Hi,Joseph,
ALSA in android does't use alsa config to control sound card like in linux. It's controls are all in ALSA HAL (tinyalsa._hal.c). So if you want to expend functions, you should add code in ALSA HAL .
ALSA in android also uses alsa-lib , So your expened function should also be based on API in alsa-lib.
Regards,
Weidong