Re: [alsa-devel] [PATCH v2 3/5] ASoC: core: add support to snd_soc_dai_get_sdw_stream()

[Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>]

On 8/13/19 1:06 PM, Srinivas Kandagatla wrote:
> 
> 
> On 13/08/2019 18:51, Pierre-Louis Bossart wrote:
>> On 8/13/19 11:50 AM, Srinivas Kandagatla wrote:
>>> Thanks for the review,
>>>
>>> On 13/08/2019 15:44, Pierre-Louis Bossart wrote:
>>>> On 8/13/19 3:35 AM, Srinivas Kandagatla wrote:
>>>>> On platforms which have smart speaker amplifiers connected via
>>>>> soundwire and modeled as aux devices in ASoC, in such usecases machine
>>>>> driver should be able to get sdw master stream from dai so that it can
>>>>> use the runtime stream to setup slave streams.
>>>>
>>>> using the _set_sdw_stream? I don't fully get the sequence with the 
>>>> wording above.
>>>
>>> Yes, using set_sdw_stream().
>>
>> Maybe I am missing something here, but I don't see where the 
>> set_sdw_stream() is called.
> 
> sorry for the confusion. It was too quick reply. :-)
> I was suppose to say sdw_stream_add_slave() instead of set_sdw_stream().

ok, so get_sdw_stream() and set_sdw_stream() are not meant to be mirrors 
or both implemented. It's just a helper to respectively get a context or 
set a context but a get-modify-set type of operation is not expected.

Do I get this right?

> 
> As Aux device is dailess there is no way to get hold of sdw stream 
> runtime for slave device associated with it.
> 
> Having snd_soc_dai_get_sdw_stream() would help machine driver to get 
> hold of sdw_stream_runtime from controller dai and setup slave streams 
> using sdw_stream_add_slave().
> 
> 
> thanks,
> srini
> 
> 
>>
>> Also I don't fully get the rule. set_sdw_stream() looks required, 
>> get_sdw_stream() is optional, is this what you are suggesting?
>>
>>>>
>>>>>
>>>>> soundwire already as a set function, get function would provide more
>>>>> flexibility to above configurations.
>>>>
>>>> I am not clear if you are asking for both to be used, or get only or 
>>>> set only?
>>>
>>> It depends on the usecase, in db845c usecase  [1] as Aux device is 
>>> dai less, machine driver is using get function to get hold of master 
>>> stream so that it can setup slave port config.
>>>
>>>
>>> Looks like there is a typo in above like
>>>
>>> This was supposed to be "soundwire already has a set function, get 
>>> function would provide more flexibility to above configurations"
>>>
>>> [1] 
>>> https://git.linaro.org/landing-teams/working/qualcomm/kernel.git/tree/sound/soc/qcom/db845c.c?h=integration-linux-qcomlt 
>>>
>>>
>>> thanks,
>>> srini
>>>
>>>>
>>>>>
>>>>> Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
>>>>> ---
>>>>>   include/sound/soc-dai.h | 10 ++++++++++
>>>>>   1 file changed, 10 insertions(+)
>>>>>
>>>>> diff --git a/include/sound/soc-dai.h b/include/sound/soc-dai.h
>>>>> index dc48fe081a20..1e01f4a302e0 100644
>>>>> --- a/include/sound/soc-dai.h
>>>>> +++ b/include/sound/soc-dai.h
>>>>> @@ -202,6 +202,7 @@ struct snd_soc_dai_ops {
>>>>>       int (*set_sdw_stream)(struct snd_soc_dai *dai,
>>>>>               void *stream, int direction);
>>>>> +    void *(*get_sdw_stream)(struct snd_soc_dai *dai, int direction);
>>>>>       /*
>>>>>        * DAI digital mute - optional.
>>>>>        * Called by soc-core to minimise any pops.
>>>>> @@ -410,4 +411,13 @@ static inline int 
>>>>> snd_soc_dai_set_sdw_stream(struct snd_soc_dai *dai,
>>>>>           return -ENOTSUPP;
>>>>>   }
>>>>> +static inline void *snd_soc_dai_get_sdw_stream(struct snd_soc_dai 
>>>>> *dai,
>>>>> +                           int direction)
>>>>> +{
>>>>> +    if (dai->driver->ops->get_sdw_stream)
>>>>> +        return dai->driver->ops->get_sdw_stream(dai, direction);
>>>>> +    else
>>>>> +        return ERR_PTR(-ENOTSUPP);
>>>>> +}
>>>>> +
>>>>>   #endif
>>>>>
>>>>
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>>