ASOC的出现是为了让Codec独立于CPU,减少和CPU之间的耦合,这样同一个Codec驱动无需修 改就可以适用任何一款平台。还是以下图做参考例子:
在Machine中已经知道,snd_soc_dai_link结构就指明了该Machine所使用的Platform和Codec。在Codec这边通过codec_dai和Platform侧的cpu_dai相互通信,既然相互通信,就需要遵守一定的规则,其中codec_dai和cpu_dai统一抽象为struct snd_soc_dai结构,而将dai的相关操作使用snd_soc_dai_driver抽象。同时也需要对所有的codec设备进行抽象封装,linux使用snd_soc_codec进行所有codec设备的抽象,而将codec的驱动抽象为snd_soc_codec_driver结构。
所有简单来说,Codec侧有四个重要的数据结构:
struct snd_soc_dai,struct snd_soc_dai_driver,struct snd_soc_codec,struct snd_soc_codec_driver。
分析例子:
machine: sound\soc\samsung\s3c24xx_uda134x.c
platform: sound\soc\samsung\s3c24xx-i2s.c
codec: sound\soc\codecs\uda134x.c
如何找到codec的代码呢? 答案是通过machine中的snd_soc_dai_link结构:
static struct snd_soc_dai_link s3c24xx_uda134x_dai_link = {
.name = "UDA134X",
.stream_name = "UDA134X",
.codec_name = "uda134x-codec",
.codec_dai_name = "uda134x-hifi",
.cpu_dai_name = "s3c24xx-iis",
.ops = &s3c24xx_uda134x_ops,
.platform_name = "s3c24xx-iis",
};
在内核中搜索codec_name="uda134x-codec",会在kernel/sound/soc/codec/uda134x.c中发现。
static struct platform_driver uda134x_codec_driver = {
.driver = {
.name = "uda134x-codec",
},
.probe = uda134x_codec_probe,
.remove = uda134x_codec_remove,
};
之间查看此platform_driver的probe函数。
static int uda134x_codec_probe(struct platform_device *pdev)
{
struct uda134x_platform_data *pd = pdev->dev.platform_data;
struct uda134x_priv *uda134x;
int ret;
if (!pd) {
dev_err(&pdev->dev, "Missing L3 bitbang function\n");
return -ENODEV;
}
uda134x = devm_kzalloc(&pdev->dev, sizeof(*uda134x), GFP_KERNEL);
if (!uda134x)
return -ENOMEM;
uda134x->pd = pd;
platform_set_drvdata(pdev, uda134x);
if (pd->l3.use_gpios) {
ret = l3_set_gpio_ops(&pdev->dev, &uda134x->pd->l3);
if (ret < 0)
return ret;
}
uda134x->regmap = devm_regmap_init(&pdev->dev, NULL, pd,
&uda134x_regmap_config);
if (IS_ERR(uda134x->regmap))
return PTR_ERR(uda134x->regmap);
return snd_soc_register_codec(&pdev->dev,
&soc_codec_dev_uda134x, &uda134x_dai, 1);
}
此出通过snd_soc_register_codec函数注册了uda134x的codec,同时传入了snd_soc_codec_driver和snd_soc_dai_driver结构。
static const struct snd_soc_codec_driver soc_codec_dev_uda134x = {
.probe = uda134x_soc_probe,
.set_bias_level = uda134x_set_bias_level,
.suspend_bias_off = true,
.component_driver = {
.dapm_widgets = uda134x_dapm_widgets,
.num_dapm_widgets = ARRAY_SIZE(uda134x_dapm_widgets),
.dapm_routes = uda134x_dapm_routes,
.num_dapm_routes = ARRAY_SIZE(uda134x_dapm_routes),
},
};
snd_soc_dai_driver结构:
static const struct snd_soc_dai_ops uda134x_dai_ops = {
.startup = uda134x_startup,
.shutdown = uda134x_shutdown,
.hw_params = uda134x_hw_params,
.digital_mute = uda134x_mute,
.set_sysclk = uda134x_set_dai_sysclk,
.set_fmt = uda134x_set_dai_fmt,
};
static struct snd_soc_dai_driver uda134x_dai = {
.name = "uda134x-hifi",
/* playback capabilities */
.playback = {
.stream_name = "Playback",
.channels_min = 1,
.channels_max = 2,
.rates = UDA134X_RATES,
.formats = UDA134X_FORMATS,
},
/* capture capabilities */
.capture = {
.stream_name = "Capture",
.channels_min = 1,
.channels_max = 2,
.rates = UDA134X_RATES,
.formats = UDA134X_FORMATS,
},
/* pcm operations */
.ops = &uda134x_dai_ops,
};
/**
* snd_soc_register_codec - Register a codec with the ASoC core
