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.