Comment 7 for bug 1002978

Just to let you know my findings since two years . There is a closed source kernel (in Linpus for Acer Aspire One) driver to handle this kind of small array microphone from Fortemedia (here on Acer Ferrari One 200).
There are in fact 4 channels ie 2 stereo signals (force channels_max to 4 in hda_intel and patch_realtek). This is done to let fmaudio kernel driver (heavily plugged into hda_intel, infringing on the gpl in various ways) do beam, noise processing and other nifty things.
I started works on this. Please tell me if you are interested in my hacks (I managed to get the 4 streams and record them then work in audacity to try to decipher the noise reduction). I also started work on a pulseaudio module (I do not think the audio postprocessing should be done in kernel) fmaaudiosma which I talked upon on pulseaudio ML but this was sent before I found about the 4 channels trick.