1. struct snd_card
1.1. snd_card是什麼
1.2. snd_card的定義
-
/* main structure for soundcard */
-
-
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 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 */
-
int free_on_last_close; /* free in context of file_release */
-
wait_queue_head_t shutdown_sleep;
-
struct device *dev; /* device assigned to this card */
-
#ifndef CONFIG_SYSFS_DEPRECATED
-
struct device *card_dev; /* cardX object for sysfs */
-
#endif
-
-
#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
-
};
-
struct list_head devices 記錄該聲卡下所有邏輯設備的鏈表
-
struct list_head controls 記錄該聲卡下所有的控制單元的鏈表
-
void *private_data 聲卡的私有數據,可以在創建聲卡時通過參數指定數據的大小
2. 聲卡的建立流程
2.1.1. 第一步,創建snd_card的一個實例
-
struct snd_card *card;
-
int err;
-
....
-
err = snd_card_create(index, id, THIS_MODULE, 0, &card);
-
index 一個整數值,該聲卡的編號
-
id 字符串,聲卡的標識符
-
第四個參數 該參數決定在創建snd_card實例時,需要同時額外分配的私有數據的大小,該數據的指針最終會賦值給snd_card的private_data數據成員
-
card 返回所創建的snd_card實例的指針
2.1.2. 第二步,創建聲卡的芯片專用數據
-
通過上一步中snd_card_create()中的第四個參數,讓snd_card_create自己創建
-
// struct mychip 用於保存專用數據
-
err = snd_card_create(index, id, THIS_MODULE,
-
sizeof(struct mychip), &card);
-
// 從private_data中取出
-
struct mychip *chip = card->private_data;
-
自己創建:
-
struct mychip {
-
struct snd_card *card;
-
....
-
};
-
struct snd_card *card;
-
struct mychip *chip;
-
-
chip = kzalloc(sizeof(*chip), GFP_KERNEL);
-
......
-
err = snd_card_create(index[dev], id[dev], THIS_MODULE, 0, &card);
-
// 專用數據記錄snd_card實例
-
chip->card = card;
-
.....
-
static int snd_mychip_dev_free(struct snd_device *device)
-
{
-
return snd_mychip_free(device->device_data);
-
}
-
-
static struct snd_device_ops ops = {
-
.dev_free = snd_mychip_dev_free,
-
};
-
....
-
snd_device_new(card, SNDRV_DEV_LOWLEVEL, chip, &ops);
2.1.3. 第三步,設置Driver的ID和名字
-
strcpy(card->driver, "My Chip");
-
strcpy(card->shortname, "My Own Chip 123");
-
sprintf(card->longname, "%s at 0x%lx irq %i",
-
card->shortname, chip->ioport, chip->irq);
2.1.4. 第四步,創建聲卡的功能部件(邏輯設備),例如PCM,Mixer,MIDI等
2.1.5. 第五步,註冊聲卡
-
err = snd_card_register(card);
-
if (err < 0) {
-
snd_card_free(card);
-
return err;
-
}
2.2. 一個實際的例子
-
static int __devinit pxa2xx_ac97_probe(struct platform_device *dev)
-
{
-
struct snd_card *card;
-
struct snd_ac97_bus *ac97_bus;
-
struct snd_ac97_template ac97_template;
-
int ret;
-
pxa2xx_audio_ops_t *pdata = dev->dev.platform_data;
-
-
if (dev->id >= 0) {
-
dev_err(&dev->dev, "PXA2xx has only one AC97 port./n");
-
ret = -ENXIO;
-
goto err_dev;
-
}
-
////(1)////
-
ret = snd_card_create(SNDRV_DEFAULT_IDX1, SNDRV_DEFAULT_STR1,
-
THIS_MODULE, 0, &card);
-
if (ret < 0)
-
goto err;
-
-
card->dev = &dev->dev;
-
////(3)////
-
strncpy(card->driver, dev->dev.driver->name, sizeof(card->driver));
-
-
////(4)////
-
ret = pxa2xx_pcm_new(card, &pxa2xx_ac97_pcm_client, &pxa2xx_ac97_pcm);
-
if (ret)
-
goto err;
-
////(2)////
-
ret = pxa2xx_ac97_hw_probe(dev);
-
if (ret)
-
goto err;
-
-
////(4)////
-
ret = snd_ac97_bus(card, 0, &pxa2xx_ac97_ops, NULL, &ac97_bus);
-
if (ret)
-
goto err_remove;
-
memset(&ac97_template, 0, sizeof(ac97_template));
-
ret = snd_ac97_mixer(ac97_bus, &ac97_template, &pxa2xx_ac97_ac97);
-
if (ret)
-
goto err_remove;
-
////(3)////
-
snprintf(card->shortname, sizeof(card->shortname),
-
"%s", snd_ac97_get_short_name(pxa2xx_ac97_ac97));
-
snprintf(card->longname, sizeof(card->longname),
-
"%s (%s)", dev->dev.driver->name, card->mixername);
-
-
if (pdata && pdata->codec_pdata[0])
-
