How to call the framework layer of audio to hal (take setparameters as an example)

First look at
AudioManager's setParameters from the application to the hal process analysis android6.0 to
see the last two grids:
audio_hw_device_t ->set_parameters() is the interface of the upper layer to call the hal layer,
causing the lower layer ***audio_hw->adev_set_parameters()*** to be executed.
The connection between them is established through
legacy_adev_open .

What does legacy_adev_open do?
1 First link audio_hw_device_t (call from the hal upper layer)
andaudio_hw (hal layer)2 Then audio_hw (hal layer) to establish a connection with the function set by the manufacturer
(ladev->hwif = XXXXXXXXXX;)
can refer to the legacy_adev_open file
Android Framework Audio Sub System (12) HAL layer analysis