Linux ALSA声卡驱动之四：Codec 以及Codec |
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Linux ALSA声卡驱动之四：Codec 以及Codec
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ALSA声卡驱动：
1.Linux ALSA声卡驱动之一：ALSA架构简介和ASOC架构简介
2.Linux ALSA声卡驱动之二：Platform
3. Linux ALSA声卡驱动之三：Platform之Cpu_dai
4. Linux ALSA声卡驱动之四：Codec 以及Codec_dai
5.Linux ALSA声卡驱动之五：Machine 以及ALSA声卡的注册
6.Linux ALSA声卡驱动之六：PCM的注册流程
7.Linux ALSA声卡驱动之七：录音(Capture) 调用流程
一. Codec简介
在移动设备中，Codec的作用可以归结为4种，分别是： 对PCM等信号进行D/A转换，把数字的音频信号转换为模拟信号对Mic、Linein或者其他输入源的模拟信号进行A/D转换，把模拟的声音信号转变CPU能够处理的数字信号对音频通路进行控制，比如播放音乐，收听调频收音机，又或者接听电话时，音频信号在codec内的流通路线是不一样的对音频信号做出相应的处理，例如音量控制，功率放大，EQ控制等二、 Codec和codec_dai 的注册：snd_soc_register_codec 在第一章（Linux ALSA声卡驱动之一：ALSA架构简介和ASOC架构简介）以及介绍了platfrom可以细分platform和cpu_dai,codec可以细分codec和codec_dai ,platform和cpu_dai都有各自的驱动注册。由此猜想codec和codec_dai也是由各自的驱动注册吧，但实际却不是这样，mtk平台codec和codec_dai两部分代码都由一个驱动注册 mtk-soc-codec-63xx.c snd_soc_register_codec，其实如果拆分出来也是可以。 2.1 snd_soc_register_codec函数时序图
从上述的时序图不难看出，通过snd_soc_register_codec ， snd_soc_register_dais ， snd_soc_component_add_unlocked ， list_add(&codec->list, &codec_list)这几个函数的转变，最终会把相应的component->list添加到component_list链表 ，codec->list添加到codec_list链表。下面我们看具体的代码细节 2.2 snd_soc_register_codec 函数相关结构体图结合下图我们可以比较清晰的知道各个结构体之间的关系： 结构体snd_soc_dai 通过*driver 维护snd_soc_codec_driver ，*driver就是mtk_6357_dai_codecs。snd_soc_dai的初始化也是通过mtk_6357_dai_codecs。 通过list_add(&dai->list, &component->dai_list)，把自己添加到snd_soc_component中 snd_soc_component 通过mtk_6357_dai_codecs初始化赋值，并且*dai_drv指向mtk_6357_dai_codecs ，*driver维护snd_soc_component_driver结构体，dai_list链表头, 下面挂载snd_soc_dai：snd_soc_dai->list list_add(&dai->list, &component->dai_list)。通过list_add(&component->list, &component_list) 把snd_soc_component添加到全局链表component_list中
2.3 snd_soc_register_codec函数实现细节 2.3.1 mtk_mt6357_codec_dev_probe函数 static int mtk_mt6357_codec_dev_probe(struct platform_device *pdev) { pdev->dev.coherent_dma_mask = DMA_BIT_MASK(64); if (pdev->dev.dma_mask == NULL) pdev->dev.dma_mask = &pdev->dev.coherent_dma_mask; if (pdev->dev.of_node) { dev_set_name(&pdev->dev, "%s", MT_SOC_CODEC_NAME); /* check if use hp depop flow */ //读取use_hp_depop_flow属性值 of_property_read_u32(pdev->dev.of_node, "use_hp_depop_flow", &mUseHpDepopFlow); pr_debug("%s(), use_hp_depop_flow = %d\n", __func__, mUseHpDepopFlow); } else { pr_debug("%s(), pdev->dev.of_node = NULL!!!\n", __func__); } pr_debug("%s: dev name %s\n", __func__, dev_name(&pdev->dev)); return snd_soc_register_codec(&pdev->dev, &soc_mtk_codec, mtk_6357_dai_codecs, ARRAY_SIZE(mtk_6357_dai_codecs)); } soc_mtk_codec 这个结构体我们暂时不分析，其中不难看出，主要是对probe remove read write 函数的驱动层实现 static struct snd_soc_codec_driver soc_mtk_codec = { .probe = mt6357_codec_probe, .remove = mt6357_codec_remove, .read = mt6357_read, .write = mt6357_write, }; mtk_6357_dai_codecs static struct snd_soc_dai_driver mtk_6357_dai_codecs[] = { { .name = MT_SOC_CODEC_TXDAI_NAME, .ops = &mt6323_aif1_dai_ops, .playback = { .stream_name = MT_SOC_DL1_STREAM_NAME, .channels_min = 1, .channels_max = 2, .rates = SNDRV_PCM_RATE_8000_192000, .formats = SND_SOC_ADV_MT_FMTS, }, }, { .name = MT_SOC_CODEC_RXDAI_NAME, .ops = &mt6323_aif1_dai_ops, .capture = { .stream_name = MT_SOC_UL1_STREAM_NAME, .channels_min = 1, .channels_max = 2, .rates = SOC_HIGH_USE_RATE, .formats = SND_SOC_ADV_MT_FMTS, }, }, { .name = MT_SOC_CODEC_TDMRX_DAI_NAME, .ops = &mt6323_aif1_dai_ops, .capture = { .stream_name = MT_SOC_TDM_CAPTURE_STREAM_NAME, .channels_min = 2, .channels_max = 2, .rates = SNDRV_PCM_RATE_8000_192000, .formats = (SNDRV_PCM_FMTBIT_U8 | SNDRV_PCM_FMTBIT_S8 | SNDRV_PCM_FMTBIT_U16_LE | SNDRV_PCM_FMTBIT_S16_LE | SNDRV_PCM_FMTBIT_U16_BE | SNDRV_PCM_FMTBIT_S16_BE | SNDRV_PCM_FMTBIT_U24_LE | SNDRV_PCM_FMTBIT_S24_LE | SNDRV_PCM_FMTBIT_U24_BE | SNDRV_PCM_FMTBIT_S24_BE | SNDRV_PCM_FMTBIT_U24_3LE | SNDRV_PCM_FMTBIT_S24_3LE | SNDRV_PCM_FMTBIT_U24_3BE | SNDRV_PCM_FMTBIT_S24_3BE | SNDRV_PCM_FMTBIT_U32_LE | SNDRV_PCM_FMTBIT_S32_LE | SNDRV_PCM_FMTBIT_U32_BE | SNDRV_PCM_FMTBIT_S32_BE), }, }, { .name = MT_SOC_CODEC_I2S0TXDAI_NAME, .ops = &mt6323_aif1_dai_ops, .playback = { .stream_name = MT_SOC_I2SDL1_STREAM_NAME, .channels_min = 1, .channels_max = 2, .rate_min = 8000, .rate_max = 192000, .rates = SNDRV_PCM_RATE_8000_192000, .formats = SND_SOC_ADV_MT_FMTS, }, }, ........
如上代码也就是对snd_soc_dai_driver结构体赋值，取得mtk_6357_dai_codecs数组，这个跟上一章节(Linux ALSA声卡驱动之三：Platform之Cpu_dai)，mtk_dai_stub_dai 数组获取一样。下面是snd_soc_dai_driver 和snd_soc_pcm_stream 两个结构体的构成。 snd_soc_dai_driver struct snd_soc_dai_driver { /* DAI description */ const char *name; unsigned int id; unsigned int base; /* DAI driver callbacks */ int (*probe)(struct snd_soc_dai *dai); int (*remove)(struct snd_soc_dai *dai); int (*suspend)(struct snd_soc_dai *dai); int (*resume)(struct snd_soc_dai *dai); /* compress dai */ int (*compress_new)(struct snd_soc_pcm_runtime *rtd, int num); /* DAI is also used for the control bus */ bool bus_control; /* ops */ const struct snd_soc_dai_ops *ops;//一个struct snd_soc_dai_ops类型的结构, 该dai的操作函数集 /* DAI capabilities */ struct snd_soc_pcm_stream capture; struct snd_soc_pcm_stream playback; unsigned int symmetric_rates:1; unsigned int symmetric_channels:1; unsigned int symmetric_samplebits:1; /* probe ordering - for components with runtime dependencies */ int probe_order; int remove_order; } snd_soc_pcm_stream struct snd_soc_pcm_stream { const char *stream_name; u64 formats; //这个格式定义在pcm.h SNDRV_PCM_FMTBITxxxx /* SNDRV_PCM_FMTBIT_* */ unsigned int rates; //采样率 我们常说16k 48k /* SNDRV_PCM_RATE_* */ unsigned int rate_min; //最小采样率 /* min rate */ unsigned int rate_max; //最大采样率 /* max rate */ unsigned int channels_min; //最小通道数，单声道1/* min channels */ unsigned int channels_max; //最大通道数 立体声道2/* max channels */ unsigned int sig_bits; //位数 8 还是16 /* number of bits of content */ }
2.3.1 snd_soc_register_codec codec_drv的值赋值到codec->componentcodec_drv和dai_drv都挂载到 codec->component->dai_list，期间还会生出snd_soc_dai也会挂载到 codec->component codec->list 挂载到全局变量codec_list 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; // //codec_drv的值赋值到codec->component if (codec_drv->controls) { codec->component.controls = codec_drv->controls; codec->component.num_controls = codec_drv->num_controls; } if (codec_drv->dapm_widgets) { codec->component.dapm_widgets = codec_drv->dapm_widgets; codec->component.num_dapm_widgets = codec_drv->num_dapm_widgets; } if (codec_drv->dapm_routes) { codec->component.dapm_routes = codec_drv->dapm_routes; codec->component.num_dapm_routes = codec_drv->num_dapm_routes; } 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->write) codec->component.write = snd_soc_codec_drv_write; if (codec_drv->read) codec->component.read = snd_soc_codec_drv_read; 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); } //依据dai_drv 创建snd_soc_dai 并且添加到 codec->component->dai_list 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; } //从component.dai_list中取出dai，并且codec赋值到dai->codec , list_for_each_entry(dai, &codec->component.dai_list, list) dai->codec = codec; mutex_lock(&client_mutex); //codec->component->list添加到component_list ，至此cpu dai 的component 和codec dai 的component都添加到component_list snd_soc_component_add_unlocked(&codec->component); //codec->list添加到codec_list中 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; } 2.3.2 snd_soc_register_dais 初始化snd_soc_component，并赋值。