text: // SPDX-License-Identifier: GPL-2.0-or-later
  /*
   *  Advanced Linux Sound Architecture
   *  Copyright (c) by Jaroslav Kysela <perex@perex.cz>
   */
  
  #include <linux/init.h>
  #include <linux/slab.h>
  #include <linux/time.h>
  #include <linux/device.h>
  #include <linux/module.h>
  #include <sound/core.h>
  #include <sound/minors.h>
  #include <sound/info.h>
  #include <sound/control.h>
  #include <sound/initval.h>
  #include <linux/kmod.h>
  #include <linux/mutex.h>
  
  static int major = CONFIG_SND_MAJOR;
  int snd_major;
  EXPORT_SYMBOL(snd_major);
  
  static int cards_limit = 1;
  
  MODULE_AUTHOR("Jaroslav Kysela <perex@perex.cz>");
  MODULE_DESCRIPTION("Advanced Linux Sound Architecture driver for soundcards.");
  MODULE_LICENSE("GPL");
  module_param(major, int, 0444);
  MODULE_PARM_DESC(major, "Major # for sound driver.");
  module_param(cards_limit, int, 0444);
  MODULE_PARM_DESC(cards_limit, "Count of auto-loadable soundcards.");
  MODULE_ALIAS_CHARDEV_MAJOR(CONFIG_SND_MAJOR);
  
  /* this one holds the actual max. card number currently available.
   * as default, it's identical with cards_limit option.  when more
   * modules are loaded manually, this limit number increases, too.
   */
  int snd_ecards_limit;
  EXPORT_SYMBOL(snd_ecards_limit);
  
  static struct snd_minor *snd_minors[SNDRV_OS_MINORS];
  static DEFINE_MUTEX(sound_mutex);
  
  #ifdef CONFIG_MODULES
  
  /**
   * snd_request_card - try to load the card module
   * @card: the card number
   *
   * Tries to load the module "snd-card-X" for the given card number
   * via request_module.  Returns immediately if already loaded.
   */
  void snd_request_card(int card)
  {
  	if (snd_card_locked(card))
  		return;
  	if (card < 0 || card >= cards_limit)
  		return;
  	request_module("snd-card-%i", card);
  }
  EXPORT_SYMBOL(snd_request_card);
  
  static void snd_request_other(int minor)
  {
  	char *str;
  
  	switch (minor) {
  	case SNDRV_MINOR_SEQUENCER:	str = "snd-seq";	break;
  	case SNDRV_MINOR_TIMER:		str = "snd-timer";	break;
  	default:			return;
  	}
  	request_module(str);
  }
  
  #endif	/* modular kernel */
  
  /**
   * snd_lookup_minor_data - get user data of a registered device
   * @minor: the minor number
   * @type: device type (SNDRV_DEVICE_TYPE_XXX)
   *
   * Checks that a minor device with the specified type is registered, and returns
   * its user data pointer.
   *
   * This function increments the reference counter of the card instance
   * if an associated instance with the given minor number and type is found.
   * The caller must call snd_card_unref() appropriately later.
   *
   * Return: The user data pointer if the specified device is found. %NULL
   * otherwise.
   */
  void *snd_lookup_minor_data(unsigned int minor, int type)
  {
  	struct snd_minor *mreg;
  	void *private_data;
  
  	if (minor >= ARRAY_SIZE(snd_minors))
  		return NULL;
  	mutex_lock(&sound_mutex);
  	mreg = snd_minors[minor];
  	if (mreg && mreg->type == type) {
  		private_data = mreg->private_data;
  		if (private_data && mreg->card_ptr)
  			get_device(&mreg->card_ptr->card_dev);
  	} else
  		private_data = NULL;
  	mutex_unlock(&sound_mutex);
  	return private_data;
  }
  EXPORT_SYMBOL(snd_lookup_minor_data);
  
  #ifdef CONFIG_MODULES
  static struct snd_minor *autoload_device(unsigned int minor)
  {
  	int dev;
  	mutex_unlock(&sound_mutex); /* release lock temporarily */
  	dev = SNDRV_MINOR_DEVICE(minor);
  	if (dev == SNDRV_MINOR_CONTROL) {
  		/* /dev/aloadC? */
  		int card = SNDRV_MINOR_CARD(minor);
  		struct snd_card *ref = snd_card_ref(card);
  		if (!ref)
  			snd_request_card(card);
  		else
  			snd_card_unref(ref);
  	} else if (dev == SNDRV_MINOR_GLOBAL) {
  		/* /dev/aloadSEQ */
  		snd_request_other(minor);
  	}
  	mutex_lock(&sound_mutex); /* reacuire lock */
  	return snd_minors[minor];
  }
  #else /* !CONFIG_MODULES */
  #define autoload_device(minor)	NULL
  #endif /* CONFIG_MODULES */
  
