linux-kernel - RE: [PATCH v2] ASoC: bdw-rt5650: remove 3-channel capture support

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Date:   Mon, 13 Apr 2020 14:29:11 +0000
From:   "Lu, Brent" <brent.lu@...el.com>
To:     Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>,
        "alsa-devel@...a-project.org" <alsa-devel@...a-project.org>
CC:     Guennadi Liakhovetski <guennadi.liakhovetski@...ux.intel.com>,
        "Rojewski, Cezary" <cezary.rojewski@...el.com>,
        Kuninori Morimoto <kuninori.morimoto.gx@...esas.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Takashi Iwai <tiwai@...e.com>,
        Jie Yang <yang.jie@...ux.intel.com>,
        Liam Girdwood <liam.r.girdwood@...ux.intel.com>,
        Ben Zhang <benzh@...omium.org>,
        "Chiang, Mac" <mac.chiang@...el.com>,
        "Mark Brown" <broonie@...nel.org>
Subject: RE: [PATCH v2] ASoC: bdw-rt5650: remove 3-channel capture support

> 
> That looks like an error caught by the ALSA conformance tool?
> 
> What are the odds that we have a similar issue with the other broadwell
> drivers which don't have a constraint on the number of channels either on
> their 'System PCM' dailink?
> 
> Thanks
> -Pierre
> 

Yes. That's why I am sending patch for this old BDW platform...

So far as I know only 'buddy' supports 2/4-channel recording while other BDW
Chrome products should support stereo recording only. Therefore, this defect
should only be triggered by the ALSA conformance tool.

I am think about implementing the constraint in FE DAI's startup() callback
instead of DAI Link's callback. Since the channels_max is 4 for the capture
stream, ALSA conformance tool will always test 3-channel recording on any
platforms using this driver. Does it make sense to you?

sound/soc/intel/haswell/sst-haswell-pcm.c:
static struct snd_soc_dai_driver hsw_dais[] = {
	{
		.name  = "System Pin",
		.id = HSW_PCM_DAI_ID_SYSTEM,
		.playback = {
			.stream_name = "System Playback",
			.channels_min = 2,
			.channels_max = 2,
			.rates = SNDRV_PCM_RATE_48000,
			.formats = SNDRV_PCM_FMTBIT_S24_LE | SNDRV_PCM_FMTBIT_S16_LE,
		},
		.capture = {
			.stream_name = "Analog Capture",
			.channels_min = 2,
			.channels_max = 4,
			.rates = SNDRV_PCM_RATE_48000,
			.formats = SNDRV_PCM_FMTBIT_S24_LE | SNDRV_PCM_FMTBIT_S16_LE,
		},
	},


Regards,
Brent