Missing documentation for Audioreach topology files

[Jens Reidel <adrian@xxxxxxxxxxxx>]

Hi everyone,

I am currently bringing up Xiaomi SM8450/SM8475 mobile phones and have a few 
working well enough to try and get the WCD and audio in general working. All 
is fine, until this:

[   35.366229] qcom-apm gprsvc:service:2:1: Direct firmware load for qcom/
sm8450/Xiaomi 12-tplg.bin failed with error -2
[   35.366244] qcom-apm gprsvc:service:2:1: tplg firmware loading qcom/sm8450/
Xiaomi 12-tplg.bin failed -2
[   35.366250] qcom-apm gprsvc:service:2:1: ASoC: error at 
snd_soc_component_probe on gprsvc:service:2:1: -2

After searching around a bit, I stumbled across this Linaro repository: 
https://git.codelinaro.org/linaro/qcomlt/audioreach-topology
Apparently you're supposed to write the topology in a M4-preprocessed file that 
gets turned into an ALSA UCM topology config and then compiled with alsatplg.
However, there is zero documentation on the preprocessor macros and how you're 
actually supposed to write the topology file. Am I missing something or is 
there no public documentation and tooling for how to use this kernel 
interface?

Best regards,
Jens