ASoC: Add utility to parse DAPM routes from device tree

Implement snd_soc_of_parse_audio_routing(), a utility function that can
parses a simple DAPM route table from device tree.The machine driver
specifies the DT property to use, since this is binding-specific.
Signed-off-by: Stephen Warren <swarren@nvidia.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>

include/sound/soc.h

@@ -963,6 +963,8 @@ void snd_soc_util_exit(void);
 
 int snd_soc_of_parse_card_name(struct snd_soc_card *card,
 			       const char *propname);
+int snd_soc_of_parse_audio_routing(struct snd_soc_card *card,
+				   const char *propname);
 
 #include <sound/soc-dai.h>
 

sound/soc/soc-core.c

@@ -3342,6 +3342,63 @@ int snd_soc_of_parse_card_name(struct snd_soc_card *card,
 }
 EXPORT_SYMBOL_GPL(snd_soc_of_parse_card_name);
 
+int snd_soc_of_parse_audio_routing(struct snd_soc_card *card,
+				   const char *propname)
+{
+	struct device_node *np = card->dev->of_node;
+	int num_routes;
+	struct snd_soc_dapm_route *routes;
+	int i, ret;
+
+	num_routes = of_property_count_strings(np, propname);
+	if (num_routes & 1) {
+		dev_err(card->dev,
+			"Property '%s's length is not even\n",
+			propname);
+		return -EINVAL;
+	}
+	num_routes /= 2;
+	if (!num_routes) {
+		dev_err(card->dev,
+			"Property '%s's length is zero\n",
+			propname);
+		return -EINVAL;
+	}
+
+	routes = devm_kzalloc(card->dev, num_routes * sizeof(*routes),
+			      GFP_KERNEL);
+	if (!routes) {
+		dev_err(card->dev,
+			"Could not allocate DAPM route table\n");
+		return -EINVAL;
+	}
+
+	for (i = 0; i < num_routes; i++) {
+		ret = of_property_read_string_index(np, propname,
+			2 * i, &routes[i].sink);
+		if (ret) {
+			dev_err(card->dev,
+				"Property '%s' index %d could not be read: %d\n",
+				propname, 2 * i, ret);
+			return -EINVAL;
+		}
+		ret = of_property_read_string_index(np, propname,
+			(2 * i) + 1, &routes[i].source);
+		if (ret) {
+			dev_err(card->dev,
+				"Property '%s' index %d could not be read: %d\n",
+				propname, (2 * i) + 1, ret);
+			return -EINVAL;
+		}
+	}
+
+	card->num_dapm_routes = num_routes;
+	card->dapm_routes = routes;
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(snd_soc_of_parse_audio_routing);
+
 static int __init snd_soc_init(void)
 {
 #ifdef CONFIG_DEBUG_FS