(1) ASoC被分为Machine、Platform和Codec三大部分，其中的Machine驱动负责Platform和Codec之间的耦合以及部分和设备或板子特定的代码，Machine驱动负责处理机器特有的一些控件和音频事件（例如，当播放音频时，需要先行打开一个放大器）；单独的Platform和Codec驱动是不能工作的，它必须由Machine驱动把它们结合在一起才能完成整个设备的音频处理工作。
ASoC的一切都从Machine驱动开始，包括声卡的注册，绑定Platform和Codec驱动等等，下面就让我们从Machine驱动开始讨论吧。
(1) 我们驱动machine platform_device 和platform_driver得注册
platform device arch/mips/xburst/soc-x1630/common/platform.c struct platform_device snd_alsa_device = { .name = "ingenic-alsa", };
platform driver static struct snd_soc_dai_link pd_x1830_audio_dais[] = { [0] = { .name = "pd_x1830_audio ICDC", .stream_name = "pd_x1830_audio ICDC", .platform_name = "jz-asoc-aic-dma", .cpu_dai_name = "jz-asoc-aic-i2s", .init = pd_x1830_audio_dlv_dai_link_init, .codec_dai_name = "icdc-d4-hifi", .codec_name = "icdc-d4", .dai_fmt = SND_SOC_DAIFMT_I2S|SND_SOC_DAIFMT_CBM_CFM, .ops = &pd_x1830_audio_i2s_ops, }, [1] = { .name = "canna DMIC", .stream_name = "canna DMIC", .platform_name = "jz-asoc-dmic-dma", .cpu_dai_name = "jz-asoc-dmic", .codec_dai_name = "dmic-codec-hifi", .codec_name = "jz-asoc-dmic", },
};
static struct snd_soc_card pd_x1830_audio = { .name = UNI_SOUND_CARD_NAME, .owner = THIS_MODULE, .dai_link = pd_x1830_audio_dais, .num_links = ARRAY_SIZE(pd_x1830_audio_dais), };
static int snd_pd_x1830_audio_probe(struct platform_device *pdev) { pd_x1830_audio.dev = &pdev->dev; ret = snd_soc_register_card(&pd_x1830_audio); //注册声卡设备 }
static struct platform_driver snd_pd_x1830_audio_driver = { .driver = { .owner = THIS_MODULE, .name = "ingenic-alsa", .pm = &snd_soc_pm_ops, }, .probe = snd_pd_x1830_audio_probe, .remove = snd_pd_x1830_audio_remove, }; module_platform_driver(snd_pd_x1830_audio_driver);
通过snd_soc_card结构，又引出了Machine驱动的另外两个个数据结构： snd_soc_dai_link（实例：pd_x1830_audio_dais ） snd_soc_ops（实例：pd_x1830_audio_i2s_ops ）
其中，snd_soc_dai_link中，指定了Platform、Codec、codec_dai、cpu_dai的名字，稍后Machine驱动将会利用这些名字去匹配已经在系统中注册的platform，codec，dai，这些注册的部件都是在另外相应的Platform驱动和Codec驱动的代码文件中定义的，这样看来，Machine驱动的设备初始化代码无非就是选择合适Platform和Codec以及dai，用他们填充以上几个数据结构，然后注册Platform设备即可。当然还要实现连接Platform和Codec的dai_link对应的ops实现，本例就是pd_x1830_audio_i2s_ops，它只实现了hw_params函数：pd_x1830_audio_i2s_hw_params。
sound/soc/soc-core.c static int __init snd_soc_init(void) { return platform_driver_register(&soc_driver); //这个驱动的probe我们没有走 }
static int soc_probe(struct platform_device *pdev)
分析我们probe干的活 static int snd_pd_x1830_audio_probe(struct platform_device *pdev) { pd_x1830_audio.dev = &pdev->dev; ret = snd_soc_register_card(&pd_x1830_audio); //注册声卡设备 }
int snd_soc_register_card(struct snd_soc_card *card) { for (i = 0; i < card->num_links; i++) { struct snd_soc_dai_link *link = &card->dai_link[i];
/* * Codec must be specified by 1 of name or OF node, * not both or neither. */ if (!!link->codec_name == !!link->codec_of_node) { dev_err(card->dev, "ASoC: Neither/both codec" " name/of_node are set for %s\n", link->name); return -EINVAL; } /* Codec DAI name must be specified */ if (!link->codec_dai_name) { dev_err(card->dev, "ASoC: codec_dai_name not" " set for %s\n", link->name); return -EINVAL; }
