sound / core / sound.c file_operations achieved the top level, which play the role of transit
sound / core / control.c control interface implements file_operations
sound / core / pcm_native.c realized playback, capture of file_operations
These provisions file_operations the ALSA Interface
How to write drivers? Implementation code can be hardware-related:
Distribution, settings, and registration snd_card structure:
1. snd_card_create // which will create an interface control
2. snd_pcm_new // which will create playback, capture interfaces
3. snd_card_register