codec reg cache初始化

1. 注册codec时添加reg cache

static struct snd_soc_codec_driver soc_codec_driver = {
	......

	.reg_cache_size = MSM8X16_WCD_CACHE_SIZE,
	.reg_cache_default = msm8x16_wcd_reset_reg_defaults,
	.reg_word_size = 1,

	......
};

static int msm8x16_wcd_spmi_probe(struct spmi_device *spmi)
{
	......

	ret = snd_soc_register_codec(&spmi->dev, &soc_codec_driver,
				     msm8x16_wcd_i2s_dai,
				     ARRAY_SIZE(msm8x16_wcd_i2s_dai));
	......
}

int snd_soc_register_codec(struct device *dev,
			   const struct snd_soc_codec_driver *codec_drv,
			   struct snd_soc_dai_driver *dai_drv,
			   int num_dai)
{
	......

	if (codec_drv->reg_cache_size && codec_drv->reg_word_size) {
		reg_size = codec_drv->reg_cache_size * codec_drv->reg_word_size;
		codec->reg_size = reg_size; //得到codec的cache大小并保存在codec->reg_size中
		/* it is necessary to make a copy of the default register cache
		 * because in the case of using a compression type that requires
		 * the default register cache to be marked as the
		 * kernel might have freed the array by the time we initialize
		 * the cache.
		 */
		if (codec_drv->reg_cache_default) {
			//将reg cache保存在codec->reg_def_copy中
			codec->reg_def_copy = kmemdup(codec_drv->reg_cache_default,
						      reg_size, GFP_KERNEL);
			if (!codec->reg_def_copy) {
				ret = -ENOMEM;
				goto fail_codec_name;
			}
		}
	}
	......
}

　　

2. 注册声卡时为codec初始化reg cache

static int snd_soc_instantiate_card(struct snd_soc_card *card)
{
	......

	/* initialize the register cache for each available codec */
	list_for_each_entry(codec, &codec_list, list) {
		if (codec->cache_init)
			continue;
		/* by default we don't override the compress_type */
		compress_type = 0;
		/* check to see if we need to override the compress_type */
		for (i = 0; i < card->num_configs; ++i) {
			codec_conf = &card->codec_conf[i];
			if (!strcmp(codec->name, codec_conf->dev_name)) {
				compress_type = codec_conf->compress_type;
				if (compress_type && compress_type != codec->compress_type)
					break;
			}
		}

		ret = snd_soc_init_codec_cache(codec, compress_type);
		if (ret < 0)
			goto base_error;
	}
	
	......
}

static int snd_soc_init_codec_cache(struct snd_soc_codec *codec,
				    enum snd_soc_compress_type compress_type)
{
	int ret;

	/* 如果cache已完成初始化，返回 */
	if (codec->cache_init)
		return 0;

	/* override the compress_type if necessary */
	if (compress_type && codec->compress_type != compress_type)
		codec->compress_type = compress_type;
	ret = snd_soc_cache_init(codec);
	......
	/* 标记codec的cache已初始化好 */
	codec->cache_init = 1;
	return 0;
}

int snd_soc_cache_init(struct snd_soc_codec *codec)
{
	int i;

	for (i = 0; i < ARRAY_SIZE(cache_types); ++i)
		if (cache_types[i].id == codec->compress_type)
			break;

	/* Fall back to flat compression */
	if (i == ARRAY_SIZE(cache_types)) {
		dev_warn(codec->dev, "ASoC: Could not match compress type: %d\n",
			 codec->compress_type);
		i = 0;
	}

	mutex_init(&codec->cache_rw_mutex);
	codec->cache_ops = &cache_types[i]; //初始化codec的cache_ops

	if (codec->cache_ops->init) {
		/* snd_soc_flat_cache_init() */
		return codec->cache_ops->init(codec);
	}
	return -ENOSYS;
}

static int snd_soc_flat_cache_init(struct snd_soc_codec *codec)
{
	if (codec->reg_def_copy)
		codec->reg_cache = kmemdup(codec->reg_def_copy,
					   codec->reg_size, GFP_KERNEL); //从codec->reg_def_copy复制一份cache保存在codec->reg_cache中
	else
		codec->reg_cache = kzalloc(codec->reg_size, GFP_KERNEL);
	if (!codec->reg_cache)
		return -ENOMEM;

	return 0;
}