ASoC: Add utility to set a card's name from device tree

Implement snd_soc_of_parse_card_name(), a utility function that sets a
card's name 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

@@ -961,6 +961,9 @@ static inline bool snd_soc_volsw_is_stereo(struct soc_mixer_control *mc)
 int snd_soc_util_init(void);
 void snd_soc_util_exit(void);
 
+int snd_soc_of_parse_card_name(struct snd_soc_card *card,
+			       const char *propname);
+
 #include <sound/soc-dai.h>
 
 #ifdef CONFIG_DEBUG_FS

sound/soc/soc-core.c

@@ -32,6 +32,7 @@
 #include <linux/platform_device.h>
 #include <linux/ctype.h>
 #include <linux/slab.h>
+#include <linux/of.h>
 #include <sound/ac97_codec.h>
 #include <sound/core.h>
 #include <sound/jack.h>
@@ -3317,6 +3318,30 @@ void snd_soc_unregister_codec(struct device *dev)
 }
 EXPORT_SYMBOL_GPL(snd_soc_unregister_codec);
 
+/* Retrieve a card's name from device tree */
+int snd_soc_of_parse_card_name(struct snd_soc_card *card,
+			       const char *propname)
+{
+	struct device_node *np = card->dev->of_node;
+	int ret;
+
+	ret = of_property_read_string_index(np, propname, 0, &card->name);
+	/*
+	 * EINVAL means the property does not exist. This is fine providing
+	 * card->name was previously set, which is checked later in
+	 * snd_soc_register_card.
+	 */
+	if (ret < 0 && ret != -EINVAL) {
+		dev_err(card->dev,
+			"Property '%s' could not be read: %d\n",
+			propname, ret);
+		return ret;
+	}
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(snd_soc_of_parse_card_name);
+
 static int __init snd_soc_init(void)
 {
 #ifdef CONFIG_DEBUG_FS