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Date: Mon, 17 Feb 2020 18:12:45 +0100 From: Stephan Gerhold <stephan@...hold.net> To: Mark Brown <broonie@...nel.org> Cc: Sameer Pujar <spujar@...dia.com>, tiwai@...e.com, perex@...ex.cz, alsa-devel@...a-project.org, linux-kernel@...r.kernel.org, Jerome Brunet <jbrunet@...libre.com> Subject: Re: [alsa-devel] [RFC] ASoC: soc-pcm: crash in snd_soc_dapm_new_dai On Mon, Feb 17, 2020 at 03:43:01PM +0000, Mark Brown wrote: > On Mon, Feb 17, 2020 at 03:41:20PM +0100, Stephan Gerhold wrote: > > > I'm a bit confused about this patch, isn't SNDRV_PCM_STREAM_PLAYBACK > > used for both cpu_dai and codec_dai in the playback case? > > It is in the normal case, but with a CODEC<->CODEC link (which was what > this was targeting) we need to bodge things by swapping playback and > capture on one end of the link. I see. Looking at the code again I'm guessing the cause of the crash "fixed" by this patch is commit a342031cdd08 ("ASoC: create pcm for codec2codec links as well") where the codec2codec case was sort of patched in. This is what we had before this patch: /* Adapt stream for codec2codec links */ struct snd_soc_pcm_stream *cpu_capture = rtd->dai_link->params ? &cpu_dai->driver->playback : &cpu_dai->driver->capture; struct snd_soc_pcm_stream *cpu_playback = rtd->dai_link->params ? &cpu_dai->driver->capture : &cpu_dai->driver->playback; This does the swapping you mentioned, so I guess rtd->dai_link->params is only set for the codec2codec case? for_each_rtd_codec_dai(rtd, i, codec_dai) { if (snd_soc_dai_stream_valid(codec_dai, SNDRV_PCM_STREAM_PLAYBACK) && snd_soc_dai_stream_valid(cpu_dai, SNDRV_PCM_STREAM_PLAYBACK)) playback = 1; if (snd_soc_dai_stream_valid(codec_dai, SNDRV_PCM_STREAM_CAPTURE) && snd_soc_dai_stream_valid(cpu_dai, SNDRV_PCM_STREAM_CAPTURE)) capture = 1; } capture = capture && cpu_capture->channels_min; playback = playback && cpu_playback->channels_min; And this does a part of the check in snd_soc_dai_stream_valid(), but without the NULL check of cpu_capture/cpu_playback. (Maybe that is the cause of the crash.) >From my limited understanding, I would say that a much simpler way to implement this would be: /* Adapt stream for codec2codec links */ int cpu_capture = rtd->dai_link->params ? SNDRV_PCM_STREAM_PLAYBACK : SNDRV_PCM_STREAM_CAPTURE; int cpu_playback = rtd->dai_link->params ? SNDRV_PCM_STREAM_CAPTURE : SNDRV_PCM_STREAM_PLAYBACK; for_each_rtd_codec_dai(rtd, i, codec_dai) { if (snd_soc_dai_stream_valid(codec_dai, SNDRV_PCM_STREAM_PLAYBACK) && snd_soc_dai_stream_valid(cpu_dai, cpu_playback)) playback = 1; if (snd_soc_dai_stream_valid(codec_dai, SNDRV_PCM_STREAM_CAPTURE) && snd_soc_dai_stream_valid(cpu_dai, cpu_capture)) capture = 1; } since snd_soc_dai_stream_valid() does both the NULL-check and the "channels_min" check. But I'm really not familar with the codec2codec case and am unable to test it :) What do you think? Thanks, Stephan
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