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Subject: Re: [PATCH] ASoC: core: restore dpcm flags semantics
To:     Jerome Brunet <jbrunet@baylibre.com>,
        Mark Brown <broonie@kernel.org>,
        Liam Girdwood <lgirdwood@gmail.com>
Cc:     alsa-devel@alsa-project.org, linux-kernel@vger.kernel.org,
        linux-amlogic@lists.infradead.org,
        Kevin Hilman <khilman@baylibre.com>, zhangn1985@outlook.com,
        Stephan Gerhold <stephan@gerhold.net>
References: <20200723180533.220312-1-pierre-louis.bossart@linux.intel.com>
 <20200729154639.1983854-1-jbrunet@baylibre.com>
From:   Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Message-ID: <2ad13f95-434d-376a-bc38-b209623b461e@linux.intel.com>
Date:   Wed, 29 Jul 2020 10:56:05 -0500
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On 7/29/20 10:46 AM, Jerome Brunet wrote:
> commit b73287f0b0745 ('ASoC: soc-pcm: dpcm: fix playback/capture checks')
> changed dpcm_playback and dpcm_capture semantic by throwing an error if
> these flags are not aligned with DAIs capabilities on the link.
> 
> The former semantic did not force the flags and DAI caps to be aligned.
> The flag previously allowed card drivers to disable a stream direction on
> a link (whether or not such feature is deemed useful).
> 
> With change ('ASoC: core: use less strict tests for dailink capabilities')
> an error is thrown if the flags and and the DAI caps are not aligned. Those
> parameters were not meant to aligned initially. No technical reason was
> given about why cards should now be considered "broken" in such condition
> is not met, or why it should be considered to be an improvement to enforce
> that.
> 
> Forcing the flags to be aligned with DAI caps just make the information
> the flag carry redundant with DAI caps, breaking a few cards along the way.
> 
> This change drops the added error conditions and restore the initial flag
> semantics.

or rather lack thereof.

I am ok to move dev_err to dev_warn and remove the return -EINVAL, but I 
maintain that we have to reach a point where configurations make sense 
before we can clean them up. If we implicitly push issues under the rug 
by not even being aware of them we'll never make progress.

> 
> Cc: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
> Signed-off-by: Jerome Brunet <jbrunet@baylibre.com>
> ---
> 
>   Hi Mark,
> 
>   Because b73287f0b0745 ('ASoC: soc-pcm: dpcm: fix playback/capture checks')
>   introduced more than one problem, the change
>   "ASoC: core: use less strict tests for dailink capabilities" [0] is still
>   necessary but the change of semantic remains a problem with it.
> 
>   This patch applies on top of it.
> 
>   sound/soc/soc-pcm.c | 14 --------------
>   1 file changed, 14 deletions(-)
> 
> diff --git a/sound/soc/soc-pcm.c b/sound/soc/soc-pcm.c
> index 00ac1cbf6f88..2e205b738eae 100644
> --- a/sound/soc/soc-pcm.c
> +++ b/sound/soc/soc-pcm.c
> @@ -2749,13 +2749,6 @@ int soc_new_pcm(struct snd_soc_pcm_runtime *rtd, int num)
>   					break;
>   				}
>   			}
> -
> -			if (!playback) {
> -				dev_err(rtd->card->dev,
> -					"No CPU DAIs support playback for stream %s\n",
> -					rtd->dai_link->stream_name);
> -				return -EINVAL;
> -			}
>   		}
>   		if (rtd->dai_link->dpcm_capture) {
>   			stream = SNDRV_PCM_STREAM_CAPTURE;
> @@ -2766,13 +2759,6 @@ int soc_new_pcm(struct snd_soc_pcm_runtime *rtd, int num)
>   					break;
>   				}
>   			}
> -
> -			if (!capture) {
> -				dev_err(rtd->card->dev,
> -					"No CPU DAIs support capture for stream %s\n",
> -					rtd->dai_link->stream_name);
> -				return -EINVAL;
> -			}
>   		}
>   	} else {
>   		/* Adapt stream for codec2codec links */
>