[alsa-devel] bugs in "ASoC: core - Optimise and refactor pcm_new() to pass only rtd"?

Mark Brown broonie at opensource.wolfsonmicro.com
Wed Dec 14 14:34:48 CET 2011

On Wed, Dec 14, 2011 at 12:43:50PM +0000, James Hogan wrote:

> I've bisected a problem with an out of tree set of asoc drivers down to commit
> 552d1ef6b5a98d7b95959d5b139071e3c90cebf1 ("ASoC: core - Optimise and refactor
> pcm_new() to pass only rtd"). By the looks of it this change was intended not 
> to change the workings of the code, however the dai parameter of pcm_new used
> to be passed codec_dai in soc_new_pcm() (initialised from rtd->codec_dai), but
> each driver now sets it's dai to rtd->cpu_dai instead. This seems to make the
> driver check the wrong dai's driver->capture.channels_min in the pcm_new
> callback, which makes it dereference
> pcm->streams[SNDRV_PCM_STREAM_CAPTURE].substream in the driver's
> preallocate_dma_buffer() function which can be NULL. Is this a bug (in every
> pcm asoc driver) that just happens not to have been noticed, or have I
> misunderstood it?

Your drivers should never have beenn relying on this behaviour of the
core - see changes in the pxa and fsl drivers which remove similar
assumptions.  The CPU driver should be checking for the substream if
it's looking to see if a particular substream is present, not peering
inside the DAI for a random parameter.

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