ALSA lib-->ALSA core调用时序

snd_pcm_open:open()->snd_open()(sound.c)->snd_pcm_playback_open()

  

snd_pcm_params_any:

snd_pcm_hw_params_set_xx

snd_pcm_hw_params:

snd_pcm_sw_params:

snd_pcm_prepare:

  

snd_pcm_writei:

  

snd_pcm_drop:

 snd_pcm_close: