[U-Boot] [PATCH v7 08/13] mtd: uclass: search for an equivalent MTD name with the mtdids

[Miquel Raynal]

Using an MTD device (resp. partition) name in mtdparts is simple and
straightforward. However, for a long time already, another name was
given in mtdparts to indicate a device (resp. partition) so the
"mtdids" environment variable was created to do the match.

Let's create a function that, from an MTD device (resp. partition)
name, search for the equivalent name in the "mtdparts" environment
variable thanks to the "mtdids" string.

Signed-off-by: Miquel Raynal <miquel.raynal at bootlin.com>
---
 drivers/mtd/mtdpart.c          | 62 ++++++++++++++++++++++++++++++++++
 include/linux/mtd/partitions.h |  2 ++
 2 files changed, 64 insertions(+)

diff --git a/drivers/mtd/mtdpart.c b/drivers/mtd/mtdpart.c
index d9708da2ae..096351e48b 100644
--- a/drivers/mtd/mtdpart.c
+++ b/drivers/mtd/mtdpart.c
@@ -263,6 +263,68 @@ int mtd_parse_partitions(struct mtd_info *parent, const char **_mtdparts,
 	return 0;
 }
 
+/**
+ * mtd_search_alternate_name - Search an alternate name for @mtdname thanks to
+ *                             the mtdids legacy environment variable.
+ *
+ * The mtdids string is a list of comma-separated 'dev_id=mtd_id' tupples.
+ * Check if one of the mtd_id matches mtdname, in this case save dev_id in
+ * altname.
+ *
+ * @mtdname: Current MTD device name
+ * @altname: Alternate name to return
+ * @max_len: Length of the alternate name buffer
+ *
+ * @return 0 on success, an error otherwise.
+ */
+int mtd_search_alternate_name(const char *mtdname, char *altname,
+			      unsigned int max_len)
+{
+	const char *mtdids, *equal, *comma, *dev_id, *mtd_id;
+	int dev_id_len, mtd_id_len;
+
+	mtdids = env_get("mtdids");
+	if (!mtdids)
+		return -EINVAL;
+
+	do {
+		/* Find the '=' sign */
+		dev_id = mtdids;
+		equal = strchr(dev_id, '=');
+		if (!equal)
+			break;
+
+		dev_id_len = equal - mtdids;
+		mtd_id = equal + 1;
+
+		/* Find the end of the tupple */
+		comma = strchr(mtdids, ',');
+		if (comma)
+			mtd_id_len = comma - equal;
+		else
+			mtd_id_len = &mtdids[strlen(mtdids)] - equal;
+
+		if (!dev_id_len || !mtd_id_len)
+			return -EINVAL;
+
+		if (dev_id_len + 1 > max_len)
+			continue;
+
+		/* Compare the name we search with the current mtd_id */
+		if (!strncmp(mtdname, mtd_id, mtd_id_len)) {
+			strncpy(altname, dev_id, dev_id_len);
+			altname[dev_id_len] = 0;
+
+			return 0;
+		}
+
+		/* Go to the next tupple */
+		mtdids = comma + 1;
+	} while (comma);
+
+	return -EINVAL;
+}
+
 /*
  * MTD methods which simply translate the effective address and pass through
  * to the _real_ device.
diff --git a/include/linux/mtd/partitions.h b/include/linux/mtd/partitions.h
index ed4ece5e13..082a4966ea 100644
--- a/include/linux/mtd/partitions.h
+++ b/include/linux/mtd/partitions.h
@@ -88,5 +88,7 @@ int mtd_del_partition(struct mtd_info *master, int partno);
 uint64_t mtd_get_device_size(const struct mtd_info *mtd);
 int mtd_parse_partitions(struct mtd_info *parent, const char **_mtdparts,
 			 struct mtd_partition **_parts, int *_nb_parts);
+int mtd_search_alternate_name(const char *mtdname, char *altname,
+			      unsigned int max_len);
 
 #endif
-- 
2.17.1