[alsa-devel] [PATCH v3 1/2] ASoC: core: allow DAI PCM controls bound to PCM device

[Takashi Sakamoto]

On Nov 28 2016 18:33, Arnaud Pouliquen wrote:
> In case of several instances of the same PCM control (e.g IEC controls).
> Application should be able to address the control using the
> device field number, according to the PCM character device.
> This patch allows to link DAI PCM controls to the PCM device.
> During DAI_link probe, PCM controls are added after device field is forced
> to the PCM device number.
>
> Signed-off-by: Arnaud Pouliquen <arnaud.pouliquen at st.com>
> ---
>  include/sound/soc-dai.h |  4 ++++
>  sound/soc/soc-core.c    | 28 ++++++++++++++++++++++++++++
>  2 files changed, 32 insertions(+)
>
> diff --git a/include/sound/soc-dai.h b/include/sound/soc-dai.h
> index 964b7de..93624c9 100644
> --- a/include/sound/soc-dai.h
> +++ b/include/sound/soc-dai.h
> @@ -247,6 +247,10 @@ struct snd_soc_dai_driver {
>  	/* probe ordering - for components with runtime dependencies */
>  	int probe_order;
>  	int remove_order;
> +
> +	/* Optional PCM controls to bind to PCM device on DAIs link*/
> +	const struct snd_kcontrol_new *pcm_controls;
> +	int num_pcm_controls;
>  };
>
>  /*
> diff --git a/sound/soc/soc-core.c b/sound/soc/soc-core.c
> index 4afa8db..ace83c9 100644
> --- a/sound/soc/soc-core.c
> +++ b/sound/soc/soc-core.c
> @@ -1552,6 +1552,25 @@ static int soc_probe_dai(struct snd_soc_dai *dai, int order)
>  	return 0;
>  }
>
> +static int soc_link_dai_pcm_controls(struct snd_soc_dai **dais, int num_dais,
> +				     struct snd_soc_pcm_runtime *rtd)
> +{
> +	struct snd_kcontrol_new kctl;
> +	int i, j, err;
> +
> +	for (i = 0; i < num_dais; ++i) {
> +		for (j = 0; j < dais[i]->driver->num_pcm_controls; j++) {
> +			kctl = dais[i]->driver->pcm_controls[j];
> +			if (!rtd->dai_link->no_pcm)
> +				kctl.device = rtd->pcm->device;

For the above codes, please request some comment to the other developers 
working for ALSA SoC part. I'm not so experienced developer for this 
part, sorry.

> +			if (snd_soc_add_dai_controls(dais[i], &kctl, 1))
> +				return err;

Return value from snd_soc_add_dai_controls() should be assigned to the 
'err' variable, I think.

> +		}
> +	}
> +
> +	return 0;
> +}
> +
>  static int soc_link_dai_widgets(struct snd_soc_card *card,
>  				struct snd_soc_dai_link *dai_link,
>  				struct snd_soc_pcm_runtime *rtd)
> @@ -1663,6 +1682,15 @@ static int soc_probe_link_dais(struct snd_soc_card *card,
>  				       dai_link->stream_name, ret);
>  				return ret;
>  			}
> +
> +			/* Bind DAIs pcm controls to the PCM device */
> +			ret = soc_link_dai_pcm_controls(&cpu_dai, 1, rtd);
> +			if (ret < 0)
> +				return ret;
> +			ret = soc_link_dai_pcm_controls(rtd->codec_dais,
> +							rtd->num_codecs, rtd);
> +			if (ret < 0)
> +				return ret;
>  		} else {
>  			INIT_DELAYED_WORK(&rtd->delayed_work,
>  						codec2codec_close_delayed_work);

In the other part of this subsystem, the first parameter of helper 
functions typically represents a 'subject'. In this context, the subject 
is PCM runtime specialized for ALSA SoC part, which get some new control 
element sets for the PCM runtime. Therefore, it's better to move the 
'rtd' parameter to the first argument. (This is not so strong demand, 
and somewhat depends on developers' taste. Furthermore, I have no 
self-confidence to tell my intension to you correctly in English...)


Regards

Takashi Sakamoto