dai_drv for循环逐一取出snd_soc_dai_driver 创建新的snd_soc_dai 并且挂在component->dai_list static int snd_soc_register_dais(struct snd_soc_component *component, struct snd_soc_dai_driver *dai_drv, size_t count, bool legacy_dai_naming) { struct device *dev = component->dev; struct snd_soc_dai *dai; unsigned int i; int ret; dev_dbg(dev, "ASoC: dai register %s #%Zu\n", dev_name(dev), count); //snd_soc_dai_driver 添加到snd_soc_component component->dai_drv = dai_drv; component->num_dai = count; for (i = 0; i < count; i++) { dai = kzalloc(sizeof(struct snd_soc_dai), GFP_KERNEL); if (dai == NULL) { ret = -ENOMEM; goto err; } /* * 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. */ //snd_soc_dai_driver name 赋值到snd_soc_dai name 并且赋值 id if (count == 1 && legacy_dai_naming && (dai_drv[i].id == 0 || dai_drv[i].name == NULL)) { dai->name = fmt_single_name(dev, &dai->id); } else { dai->name = fmt_multiple_name(dev, &dai_drv[i]); if (dai_drv[i].id) dai->id = dai_drv[i].id; else dai->id = i; } if (dai->name == NULL) { kfree(dai); ret = -ENOMEM; goto err; } // 创建新的snd_soc_dai 并且挂在component->dai_list dai->component = component; dai->dev = dev; dai->driver = &dai_drv[i]; //ops 由dai_drv赋值的， 可能是cpu dai 就是：mtk_dai_stub_dai ,codec dai:mtk_6357_dai_codecs if (!dai->driver->ops) dai->driver->ops = &null_dai_ops; list_add(&dai->list, &component->dai_list); dev_dbg(dev, "ASoC: Registered DAI '%s'\n", dai->name); } return 0; err: snd_soc_unregister_dais(component); return ret; } 2.3.3 struct snd_soc_dai 由核心层内部创建和维护, 用于代表一个dai. 可以是cpu_dai或codec_dai struct snd_soc_dai { const char *name;//该dai的名称, ASoC核心层靠name来区分不同的dai. int id;//应该是核心层自动分配的一个id号 struct device *dev; /* driver ops */ struct snd_soc_dai_driver *driver;//指向下属的snd_soc_dai_driver, 该结构体一般由底层驱动实现 /* DAI runtime info */ unsigned int capture_active:1; /* stream is in use */ unsigned int playback_active:1; /* stream is in use */ unsigned int symmetric_rates:1; unsigned int symmetric_channels:1; unsigned int symmetric_samplebits:1; unsigned int active; unsigned char probed:1; struct snd_soc_dapm_widget *playback_widget; struct snd_soc_dapm_widget *capture_widget; /* DAI DMA data */ void *playback_dma_data; void *capture_dma_data; /* Symmetry data - only valid if symmetry is being enforced */ unsigned int rate; unsigned int channels; unsigned int sample_bits; /* parent platform/codec */ struct snd_soc_codec *codec; struct snd_soc_component *component; /* CODEC TDM slot masks and params (for fixup) */ unsigned int tx_mask; unsigned int rx_mask; struct list_head list;//用于把自己挂载到component->dai_list下. list_add(&dai->list, &component->dai_list) }; 2.3.4 struct snd_soc_component 当底层驱动注册platform、codec+codec dai、cpu dai时, 核心层都会创建一个对应的snd_soc_component,并且会挂到component_list 链表 struct snd_soc_component { const char *name; //这个跟device_driver->name 和snd_soc_component_driver->id有关， int id; const char *name_prefix; struct device *dev; struct snd_soc_card *card; unsigned int active; unsigned int ignore_pmdown_time:1; /* pmdown_time is