Linux音频驱动-Card创建

struct snd_card {
	int number;			/* number of soundcard (index to
								snd_cards) */

	char id[16];			/* id string of this card */
	char driver[16];		/* driver name */
	char shortname[32];		/* short name of this soundcard */
	char longname[80];		/* name of this soundcard */
	char mixername[80];		/* mixer name */
	char components[128];		/* card components delimited with
								space */
	struct module *module;		/* top-level module */

	void *private_data;		/* private data for soundcard */
	void (*private_free) (struct snd_card *card); /* callback for freeing of
								private data */
	struct list_head devices;	/* devices */

	unsigned int last_numid;	/* last used numeric ID */
	struct rw_semaphore controls_rwsem;	/* controls list lock */
	rwlock_t ctl_files_rwlock;	/* ctl_files list lock */
	int controls_count;		/* count of all controls */
	int user_ctl_count;		/* count of all user controls */
	struct list_head controls;	/* all controls for this card */
	struct list_head ctl_files;	/* active control files */
	struct mutex user_ctl_lock;	/* protects user controls against
					   concurrent access */

	struct snd_info_entry *proc_root;	/* root for soundcard specific files */
	struct snd_info_entry *proc_id;	/* the card id */
	struct proc_dir_entry *proc_root_link;	/* number link to real id */

	struct list_head files_list;	/* all files associated to this card */
	struct snd_shutdown_f_ops *s_f_ops; /* file operations in the shutdown
								state */
	spinlock_t files_lock;		/* lock the files for this card */
	int shutdown;			/* this card is going down */
	struct completion *release_completion;
	struct device *dev;		/* device assigned to this card */
	struct device card_dev;		/* cardX object for sysfs */
	bool registered;		/* card_dev is registered? */

#ifdef CONFIG_PM
	unsigned int power_state;	/* power state */
	struct mutex power_lock;	/* power lock */
	wait_queue_head_t power_sleep;
#endif

#if defined(CONFIG_SND_MIXER_OSS) || defined(CONFIG_SND_MIXER_OSS_MODULE)
	struct snd_mixer_oss *mixer_oss;
	int mixer_oss_change_count;
#endif
};

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;
	if (extra_size > 0)
		card->private_data = (char *)card + sizeof(struct snd_card);
	if (xid)
		strlcpy(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);
		kfree(card);
		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;
	card->module = module;
	INIT_LIST_HEAD(&card->devices);
	init_rwsem(&card->controls_rwsem);
	rwlock_init(&card->ctl_files_rwlock);
	mutex_init(&card->user_ctl_lock);
	INIT_LIST_HEAD(&card->controls);
	INIT_LIST_HEAD(&card->ctl_files);
	spin_lock_init(&card->files_lock);
	INIT_LIST_HEAD(&card->files_list);
#ifdef CONFIG_PM
	mutex_init(&card->power_lock);
	init_waitqueue_head(&card->power_sleep);
#endif

	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_attr_groups;
	err = kobject_set_name(&card->card_dev.kobj, "card%d", idx);
	if (err < 0)
		goto __error;

	/* 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;
	}
	*card_ret = card;
	return 0;

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

static int __init init_soundcore(void)
{
	int rc;

	rc = init_oss_soundcore();
	if (rc)
		return rc;

	sound_class = class_create(THIS_MODULE, "sound");
	if (IS_ERR(sound_class)) {
		cleanup_oss_soundcore();
		return PTR_ERR(sound_class);
	}

	sound_class->devnode = sound_devnode;

	return 0;
}

int snd_info_card_create(struct snd_card *card)
{
	char str[8];
	struct snd_info_entry *entry;

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

	sprintf(str, "card%i", card->number);
	if ((entry = snd_info_create_module_entry(card->module, str, NULL)) == NULL)
		return -ENOMEM;
	entry->mode = S_IFDIR | S_IRUGO | S_IXUGO;
	if (snd_info_register(entry) < 0) {
		snd_info_free_entry(entry);
		return -ENOMEM;
	}
	card->proc_root = entry;
	return 0;
}

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;
	}

	if ((err = snd_device_register_all(card)) < 0)
		return err;
	mutex_lock(&snd_card_mutex);
	if (snd_cards[card->number]) {
		/* already registered */
		mutex_unlock(&snd_card_mutex);
		return 0;
	}
	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);
	init_info_for_card(card);
#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;
}

int snd_device_register_all(struct snd_card *card)
{
	struct snd_device *dev;
	int err;
	
	if (snd_BUG_ON(!card))
		return -ENXIO;
	list_for_each_entry(dev, &card->devices, list) {
		err = __snd_device_register(dev);
		if (err < 0)
			return err;
	}
	return 0;
}

static int __snd_device_register(struct snd_device *dev)
{
	if (dev->state == SNDRV_DEV_BUILD) {
		if (dev->ops->dev_register) {
			int err = dev->ops->dev_register(dev);
			if (err < 0)
				return err;
		}
		dev->state = SNDRV_DEV_REGISTERED;
	}
	return 0;
}