[alsa-devel] Question about FE & BE DPCM

[Daniel Baluta]

On Tue, Oct 15, 2019 at 4:15 AM Kuninori Morimoto
<kuninori.morimoto.gx at renesas.com> wrote:
>
>
> Hi Daniel
>
> > »       /* BE is dummy */
> > »       »       codecs->of_node»»       = NULL;
> > »       »       codecs->dai_name»       = "snd-soc-dummy-dai";
> > »       »       codecs->name»   »       = "snd-soc-dummy";
> >
> > »       »       /* FE settings */
> > »       »       dai_link->dynamic»      »       = 1;
> > »       »       dai_link->dpcm_merged_format»   = 1;
>
> Ahh, indeed... it is wrong comment.
> It should be /* Codec is dummy */ here.
> I will post fixup patch, soon.
>
> Current simple-card is assuming
>
>         FE: CPU-dummy
>         BE: dummy-Codec
>
> > asoc_simple_canonicalize_platform function where it does say:
> >
> > »        * DPCM BE can be no platform.
> > »        * Alloced memory will be waste, but not leak.
> > »        */
> > »       if (!dai_link->platforms->of_node)
> > »       »       dai_link->num_platforms = 0;
> >
> > But I do want to create a BE with a platform. So, should I try to
> > revert the following
>
> I see.
> I'm not using but someone added asoc_simple_parse_platform().
> Maybe it can help you (?), but it is not called/used under DPCM case.
> If you can support it under DPCM, asoc_simple_canonicalize_platform()
> is no longer your issue ?

Yes, this would definitely help. Now I'm trying to figure out an acceptable
way to create just one link with:

FE: CPU-dummy
BE: dummy-Codec

Or even better just one:

BE: dummy-Codec.

Both audio-graph-card.c and simple-card.c deal with DPCM only with
this conditions:

»       »       »       /*
»       »       »        * It is DPCM
»       »       »        * if Codec port has many endpoints,
»       »       »        * or has convert-xxx property
»       »       »        */

or

»       »       »       if (dpcm_selectable &&
»       »       »           (num > 2 ||
»       »       »            adata.convert_rate || adata.convert_channels))