You are talking about Android but this thread is Linux related (it is a complete different story when it comes to the media driver).
The Android kernel does integrate the v4l2 kernel changes to support HAL3 . However this AOSP doesn't seem to execute the mm-qcamera-daemon (the proprietary code that sets up the video pipelines required to get sensor input).
Until that runs, you have no chances of getting processed output from the sensor: mm-qcamera-daemon is required to setup the sensor, CSIPHY, CSID, CCI, ISP etc.
This RFC a fair description of the multimedia driver in case you are curious (I recommend you follow the discussion, I found it to be interesting)
The android HAL talks to the daemon via unix sockets and via v4l2 requests that are routed back to the daemon: basically no daemon means no hardware setup happening (even if you manage to do the basic i2c sensor initialization you wont get the pipeline running)