[alsa-devel] [RFT v3 3/3] ASoC: core: Add support for DAI multicodec

[Lars-Peter Clausen]

On 04/24/2014 02:01 PM, Benoit Cousson wrote:
> DAI link assumes a one to one mapping between CPU DAI and CODEC. In
> some cases, the same CPU DAI can be connected to several codecs.
> This is the case for example, if you connect two mono codecs to the
> same I2S link in order to have a stereo card.
> The current ASoC implementation does not allow such setup.
>
> Add support for DAI links composed of a single CPU DAI and multiple
> CODECs. Sound cards have to pass the CODECs array in the corresponding
> DAI link through a new 'snd_soc_dai_link_component' struct. Each CODEC in
> this array is described in the same manner single CODEC DAIs are
> (either DT/OF node or codec_name).
>
> Fix a trailing space in the header as well.
>
> Based on an original code done by Misael.
>
> Signed-off-by: Benoit Cousson <bcousson at baylibre.com>
> Signed-off-by: Misael Lopez Cruz <misael.lopez at ti.com>
> Signed-off-by: Fabien Parent <fparent at baylibre.com>

Some thoughts on the parameter fixup.

> ---
>   include/sound/soc-dai.h  |   5 +
>   include/sound/soc.h      |  13 ++
>   sound/soc/soc-compress.c |  83 +++++---
>   sound/soc/soc-core.c     | 364 ++++++++++++++++++++++-----------
>   sound/soc/soc-dapm.c     |  71 ++++---
>   sound/soc/soc-pcm.c      | 512 ++++++++++++++++++++++++++++++++---------------
>   6 files changed, 715 insertions(+), 333 deletions(-)
>
> diff --git a/include/sound/soc-dai.h b/include/sound/soc-dai.h
> index fad7676..6985851 100644
> --- a/include/sound/soc-dai.h
> +++ b/include/sound/soc-dai.h
> @@ -274,6 +274,11 @@ struct snd_soc_dai {
>   	struct snd_soc_codec *codec;
>   	struct snd_soc_component *component;
>
> +	/* CODEC TDM slot masks and params (for fixup) */
> +	unsigned int tx_mask;
> +	unsigned int rx_mask;
> +	struct snd_pcm_hw_params params[2];

snd_pcm_hw_params is rather large, given that for a lot of setups we don't 
need it it might be better to make this a pointer and only allocate the 
params struct when needed.

[...]
> @@ -3624,17 +3697,26 @@ static int snd_soc_xlate_tdm_slot_mask(unsigned int slots,
>   int snd_soc_dai_set_tdm_slot(struct snd_soc_dai *dai,
>   	unsigned int tx_mask, unsigned int rx_mask, int slots, int slot_width)
>   {
> +	int ret = 0;
> +
>   	if (dai->driver && dai->driver->ops->xlate_tdm_slot_mask)
>   		dai->driver->ops->xlate_tdm_slot_mask(slots,
>   						&tx_mask, &rx_mask);
>   	else
>   		snd_soc_xlate_tdm_slot_mask(slots, &tx_mask, &rx_mask);
>
> +	if (dai->codec) {
> +		dai->tx_mask = tx_mask;
> +		dai->rx_mask = rx_mask;
> +	}

I don't think it makes sense to artificially limit this to just CODECs. 
While we do not support multiple CPU DAIs (yet?) adding the check for CODECs 
just makes the code more complex, but doesn't gain us anything.


[...]
> +	for (i = 0; i < rtd->num_codecs; i++) {
> +		struct snd_soc_dai *codec_dai = rtd->codec_dais[i];
> +		struct snd_pcm_hw_params *codec_params;
> +
> +		codec_params = &codec_dai->params[substream->stream];

The fixed up params are only ever used in here. Do we really need to keep 
two copies per CODEC DAI around?

> +
> +		/* copy params for each codec */
> +		memcpy(codec_params, params, sizeof(struct snd_pcm_hw_params));
> +
> +		/* fixup params based on TDM slot masks */
> +		if (codec_dai->tx_mask)
> +			soc_pcm_codec_params_fixup(codec_params,
> +						   codec_dai->tx_mask);
> +		if (codec_dai->rx_mask)
> +			soc_pcm_codec_params_fixup(codec_params,
> +						   codec_dai->rx_mask);
> +

If we fix-up the number of channels to be always the number of slots should 
we also setup a constraint for userspace that the number of channels must 
match the number of channels specified in the CPU DAI mask? Or should we 
check how many of the channels in the CODEC mask are actually active and 
fix-up the the number of channels according to that?

> +		if (codec_dai->driver->ops &&
> +		    codec_dai->driver->ops->hw_params) {
> +			ret = codec_dai->driver->ops->hw_params(substream,
> +						codec_params, codec_dai);
> +			if (ret < 0) {
> +				dev_err(codec_dai->dev,
> +					"ASoC: can't set %s hw params: %d\n",
> +					codec_dai->name, ret);
> +				goto codec_err;
> +			}
>   		}

I think it makes sense to factor this whole block out into a helper 
function. E.g. soc_dai_hw_params(struct snd_soc_dai* dai, struct hw_params 
*params);. This will make it possible to also use it in other places like 
the dapm_dai_link_event() function.

> +
> +		codec_dai->rate = params_rate(codec_params);
> +		codec_dai->channels = params_channels(codec_params);
> +		codec_dai->sample_bits = snd_pcm_format_physical_width(
> +						params_format(codec_params));
>   	}
>
[...]