Hello everybody on alsa-devel,

I'm adding a new model to the patch_realtek.c file that supports all features my alc888-codec together with the laptop hardware offers. Everything works fine and can be used through alsa, except two things, because I did not find any usable information on them:

1. My laptop has an built-in digital microphone, that is connected to this codec according to the information I can get when using windows. The ALC888 datasheet shows that there are pins for digital microphone support. Thus I assume that they are used for the microphone. Those pins are share their functionality with GPIO pins: GPIO0/DMIC-CLK and GPIO1/DMIC-DATA. Unfortunally the datasheet does not provide further information on how to switch between GPIO and DMIC mode of those pins. Furthermore there is no information where the digital data can be found and how to transfer them over the HDA-Bus to the application.

Does anybody have additional information on how to use digital microphones on realtek codecs?

2. Perhaps enabling the digital microphone is related to the so-called "Realtek Defined Registers" that can be found on NID=0x20 as processing coefficients. Furthermore the alc888 supports additional features like equalizer or echo-cancellation, etc. that can be controlled by these registers, as I suppose.

Does anybody have information how what these registers and their contents mean? The datasheet does not provide any information.

I hope you can help me.

Sebsatian Konopka