ALSA: pcm: add a helper function to constrain mask-type parameters

Application of constraints to mask-type parameters for PCM substream is
done in a call of snd_pcm_hw_refine(), while the function includes much
codes and is not enough friendly to readers.

This commit splits the codes to a separated function so that readers can
get it easily. I leave desicion into compilers to merge the function into
its callee.
Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

sound/core/pcm_native.c

@@ -253,6 +253,39 @@ static bool hw_support_mmap(struct snd_pcm_substream *substream)
 	return true;
 }
 
+static int constrain_mask_params(struct snd_pcm_substream *substream,
+				 struct snd_pcm_hw_params *params)
+{
+	struct snd_pcm_hw_constraints *constrs =
+					&substream->runtime->hw_constraints;
+	struct snd_mask *m;
+	unsigned int k;
+	struct snd_mask old_mask;
+	int changed;
+
+	for (k = SNDRV_PCM_HW_PARAM_FIRST_MASK; k <= SNDRV_PCM_HW_PARAM_LAST_MASK; k++) {
+		m = hw_param_mask(params, k);
+		if (snd_mask_empty(m))
+			return -EINVAL;
+		if (!(params->rmask & (1 << k)))
+			continue;
+
+		if (trace_hw_mask_param_enabled())
+			old_mask = *m;
+
+		changed = snd_mask_refine(m, constrs_mask(constrs, k));
+
+		trace_hw_mask_param(substream, k, 0, &old_mask, m);
+
+		if (changed)
+			params->cmask |= 1 << k;
+		if (changed < 0)
+			return changed;
+	}
+
+	return 0;
+}
+
 int snd_pcm_hw_refine(struct snd_pcm_substream *substream, 
 		      struct snd_pcm_hw_params *params)
 {
@@ -265,6 +298,7 @@ int snd_pcm_hw_refine(struct snd_pcm_substream *substream,
 	unsigned int vstamps[SNDRV_PCM_HW_PARAM_LAST_INTERVAL + 1];
 	unsigned int stamp = 2;
 	int changed, again;
+	int err;
 
 	struct snd_mask __maybe_unused old_mask;
 	struct snd_interval __maybe_unused old_interval;
@@ -278,25 +312,9 @@ int snd_pcm_hw_refine(struct snd_pcm_substream *substream,
 		params->rate_den = 0;
 	}
 
-	for (k = SNDRV_PCM_HW_PARAM_FIRST_MASK; k <= SNDRV_PCM_HW_PARAM_LAST_MASK; k++) {
-		m = hw_param_mask(params, k);
-		if (snd_mask_empty(m))
-			return -EINVAL;
-		if (!(params->rmask & (1 << k)))
-			continue;
-
-		if (trace_hw_mask_param_enabled())
-			old_mask = *m;
-
-		changed = snd_mask_refine(m, constrs_mask(constrs, k));
-
-		trace_hw_mask_param(substream, k, 0, &old_mask, m);
-
-		if (changed)
-			params->cmask |= 1 << k;
-		if (changed < 0)
-			return changed;
-	}
+	err = constrain_mask_params(substream, params);
+	if (err < 0)
+		return err;
 
 	for (k = SNDRV_PCM_HW_PARAM_FIRST_INTERVAL; k <= SNDRV_PCM_HW_PARAM_LAST_INTERVAL; k++) {
 		i = hw_param_interval(params, k);