PCM3168A: struct snd_soc_dai_driver's configuration

Tool/software:

Hi expert,

I did some tests with different configuration about struct snd_soc_dai_driver, the results are as below:

configuration one:

static struct snd_soc_dai_driver pcm3168a_dais[] = {
	{
		.name = "pcm3168a-dac",
		.id = PCM3168A_DAI_DAC,
		.playback = {
			.stream_name = "Playback",
			.channels_min = 1,
			.channels_max = 8,
			.rates = SNDRV_PCM_RATE_8000_192000,
			.formats = PCM3168A_FORMATS
		},
		.ops = &pcm3168a_dai_ops
	},
	{
		.name = "pcm3168a-adc",
		.id = PCM3168A_DAI_ADC,
		.capture = {
			.stream_name = "Capture",
			.channels_min = 1,
			.channels_max = 6,
			.rates = SNDRV_PCM_RATE_8000_96000,
			.formats = PCM3168A_FORMATS
		},
		.ops = &pcm3168a_dai_ops
	},
};

result: When aplay mono(stereo) wav file, VOUT1\VOUT2 have audio signal, VOUT3\VOUT4\VOUT5\VOUT6\VOUT7\VOUT8 don't have aduio signal.

When aplay eight-channel wav file,  VOUT1\VOUT2  VOUT3\VOUT4\VOUT5\VOUT6\VOUT7\VOUT8 all have aduio signal.

configuration 2:

static struct snd_soc_dai_driver pcm3168a_dais[] = {
	{
		.name = "pcm3168a-dac",
		.id = PCM3168A_DAI_DAC,
		.playback = {
			.stream_name = "Playback",
			.channels_min = 1,
			.channels_max = 4,
			.rates = SNDRV_PCM_RATE_8000_192000,
			.formats = PCM3168A_FORMATS
		},
		.ops = &pcm3168a_dai_ops
	},
	{
		.name = "pcm3168a-adc",
		.id = PCM3168A_DAI_ADC,
		.capture = {
			.stream_name = "Capture",
			.channels_min = 1,
			.channels_max = 6,
			.rates = SNDRV_PCM_RATE_8000_96000,
			.formats = PCM3168A_FORMATS
		},
		.ops = &pcm3168a_dai_ops
	},
};

result:  When aplay mono(stereo) wav file, VOUT1\VOUT2 have audio signal, VOUT3\VOUT4\VOUT5\VOUT6\VOUT7\VOUT8 don't have aduio signal.

When aplay eight-channel wav file,  VOUT1\VOUT2  VOUT3\VOUT4\VOUT5\VOUT6\VOUT7\VOUT8 all have aduio signal.

When aplay eight-channel wav file, how come VOUT5\VOUT6\VOUT7\VOUT8 also have aduio signal?

configuration three:

static struct snd_soc_dai_driver pcm3168a_dais[] = {
	{
		.name = "pcm3168a-dac",
		.id = PCM3168A_DAI_DAC,
		.playback = {
			.stream_name = "Playback",
			.channels_min = 7,
			.channels_max = 8,
			.rates = SNDRV_PCM_RATE_8000_192000,
			.formats = PCM3168A_FORMATS
		},
		.ops = &pcm3168a_dai_ops
	},
	{
		.name = "pcm3168a-adc",
		.id = PCM3168A_DAI_ADC,
		.capture = {
			.stream_name = "Capture",
			.channels_min = 1,
			.channels_max = 6,
			.rates = SNDRV_PCM_RATE_8000_96000,
			.formats = PCM3168A_FORMATS
		},
		.ops = &pcm3168a_dai_ops
	},
};

result: 

When aplay mono(stereo) wav file, VOUT1\VOUT2\VOUT3\VOUT4\VOUT5\VOUT6\VOUT7\VOUT8 all have aduio signal.

When aplay eight-channel wav file,  VOUT1\VOUT2  VOUT3\VOUT4\VOUT5\VOUT6\VOUT7\VOUT8 all have aduio signal.

What i want ask:

1. What's  the particularly meaning of channels_min\channels_max in PCM3168A? 

At context playback, what's the corresponding relationship among channels_min\channels_max, DIN1-DIN4, VOUT1-VOUT8?

At context capture,  what's the corresponding relationship among channels_min\channels_max, DOUT1-DOUT3, VIN1-VIN6?

2. If it's possible to have four playback devices(such as pcmC0D0p,pcmC0D1p,pcmC0D2p,pcmC0D3p), pcmC0D0p is bind to VOUT1&VOUT2, pcmC0D1p is bind to VOUT3&VOUT4,pcmC0D2p is bind to VOUT5&VOUT6,pcmC0D3p is bind to VOUT7&VOUT8?

so that when use pcmC0D0p to playback wav(mono\stereo\three-channel\four-channel\...\eight-channel) file,just VOUT1&VOUT2 can hear sound and VOUT3-VOUT8 can't hear sound; when use pcmC0D1p to playback wav(mono\stereo\three-channel\four-channel\...\eight-channel) file,just VOUT3&VOUT4 can hear sound and the other six can't hear sound;when use pcmC0D2p to playback wav(mono\stereo\three-channel\four-channel\...\eight-channel) file,just VOUT5&VOUT6 can hear sound and the other six can't hear sound;when use pcmC0D3p to playback wav(mono\stereo\three-channel\four-channel\...\eight-channel) file,just VOUT7&VOUT8 can hear sound and the other six can't hear sound.

Thanks & Best Regards!