[alsa-devel] [PATCH 2/4] ASoC: compress: Clarify the intent of current compressed ops handling

[Vinod Koul]

On Thu, Apr 26, 2018 at 05:30:05PM +0100, Charles Keepax wrote:
> It is proposed that the model adopted for compressed component
> support currently should be that multiple components are supported
> on a compressed DAI but that they must provide a unified set of
> capabilities. So for example having multiple components involved in
> the decode is fine but the core will not presently attempt to make
> smart decisions like offloading MP3 to this component and AAC another.

Well this is supposed to be entirely a userspace call, we just present
devices with capabilities and the usespace decides... Btw capabilities are
supposed to be dynamic.

Looking at the code again now, I realized that we are treating compress like
PCM. It makes little sense to me to have multiple components for a
compressed device, does that model on your systems..?

> To implement this it is suggested that callbacks configuring the state
> of the components (trigger, set_params, ack and set_metadata) should be
> called on all components and required to succeed on all components
> before being considered to have succeeded. However for callbacks that
> return information from the driver (copy, get_metadata, pointer,
> get_codec_caps, get_caps and get_params) it is expected that either
> there is only a single provider on the link or that all components
> will return identical results.
> 
> Essentially this matches the current implementation of the code and
> only small clean ups are undertaken here.

> For callbacks configuring the state of the components simplify the
> code a little and make intention clearer by aborting as soon as an
> error is encountered. The operation has already failed and there is
> nothing to be gained from processing the additional callbacks.
> 
> For callbacks returning information from the driver only look for the
> first callback provided, currently the code will call every callback
> only returning the information provided by the last. Again this makes
> the currently supported feature set a little more clear.

Btw code changes look fine but I think we need broader cleanup here...

-- 
~Vinod