/* * Platform may be specified by either name or OF node, but * can be left unspecified, and a dummy platform will be used. */ if (link->platform_name && link->platform_of_node) { dev_err(card->dev, "ASoC: Both platform name/of_node" " are set for %s\n", link->name); return -EINVAL; }
/* * CPU device may be specified by either name or OF node, but * can be left unspecified, and will be matched based on DAI * name alone.. */ if (link->cpu_name && link->cpu_of_node) { dev_err(card->dev, "ASoC: Neither/both " "cpu name/of_node are set for %s\n",link->name); return -EINVAL; } /* * At least one of CPU DAI name or CPU device name/node must be * specified */ if (!link->cpu_dai_name && !(link->cpu_name || link->cpu_of_node)) { dev_err(card->dev, "ASoC: Neither cpu_dai_name nor " "cpu_name/of_node are set for %s\n", link->name); return -EINVAL; } }
snd_soc_initialize_card_lists(card); //系统中所有的Codec、DAI、Platform都在注册时连接到这三个全局链表上 INIT_LIST_HEAD(&card->dai_dev_list); INIT_LIST_HEAD(&card->codec_dev_list); INIT_LIST_HEAD(&card->platform_dev_list); INIT_LIST_HEAD(&card->widgets); INIT_LIST_HEAD(&card->paths); INIT_LIST_HEAD(&card->dapm_list);
card->rtd = devm_kzalloc(card->dev, sizeof(struct snd_soc_pcm_runtime) * (card->num_links + card->num_aux_devs), GFP_KERNEL);
for (i = 0; i < card->num_links; i++) card->rtd[i].dai_link = &card->dai_link[i];
INIT_LIST_HEAD(&card->list); INIT_LIST_HEAD(&card->dapm_dirty); card->instantiated = 0; mutex_init(&card->mutex); mutex_init(&card->dapm_mutex);
ret = snd_soc_instantiate_card(card); if (ret != 0) soc_cleanup_card_debugfs(card);
return ret;
}
//snd_pd_x1830_audio_probe函数本身很简单，通过snd_soc_register_card，为snd_soc_pcm_runtime数组申请内存，每一个dai_link对应snd_soc_pcm_runtime数组的一个单元，然后把snd_soc_card中的dai_link配置复制到相应的snd_soc_pcm_runtime中，最后，大部分的工作都在snd_soc_instantiate_card中实现，下面就看看snd_soc_instantiate_card做了些什么：
static int snd_soc_instantiate_card(struct snd_soc_card *card) { /* bind DAIs */ for (i = 0; i < card->num_links; i++) { ret = soc_bind_dai_link(card, i); if (ret != 0) goto base_error; } //ASoC定义了三个全局的链表头变量：codec_list、dai_list、platform_list，系统中所有的Codec、DAI、Platform都在注册时连接到这三个全局链表上。soc_bind_dai_link函数逐个扫描这三个链表，根据card->dai_link[]中的名称进行匹配，匹配后把相应的codec，dai和platform实例赋值到card->rtd[]中（snd_soc_pcm_runtime）。经过这个过程后，snd_soc_pcm_runtime：（card->rtd）中保存了本Machine中使用的Codec，DAI和Platform驱动的信息
/* 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; }
/* card bind complete so register a sound card */ ret = snd_card_create(SNDRV_DEFAULT_IDX1, SNDRV_DEFAULT_STR1, card->owner, 0, &card->snd_card); if (ret < 0) { dev_err(card->dev, "ASoC: can't create sound card for" " card %s: %d\n", card->name, ret); goto base_error; } card->snd_card->dev = card->dev;
card->dapm.bias_level = SND_SOC_BIAS_OFF; card->dapm.dev = card->dev; card->dapm.card = card; list_add(&card->dapm.list, &card->dapm_list); //初始化Codec的寄存器缓存，然后调用标准的alsa函数创建声卡实例
/* initialise the sound card only once */ if (card->probe) { ret = card->probe(card); //依次调用各个子结构的probe函数 if (ret < 0) goto card_probe_error; } //
