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The HDAudio ASoC support relies on the set_tdm_slots() helper to store
the HDaudio stream tag in the tx_mask. This only works because of the
pre-existing order in soc-pcm.c, where the hw_params() is handled for
codec_dais *before* cpu_dais. When the order is reversed, the
stream_tag is used as a mask in the codec fixup functions:

	/* fixup params based on TDM slot masks */
	if (substream->stream == SNDRV_PCM_STREAM_PLAYBACK &&
	    codec_dai->tx_mask)
		soc_pcm_codec_params_fixup(&codec_params,
					   codec_dai->tx_mask);

As a result of this confusion, the codec_params_fixup() ends-up
generating bad channel masks, depending on what stream_tag was
allocated.

We could add a flag to state that the tx_mask is really not a mask,
but it would be quite ugly to persist in overloading concepts.

Instead, this patch suggests a more generic get/set 'stream' API based
on the existing model for SoundWire. We can expand the concept to
store 'stream' opaq...