ignored at stop */ unsigned int registered_as_component:1;//在snd_soc_register_component时修改为1 struct list_head list;//用于把自己挂载到全局链表component_list下 ,component_list 实在soc-core 中保持的全局变量 struct snd_soc_dai_driver *dai_drv;//dai 有可能是cpu dai 也有可能是 codec dai 是一个数组 int num_dai;//dai 的数量 const struct snd_soc_component_driver *driver;//指向下属的snd_soc_component_driver, 该结构体一般由底层平台驱动实现 struct list_head dai_list;//链表头, 挂接snd_soc_dai->list list_add(&dai->list, &component->dai_list) int (*read)(struct snd_soc_component *, unsigned int, unsigned int *); int (*write)(struct snd_soc_component *, unsigned int, unsigned int); struct regmap *regmap; int val_bytes; struct mutex io_mutex; /* attached dynamic objects */ struct list_head dobj_list; #ifdef CONFIG_DEBUG_FS struct dentry *debugfs_root; #endif /* * DO NOT use any of the fields below in drivers, they are temporary and * are going to be removed again soon. If you use them in driver code the * driver will be marked as BROKEN when these fields are removed. */ /* Don't use these, use snd_soc_component_get_dapm() */ struct snd_soc_dapm_context dapm; const struct snd_kcontrol_new *controls; unsigned int num_controls; const struct snd_soc_dapm_widget *dapm_widgets; unsigned int num_dapm_widgets; const struct snd_soc_dapm_route *dapm_routes; unsigned int num_dapm_routes; struct snd_soc_codec *codec; int (*probe)(struct snd_soc_component *); void (*remove)(struct snd_soc_component *); #ifdef CONFIG_DEBUG_FS void (*init_debugfs)(struct snd_soc_component *component); const char *debugfs_prefix; #endif }; 2.3.5 struct snd_soc_component_driver 底层驱动需要填充该结构体, 然后向ASoC核心层注册 struct snd_soc_component_driver { //ASoC核心层用名字区分不同的snd_soc_component_driver. //注意这个name与snd_soc_component->name不是同一个. 这里的name由驱动编写者填入, 而component->name由系统自动生成. const char *name; /* Default control and setup, added after probe() is run */ const struct snd_kcontrol_new *controls; unsigned int num_controls; //dapm_widgets、dapm_routes : 与dapm相关, dapm其实是对kcontrol做了一层封装 const struct snd_soc_dapm_widget *dapm_widgets; unsigned int num_dapm_widgets; const struct snd_soc_dapm_route *dapm_routes; unsigned int num_dapm_routes; int (*probe)(struct snd_soc_component *); void (*remove)(struct snd_soc_component *); /* DT */ int (*of_xlate_dai_name)(struct snd_soc_component *component, struct of_phandle_args *args, const char **dai_name); void (*seq_notifier)(struct snd_soc_component *, enum snd_soc_dapm_type, int subseq); int (*stream_event)(struct snd_soc_component *, int event); /* probe ordering - for components with runtime dependencies */ int probe_order; int remove_order; }; 2.3.6 struct snd_soc_codec struct snd_soc_codec { struct device *dev; const struct snd_soc_codec_driver *driver; struct list_head list; struct list_head card_list; /* runtime */ unsigned int cache_bypass:1; /* Suppress access to the cache */ unsigned int suspended:1; /* Codec is in suspend PM state */ unsigned int cache_init:1; /* codec cache has been initialized */ /* codec IO */ void *control_data; /* codec control (i2c/3wire) data */ hw_write_t hw_write; void *reg_cache; /* component */ struct snd_soc_component component; #ifdef CONFIG_DEBUG_FS struct dentry *debugfs_reg; #endif }; 总结： 梳理完，你会发现，其实跟前面的platform cpu_dai一样都是初始化结构体snd_soc_component 和snd_soc_codec 并且把这两个结构体挂到component_list 和code_list中。以供soc_bind_dai_link绑定cpu_dai 、codec_dai 、codec、platform使用。 |
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