  static int snd_open(struct inode *inode, struct file *file)
  {
  	unsigned int minor = iminor(inode);
  	struct snd_minor *mptr = NULL;
  	const struct file_operations *new_fops;
  	int err = 0;
  
  	if (minor >= ARRAY_SIZE(snd_minors))
  		return -ENODEV;
  	mutex_lock(&sound_mutex);
  	mptr = snd_minors[minor];
  	if (mptr == NULL) {
  		mptr = autoload_device(minor);
  		if (!mptr) {
  			mutex_unlock(&sound_mutex);
  			return -ENODEV;
  		}
  	}
  	new_fops = fops_get(mptr->f_ops);
  	mutex_unlock(&sound_mutex);
  	if (!new_fops)
  		return -ENODEV;
  	replace_fops(file, new_fops);
  
  	if (file->f_op->open)
  		err = file->f_op->open(inode, file);
  	return err;
  }
  
  static const struct file_operations snd_fops =
  {
  	.owner =	THIS_MODULE,
  	.open =		snd_open,
  	.llseek =	noop_llseek,
  };
  
  #ifdef CONFIG_SND_DYNAMIC_MINORS
  static int snd_find_free_minor(int type, struct snd_card *card, int dev)
  {
  	int minor;
  
  	/* static minors for module auto loading */
  	if (type == SNDRV_DEVICE_TYPE_SEQUENCER)
  		return SNDRV_MINOR_SEQUENCER;
  	if (type == SNDRV_DEVICE_TYPE_TIMER)
  		return SNDRV_MINOR_TIMER;
  
  	for (minor = 0; minor < ARRAY_SIZE(snd_minors); ++minor) {
  		/* skip static minors still used for module auto loading */
  		if (SNDRV_MINOR_DEVICE(minor) == SNDRV_MINOR_CONTROL)
  			continue;
  		if (minor == SNDRV_MINOR_SEQUENCER ||
  		    minor == SNDRV_MINOR_TIMER)
  			continue;
  		if (!snd_minors[minor])
  			return minor;
  	}
  	return -EBUSY;
  }
  #else
  static int snd_find_free_minor(int type, struct snd_card *card, int dev)
  {
  	int minor;
  
  	switch (type) {
  	case SNDRV_DEVICE_TYPE_SEQUENCER:
  	case SNDRV_DEVICE_TYPE_TIMER:
  		minor = type;
  		break;
  	case SNDRV_DEVICE_TYPE_CONTROL:
  		if (snd_BUG_ON(!card))
  			return -EINVAL;
  		minor = SNDRV_MINOR(card->number, type);
  		break;
  	case SNDRV_DEVICE_TYPE_HWDEP:
  	case SNDRV_DEVICE_TYPE_RAWMIDI:
  	case SNDRV_DEVICE_TYPE_PCM_PLAYBACK:
  	case SNDRV_DEVICE_TYPE_PCM_CAPTURE:
  	case SNDRV_DEVICE_TYPE_COMPRESS:
  		if (snd_BUG_ON(!card))
  			return -EINVAL;
  		minor = SNDRV_MINOR(card->number, type + dev);
  		break;
  	default:
  		return -EINVAL;
  	}
  	if (snd_BUG_ON(minor < 0 || minor >= SNDRV_OS_MINORS))
  		return -EINVAL;
  	if (snd_minors[minor])
  		return -EBUSY;
  	return minor;
  }
  #endif
  
  /**
   * snd_register_device - Register the ALSA device file for the card
   * @type: the device type, SNDRV_DEVICE_TYPE_XXX
   * @card: the card instance
   * @dev: the device index
   * @f_ops: the file operations
   * @private_data: user pointer for f_ops->open()
   * @device: the device to register
   *
   * Registers an ALSA device file for the given card.
   * The operators have to be set in reg parameter.
   *
   * Return: Zero if successful, or a negative error code on failure.
   */
  int snd_register_device(int type, struct snd_card *card, int dev,
  			const struct file_operations *f_ops,
  			void *private_data, struct device *device)
  {
  	int minor;
  	int err = 0;
  	struct snd_minor *preg;
  
  	if (snd_BUG_ON(!device))
  		return -EINVAL;
  
  	preg = kmalloc(sizeof *preg, GFP_KERNEL);
  	if (preg == NULL)
  		return -ENOMEM;
  	preg->type = type;
  	preg->card = card ? card->number : -1;
  	preg->device = dev;
  	preg->f_ops = f_ops;
  	preg->private_data = private_data;
  	preg->card_ptr = card;
  	mutex_lock(&sound_mutex);
  	minor = snd_find_free_minor(type, card, dev);
  	if (minor < 0) {
  		err = minor;
  		goto error;
  	}
  
  	preg->dev = device;
  	device->devt = MKDEV(major, minor);
  	err = device_add(device);
  	if (err < 0)
  		goto error;
  
  	snd_minors[minor] = preg;
   error:
  	mutex_unlock(&sound_mutex);
  	if (err < 0)
  		kfree(preg);
  	return err;
  }
  EXPORT_SYMBOL(snd_register_device);
  
