Re: [alsa-devel] [RFC PATCH 31/40] soundwire: intel: move shutdown() callback and don't export symbol

Pierre-Louis Bossart
2019-08-14T19:31:47Z

>>>> +void intel_shutdown(struct snd_pcm_substream *substream,
>>>> +            struct snd_soc_dai *dai)
>>>> +{
>>>> +    struct sdw_cdns_dma_data *dma;
>>>> +
>>>> +    dma = snd_soc_dai_get_dma_data(dai, substream);
>>>> +    if (!dma)
>>>> +        return;
>>>> +
>>>> +    snd_soc_dai_set_dma_data(dai, substream, NULL);
>>>> +    kfree(dma);
>>>> +}
>>>
>>> Correct me if I'm wrong, but do we really need to _get_dma_ here?
>>> _set_dma_ seems bulletproof, same for kfree.
>>
>> I must admit I have no idea why we have a reference to DMAs here, this looks
>> like an abuse to store a dai-specific context, and the initial test looks
>> like copy-paste to detect invalid configs, as done in other callbacks. Vinod
>> and Sanyog might have more history than me here.
>
> I dont see snd_soc_dai_set_dma_data() call for
> sdw_cdns_dma_data so somthing is missing (at least in upstream code)
>
> IIRC we should have a snd_soc_dai_set_dma_data() in alloc or some
> initialization routine and we free it here.. Sanyog?

Vinod, I double-checked that we do not indeed have a call to
snd_soc_dai_dma_data(), but there is code in cdns_set_stream() that sets
the relevant dai->playback/capture_dma_data, see below

I am not a big fan of this code, touching the ASoC core internal fields
isn't a good idea in general.

Also not sure why for a DAI we need both _drvdata and _dma_data
(especially for this case where the information stored has absolutely
nothing to do with DMAs).

If the idea was to keep a context that is direction-dependent, that's
likely unnecessary. For the Intel/Cadence case the interfaces can be
configured as playback OR capture, not both concurrently, so the "dma"
information could have been stored in the generic DAI _drvdata.

I have other things to look into for now but this code will likely need
to be cleaned-up at some point to remove unnecessary parts.

int cdns_set_sdw_stream(struct snd_soc_dai *dai,
void *stream, bool pcm, int direction)
{
struct sdw_cdns *cdns = snd_soc_dai_get_drvdata(dai);
struct sdw_cdns_dma_data *dma;

dma = kzalloc(sizeof(*dma), GFP_KERNEL);
if (!dma)
return -ENOMEM;

if (pcm)
dma->stream_type = SDW_STREAM_PCM;
else
dma->stream_type = SDW_STREAM_PDM;

dma->bus = &cdns->bus;
dma->link_id = cdns->instance;

dma->stream = stream;

>>> this is equivalent to snd_soc_dai_dma_data()

if (direction == SNDRV_PCM_STREAM_PLAYBACK)
dai->playback_dma_data = dma;
else
dai->capture_dma_data = dma;
<<<<
return 0;
}
EXPORT_SYMBOL(cdns_set_sdw_stream);