundcard structure
 *  @nid: new identification string
 *
 *  This function sets the card identification and checks for name
 *  collisions.
 */
void snd_card_set_id(struct snd_card *card, const char *nid)
{
        /* check if user specified own card->id */
        if (card->id[0] != '\0')
                return;
        mutex_lock(&snd_card_mutex);
        snd_card_set_id_no_lock(card, nid, nid);
        mutex_unlock(&snd_card_mutex);
}
EXPORT_SYMBOL(snd_card_set_id);

static ssize_t id_show(struct device *dev,
                       struct device_attribute *attr, char *buf)
{
        struct snd_card *card = container_of(dev, struct snd_card, card_dev);
        return scnprintf(buf, PAGE_SIZE, "%s\n", card->id);
}

static ssize_t id_store(struct device *dev, struct device_attribute *attr,
                        const char *buf, size_t count)
{
        struct snd_card *card = container_of(dev, struct snd_card, card_dev);
        char buf1[sizeof(card->id)];
        size_t copy = count > sizeof(card->id) - 1 ?
                                        sizeof(card->id) - 1 : count;
        size_t idx;
        int c;

        for (idx = 0; idx < copy; idx++) {
                c = buf[idx];
                if (!isalnum(c) && c != '_' && c != '-')
                        return -EINVAL;
        }
        memcpy(buf1, buf, copy);
        buf1[copy] = '\0';
        mutex_lock(&snd_card_mutex);
        if (!card_id_ok(NULL, buf1)) {
                mutex_unlock(&snd_card_mutex);
                return -EEXIST;
        }
        strcpy(card->id, buf1);
        snd_info_card_id_change(card);
        mutex_unlock(&snd_card_mutex);

        return count;
}

static DEVICE_ATTR_RW(id);

static ssize_t number_show(struct device *dev,
                           struct device_attribute *attr, char *buf)
{
        struct snd_card *card = container_of(dev, struct snd_card, card_dev);
        return scnprintf(buf, PAGE_SIZE, "%i\n", card->number);
}

static DEVICE_ATTR_RO(number);

static struct attribute *card_dev_attrs[] = {
        &dev_attr_id.attr,
        &dev_attr_number.attr,
        NULL
};

static const struct attribute_group card_dev_attr_group = {
        .attrs  = card_dev_attrs,
};

/**
 * snd_card_add_dev_attr - Append a new sysfs attribute group to card
 * @card: card instance
 * @group: attribute group to append
 */
int snd_card_add_dev_attr(struct snd_card *card,
                          const struct attribute_group *group)
{
        int i;

        /* loop for (arraysize-1) here to keep NULL at the last entry */
        for (i = 0; i < ARRAY_SIZE(card->dev_groups) - 1; i++) {
                if (!card->dev_groups[i]) {
                        card->dev_groups[i] = group;
                        return 0;
                }
        }

        dev_err(card->dev, "Too many groups assigned\n");
        return -ENOSPC;
}
EXPORT_SYMBOL_GPL(snd_card_add_dev_attr);

static void trigger_card_free(void *data)
{
        snd_card_free(data);
}

/**
 *  snd_card_register - register the soundcard
 *  @card: soundcard structure
 *
 *  This function registers all the devices assigned to the soundcard.
 *  Until calling this, the ALSA control interface is blocked from the
 *  external accesses.  Thus, you should call this function at the end
 *  of the initialization of the card.
 *
 *  Return: Zero otherwise a negative error code if the registration failed.
 */
int snd_card_register(struct snd_card *card)
{
        int err;

        if (snd_BUG_ON(!card))
                return -EINVAL;

        if (!card->registered) {
                err = device_add(&card->card_dev);
                if (err < 0)
                        return err;
                card->registered = true;
        } else {
                if (card->managed)
                        devm_remove_action(card->dev, trigger_card_free, card);
        }

        if (card->managed) {
                err = devm_add_action(card->dev, trigger_card_free, card);
                if (err < 0)
                        return err;
        }

        err = snd_device_register_all(card);
        if (err < 0)
                return err;
        mutex_lock(&snd_card_mutex);
        if (snd_cards[card->number]) {
                /* already registered */
                mutex_unlock(&snd_card_mutex);
                return snd_info_card_register(card); /* register pending info */
        }
        if (*card->id) {
                /* make a unique id name from the given string */
                char tmpid[sizeof(card->id)];
                memcpy(tmpid, card->id, sizeof(card->id));
                snd_card_set_id_no_lock(card, tmpid, tmpid);
        } else {
                /* create an id from either shortname or longname */
                const char *src;
                src = *card->shortname ? card->shortname : card->longname;
                snd_card_set_id_no_lock(card, src,
                                        retrieve_id_from_card_name(src));
        }
        snd_cards[card->number] = card;
        mutex_unlock(&snd_card_mutex);
        err = snd_info_card_register(card);
        if (err < 0)
                return err;