*
* @dev: The parent device for this codec
* @codec_drv: Codec driver
* @dai_drv: The associated DAI driver
* @num_dai: Number of DAIs
*/
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)
{
struct snd_soc_dapm_context *dapm;
struct snd_soc_codec *codec;
struct snd_soc_dai *dai;
int ret, i;
dev_dbg(dev, "codec register %s\n", dev_name(dev));
codec = kzalloc(sizeof(struct snd_soc_codec), GFP_KERNEL);
if (codec == NULL)
return -ENOMEM;
codec->component.codec = codec;
ret = snd_soc_component_initialize(&codec->component,
&codec_drv->component_driver, dev);
if (ret)
goto err_free;
if (codec_drv->probe)
codec->component.probe = snd_soc_codec_drv_probe;
if (codec_drv->remove)
codec->component.remove = snd_soc_codec_drv_remove;
if (codec_drv->suspend)
codec->component.suspend = snd_soc_codec_drv_suspend;
if (codec_drv->resume)
codec->component.resume = snd_soc_codec_drv_resume;
if (codec_drv->write)
codec->component.write = snd_soc_codec_drv_write;
if (codec_drv->read)
codec->component.read = snd_soc_codec_drv_read;
if (codec_drv->set_sysclk)
codec->component.set_sysclk = snd_soc_codec_set_sysclk_;
if (codec_drv->set_pll)
codec->component.set_pll = snd_soc_codec_set_pll_;
if (codec_drv->set_jack)
codec->component.set_jack = snd_soc_codec_set_jack_;
codec->component.ignore_pmdown_time = codec_drv->ignore_pmdown_time;
dapm = snd_soc_codec_get_dapm(codec);
dapm->idle_bias_off = codec_drv->idle_bias_off;
dapm->suspend_bias_off = codec_drv->suspend_bias_off;
if (codec_drv->seq_notifier)
dapm->seq_notifier = codec_drv->seq_notifier;
if (codec_drv->set_bias_level)
dapm->set_bias_level = snd_soc_codec_set_bias_level;
codec->dev = dev;
codec->driver = codec_drv;
codec->component.val_bytes = codec_drv->reg_word_size;
#ifdef CONFIG_DEBUG_FS
codec->component.init_debugfs = soc_init_codec_debugfs;
codec->component.debugfs_prefix = "codec";
#endif
if (codec_drv->get_regmap)
codec->component.regmap = codec_drv->get_regmap(dev);
for (i = 0; i < num_dai; i++) {
fixup_codec_formats(&dai_drv[i].playback);
fixup_codec_formats(&dai_drv[i].capture);
}
ret = snd_soc_register_dais(&codec->component, dai_drv, num_dai, false);
if (ret < 0) {
dev_err(dev, "ASoC: Failed to register DAIs: %d\n", ret);
goto err_cleanup;
}
list_for_each_entry(dai, &codec->component.dai_list, list)
dai->codec = codec;
mutex_lock(&client_mutex);
snd_soc_component_add_unlocked(&codec->component);
list_add(&codec->list, &codec_list);
mutex_unlock(&client_mutex);
dev_dbg(codec->dev, "ASoC: Registered codec '%s'\n",
codec->component.name);
return 0;
err_cleanup:
snd_soc_component_cleanup(&codec->component);
err_free:
kfree(codec);
return ret;
}
codec = kzalloc(sizeof(struct snd_soc_codec), GFP_KERNEL);
if (codec == NULL)
return -ENOMEM;
codec->component.codec = codec;
ret = snd_soc_component_initialize(&codec->component,
&codec_drv->component_driver, dev);
if (ret)
goto err_free;
if (codec_drv->probe)
codec->component.probe = snd_soc_codec_drv_probe;
if (codec_drv->remove)
codec->component.remove = snd_soc_codec_drv_remove;
if (codec_drv->suspend)
codec->component.suspend = snd_soc_codec_drv_suspend;
if (codec_drv->resume)
