dummy codec

1. 什么情況下需要用到虛擬codec

一般在linux 或者 android 系統(tǒng)中，沒有外掛codec，主控上也沒內置codec，但是外掛了一個i2s、spdif的接口的芯片；
比如說lt9611 ，芯片內置i2s 接口，用于接收主控的i2s 音頻信號，等案例
這個時候就需要一個dummy codec ，掛到平臺上，注冊聲卡出來。

當播放音頻時：主控播放*.wav ----平臺i2s rx ------設備lt9611 i2s —>輸出

2. 虛擬codec 的注冊到平臺的原理

實際上，就是模擬出一個codec，只有codec驅動的框架，在框架里添加codec DAI
codec dai 和平臺dai 在machine 注冊匹配的時候，能夠link上，就會注冊聲卡出來。

3.參考代碼

#include <linux/module.h> #include <linux/platform_device.h> #include <linux/slab.h> #include <sound/core.h> #include <sound/tlv.h> #include <sound/soc.h> #include <sound/soc-dapm.h> #include <sound/initval.h> #include <linux/of.h> #include <sound/soc.h>struct dummy_codec_private {struct platform_device *dummy_codec; };#define DUMMY_CODEC_RATES (SNDRV_PCM_RATE_8000_192000) #define DUMMY_CODEC_FORMATS (SNDRV_PCM_FMTBIT_S16_LE |\SNDRV_PCM_FMTBIT_S24_LE | SNDRV_PCM_FMTBIT_S32_LE)static int dummy_codec_pcm_hw_params(struct snd_pcm_substream *substream,struct snd_pcm_hw_params *params,struct snd_soc_dai *dai) {return 0; }static int dummy_codec_set_dai_fmt(struct snd_soc_dai *codec_dai,unsigned int fmt) {return 0; }static int dummy_codec_mute(struct snd_soc_dai *dai, int mute) {return 0; }#ifdef DUMMY_CODEC_ZYY static const struct snd_soc_dapm_widget dummy_codec_dapm_widgets[] = {/* Output Side *//* DACs */SND_SOC_DAPM_DAC("Left DAC", "HIFI Playback",SND_SOC_NOPM, 0, 0),SND_SOC_DAPM_DAC("Right DAC", "HIFI Playback",SND_SOC_NOPM, 7, 0),/* Output Lines */SND_SOC_DAPM_OUTPUT("LOUTL"),SND_SOC_DAPM_OUTPUT("LOUTR"),};static const struct snd_soc_dapm_route dummy_codec_dapm_routes[] = {{"LOUTL", NULL, "Left DAC"},{"LOUTR", NULL, "Right DAC"}, }; #endifstatic struct snd_soc_dai_ops dummy_codec_ops = {.hw_params = dummy_codec_pcm_hw_params,.set_fmt = dummy_codec_set_dai_fmt,.digital_mute = dummy_codec_mute, };struct snd_soc_dai_driver dummy_codec_dai = {.name = "dummy",//.id = 1,.playback = {.stream_name = "HIFI Playback",.channels_min = 1,.channels_max = 8,.rates = DUMMY_CODEC_RATES,.formats = DUMMY_CODEC_FORMATS,},.capture = {.stream_name = "HIFI Capture",.channels_min = 1,.channels_max = 2,.rates = DUMMY_CODEC_RATES,.formats = DUMMY_CODEC_FORMATS,},.ops = &dummy_codec_ops, };static int dummy_codec_probe(struct snd_soc_component *component) {struct dummy_codec_private *dummy_codec;dummy_codec = snd_soc_component_get_drvdata(component);if(dummy_codec == NULL){pr_err("%s, codec is not registered\n", __func__);printk("zyy.........................%s..................%d",__func__,__LINE__);return 0;}return 0; }static void dummy_codec_remove(struct snd_soc_component *component) { if(component == NULL)printk("zyy.........................%s..................%d",__func__,__LINE__);return; };struct snd_soc_component_driver soc_codec_dev_dummy_codec = {.probe = dummy_codec_probe,.remove = dummy_codec_remove, #ifdef DUMMY_CODEC_ZYY.dapm_widgets = dummy_codec_dapm_widgets,.num_dapm_widgets = ARRAY_SIZE(dummy_codec_dapm_widgets),.dapm_routes = dummy_codec_dapm_routes,.num_dapm_routes = ARRAY_SIZE(dummy_codec_dapm_routes), #endif };static const struct of_device_id dummy_codec_dt_match[] = {{.compatible = "dummy_codec",},{}, };static int dummy_codec_platform_probe(struct platform_device *pdev) {struct dummy_codec_private *dummy_codec;int ret;printk("zyy.........................%s..................%d",__func__,__LINE__);dummy_codec = kzalloc(sizeof(struct dummy_codec_private), GFP_KERNEL);if (dummy_codec == NULL)return -ENOMEM;ret = devm_snd_soc_register_component(&pdev->dev, &soc_codec_dev_dummy_codec,&dummy_codec_dai, 1);if (ret < 0)printk("zyy.........................%s..................%d",__func__,__LINE__);return ret; }static int dummy_codec_platform_remove(struct platform_device *pdev) {snd_soc_unregister_component(&pdev->dev);return 0; }static struct platform_driver dummy_codec_platform_driver = {.driver = {.name = "dummy",.owner = THIS_MODULE,.of_match_table = dummy_codec_dt_match,},.probe = dummy_codec_platform_probe,.remove = dummy_codec_platform_remove, };static int __init dummy_codec_init(void) {return platform_driver_register(&dummy_codec_platform_driver); }static void __exit dummy_codec_exit(void) {platform_driver_unregister(&dummy_codec_platform_driver); }module_init(dummy_codec_init); module_exit(dummy_codec_exit);MODULE_AUTHOR("ZYY, Inc."); MODULE_DESCRIPTION("ASoC dummy_codec driver"); MODULE_LICENSE("GPL");

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