#if IS_ENABLED(CONFIG_SND_MIXER_OSS)
        if (snd_mixer_oss_notify_callback)
                snd_mixer_oss_notify_callback(card, SND_MIXER_OSS_NOTIFY_REGISTER);
#endif
        return 0;
}
EXPORT_SYMBOL(snd_card_register);

#ifdef CONFIG_SND_PROC_FS
static void snd_card_info_read(struct snd_info_entry *entry,
                               struct snd_info_buffer *buffer)
{
        int idx, count;
        struct snd_card *card;

        for (idx = count = 0; idx < SNDRV_CARDS; idx++) {
                mutex_lock(&snd_card_mutex);
                card = snd_cards[idx];
                if (card) {
                        count++;
                        snd_iprintf(buffer, "%2i [%-15s]: %s - %s\n",
                                        idx,
                                        card->id,
                                        card->driver,
                                        card->shortname);
                        snd_iprintf(buffer, "                      %s\n",
                                        card->longname);
                }
                mutex_unlock(&snd_card_mutex);
        }
        if (!count)
                snd_iprintf(buffer, "--- no soundcards ---\n");
}

#ifdef CONFIG_SND_OSSEMUL
void snd_card_info_read_oss(struct snd_info_buffer *buffer)
{
        int idx, count;
        struct snd_card *card;

        for (idx = count = 0; idx < SNDRV_CARDS; idx++) {
                mutex_lock(&snd_card_mutex);
                card = snd_cards[idx];
                if (card) {
                        count++;
                        snd_iprintf(buffer, "%s\n", card->longname);
                }
                mutex_unlock(&snd_card_mutex);
        }
        if (!count) {
                snd_iprintf(buffer, "--- no soundcards ---\n");
        }
}

#endif

#ifdef MODULE
static void snd_card_module_info_read(struct snd_info_entry *entry,
                                      struct snd_info_buffer *buffer)
{
        int idx;
        struct snd_card *card;

        for (idx = 0; idx < SNDRV_CARDS; idx++) {
                mutex_lock(&snd_card_mutex);
                card = snd_cards[idx];
                if (card)
                        snd_iprintf(buffer, "%2i %s\n",
                                    idx, card->module->name);
                mutex_unlock(&snd_card_mutex);
        }
}
#endif

int __init snd_card_info_init(void)
{
        struct snd_info_entry *entry;

        entry = snd_info_create_module_entry(THIS_MODULE, "cards", NULL);
        if (! entry)
                return -ENOMEM;
        entry->c.text.read = snd_card_info_read;
        if (snd_info_register(entry) < 0)
                return -ENOMEM; /* freed in error path */

#ifdef MODULE
        entry = snd_info_create_module_entry(THIS_MODULE, "modules", NULL);
        if (!entry)
                return -ENOMEM;
        entry->c.text.read = snd_card_module_info_read;
        if (snd_info_register(entry) < 0)
                return -ENOMEM; /* freed in error path */
#endif

        return 0;
}
#endif /* CONFIG_SND_PROC_FS */

/**
 *  snd_component_add - add a component string
 *  @card: soundcard structure
 *  @component: the component id string
 *
 *  This function adds the component id string to the supported list.
 *  The component can be referred from the alsa-lib.
 *
 *  Return: Zero otherwise a negative error code.
 */
  
int snd_component_add(struct snd_card *card, const char *component)
{
        char *ptr;

        int len = strlen(component);

        ptr = strstr(card->components, component);
        if (ptr != NULL) {
                if (ptr[len] == '\0' || ptr[len] == ' ')        /* already there */
                        return 1;
        }
        if (strlen(card->components) + 1 + len + 1 > sizeof(card->components)) {
                snd_BUG();
                return -ENOMEM;
        }
        if (card->components[0] != '\0')
                strcat(card->components, " ");
        strcat(card->components, component);
        return 0;
}
EXPORT_SYMBOL(snd_component_add);

