linux/sound/core/sound.c

// SPDX-License-Identifier: GPL-2.0-or-later
/*
 *  Advanced Linux Sound Architecture
 *  Copyright (c) by Jaroslav Kysela <[email protected]>
 */

#include <linux/init.h>
#include <linux/slab.h>
#include <linux/time.h>
#include <linux/device.h>
#include <linux/module.h>
#include <linux/debugfs.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 = …;
int snd_major;
EXPORT_SYMBOL(…);

static int cards_limit = …;

MODULE_AUTHOR(…) …;
MODULE_DESCRIPTION(…) …;
MODULE_LICENSE(…) …;
module_param(major, int, 0444);
MODULE_PARM_DESC(…) …;
module_param(cards_limit, int, 0444);
MODULE_PARM_DESC(…) …;
MODULE_ALIAS_CHARDEV_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(…);

#ifdef CONFIG_SND_DEBUG
struct dentry *sound_debugfs_root;
EXPORT_SYMBOL_GPL(…);
#endif

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)
{ … }
EXPORT_SYMBOL(…);

static void snd_request_other(int minor)
{ … }

#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)
{ … }
EXPORT_SYMBOL(…);

#ifdef CONFIG_MODULES
static struct snd_minor *autoload_device(unsigned int minor)
{ … }
#else /* !CONFIG_MODULES */
#define autoload_device …
#endif /* CONFIG_MODULES */

static int snd_open(struct inode *inode, struct file *file)
{ … }

static const struct file_operations snd_fops = …;

#ifdef CONFIG_SND_DYNAMIC_MINORS
static int snd_find_free_minor(int type, struct snd_card *card, int dev)
{ … }
#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)
{ … }
EXPORT_SYMBOL(…);

/**
 * 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)
{ … }
EXPORT_SYMBOL(…);

#ifdef CONFIG_SND_PROC_FS
/*
 *  INFO PART
 */
static const char *snd_device_type_name(int type)
{ … }

static void snd_minor_info_read(struct snd_info_entry *entry, struct snd_info_buffer *buffer)
{ … }

int __init snd_minor_info_init(void)
{ … }
#endif /* CONFIG_SND_PROC_FS */

/*
 *  INIT PART
 */

static int __init alsa_sound_init(void)
{ … }

static void __exit alsa_sound_exit(void)
{ … }

subsys_initcall(alsa_sound_init);
module_exit(alsa_sound_exit);