How do I substitute LINE_IN for MIC on A10s under Android?

[kbro]

The A10s board has a 3.5mm LINE_IN socket and empty pads on MIC1 and MIC2.

I want to record audio from the LINE_IN input, but the MediaRecorder class doesn't appear to support it - see http://developer.android.com/reference/android/media/MediaRecorder.AudioSource.html

I know from having played with AlsaMixer (https://play.google.com/store/apps/details?id=com.skvalex.alsamixer&hl=en) that I can cause an audio recorder app that is currently recording the (silent) MIC input to record music from LINE_IN instead by writing the value "0" to the ADC Input Source register (it starts off as "2" which means MIC1 is the input).

So my cunning question is this ... is there a config file that has the setting "value to select MIC input as ADC Input Source = 2" that I can change to 0 so that LINE_IN is always selected as the "microphone".

A bit of an ugly hack, I agree, but it will allow me to do what I want to do a whole lot quicker than I'm doing its now.