kernel: add pending fitblk uImage.FIT sub-image block driver

Add 'fitblk' driver to replace the rejected/deprecated uImage.FIT
partition parser.
To use the new driver, add phandle /chosen/rootdisk and point it to
the MTD partition, UBI volume or block device holding the uImage.FIT.

Signed-off-by: Daniel Golle <daniel@makrotopia.org>

3 files changed, 758 insertions, 0 deletions

diff --git a/target/linux/generic/config-6.1 b/target/linux/generic/config-6.1
index ce1bfcd5bf..8ad72cc6db 100644
--- a/target/linux/generic/config-6.1
+++ b/target/linux/generic/config-6.1
@@ -7073,6 +7073,7 @@ CONFIG_UEVENT_HELPER_PATH="/sbin/hotplug"
 # CONFIG_UHID is not set
 CONFIG_UID16=y
 # CONFIG_UIO is not set
+# CONFIG_UIMAGE_FIT_BLK is not set
 # CONFIG_ULTRA is not set
 # CONFIG_ULTRIX_PARTITION is not set
 # CONFIG_UNICODE is not set
diff --git a/target/linux/generic/pending-6.1/510-block-add-uImage.FIT-subimage-block-driver.patch b/target/linux/generic/pending-6.1/510-block-add-uImage.FIT-subimage-block-driver.patch
new file mode 100644
index 0000000000..7ee66b318c
--- /dev/null
+++ b/target/linux/generic/pending-6.1/510-block-add-uImage.FIT-subimage-block-driver.patch
@@ -0,0 +1,732 @@
+From 6173a065cb395d4a9528c4e49810af127db68141 Mon Sep 17 00:00:00 2001
+From: Daniel Golle <daniel@makrotopia.org>
+Date: Wed, 16 Nov 2022 12:49:52 +0000
+Subject: [PATCH 1/2] block: add uImage.FIT subimage block driver
+
+Add a small block driver which exposes filesystem sub-images contained
+in U-Boot uImage.FIT images as block devices.
+
+The uImage.FIT image has to be stored directly on a block device or
+partition, MTD device or partition, or UBI volume.
+
+The driver is intended for systems using the U-Boot bootloader and
+uses the root device hint left by the bootloader (or the user) in
+the 'chosen' section of the device-tree.
+
+Example:
+/dts-v1/;
+/ {
+        chosen {
+                rootdisk = <&mmc0_part3>;
+        };
+};
+
+Signed-off-by: Daniel Golle <daniel@makrotopia.org>
+---
+ MAINTAINERS                 |   6 +
+ drivers/block/Kconfig       |  12 +
+ drivers/block/Makefile      |   2 +
+ drivers/block/fitblk.c      | 658 ++++++++++++++++++++++++++++++++++++
+ drivers/block/open          |   4 +
+ include/uapi/linux/fitblk.h |  10 +
+ 6 files changed, 692 insertions(+)
+ create mode 100644 drivers/block/fitblk.c
+ create mode 100644 drivers/block/open
+ create mode 100644 include/uapi/linux/fitblk.h
+
+--- a/MAINTAINERS
++++ b/MAINTAINERS
+@@ -21052,6 +21052,12 @@ F:	Documentation/filesystems/ubifs-authe
+ F:	Documentation/filesystems/ubifs.rst
+ F:	fs/ubifs/
+ 
++U-BOOT UIMAGE.FIT PARSER
++M:	Daniel Golle <daniel@makrotopia.org>
++L:	linux-block@vger.kernel.org
++S:	Maintained
++F:	drivers/block/fitblk.c
++
+ UBLK USERSPACE BLOCK DRIVER
+ M:	Ming Lei <ming.lei@redhat.com>
+ L:	linux-block@vger.kernel.org
+--- a/drivers/block/Kconfig
++++ b/drivers/block/Kconfig
+@@ -383,6 +383,18 @@ config VIRTIO_BLK
+ 	  This is the virtual block driver for virtio.  It can be used with
+           QEMU based VMMs (like KVM or Xen).  Say Y or M.
+ 
++config UIMAGE_FIT_BLK
++	bool "uImage.FIT block driver"
++	help
++	  This driver allows using filesystems contained in uImage.FIT images
++	  by mapping them as block devices.