/* probe all components used by DAI links on this card */ for (order = SND_SOC_COMP_ORDER_FIRST; order <= SND_SOC_COMP_ORDER_LAST; order++) { for (i = 0; i < card->num_links; i++) { ret = soc_probe_link_components(card, i, order); //ret = soc_probe_codec(card, cpu_dai->codec); --->codec->driver->probe ret = soc_probe_platform(card, platform);--->platform->driver->probe if (ret < 0) { dev_err(card->dev, "ASoC: failed to instantiate card %d\n", ret); goto probe_dai_err; } } }
/* probe all DAI links on this card */ for (order = SND_SOC_COMP_ORDER_FIRST; order <= SND_SOC_COMP_ORDER_LAST; order++) { for (i = 0; i < card->num_links; i++) { ret = soc_probe_link_dais(card, i, order); //cpu_dai->driver->probe //codec_dai->driver->probe
if (ret < 0) { dev_err(card->dev, "ASoC: failed to instantiate card %d\n", ret); goto probe_dai_err; } } }
}
static int soc_probe_link_dais(struct snd_soc_card *card, int num, int order) //该函数出了挨个调用了codec，dai和platform驱动的probe函数 cpu_dai->driver->probe codec_dai->driver->probe { /* probe the cpu_dai */ if (!cpu_dai->probed && cpu_dai->driver->probe_order == order) { if (!cpu_dai->codec) { cpu_dai->dapm.card = card; if (!try_module_get(cpu_dai->dev->driver->owner)) return -ENODEV;
list_add(&cpu_dai->dapm.list, &card->dapm_list); snd_soc_dapm_new_dai_widgets(&cpu_dai->dapm, cpu_dai); }
if (cpu_dai->driver->probe) { ret = cpu_dai->driver->probe(cpu_dai); if (ret < 0) { dev_err(cpu_dai->dev, "ASoC: failed to probe CPU DAI %s: %d\n", cpu_dai->name, ret); module_put(cpu_dai->dev->driver->owner); return ret; } } cpu_dai->probed = 1; /* mark cpu_dai as probed and add to card dai list */ list_add(&cpu_dai->card_list, &card->dai_dev_list); }
/* probe the CODEC DAI */ if (!codec_dai->probed && codec_dai->driver->probe_order == order) { if (codec_dai->driver->probe) { ret = codec_dai->driver->probe(codec_dai); if (ret < 0) { dev_err(codec_dai->dev, "ASoC: failed to probe CODEC DAI %s: %d\n", codec_dai->name, ret); return ret; } /* mark codec_dai as probed and add to card dai list */ codec_dai->probed = 1; list_add(&codec_dai->card_list, &card->dai_dev_list); }
if (!dai_link->params) { /* create the pcm */ ret = soc_new_pcm(rtd, num); if (ret < 0) { dev_err(card->dev, "ASoC: can't create pcm %s :%d\n", dai_link->stream_name, ret); return ret; } //该函数出了挨个调用了codec，dai和platform驱动的probe函数外，在最后还调用了soc_new_pcm()函数用于创建标准alsa驱动的pcm逻辑设备
if (!dai_link->params) { /* create the pcm */ ret = soc_new_pcm(rtd, num); if (ret < 0) { dev_err(card->dev, "ASoC: can't create pcm %s :%d\n", dai_link->stream_name, ret); return ret; } } else { /* link the DAI widgets */ play_w = codec_dai->playback_widget; capture_w = cpu_dai->capture_widget; if (play_w && capture_w) { ret = snd_soc_dapm_new_pcm(card, dai_link->params, capture_w, play_w); if (ret != 0) { dev_err(card->dev, "ASoC: Can't link %s to %s: %d\n", play_w->name, capture_w->name, ret); return ret; } }
