mtd: spi-nor: allow NULL as chip name and try to auto detect it

This will allow spi-nor users to plainly use JEDEC to detect flash chip.
Signed-off-by: Rafał Miłecki <zajec5@gmail.com>
Signed-off-by: Brian Norris <computersforpeace@gmail.com>

drivers/mtd/spi-nor/spi-nor.c

@@ -938,13 +938,21 @@ int spi_nor_scan(struct spi_nor *nor, const char *name, enum read_mode mode)
 	if (ret)
 		return ret;
 
+	/* Try to auto-detect if chip name wasn't specified */
+	if (!name)
+		id = spi_nor_read_id(nor);
+	else
 		id = spi_nor_match_id(name);
-	if (!id)
+	if (IS_ERR_OR_NULL(id))
 		return -ENOENT;
 
 	info = (void *)id->driver_data;
 
-	if (info->id_len) {
+	/*
+	 * If caller has specified name of flash model that can normally be
+	 * detected using JEDEC, let's verify it.
+	 */
+	if (name && info->id_len) {
 		const struct spi_device_id *jid;
 
 		jid = spi_nor_read_id(nor);