++
++	  It can currently not be built as a module due to libfdt symbols not
++	  being exported.
++
++	  Say Y if you want to mount filesystems sub-images of a uImage.FIT
++	  stored in a block device partition, mtdblock or ubiblock device.
++
+ config BLK_DEV_RBD
+ 	tristate "Rados block device (RBD)"
+ 	depends on INET && BLOCK
+--- a/drivers/block/Makefile
++++ b/drivers/block/Makefile
+@@ -39,4 +39,6 @@ obj-$(CONFIG_BLK_DEV_NULL_BLK)	+= null_b
+ 
+ obj-$(CONFIG_BLK_DEV_UBLK)			+= ublk_drv.o
+ 
++obj-$(CONFIG_UIMAGE_FIT_BLK)	+= fitblk.o
++
+ swim_mod-y	:= swim.o swim_asm.o
+--- /dev/null
++++ b/drivers/block/fitblk.c
+@@ -0,0 +1,635 @@
++// SPDX-License-Identifier: GPL-2.0-only
++/*
++ * uImage.FIT virtual block device driver.
++ *
++ * Copyright (C) 2023 Daniel Golle
++ * Copyright (C) 2007 Nick Piggin
++ * Copyright (C) 2007 Novell Inc.
++ *
++ * Initially derived from drivers/block/brd.c which is in parts derived from
++ * drivers/block/rd.c, and drivers/block/loop.c, copyright of their respective
++ * owners.
++ *
++ * uImage.FIT headers extracted from Das U-Boot
++ *  (C) Copyright 2008 Semihalf
++ *  (C) Copyright 2000-2005
++ *  Wolfgang Denk, DENX Software Engineering, wd@denx.de.
++ */
++
++#include <linux/init.h>
++#include <linux/initrd.h>
++#include <linux/module.h>
++#include <linux/moduleparam.h>
++#include <linux/major.h>
++#include <linux/blkdev.h>
++#include <linux/blkpg.h>
++#include <linux/blk-mq.h>
++#include <linux/ctype.h>
++#include <linux/hdreg.h>
++#include <linux/list.h>
++#include <linux/mutex.h>
++#include <linux/of.h>
++#include <linux/of_device.h>
++#include <linux/of_fdt.h>
++#include <linux/pagemap.h>
++#include <linux/platform_device.h>
++#include <linux/property.h>
++#include <linux/refcount.h>
++#include <linux/task_work.h>
++#include <linux/types.h>
++#include <linux/libfdt.h>
++#include <linux/mtd/mtd.h>
++#include <linux/root_dev.h>
++#include <uapi/linux/fitblk.h>
++
++#define FIT_DEVICE_PREFIX	"fit"
++
++/* maximum number of pages used for the uImage.FIT index structure */
++#define FIT_MAX_PAGES		1024
++
++/* minimum free sectors to map as read-write "remainder" volume */
++#define MIN_FREE_SECT		16
++
++/* maximum number of mapped loadables */
++#define MAX_FIT_LOADABLES	16
++
++/* constants for uImage.FIT structrure traversal */
++#define FIT_IMAGES_PATH		"/images"
++#define FIT_CONFS_PATH		"/configurations"
++
++/* hash/signature/key node */
++#define FIT_HASH_NODENAME	"hash"
++#define FIT_ALGO_PROP		"algo"
++#define FIT_VALUE_PROP		"value"
++#define FIT_IGNORE_PROP		"uboot-ignore"
++#define FIT_SIG_NODENAME	"signature"
++#define FIT_KEY_REQUIRED	"required"
++#define FIT_KEY_HINT		"key-name-hint"
++
++/* cipher node */
++#define FIT_CIPHER_NODENAME	"cipher"
++#define FIT_ALGO_PROP		"algo"
++
++/* image node */
++#define FIT_DATA_PROP		"data"
++#define FIT_DATA_POSITION_PROP	"data-position"
++#define FIT_DATA_OFFSET_PROP	"data-offset"
++#define FIT_DATA_SIZE_PROP	"data-size"
++#define FIT_TIMESTAMP_PROP	"timestamp"
++#define FIT_DESC_PROP		"description"
++#define FIT_ARCH_PROP		"arch"
++#define FIT_TYPE_PROP		"type"
++#define FIT_OS_PROP		"os"