  /**
   * snd_unregister_device - unregister the device on the given card
   * @dev: the device instance
   *
   * Unregisters the device file already registered via
   * snd_register_device().
   *
   * Return: Zero if successful, or a negative error code on failure.
   */
  int snd_unregister_device(struct device *dev)
  {
  	int minor;
  	struct snd_minor *preg;
  
  	mutex_lock(&sound_mutex);
  	for (minor = 0; minor < ARRAY_SIZE(snd_minors); ++minor) {
  		preg = snd_minors[minor];
  		if (preg && preg->dev == dev) {
  			snd_minors[minor] = NULL;
  			device_del(dev);
  			kfree(preg);
  			break;
  		}
  	}
  	mutex_unlock(&sound_mutex);
  	if (minor >= ARRAY_SIZE(snd_minors))
  		return -ENOENT;
  	return 0;
  }
  EXPORT_SYMBOL(snd_unregister_device);
  
  #ifdef CONFIG_SND_PROC_FS
  /*
   *  INFO PART
   */
  static const char *snd_device_type_name(int type)
  {
  	switch (type) {
  	case SNDRV_DEVICE_TYPE_CONTROL:
  		return "control";
  	case SNDRV_DEVICE_TYPE_HWDEP:
  		return "hardware dependent";
  	case SNDRV_DEVICE_TYPE_RAWMIDI:
  		return "raw midi";
  	case SNDRV_DEVICE_TYPE_PCM_PLAYBACK:
  		return "digital audio playback";
  	case SNDRV_DEVICE_TYPE_PCM_CAPTURE:
  		return "digital audio capture";
  	case SNDRV_DEVICE_TYPE_SEQUENCER:
  		return "sequencer";
  	case SNDRV_DEVICE_TYPE_TIMER:
  		return "timer";
  	default:
  		return "?";
  	}
  }
  
  static void snd_minor_info_read(struct snd_info_entry *entry, struct snd_info_buffer *buffer)
  {
  	int minor;
  	struct snd_minor *mptr;
  
  	mutex_lock(&sound_mutex);
  	for (minor = 0; minor < SNDRV_OS_MINORS; ++minor) {
  		if (!(mptr = snd_minors[minor]))
  			continue;
  		if (mptr->card >= 0) {
  			if (mptr->device >= 0)
  				snd_iprintf(buffer, "%3i: [%2i-%2i]: %s\n",
  					    minor, mptr->card, mptr->device,
  					    snd_device_type_name(mptr->type));
  			else
  				snd_iprintf(buffer, "%3i: [%2i]   : %s\n",
  					    minor, mptr->card,
  					    snd_device_type_name(mptr->type));
  		} else
  			snd_iprintf(buffer, "%3i:        : %s\n", minor,
  				    snd_device_type_name(mptr->type));
  	}
  	mutex_unlock(&sound_mutex);
  }
  
  int __init snd_minor_info_init(void)
  {
  	struct snd_info_entry *entry;
  
  	entry = snd_info_create_module_entry(THIS_MODULE, "devices", NULL);
  	if (!entry)
  		return -ENOMEM;
  	entry->c.text.read = snd_minor_info_read;
  	return snd_info_register(entry); /* freed in error path */
  }
  #endif /* CONFIG_SND_PROC_FS */
  
  /*
   *  INIT PART
   */
  
  static int __init alsa_sound_init(void)
  {
  	snd_major = major;
  	snd_ecards_limit = cards_limit;
  	if (register_chrdev(major, "alsa", &snd_fops)) {
  		pr_err("ALSA core: unable to register native major device number %d\n", major);
  		return -EIO;
  	}
  	if (snd_info_init() < 0) {
  		unregister_chrdev(major, "alsa");
  		return -ENOMEM;
  	}
  #ifndef MODULE
  	pr_info("Advanced Linux Sound Architecture Driver Initialized.\n");
  #endif
  	return 0;
  }
  
  static void __exit alsa_sound_exit(void)
  {
  	snd_info_done();
  	unregister_chrdev(major, "alsa");
  }
  
  subsys_initcall(alsa_sound_init);
  module_exit(alsa_sound_exit);
  