Subject: ubi: auto-attach mtd device named "ubi" or "data" on boot
From: Daniel Golle <[email-masked]>

Signed-off-by: Daniel Golle <[email-masked]>
---
 drivers/mtd/ubi/build.c | 36 ++++++++++++++++++++++++++++++++++++
 1 file changed, 36 insertions(+)

--- a/drivers/mtd/ubi/build.c
+++ b/drivers/mtd/ubi/build.c
@@ -1192,6 +1192,73 @@ static struct mtd_info * __init open_mtd
 	return mtd;
 }
 
+/*
+ * This function tries attaching mtd partitions named either "ubi" or "data"
+ * during boot.
+ */
+static void __init ubi_auto_attach(void)
+{
+	int err;
+	struct mtd_info *mtd;
+	loff_t offset = 0;
+	size_t len;
+	char magic[4];
+
+	/* try attaching mtd device named "ubi" or "data" */
+	mtd = open_mtd_device("ubi");
+	if (IS_ERR(mtd))
+		mtd = open_mtd_device("data");
+
+	if (IS_ERR(mtd))
+		return;
+
+	/* get the first not bad block */
+	if (mtd_can_have_bb(mtd))
+		while (mtd_block_isbad(mtd, offset)) {
+			offset += mtd->erasesize;
+
+			if (offset > mtd->size) {
+				pr_err("UBI error: Failed to find a non-bad "
+				       "block on mtd%d\n", mtd->index);
+				goto cleanup;
+			}
+		}
+
+	/* check if the read from flash was successful */
+	err = mtd_read(mtd, offset, 4, &len, (void *) magic);
+	if ((err && !mtd_is_bitflip(err)) || len != 4) {
+		pr_err("UBI error: unable to read from mtd%d\n", mtd->index);
+		goto cleanup;
+	}
+
+	/* check for a valid ubi magic */
+	if (strncmp(magic, "UBI#", 4)) {
+		pr_err("UBI error: no valid UBI magic found inside mtd%d\n", mtd->index);
+		goto cleanup;
+	}
+
+	/* don't auto-add media types where UBI doesn't makes sense */
+	if (mtd->type != MTD_NANDFLASH &&
+	    mtd->type != MTD_NORFLASH &&
+	    mtd->type != MTD_DATAFLASH &&
+	    mtd->type != MTD_MLCNANDFLASH)
+		goto cleanup;
+
+	mutex_lock(&ubi_devices_mutex);
+	pr_notice("UBI: auto-attach mtd%d\n", mtd->index);
+	err = ubi_attach_mtd_dev(mtd, UBI_DEV_NUM_AUTO, 0, 0);
+	mutex_unlock(&ubi_devices_mutex);
+	if (err < 0) {
+		pr_err("UBI error: cannot attach mtd%d\n", mtd->index);
+		goto cleanup;
+	}
+
+	return;
+
+cleanup:
+	put_mtd_device(mtd);
+}
+
 static int __init ubi_init(void)
 {
 	int err, i, k;
@@ -1275,6 +1342,12 @@ static int __init ubi_init(void)
 		}
 	}
 
+	/* auto-attach mtd devices only if built-in to the kernel and no ubi.mtd
+	 * parameter was given */
+	if (IS_ENABLED(CONFIG_MTD_ROOTFS_ROOT_DEV) &&
+	    !ubi_is_module() && !mtd_devs)
+		ubi_auto_attach();
+
 	err = ubiblock_init();
 	if (err) {
 		pr_err("UBI error: block: cannot initialize, error %d\n", err);