++#define FIT_COMP_PROP		"compression"
++#define FIT_ENTRY_PROP		"entry"
++#define FIT_LOAD_PROP		"load"
++
++/* configuration node */
++#define FIT_KERNEL_PROP		"kernel"
++#define FIT_FILESYSTEM_PROP	"filesystem"
++#define FIT_RAMDISK_PROP	"ramdisk"
++#define FIT_FDT_PROP		"fdt"
++#define FIT_LOADABLE_PROP	"loadables"
++#define FIT_DEFAULT_PROP	"default"
++#define FIT_SETUP_PROP		"setup"
++#define FIT_FPGA_PROP		"fpga"
++#define FIT_FIRMWARE_PROP	"firmware"
++#define FIT_STANDALONE_PROP	"standalone"
++
++/* fitblk driver data */
++static const char *_fitblk_claim_ptr = "I belong to fitblk";
++static const char *ubootver;
++struct device_node *rootdisk;
++static struct platform_device *pdev;
++static LIST_HEAD(fitblk_devices);
++static DEFINE_MUTEX(devices_mutex);
++refcount_t num_devs;
++
++struct fitblk {
++	struct platform_device	*pdev;
++	struct block_device	*lower_bdev;
++	sector_t		start_sect;
++	struct gendisk		*disk;
++	struct work_struct	remove_work;
++	struct list_head	list;
++	bool			dead;
++};
++
++static int fitblk_open(struct block_device *bdev, fmode_t mode)
++{
++	struct fitblk *fitblk = bdev->bd_disk->private_data;
++
++	if (fitblk->dead)
++		return -ENOENT;
++
++	return 0;
++}
++
++static void fitblk_release(struct gendisk *disk, fmode_t mode)
++{
++	return;
++}
++
++static void fitblk_submit_bio(struct bio *orig_bio)
++{
++	struct bio *bio = orig_bio;
++	struct fitblk *fitblk = bio->bi_bdev->bd_disk->private_data;
++
++	if (fitblk->dead)
++		return;
++
++	/* mangle bio and re-submit */
++	while (bio) {
++		bio->bi_iter.bi_sector += fitblk->start_sect;
++		bio->bi_bdev = fitblk->lower_bdev;
++		bio = bio->bi_next;
++	}
++	submit_bio(orig_bio);
++}
++
++static void fitblk_remove(struct fitblk *fitblk)
++{
++	blk_mark_disk_dead(fitblk->disk);
++	mutex_lock(&devices_mutex);
++	fitblk->dead = true;
++	list_del(&fitblk->list);
++	mutex_unlock(&devices_mutex);
++
++	schedule_work(&fitblk->remove_work);
++}
++
++static int fitblk_ioctl(struct block_device *bdev, fmode_t mode,
++			unsigned int cmd, unsigned long arg)
++{
++	struct fitblk *fitblk = bdev->bd_disk->private_data;
++
++	if (!capable(CAP_SYS_ADMIN))
++		return -EACCES;
++
++	if (fitblk->dead)
++		return -ENOENT;
++
++	switch (cmd) {
++	case FITBLK_RELEASE:
++		fitblk_remove(fitblk);
++		break;
++	default:
++		return -EINVAL;
++	}
++
++	return 0;
++}
++
++static const struct block_device_operations fitblk_fops = {
++	.owner		= THIS_MODULE,
++	.ioctl		= fitblk_ioctl,
++	.open		= fitblk_open,
++	.release	= fitblk_release,
++	.submit_bio	= fitblk_submit_bio,
++};
++
++static void fitblk_purge(struct work_struct *work)
++{
++	struct fitblk *fitblk = container_of(work, struct fitblk, remove_work);
++
++	//del_gendisk(fitblk->disk); // causes crash, not doing it doesn't matter
++	refcount_dec(&num_devs);
++	platform_device_del(fitblk->pdev);
++	platform_device_put(fitblk->pdev);
++
++	if (refcount_dec_if_one(&num_devs)) {
++		sysfs_remove_link(&pdev->dev.kobj, "lower_dev");
++		blkdev_put(fitblk->lower_bdev, FMODE_READ | FMODE_EXCL);
++	}
++
++	kfree(fitblk);
++}
++
