Re: [RFC 08/13] ASoC: Intel: avs: Declare path and its components

[Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>]

>>> +struct avs_path {
>>> +    u32 dma_id;
>>
>> that is very surprising...
>>
>> This would seem to limit the concept of an avs path to a single host DMA
>> channel, which somewhat contradicts that there can be multiple pipelines
>> in the same path, or that a path can contain mixers.
>>
>> And even if this is a single dma, what does this represent? the
>> stream_tag? the BE DMA for SSP/DMIC?
>>
>> Please clarify the concepts first, it's frustrating to discover this at
>> patch 8.
> 
> A single path is tied to either FE or BE. So at most to a single, 
> user-visible endpoint if it's FE. If there are more FEs, then we move to 
> NxFE <-> 1xBE scenario. You can have many pipelines forming the path - 
> most of the pipelines do not contain module connected to any gateway 
> (HDA/SSP/DMIC etc.) anyway.

This should have been explained in the cover letter.

Assuming that there's a single Back-End that can handle all possible 
routing cases is a very narrow interpretation of how DPCM is supposed to 
be used, and it adds quite a few opens on routing changes that can't be 
handled with regular triggers. What happens when not all interfaces are 
handled by the DSP 'gateway' is also interesting.