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

[Lu, Brent]

> 
> 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