snd_ac97_dev_add_pdata(ac97_bus->codec[0], pdata->codec_pdata[0]);
-
snd_card_set_dev(card, &dev->dev);
-
////(5)////
-
ret = snd_card_register(card);
-
if (ret == 0) {
-
platform_set_drvdata(dev, card);
-
return 0;
-
}
-
-
err_remove:
-
pxa2xx_ac97_hw_remove(dev);
-
err:
-
if (card)
-
snd_card_free(card);
-
err_dev:
-
return ret;
-
}
-
-
static int __devexit pxa2xx_ac97_remove(struct platform_device *dev)
-
{
-
struct snd_card *card = platform_get_drvdata(dev);
-
-
if (card) {
-
snd_card_free(card);
-
platform_set_drvdata(dev, NULL);
-
pxa2xx_ac97_hw_remove(dev);
-
}
-
-
return 0;
-
}
-
-
static struct platform_driver pxa2xx_ac97_driver = {
-
.probe = pxa2xx_ac97_probe,
-
.remove = __devexit_p(pxa2xx_ac97_remove),
-
.driver = {
-
.name = "pxa2xx-ac97",
-
.owner = THIS_MODULE,
-
#ifdef CONFIG_PM
-
.pm = &pxa2xx_ac97_pm_ops,
-
#endif
-
},
-
};
-
-
static int __init pxa2xx_ac97_init(void)
-
{
-
return platform_driver_register(&pxa2xx_ac97_driver);
-
}
-
-
static void __exit pxa2xx_ac97_exit(void)
-
{
-
platform_driver_unregister(&pxa2xx_ac97_driver);
-
}
-
-
module_init(pxa2xx_ac97_init);
-
module_exit(pxa2xx_ac97_exit);
-
-
MODULE_AUTHOR("Nicolas Pitre");
-
MODULE_DESCRIPTION("AC97 driver for the Intel PXA2xx chip");
3. snd_card_create()
-
/**
-
* snd_card_create - create and initialize a soundcard structure
-
* @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
-
*
-
* Creates and initializes a soundcard structure.
-
*
-
* 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.
-
*
-
* Returns zero if successful or a negative error code.
-
*/
-
int snd_card_create(int idx, const char *xid,
-
struct module *module, int extra_size,
-
struct snd_card **card_ret)
-
card = kzalloc(sizeof(*card) + extra_size, GFP_KERNEL);
-
if (!card)
-
return -ENOMEM;
-
if (xid)
-
strlcpy(card->id, xid, sizeof(card->id));
-
if (idx < 0) {
-
for (idx2 = 0; idx2 < SNDRV_CARDS; idx2++)
-
/* idx == -1 == 0xffff means: take any free slot */
-
if (~snd_cards_lock & idx & 1<<idx2) {
-
if (module_slot_match(module, idx2)) {
-
idx = idx2;
-
break;
-
}
-
}
-
}
-
if (idx < 0) {
-
for (idx2 = 0; idx2 < SNDRV_CARDS; idx2++)
-
/* idx == -1 == 0xffff means: take any free slot */
-
if (~snd_cards_lock & idx & 1<<idx2) {
-
if (!slots[idx2] || !*slots[idx2]) {
-
idx = idx2;
-
break;
-
}
-
}
-
}
-
card->number = idx;
-
card->module = module;
-
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);
-
init_waitqueue_head(&card->shutdown_sleep);
-
#ifdef CONFIG_PM
-
mutex_init(&card->power_lock);
-
init_waitqueue_head(&card->power_sleep);
-
#endif
-
/* 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);
-
err = snd_info_card_create(card);
-
if (extra_size > 0)
-
card->private_data = (char *)card + sizeof(struct snd_card);
4. snd_card_register()
-
/**
-
* 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.
-
*
-
* Returns zero otherwise a negative error code if the registrain failed.
-
*/
-
int snd_card_register(struct snd_card *card)
-
if (!card->card_dev) {
-
card->card_dev = device_create(sound_class, card->dev,
-
MKDEV(0, 0), card,
-
"card%i", card->number);
-
if (IS_ERR(card->card_dev))
-
card->card_dev = NULL;
-
}
-
static char *sound_devnode(struct device *dev, mode_t *mode)
-
{
-
if (MAJOR(dev->devt) == SOUND_MAJOR)
-
return NULL;
-
return kasprintf(GFP_KERNEL, "snd/%s", dev_name(dev));
-
}
-
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;
-
}
-
if ((err = snd_device_register_all(card)) < 0)
-
return err;