alsa声卡/dev/snd/pcmC0D0p的open打开流程

alsa声卡/dev/snd/pcmC0D0p的open打开流程

soc_probe ==> snd_soc_register_card或者snd_soc_register_dai或者snd_soc_register_platform或者snd_soc_register_codec ==> snd_soc_instantiate_cards ==> snd_soc_instantiate_card ==> codec_dev->probe ==> uda134x_soc_probe ==> snd_soc_new_pcms ==> soc_new_pcm ==> snd_pcm_new snd_soc_new_pcms snd_card_create snd_ctl_create snd_ctl_dev_register创建"controlC%i"声卡对应的控制节点, 他的fops为snd_ctl_f_ops snd_pcm_dev_register snd_register_device_for_dev 创建"pcmC%iD%ip"或者"pcmC%iD%ic"设备节点,它的fops为snd_pcm_f_ops[2] snd_pcm_f_ops[2] ==> snd_pcm_playback_open或者snd_pcm_capture_open ==> snd_pcm_open或者oss的snd_pcm_oss_f_reg.snd_pcm_oss_open,这就对应/dev/dsp了 ==> snd_pcm_open_file或者oss的snd_pcm_oss_open_file ==> snd_pcm_open_substream ==> soc_pcm_open /* ASoC PCM operations */ static struct snd_pcm_ops soc_pcm_ops = {     .open        = soc_pcm_open,     .close        = soc_codec_close,     .hw_params    = soc_pcm_hw_params,     .hw_free    = soc_pcm_hw_free,     .prepare    = soc_pcm_prepare,     .trigger    = soc_pcm_trigger, }; ==> soc_pcm_open cpu_dai->ops->startup       // 无 platform->pcm_ops->open     // s3c_dma_open 分配DMA空间 codec_dai->ops->startup     // uda134x_startup card_dai_link->ops->startup // s3c24xx_uda134x_startup 获取clock时钟源 // cpu_dai单元 struct snd_soc_dai s3c24xx_i2s_dai = {     .name = "s3c24xx-i2s",     .id = 0,     .probe = s3c24xx_i2s_probe,     .suspend = s3c24xx_i2s_suspend,     .resume = s3c24xx_i2s_resume,     .playback = {         .channels_min = 2,         .channels_max = 2,         .rates = S3C24XX_I2S_RATES,         .formats = SNDRV_PCM_FMTBIT_S8 | SNDRV_PCM_FMTBIT_S16_LE,},     .capture = {         .channels_min = 2,         .channels_max = 2,         .rates = S3C24XX_I2S_RATES,         .formats = SNDRV_PCM_FMTBIT_S8 | SNDRV_PCM_FMTBIT_S16_LE,},     .ops = &s3c24xx_i2s_dai_ops, }; //platform单元 struct snd_soc_platform s3c24xx_soc_platform = {     .name        = "s3c24xx-audio",     .pcm_ops     = &s3c_dma_ops,     .pcm_new    = s3c_dma_new,     .pcm_free    = s3c_dma_free_dma_buffers, }; static struct snd_pcm_ops s3c_dma_ops = {     .open        = s3c_dma_open,     .close        = s3c_dma_close,     .ioctl        = snd_pcm_lib_ioctl,     .hw_params    = s3c_dma_hw_params,     .hw_free    = s3c_dma_hw_free,     .prepare    = s3c_dma_prepare,     .trigger    = s3c_dma_trigger,     .pointer    = s3c_dma_pointer,     .mmap        = s3c_dma_mmap, }; // codec_dai单元 struct snd_soc_dai uda134x_dai = {     .name = "UDA134X",     /* 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, }; //card_dai_link单元 static struct snd_soc_dai_link s3c24xx_uda134x_dai_link = {     .name = "UDA134X",     .stream_name = "UDA134X",     .codec_dai = &uda134x_dai,     .cpu_dai = &s3c24xx_i2s_dai,     .ops = &s3c24xx_uda134x_ops, };