linux-kernel - Re: [PATCH v5 00/17] ASoC: fsl_ssi: Clean up

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Date:   Wed, 17 Jan 2018 21:27:54 +0100
From:   "Maciej S. Szmigiero" <mail@...iej.szmigiero.name>
To:     Nicolin Chen <nicoleotsuka@...il.com>
Cc:     timur@...i.org, broonie@...nel.org, linux-kernel@...r.kernel.org,
        linuxppc-dev@...ts.ozlabs.org, alsa-devel@...a-project.org,
        lgirdwood@...il.com, fabio.estevam@....com, caleb@...me.org,
        arnaud.mouiche@...oxia.com, lukma@...x.de, kernel@...gutronix.de
Subject: Re: [PATCH v5 00/17] ASoC: fsl_ssi: Clean up - program flow level

On 17.01.2018 21:02, Nicolin Chen wrote:
> On Wed, Jan 17, 2018 at 08:38:48PM +0100, Maciej S. Szmigiero wrote:
> 
>> However, I have a small nitpick regarding a comment newly added in
>> this version of patch 16:
>> +		/*
>> +		 * Do not set SSI dev as the parent of AC97 CODEC device since
>> +		 * it does not have a DT node. Otherwise ASoC core will assume
>> +		 * CODEC has the same DT node as the SSI, so it may return a
>> +		 * NULL pointer of CODEC when asked for SSI via the DT node
>>
>> The second part of the last sentence isn't really true, the ASoC core
>> will return a (valid, non-NULL) CODEC object pointer when asked for
>> the SSI one if we set the SSI as the parent device of a AC'97 CODEC
>> platform device.
>>
>> The NULL pointer dereference when starting a playback that I wrote
>> about in my previous message happens because in this situation the SSI
>> DAI probe callback won't ever get called and so won't setup DMA data
>> pointers (they will remain NULL).
> 
> Well, somehow the DMA data pointer of CODEC could be described
> as "a NULL pointer of CODEC" reluctantly...it confuses people
> though.
> 
>> And this in turn will cause the ASoC DMA code to dereference these
>> NULL pointers when starting a playback (the same will probably happen
>> also when starting a capture).
>>
>> Sorry if I wasn't 100% clear about these details in my previous
>> message describing this issue.
> 
> I would prefer to send an incremental patch later to update it,
> if there are no new comments against this version; Otherwise, I
> will update it in a next version once there is a need to send a
> v6 anyway.

IMHO it is such a tiny thing that it isn't worth respinning 17
patch series just for it, it can be easily improved later via
a separate patch.

> Thanks
> 

Thanks,
Maciej