codec->component.resume = snd_soc_codec_drv_resume;
if (codec_drv->write)
codec->component.write = snd_soc_codec_drv_write;
if (codec_drv->read)
codec->component.read = snd_soc_codec_drv_read;
if (codec_drv->set_sysclk)
codec->component.set_sysclk = snd_soc_codec_set_sysclk_;
if (codec_drv->set_pll)
codec->component.set_pll = snd_soc_codec_set_pll_;
if (codec_drv->set_jack)
codec->component.set_jack = snd_soc_codec_set_jack_;
codec->component.ignore_pmdown_time = codec_drv->ignore_pmdown_time;
dapm = snd_soc_codec_get_dapm(codec);
dapm->idle_bias_off = codec_drv->idle_bias_off;
dapm->suspend_bias_off = codec_drv->suspend_bias_off;
if (codec_drv->seq_notifier)
dapm->seq_notifier = codec_drv->seq_notifier;
if (codec_drv->set_bias_level)
dapm->set_bias_level = snd_soc_codec_set_bias_level;
codec->dev = dev;
codec->driver = codec_drv;
codec->component.val_bytes = codec_drv->reg_word_size;
for (i = 0; i < num_dai; i++) {
fixup_codec_formats(&dai_drv[i].playback);
fixup_codec_formats(&dai_drv[i].capture);
}
ret = snd_soc_register_dais(&codec->component, dai_drv, num_dai, false);
if (ret < 0) {
dev_err(dev, "ASoC: Failed to register DAIs: %d\n", ret);
goto err_cleanup;
}
根据dai的数目,分配snd_soc_dai结构,根据dai的数目设置dai的名字,这是dai的传入参数驱动,然后将此dai加入到component的dai_list中。
/* Create a DAI and add it to the component's DAI list */
static struct snd_soc_dai *soc_add_dai(struct snd_soc_component *component,
struct snd_soc_dai_driver *dai_drv,
bool legacy_dai_naming)
{
struct device *dev = component->dev;
struct snd_soc_dai *dai;
dev_dbg(dev, "ASoC: dynamically register DAI %s\n", dev_name(dev));
dai = kzalloc(sizeof(struct snd_soc_dai), GFP_KERNEL);
if (dai == NULL)
return NULL;
/*
* Back in the old days when we still had component-less DAIs,
* instead of having a static name, component-less DAIs would
* inherit the name of the parent device so it is possible to
* register multiple instances of the DAI. We still need to keep
* the same naming style even though those DAIs are not
* component-less anymore.
*/
if (legacy_dai_naming &&
(dai_drv->id == 0 || dai_drv->name == NULL)) {
dai->name = fmt_single_name(dev, &dai->id);
} else {
dai->name = fmt_multiple_name(dev, dai_drv);
if (dai_drv->id)
dai->id = dai_drv->id;
else
dai->id = component->num_dai;
}
if (dai->name == NULL) {
kfree(dai);
return NULL;
}
dai->component = component;
dai->dev = dev;
dai->driver = dai_drv;
if (!dai->driver->ops)
dai->driver->ops = &null_dai_ops;
list_add(&dai->list, &component->dai_list);
component->num_dai++;
dev_dbg(dev, "ASoC: Registered DAI '%s'\n", dai->name);
return dai;
}
list_for_each_entry(dai, &codec->component.dai_list, list)
dai->codec = codec;
mutex_lock(&client_mutex);
snd_soc_component_add_unlocked(&codec->component);
list_add(&codec->list, &codec_list);
mutex_unlock(&client_mutex);
总结: 通过调用snd_soc_register_codec函数之后,分配的codec最终放入了codec_list链表中,codec下的component组件全部放入component_list链表中,codec下的dai全部存放入code->component.dai_list中。 可以在上节的Machine中看到,machine匹配codec_dai和cpu_dai也是从code->component.dai_list中获取的。
关于codec侧驱动总结:
1. 分配名字为"codec_name"的平台驱动,注册。
2. 定义struct snd_soc_codec_driver结构,设置,初始化。3. 定义struct snd_soc_dai_driver结构,设置,初始化。
4. 调用snd_soc_register_codec函数注册codec。