[alsa-devel] [PATCH] ASoC: core: allow control index different from 0

[Arnaud Pouliquen]

On 10/11/2016 10:30 AM, Charles Keepax wrote:
> On Mon, Oct 10, 2016 at 11:26:00AM +0200, Arnaud Pouliquen wrote:
>>
>>
>> On 10/09/2016 05:05 AM, Takashi Sakamoto wrote:
>>> Sorry to be late. I've review your driver in for-next branch of
>>> maintainer's tree.
>>>
>>> On Oct 8 2016 01:41, Arnaud Pouliquen wrote:
>>> But I still oppose this idea. This idea allows drivers to add control
>>> element sets of different types (int/int64/bytes etc...) with the same
>>> name and different index number. This certainly brings confusions to
>>> applications.
>> Today is already possible using the device or subdevice field instead of
>> index.
>>>
>>> In a framework of ALSA SoC part, several drivers are associated to one
>>> sound card instance can add their own control element sets. There's no
>>> mechanism to prevent my concern. This idea is bad.
>> Please tell me if i misunderstand. So for you, there is no real solution
>> to do it in a generic way. Drivers has to implement it, if they want to
>> support.
>>
>> Another solution is to declare a card per instance of control.
>> This should work for my use case and for use cases with several codecs
>> that declare same controls. But this should not work for DPCM...
>> The drawback for my use case, would be that i need to declare one card
>> per PCM device.
> 
> Apologies if I am missing the mark here, I haven't been following
> this thread in great detail. But if your main concern here is
> multiple instances of the same CODEC creating the same controls
> the normal way to handle that in ASoC is using a
> snd_soc_codec_conf struct which lets you add a prefix to all the
> controls from a specific instance of a CODEC. See
> sound/soc/samsung/bells.c for an example using it.

Codec multi instance is one of the use cases. CPU_DAI multi instance is
another one (and my main concern).
But use of a prefix_name is a good point that i have not prospected yet,
thanks.
Today it is not implemented neither for CPU_DAIs nor for simple card.
But my main drawback of the prefix name, is that this breaks the naming
of generic controls like IEC. So i can't use it.

Regards
Arnaud