++static int add_fit_subimage_device(struct block_device *lower_bdev,
++				   unsigned int slot, sector_t start_sect,
++				   sector_t nr_sect, bool readonly)
++{
++	struct fitblk *fitblk;
++	struct gendisk *disk;
++	int err;
++
++	mutex_lock(&devices_mutex);
++	if (!refcount_inc_not_zero(&num_devs))
++		return -EBADF;
++
++	fitblk = kzalloc(sizeof(struct fitblk), GFP_KERNEL);
++	if (!fitblk) {
++		err = -ENOMEM;
++		goto out_unlock;
++	}
++
++	fitblk->lower_bdev = lower_bdev;
++	fitblk->start_sect = start_sect;
++	INIT_WORK(&fitblk->remove_work, fitblk_purge);
++
++	disk = blk_alloc_disk(NUMA_NO_NODE);
++	if (!disk) {
++		err = -ENOMEM;
++		goto out_free_fitblk;
++	}
++
++	disk->first_minor = 0;
++	disk->flags = lower_bdev->bd_disk->flags | GENHD_FL_NO_PART;
++	disk->fops = &fitblk_fops;
++	disk->private_data = fitblk;
++	if (readonly) {
++		set_disk_ro(disk, 1);
++		snprintf(disk->disk_name, sizeof(disk->disk_name), FIT_DEVICE_PREFIX "%u", slot);
++	} else {
++		strcpy(disk->disk_name, FIT_DEVICE_PREFIX "rw");
++	}
++
++	set_capacity(disk, nr_sect);
++
++	disk->queue->queue_flags = lower_bdev->bd_disk->queue->queue_flags;
++	memcpy(&disk->queue->limits, &lower_bdev->bd_disk->queue->limits,
++	       sizeof(struct queue_limits));
++
++	fitblk->disk = disk;
++	fitblk->pdev = platform_device_alloc(disk->disk_name, PLATFORM_DEVID_NONE);
++	if (!fitblk->pdev) {
++		err = -ENOMEM;
++		goto out_cleanup_disk;
++	}
++
++	fitblk->pdev->dev.parent = &pdev->dev;
++	err = platform_device_add(fitblk->pdev);
++	if (err)
++		goto out_put_pdev;
++
++	err = device_add_disk(&fitblk->pdev->dev, disk, NULL);
++	if (err)
++		goto out_del_pdev;
++
++	if (!ROOT_DEV)
++		ROOT_DEV = disk->part0->bd_dev;
++
++	list_add_tail(&fitblk->list, &fitblk_devices);
++
++	mutex_unlock(&devices_mutex);
++
++	return 0;
++
++out_del_pdev:
++	platform_device_del(fitblk->pdev);
++out_put_pdev:
++	platform_device_put(fitblk->pdev);
++out_cleanup_disk:
++	put_disk(disk);
++out_free_fitblk:
++	kfree(fitblk);
++out_unlock:
++	refcount_dec(&num_devs);
++	mutex_unlock(&devices_mutex);
++	return err;
++}
++
++static int parse_fit_on_dev(struct device *dev)
++{
++	struct block_device *bdev;
++	struct address_space *mapping;
++	struct folio *folio;
++	pgoff_t f_index = 0;
++	size_t bytes_left, bytes_to_copy;
++	void *pre_fit, *fit, *fit_c;
++	u64 dsize, dsectors, imgmaxsect = 0;
++	u32 size, image_pos, image_len;
++	const __be32 *image_offset_be, *image_len_be, *image_pos_be;
++	int ret = 0, node, images, config;
++	const char *image_name, *image_type, *image_description,
++		*config_default, *config_description, *config_loadables;
++	u32 image_name_len, image_type_len, image_description_len,
++		bootconf_len, config_default_len, config_description_len,
++		config_loadables_len;
++	sector_t start_sect, nr_sects;
++	struct device_node *np = NULL;
++	const char *bootconf_c;
++	const char *loadable;
++	char *bootconf = NULL, *bootconf_term;
++	bool found;
++	int loadables_rem_len, loadable_len;
++	u16 loadcnt;
++	unsigned int slot = 0;
++
++	/* Exclusive open the block device to receive holder notifications */
++	bdev = blkdev_get_by_dev(dev->devt, FMODE_READ | FMODE_EXCL, &_fitblk_claim_ptr);
