ASoC: dpcm: Explicitly set BE DAI link supported stream directions

Some BE DAIs can be "dummy" (when the DSP is controlling the DAI) and as such
wont have set a minimum number of playback or capture channels required for BE
DAI registration (to establish supported stream directions).

Force machine drivers to explicitly set whether they support playback and capture
stream directions for every BE DAIs.
Signed-off-by: Liam Girdwood <liam.r.girdwood@linux.intel.com>
Signed-off-by: Mark Brown <broonie@linaro.org>

include/sound/soc.h

@@ -886,6 +886,10 @@ struct snd_soc_dai_link {
 	/* This DAI link can route to other DAI links at runtime (Frontend)*/
 	unsigned int dynamic:1;
 
+	/* DPCM capture and Playback support */
+	unsigned int dpcm_capture:1;
+	unsigned int dpcm_playback:1;
+
 	/* pmdown_time is ignored at stop */
 	unsigned int ignore_pmdown_time:1;
 

sound/soc/soc-pcm.c

@@ -2026,10 +2026,8 @@ int soc_new_pcm(struct snd_soc_pcm_runtime *rtd, int num)
 	int ret = 0, playback = 0, capture = 0;
 
 	if (rtd->dai_link->dynamic || rtd->dai_link->no_pcm) {
-		if (cpu_dai->driver->playback.channels_min)
-			playback = 1;
-		if (cpu_dai->driver->capture.channels_min)
-			capture = 1;
+		playback = rtd->dai_link->dpcm_playback;
+		capture = rtd->dai_link->dpcm_capture;
 	} else {
 		if (codec_dai->driver->playback.channels_min &&
 		    cpu_dai->driver->playback.channels_min)