--- zzzz-none-000/linux-4.9.276/drivers/mtd/ubi/block.c	2021-07-20 14:21:16.000000000 +0000
+++ falcon-5530-750/linux-4.9.276/drivers/mtd/ubi/block.c	2023-04-05 08:19:01.000000000 +0000
@@ -50,6 +50,7 @@
 #include <linux/scatterlist.h>
 #include <linux/idr.h>
 #include <asm/div64.h>
+#include <linux/root_dev.h>
 
 #include "ubi-media.h"
 #include "ubi.h"
@@ -104,6 +105,8 @@
 static DEFINE_MUTEX(devices_mutex);
 static int ubiblock_major;
 
+static bool rootfsname_set = false;
+
 static int __init ubiblock_set_param(const char *val,
 				     const struct kernel_param *kp)
 {
@@ -164,6 +167,42 @@
 	return 0;
 }
 
+static int __init ubiblock_set_rootfsname_param(const char *val,
+						const struct kernel_param *kp)
+{
+	size_t len;
+	struct ubiblock_param *param;
+
+	if (ubiblock_devs)
+		return (0); /* if ubi block options already set by ubi.block,
+			    * we can skip this param. */
+
+	if (!val)
+		return -EINVAL;
+
+	len = strnlen(val, UBIBLOCK_PARAM_LEN);
+	if (len == 0) {
+		pr_warn("UBI: block: empty 'rootfsname=' parameter - ignored\n");
+		return 0;
+	}
+
+	if (len == UBIBLOCK_PARAM_LEN) {
+		pr_err("UBI: block: parameter \"%s\" is too long, max. is %d\n",
+		       val, UBIBLOCK_PARAM_LEN);
+		return -EINVAL;
+	}
+
+	param = &ubiblock_param[ubiblock_devs];
+	param->ubi_num = 0;
+	param->vol_id = -1;
+	strcpy(param->name, val);
+	ubiblock_devs = 1;
+
+	rootfsname_set = true;
+
+	return (0);
+}
+
 static const struct kernel_param_ops ubiblock_param_ops = {
 	.set    = ubiblock_set_param,
 };
@@ -179,6 +218,12 @@
 			"Using both UBI device number and UBI volume number:\n"
 			"ubi.block=0,0\n");
 
+/* Fallback approach if command line uses 'rootfsname=<rootfs volume name>' */
+static const struct kernel_param_ops ubiblock_rootfsname_param_ops = {
+	.set = ubiblock_set_rootfsname_param,
+};
+__module_param_call("", rootfsname, &ubiblock_rootfsname_param_ops, NULL, 0, -1, 0);
+
 static struct ubiblock *find_dev_nolock(int ubi_num, int vol_id)
 {
 	struct ubiblock *dev;
@@ -447,6 +492,21 @@
 	dev_info(disk_to_dev(dev->gd), "created from ubi%d:%d(%s)",
 		 dev->ubi_num, dev->vol_id, vi->name);
 	mutex_unlock(&devices_mutex);
+
+	if (!strcmp(vi->name, "rootfs") &&
+	    IS_ENABLED(CONFIG_MTD_ROOTFS_ROOT_DEV) &&
+	    ROOT_DEV == 0) {
+		pr_notice("ubiblock: device ubiblock%d_%d (%s) set to be root filesystem\n",
+			  dev->ubi_num, dev->vol_id, vi->name);
+		ROOT_DEV = MKDEV(gd->major, gd->first_minor);
+	}
+
+	if (ROOT_DEV == 0 && rootfsname_set) {
+		ROOT_DEV = MKDEV(gd->major, gd->first_minor);
+		pr_notice("ubiblock: device ubiblock%d_%d (%s) set to be root filesystem\n",
+			  dev->ubi_num, dev->vol_id, vi->name);
+	}
+
 	return 0;
 
 out_free_queue:
@@ -635,6 +695,44 @@
 	}
 }
 
+#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))
+			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;
@@ -667,6 +765,10 @@
 	 */
 	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.