linux-kernel - Re: bugs in "ASoC: core - Optimise and refactor pcm

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Message-ID: <4EE8AB76.6040202@imgtec.com>
Date:	Wed, 14 Dec 2011 13:58:14 +0000
From:	James Hogan <james.hogan@...tec.com>
To:	Mark Brown <broonie@...nsource.wolfsonmicro.com>
CC:	Liam Girdwood <lrg@...com>, Jaroslav Kysela <perex@...ex.cz>,
	Takashi Iwai <tiwai@...e.de>, <alsa-devel@...a-project.org>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	Neil <neil.jones@...tec.com>
Subject: Re: bugs in "ASoC: core - Optimise and refactor pcm_new() to pass
 only rtd"?

On 12/14/2011 01:34 PM, Mark Brown wrote:
> 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.

Thanks Mark, we were basing our drivers on one of the other ones (I
think the atmel one, which still seems to do it as of v3.2-rc4).

Cheers
James

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