Subject: ubi: auto-create ubiblock device for rootfs
From: Daniel Golle <[email-masked]>

Signed-off-by: Daniel Golle <[email-masked]>
---
 drivers/mtd/ubi/block.c | 42 ++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 42 insertions(+)

--- a/drivers/mtd/ubi/block.c
+++ b/drivers/mtd/ubi/block.c
@@ -652,6 +652,47 @@ static void __init ubiblock_create_from_
 	}
 }
 
+#define UBIFS_NODE_MAGIC  0x06101831
+static inline int ubi_vol_is_ubifs(struct ubi_volume_desc *desc)
+{
+	int ret;
+	uint32_t magic_of, magic;
+	ret = ubi_read(desc, 0, (char *)&magic_of, 0, 4);
+	if (ret)
+		return 0;
+	magic = le32_to_cpu(magic_of);
+	return magic == UBIFS_NODE_MAGIC;
+}
+
+static void __init ubiblock_create_auto_rootfs(void)
+{
+	int ubi_num, ret, is_ubifs;
+	struct ubi_volume_desc *desc;
+	struct ubi_volume_info vi;
+
+	for (ubi_num = 0; ubi_num < UBI_MAX_DEVICES; ubi_num++) {
+		desc = ubi_open_volume_nm(ubi_num, "rootfs", UBI_READONLY);
+		if (IS_ERR(desc))
+			desc = ubi_open_volume_nm(ubi_num, "fit", UBI_READONLY);;
+
+		if (IS_ERR(desc))
+			continue;
+
+		ubi_get_volume_info(desc, &vi);
+		is_ubifs = ubi_vol_is_ubifs(desc);
+		ubi_close_volume(desc);
+		if (is_ubifs)
+			break;
+
+		ret = ubiblock_create(&vi);
+		if (ret)
+			pr_err("UBI error: block: can't add '%s' volume, err=%d\n",
+				vi.name, ret);
+		/* always break if we get here */
+		break;
+	}
+}
+
 static void ubiblock_remove_all(void)
 {
 	struct ubiblock *next;
@@ -684,6 +725,10 @@ int __init ubiblock_init(void)
 	 */
 	ubiblock_create_from_param();
 
+	/* auto-attach "rootfs" volume if existing and non-ubifs */
+	if (IS_ENABLED(CONFIG_MTD_ROOTFS_ROOT_DEV))
+		ubiblock_create_auto_rootfs();
+
 	/*
 	 * Block devices are only created upon user requests, so we ignore
 	 * existing volumes.