dm: core: Add a way to obtain a string list

At present we support reading a string list a string at a time. Apart
from being inefficient, this makes it impossible to separate reading of
the devicetree into the of_to_plat() method where it belongs, since any
code which needs access to the string must read it from the devicetree.

Add a function which returns the string property as an array of pointers
to the strings, which is easily used by clients.

Signed-off-by: Simon Glass <sjg@chromium.org>

drivers/core/ofnode.c

@@ -456,6 +456,32 @@ int ofnode_read_string_count(ofnode node, const char *property)
 	}
 }
 
+int ofnode_read_string_list(ofnode node, const char *property,
+			    const char ***listp)
+{
+	const char **prop;
+	int count;
+	int i;
+
+	*listp = NULL;
+	count = ofnode_read_string_count(node, property);
+	if (count < 0)
+		return count;
+	if (!count)
+		return 0;
+
+	prop = calloc(count + 1, sizeof(char *));
+	if (!prop)
+		return -ENOMEM;
+
+	for (i = 0; i < count; i++)
+		ofnode_read_string_index(node, property, i, &prop[i]);
+	prop[count] = NULL;
+	*listp = prop;
+
+	return count;
+}
+
 static void ofnode_from_fdtdec_phandle_args(struct fdtdec_phandle_args *in,
 					    struct ofnode_phandle_args *out)
 {

drivers/core/read.c

@@ -205,6 +205,12 @@ int dev_read_string_count(const struct udevice *dev, const char *propname)
 	return ofnode_read_string_count(dev_ofnode(dev), propname);
 }
 
+int dev_read_string_list(const struct udevice *dev, const char *propname,
+			 const char ***listp)
+{
+	return ofnode_read_string_list(dev_ofnode(dev), propname, listp);
+}
+
 int dev_read_phandle_with_args(const struct udevice *dev, const char *list_name,
 			       const char *cells_name, int cell_count,
 			       int index, struct ofnode_phandle_args *out_args)