play_w = cpu_dai->playback_widget; capture_w = codec_dai->capture_widget; if (play_w && capture_w) { ret = snd_soc_dapm_new_pcm(card, dai_link->params, capture_w, play_w); if (ret != 0) { dev_err(card->dev, "ASoC: Can't link %s to %s: %d\n", play_w->name, capture_w->name, ret); return ret; } } } } //成snd_card和snd_pcm的创建后，接着对dapm和dai支持的格式做出一些初始化合设置工作后，调用了 card->late_probe(card)进行一些最后的初始化合设置工作
}
int soc_new_pcm(struct snd_soc_pcm_runtime *rtd, int num) { //该函数首先初始化snd_soc_runtime中的snd_pcm_ops字段，也就是rtd->ops中的部分成员，例如open，close，hw_params等，紧接着调用标准alsa驱动中的创建pcm的函数snd_pcm_new()创建声卡的pcm实例，pcm的private_data字段设置为该runtime变量rtd，然后用platform驱动中的snd_pcm_ops替换部分pcm中的snd_pcm_ops字段，最后，调用platform驱动的pcm_new回调，该回调实现该platform下的dma内存申请和dma初始化等相关工作。到这里，声卡和他的pcm实例创建完成。 }
整个Machine驱动的初始化已经完成，通过各个子结构的probe调用，实际上，也完成了部分Platfrom驱动和Codec驱动的初始化工作，整个过程可以用一下的序列图表示
static int soc_probe_link_components(struct snd_soc_card *card, int num,int order) { ret = soc_probe_codec(card, cpu_dai->codec); --->codec->driver->probe ret = soc_probe_platform(card, platform);--->platform->driver->probe }
static int soc_probe_link_dais(struct snd_soc_card *card, int num, int order) { //该函数出了挨个调用了codec，dai和platform驱动的probe函数 cpu_dai->driver->probe codec_dai->driver->probe }
总结：
sound/soc/ingenic/asoc-board/pd_x1830_audio_icdc.c platform driver static struct snd_soc_dai_link pd_x1830_audio_dais[] = { [0] = { .name = "pd_x1830_audio ICDC", .stream_name = "pd_x1830_audio ICDC", .platform_name = "jz-asoc-aic-dma", .cpu_dai_name = "jz-asoc-aic-i2s", .init = pd_x1830_audio_dlv_dai_link_init, .codec_dai_name = "icdc-d4-hifi", .codec_name = "icdc-d4", .dai_fmt = SND_SOC_DAIFMT_I2S|SND_SOC_DAIFMT_CBM_CFM, .ops = &pd_x1830_audio_i2s_ops, },
.cpu_dai_name = "jz-asoc-aic-i2s", sound/soc/ingenic/asoc-v12/asoc-i2s-v12.c static struct platform_driver jz_i2s_plat_driver = { .probe = jz_i2s_platfrom_probe, .remove = jz_i2s_platfom_remove, .driver = { .name = "jz-asoc-aic-i2s", .owner = THIS_MODULE, }, };
.platform_name = "jz-asoc-aic-dma", sound/soc/ingenic/asoc-dma-hrtimer.c static const struct platform_device_id jz_dma_id_table[] = { { .name = "jz-asoc-aic-dma", /*aic dma*/ }, { .name = "jz-asoc-pcm-dma", /*pcmc dma*/ }, { .name = "jz-asoc-dmic-dma", /*dmic dma*/ }, {}, };
.codec_name = "icdc-d4", 内部codec驱动 sound/soc/ingenic/icodec/icdc_d4.c static struct platform_driver icdc_d4_codec_driver = { .driver = { .name = "icdc-d4", .owner = THIS_MODULE, }, .probe = icdc_d4_platform_probe, .remove = icdc_d4_platform_remove, };
.codec_dai_name = "icdc-d4-hifi" sound/soc/ingenic/icodec/icdc_d4.c static struct snd_soc_dai_driver icdc_d4_codec_dai = { .name = "icdc-d4-hifi", .playback = { .stream_name = "Playback", .channels_min = 2, .channels_max = 2, .rates = ICDC_D4_RATE, .formats = ICDC_D4_FORMATS, }, .capture = { .stream_name = "Capture", .channels_min = 1, .channels_max = 2, .rates = ICDC_D4_RATE, .formats = ICDC_D4_FORMATS, }, .symmetric_rates = 1, .ops = &icdc_d4_dai_ops, };
--------------------- 作者：技术芯 来源： 原文：https://blog.csdn.net/sinat_37817094/article/details/80490858 版权声明：本文为博主原创文章，转载请附上博文链接！
