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

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Message-ID: <f189bd38-32ec-ee7d-e0fa-4de108a18ea2@linux.intel.com>
Date:   Fri, 2 Aug 2019 12:42:29 -0500
From:   Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>
To:     Vinod Koul <vkoul@...nel.org>
Cc:     Cezary Rojewski <cezary.rojewski@...el.com>,
        alsa-devel@...a-project.org, linux-kernel@...r.kernel.org,
        tiwai@...e.de, broonie@...nel.org, gregkh@...uxfoundation.org,
        jank@...ence.com, srinivas.kandagatla@...aro.org,
        slawomir.blauciak@...el.com, Sanyog Kale <sanyog.r.kale@...el.com>
Subject: Re: [alsa-devel] [RFC PATCH 31/40] soundwire: intel: move shutdown()
 callback and don't export symbol

On 8/2/19 12:28 PM, Vinod Koul wrote:
> On 26-07-19, 09:46, Pierre-Louis Bossart wrote:
>>
>>
>> On 7/26/19 5:38 AM, Cezary Rojewski wrote:
>>> On 2019-07-26 01:40, Pierre-Louis Bossart wrote:
>>>> +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?

the code does a bunch of get_dma_data() and this seems to work, but 
indeed I don't see where the _set_dma_data() is done. magic.