Alsa sound card analysis alsa-utils call process (1)-tinyplay
Android tinyplay tinycap process and
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the PCM's open flow
soc_pom_open also calls the machine inside stratup
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From the above guess (open dependent snd_pcm_playback_open)
ALSA
inside ioctl also dependent struct file_operations snd_pcm_f_ops [2]
which is a member of (because this is a device File_operations of the file)
Feeling a reliable function analysis
analysis of the alsa sound card driver snd_pcm_start function-the real audio data sent to the external audio interface hardware