[alsa-devel] [PATCH v4 6/8] ASoC: compress: Add support for DAI multicodec

[Lars-Peter Clausen]

On 07/03/2014 01:09 PM, Benoit Cousson wrote:
> On 03/07/2014 08:41, Vinod Koul wrote:
>> On Wed, Jul 02, 2014 at 02:53:50PM +0200, Benoit Cousson wrote:
>>>>> @@ -622,23 +633,33 @@ int soc_new_compress(struct snd_soc_pcm_runtime
>>>>> *rtd, int num)
>>>>>   {
>>>>>       struct snd_soc_codec *codec = rtd->codec;
>>>>>       struct snd_soc_platform *platform = rtd->platform;
>>>>> -    struct snd_soc_dai *codec_dai = rtd->codec_dai;
>>>>>       struct snd_soc_dai *cpu_dai = rtd->cpu_dai;
>>>>>       struct snd_compr *compr;
>>>>>       struct snd_pcm *be_pcm;
>>>>>       char new_name[64];
>>>>> -    int ret = 0, direction = 0;
>>>>> -
>>>>> -    /* check client and interface hw capabilities */
>>>>> -    snprintf(new_name, sizeof(new_name), "%s %s-%d",
>>>>> -            rtd->dai_link->stream_name, codec_dai->name, num);
>>>>> -
>>>>> -    if (codec_dai->driver->playback.channels_min)
>>>>> -        direction = SND_COMPRESS_PLAYBACK;
>>>>> -    else if (codec_dai->driver->capture.channels_min)
>>>>> -        direction = SND_COMPRESS_CAPTURE;
>>>>> -    else
>>>>> -        return -EINVAL;
>>>>> +    int i, ret = 0, direction = -1;
>>>>> +
>>>>> +    for (i = 0; i < rtd->num_codecs; i++) {
>>>>> +        struct snd_soc_dai *codec_dai = rtd->codec_dais[i];
>>>>> +        /* check client and interface hw capabilities */
>>>>> +        snprintf(new_name, sizeof(new_name), "%s %s-%d",
>>>>> +             rtd->dai_link->stream_name, codec_dai->name, num);
>>>>> +
>>>>> +        if (direction < 0) {
>>>>> +            if (codec_dai->driver->playback.channels_min)
>>>>> +                direction = SND_COMPRESS_PLAYBACK;
>>>>> +            else if (codec_dai->driver->capture.channels_min)
>>>>> +                direction = SND_COMPRESS_CAPTURE;
>>>> direction wont change with multiple codecs, so this loop makes no sense
>>>> here.
>>>> For simplcity perhaps we can use cpu_dai?
>>>>> +            else
>>>>> +                return -EINVAL;
>>>>> +        } else {
>>>> when will this get executed? You have initialized direction to -1 and if
>>>> case is
>>>> always true. I think compiler will simply remove the below sinppet.
>>>
>>> direction is set to -1, then the first iteration will set it to the
>>> direction of the first codec_dai. The other iteration are just
>>> checking that there are all in the same direction and will fail
>>> otherwise.
>>>
>>>>> +            if ((codec_dai->driver->playback.channels_min &&
>>>>> +                    direction != SND_COMPRESS_PLAYBACK) ||
>>>>> +                (codec_dai->driver->capture.channels_min &&
>>>>> +                    direction != SND_COMPRESS_CAPTURE))
>>>> and what exactly are we trying to check here?
>>>
>>> That every codec_dai are in the same direction.
>>>
>>> If you think this is pointless since every DAI are always in the
>>> same direction, we can just remove it.
>> I think that will simplify it. we certainly dont expect different direction,
>> right?
>
> Lars, Mark
> Any thought on that? Does that sound reasonable to you to use only the first
> codec_dai to figure out the direction?
>

I guess it is ok. But I'm wondering if the direction shouldn't depend on the 
CPU dai rather than the CODEC dai? E.g. it is possible to have a CODEC with 
both playback and capture support in two dai_links, one for capture, one for 
playback. The check above would create a SND_COMPRESS_PLAYBACK stream in 
both cases. Even if the CPU dai only supported capture in one of the cases.

- Lars