PXA310音频(4)

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上面已经创建了codec 结构

接下来就要 register pcms 了。

snd_soc_new_pcms

首先创建snd_card

snd_card_new 位于sound/core/init.c 中

创建和初试化一个snd_card 结构体

struct snd_card *snd_card_new(int idx, const char *xid,

struct module *module, int extra_size)

{

struct snd_card *card;

int err;

if (extra_size < 0)

extra_size = 0;

card = kzalloc(sizeof(*card) + extra_size, GFP_KERNEL);

if (card == NULL)

return NULL;

分配了结构体

if (xid) {

if (!snd_info_check_reserved_words(xid))

goto __error;

strlcpy(card->id, xid, sizeof(card->id));

}

err = 0;

mutex_lock(&snd_card_mutex);

if (idx < 0) {

int idx2;

for (idx2 = 0; idx2 < SNDRV_CARDS; idx2++)

/* idx == -1 == 0xffff means: take any free slot */

if (~snd_cards_lock & idx & 1<<idx2) {

idx = idx2;

if (idx >= snd_ecards_limit)

snd_ecards_limit = idx + 1;

break;

}

} else {

if (idx < snd_ecards_limit) {

if (snd_cards_lock & (1 << idx))

err = -EBUSY; /* invalid */

} else {

if (idx < SNDRV_CARDS)

snd_ecards_limit = idx + 1; /* increase the limit */

else

err = -ENODEV;

}

注意上面的按位与操作

理论上可以有32个snd_card，找空闲的snd_card，如果能找到就说明是成功的

if (idx < 0 || err < 0) {

mutex_unlock(&snd_card_mutex);

snd_printk(KERN_ERR "cannot find the slot for index %d (range 0-%i), error: %d/n",

idx, snd_ecards_limit - 1, err);

goto __error;

}

snd_cards_lock |= 1 << idx; /* lock it */

将选card锁上

mutex_unlock(&snd_card_mutex);

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_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 */

if ((err = snd_ctl_create(card)) < 0) {

snd_printd("unable to register control minors/n");

goto __error;

}

对snd_card 进行

if ((err = snd_info_card_create(card)) < 0) {

snd_printd("unable to create card info/n");

goto __error_ctl;

}

分配了一个声音控制设置串到snd_card的device链表中去

这个控制设备提供了一些方法

static struct snd_device_ops ops = {

.dev_free = snd_ctl_dev_free,

.dev_register = snd_ctl_dev_register,

.dev_disconnect = snd_ctl_dev_disconnect,

};

关注一下提供的注册方法，这个在后面会被调用

static int snd_ctl_dev_register(struct snd_device *device)

{

struct snd_card *card = device->device_data;

int err, cardnum;

char name[16];

snd_assert(card != NULL, return -ENXIO);

cardnum = card->number;

snd_assert(cardnum >= 0 && cardnum < SNDRV_CARDS, return -ENXIO);

sprintf(name, "controlC%i", cardnum);

if ((err = snd_register_device(SNDRV_DEVICE_TYPE_CONTROL, card, -1,

&snd_ctl_f_ops, card, name)) < 0)

return err;

return 0;

}

接下来要进行真正的注册

int snd_register_device_for_dev(int type, struct snd_card *card, int dev,

const struct file_operations *f_ops,

void *private_data,

const char *name, struct device *device)

{

int minor;

struct snd_minor *preg;

snd_assert(name, 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;

mutex_lock(&sound_mutex);

#ifdef CONFIG_SND_DYNAMIC_MINORS

minor = snd_find_free_minor();

#else

minor = snd_kernel_minor(type, card, dev);

if (minor >= 0 && snd_minors[minor])

minor = -EBUSY;

#endif

if (minor < 0) {

mutex_unlock(&sound_mutex);

kfree(preg);

return minor;

}

snd_minors[minor] = preg;

在sound.c 中维护了如下数组

static struct snd_minor *snd_minors[SNDRV_OS_MINORS];

上面的代码首先创建了一个snd_minor，封装了相应的方法和数据

preg->dev = device_create(sound_class, device, MKDEV(major, minor),

"%s", name);

if (preg->dev)

dev_set_drvdata(preg->dev, private_data);

接下来真正的创建这个设备

mutex_unlock(&sound_mutex);

return 0;

}

if (extra_size > 0)

card->private_data = (char *)card + sizeof(struct snd_card);

return card;

__error_ctl:

snd_device_free_all(card, SNDRV_DEV_CMD_PRE);

__error:

kfree(card);

return NULL;

}

不过，register的时机还没有到，当前只是创建了一个控制设备结构体，将他串到了card上。

接着在proc 文件系统中创建card节点了

Card 有了，pcm呢？

Pcm的创建根据dai接口的数量来创建,pxa310 中有2个dai

也就是调用2次soc_new_pcm

首先分配runtime结构 snd_soc_pcm_runtime

Cpu dai的类型就ac97 i2s pcm 等

分配一个snd_pcm_t 结构体

为snd_pcm_t 下的播放流和采集流下的子流设置各种方法

接下来调用 platform的pcm_new方法，预先分配dmabuffer

到这里我们已经创建了2个pcm了

然后我们为card添加了一些控制设备

注册的时候将card上的所有设备一起注册了

以上就是probe 中操作的大致内容