/**
 *  snd_card_file_add - add the file to the file list of the card
 *  @card: soundcard structure
 *  @file: file pointer
 *
 *  This function adds the file to the file linked-list of the card.
 *  This linked-list is used to keep tracking the connection state,
 *  and to avoid the release of busy resources by hotplug.
 *
 *  Return: zero or a negative error code.
 */
int snd_card_file_add(struct snd_card *card, struct file *file)
{
        struct snd_monitor_file *mfile;

        mfile = kmalloc(sizeof(*mfile), GFP_KERNEL);
        if (mfile == NULL)
                return -ENOMEM;
        mfile->file = file;
        mfile->disconnected_f_op = NULL;
        INIT_LIST_HEAD(&mfile->shutdown_list);
        spin_lock(&card->files_lock);
        if (card->shutdown) {
                spin_unlock(&card->files_lock);
                kfree(mfile);
                return -ENODEV;
        }
        list_add(&mfile->list, &card->files_list);
        get_device(&card->card_dev);
        spin_unlock(&card->files_lock);
        return 0;
}
EXPORT_SYMBOL(snd_card_file_add);

/**
 *  snd_card_file_remove - remove the file from the file list
 *  @card: soundcard structure
 *  @file: file pointer
 *
 *  This function removes the file formerly added to the card via
 *  snd_card_file_add() function.
 *  If all files are removed and snd_card_free_when_closed() was
 *  called beforehand, it processes the pending release of
 *  resources.
 *
 *  Return: Zero or a negative error code.
 */
int snd_card_file_remove(struct snd_card *card, struct file *file)
{
        struct snd_monitor_file *mfile, *found = NULL;

        spin_lock(&card->files_lock);
        list_for_each_entry(mfile, &card->files_list, list) {
                if (mfile->file == file) {
                        list_del(&mfile->list);
                        spin_lock(&shutdown_lock);
                        list_del(&mfile->shutdown_list);
                        spin_unlock(&shutdown_lock);
                        if (mfile->disconnected_f_op)
                                fops_put(mfile->disconnected_f_op);
                        found = mfile;
                        break;
                }
        }
        if (list_empty(&card->files_list))
                wake_up_all(&card->remove_sleep);
        spin_unlock(&card->files_lock);
        if (!found) {
                dev_err(card->dev, "card file remove problem (%p)\n", file);
                return -ENOENT;
        }
        kfree(found);
        put_device(&card->card_dev);
        return 0;
}
EXPORT_SYMBOL(snd_card_file_remove);

#ifdef CONFIG_PM
/**
 * snd_power_ref_and_wait - wait until the card gets powered up
 * @card: soundcard structure
 *
 * Take the power_ref reference count of the given card, and
 * wait until the card gets powered up to SNDRV_CTL_POWER_D0 state.
 * The refcount is down again while sleeping until power-up, hence this
 * function can be used for syncing the floating control ops accesses,
 * typically around calling control ops.
 *
 * The caller needs to pull down the refcount via snd_power_unref() later
 * no matter whether the error is returned from this function or not.
 *
 * Return: Zero if successful, or a negative error code.
 */
int snd_power_ref_and_wait(struct snd_card *card)
{
        wait_queue_entry_t wait;
        int result = 0;

        snd_power_ref(card);
        /* fastpath */
        if (snd_power_get_state(card) == SNDRV_CTL_POWER_D0)
                return 0;
        init_waitqueue_entry(&wait, current);
        add_wait_queue(&card->power_sleep, &wait);
        while (1) {
                if (card->shutdown) {
                        result = -ENODEV;
                        break;
                }
                if (snd_power_get_state(card) == SNDRV_CTL_POWER_D0)
                        break;
                snd_power_unref(card);
                set_current_state(TASK_UNINTERRUPTIBLE);
                schedule_timeout(30 * HZ);
                snd_power_ref(card);
        }
        remove_wait_queue(&card->power_sleep, &wait);
        return result;
}
EXPORT_SYMBOL_GPL(snd_power_ref_and_wait);

/**
 * snd_power_wait - wait until the card gets powered up (old form)
 * @card: soundcard structure
 *
 * Wait until the card gets powered up to SNDRV_CTL_POWER_D0 state.
 *
 * Return: Zero if successful, or a negative error code.
 */
int snd_power_wait(struct snd_card *card)
{
        int ret;

        ret = snd_power_ref_and_wait(card);
        snd_power_unref(card);
        return ret;
}
EXPORT_SYMBOL(snd_power_wait);
#endif /* CONFIG_PM */