mtd: add new API for handling MTD registration

Lots (nearly all) mtd drivers contain nearly the similar code that
calls parse_mtd_partitions, provides some platform-default values, if
parsing fails, and registers  mtd device.

This is an aim to provide single implementation of this scenario:
mtd_device_parse_register() which will handle all this parsing and
defaults.

Artem: amended comments
Signed-off-by: Dmitry Eremin-Solenikov <dbaryshkov@gmail.com>
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>

drivers/mtd/mtdcore.c

@@ -451,6 +451,64 @@ int mtd_device_register(struct mtd_info *master,
 }
 EXPORT_SYMBOL_GPL(mtd_device_register);
 
+/**
+ * mtd_device_parse_register - parse partitions and register an MTD device.
+ *
+ * @mtd: the MTD device to register
+ * @types: the list of MTD partition probes to try, see
+ *         'parse_mtd_partitions()' for more information
+ * @origin: start address of MTD device, %0 unless you are sure you need this.
+ * @parts: fallback partition information to register, if parsing fails;
+ *         only valid if %nr_parts > %0
+ * @nr_parts: the number of partitions in parts, if zero then the full
+ *            MTD device is registered if no partition info is found
+ *
+ * This function aggregates MTD partitions parsing (done by
+ * 'parse_mtd_partitions()') and MTD device and partitions registering. It
+ * basically follows the most common pattern found in many MTD drivers:
+ *
+ * * It first tries to probe partitions on MTD device @mtd using parsers
+ *   specified in @types (if @types is %NULL, then the default list of parsers
+ *   is used, see 'parse_mtd_partitions()' for more information). If none are
+ *   found this functions tries to fallback to information specified in
+ *   @parts/@nr_parts.
+ * * If any parititioning info was found, this function registers the found
+ *   partitions.
+ * * If no partitions were found this function just registers the MTD device
+ *   @mtd and exits.
+ *
+ * Returns zero in case of success and a negative error code in case of failure.
+ */
+int mtd_device_parse_register(struct mtd_info *mtd, const char **types,
+			      unsigned long origin,
+			      const struct mtd_partition *parts,
+			      int nr_parts)
+{
+	int err;
+	struct mtd_partition *real_parts;
+
+	err = parse_mtd_partitions(mtd, types, &real_parts, origin);
+	if (err <= 0 && nr_parts) {
+		real_parts = kmemdup(parts, sizeof(*parts) * nr_parts,
+				     GFP_KERNEL);
+		err = nr_parts;
+		if (!parts)
+			err = -ENOMEM;
+	}
+
+	if (err > 0) {
+		err = add_mtd_partitions(mtd, real_parts, err);
+		kfree(real_parts);
+	} else if (err == 0) {
+		err = add_mtd_device(mtd);
+		if (err == 1)
+			err = -ENODEV;
+	}
+
+	return err;
+}
+EXPORT_SYMBOL_GPL(mtd_device_parse_register);
+
 /**
  * mtd_device_unregister - unregister an existing MTD device.
  *

include/linux/mtd/mtd.h

@@ -327,6 +327,11 @@ struct mtd_partition;
 extern int mtd_device_register(struct mtd_info *master,
 			       const struct mtd_partition *parts,
 			       int nr_parts);
+extern int mtd_device_parse_register(struct mtd_info *mtd,
+			      const char **part_probe_types,
+			      unsigned long origin,
+			      const struct mtd_partition *defparts,
+			      int defnr_parts);
 extern int mtd_device_unregister(struct mtd_info *master);
 extern struct mtd_info *get_mtd_device(struct mtd_info *mtd, int num);
 extern int __get_mtd_device(struct mtd_info *mtd);