regmap: Implement managed regmap_init()

Save error handling and unwinding code in drivers by providing managed
versions of the regmap init functions, simplifying usage.

Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>

drivers/base/regmap/regmap.c

@@ -258,6 +258,45 @@ err:
 }
 EXPORT_SYMBOL_GPL(regmap_init);
 
+static void devm_regmap_release(struct device *dev, void *res)
+{
+	regmap_exit(*(struct regmap **)res);
+}
+
+/**
+ * devm_regmap_init(): Initialise managed register map
+ *
+ * @dev: Device that will be interacted with
+ * @bus: Bus-specific callbacks to use with device
+ * @config: Configuration for register map
+ *
+ * The return value will be an ERR_PTR() on error or a valid pointer
+ * to a struct regmap.  This function should generally not be called
+ * directly, it should be called by bus-specific init functions.  The
+ * map will be automatically freed by the device management code.
+ */
+struct regmap *devm_regmap_init(struct device *dev,
+				const struct regmap_bus *bus,
+				const struct regmap_config *config)
+{
+	struct regmap **ptr, *regmap;
+
+	ptr = devres_alloc(devm_regmap_release, sizeof(*ptr), GFP_KERNEL);
+	if (!ptr)
+		return ERR_PTR(-ENOMEM);
+
+	regmap = regmap_init(dev, bus, config);
+	if (!IS_ERR(regmap)) {
+		*ptr = regmap;
+		devres_add(dev, ptr);
+	} else {
+		devres_free(ptr);
+	}
+
+	return regmap;
+}
+EXPORT_SYMBOL_GPL(devm_regmap_init);
+
 /**
  * regmap_reinit_cache(): Reinitialise the current register cache
  *