++	if (!bdev)
++		return -ENODEV;
++
++	if (IS_ERR(bdev))
++		return PTR_ERR(bdev);
++
++	mapping = bdev->bd_inode->i_mapping;
++
++	/* map first page */
++	folio = read_mapping_folio(mapping, f_index++, NULL);
++	if (IS_ERR(folio)) {
++		ret = PTR_ERR(folio);
++		goto out_blkdev;
++	}
++	pre_fit = folio_address(folio) + offset_in_folio(folio, 0);
++
++	/* uImage.FIT is based on flattened device tree structure */
++	if (fdt_check_header(pre_fit)) {
++		ret = -EINVAL;
++		folio_put(folio);
++		goto out_blkdev;
++	}
++
++	size = fdt_totalsize(pre_fit);
++
++	if (size > PAGE_SIZE * FIT_MAX_PAGES) {
++		ret = -EOPNOTSUPP;
++		folio_put(folio);
++		goto out_blkdev;
++	}
++
++	/* acquire disk size */
++	dsectors = bdev_nr_sectors(bdev);
++	dsize = dsectors << SECTOR_SHIFT;
++
++	/* abort if FIT structure is larger than disk or partition size */
++	if (size >= dsize) {
++		ret = -EFBIG;
++		folio_put(folio);
++		goto out_blkdev;
++	}
++
++	fit = kmalloc(size, GFP_KERNEL);
++	if (!fit) {
++		ret = -ENOMEM;
++		folio_put(folio);
++		goto out_blkdev;
++	}
++
++	bytes_left = size;
++	fit_c = fit;
++	while (bytes_left > 0) {
++		bytes_to_copy = min(bytes_left, folio_size(folio) - offset_in_folio(folio, 0));
++		memcpy(fit_c, pre_fit, bytes_to_copy);
++		fit_c += bytes_to_copy;
++		bytes_left -= bytes_to_copy;
++		if (bytes_left) {
++			folio_put(folio);
++			folio = read_mapping_folio(mapping, f_index++, NULL);
++			if (IS_ERR(folio)) {
++				ret = PTR_ERR(folio);
++				goto out_blkdev;
++			};
++			pre_fit = folio_address(folio) + offset_in_folio(folio, 0);
++		}
++	}
++	folio_put(folio);
++
++	/* set boot config node name U-Boot may have added to the device tree */
++	np = of_find_node_by_path("/chosen");
++	if (np) {
++		bootconf_c = of_get_property(np, "u-boot,bootconf", &bootconf_len);
++		if (bootconf_c && bootconf_len)
++			bootconf = kmemdup_nul(bootconf_c, bootconf_len, GFP_KERNEL);
++	}
++
++	if (bootconf) {
++		bootconf_term = strchr(bootconf, '#');
++		if (bootconf_term)
++			*bootconf_term = '\0';
++	}
++
++	/* find configuration path in uImage.FIT */
++	config = fdt_path_offset(fit, FIT_CONFS_PATH);
++	if (config < 0) {
++		pr_err("FIT: Cannot find %s node: %d\n",
++			FIT_CONFS_PATH, config);
++		ret = -ENOENT;
++		goto out_bootconf;
++	}
++
++	/* get default configuration node name */
++	config_default =
++		fdt_getprop(fit, config, FIT_DEFAULT_PROP, &config_default_len);
++
++	/* make sure we got either default or selected boot config node name */
++	if (!config_default && !bootconf) {
++		pr_err("FIT: Cannot find default configuration\n");
++		ret = -ENOENT;
++		goto out_bootconf;
++	}
++
++	/* find selected boot config node, fallback on default config node */
++	node = fdt_subnode_offset(fit, config, bootconf ?: config_default);
++	if (node < 0) {
++		pr_err("FIT: Cannot find %s node: %d\n",
++			bootconf ?: config_default, node);
++		ret = -ENOENT;
++		goto out_bootconf;
++	}
++
++	pr_info("FIT: Detected U-Boot %s\n", ubootver);
++
++	/* get selected configuration data */
++	config_description =
++		fdt_getprop(fit, node, FIT_DESC_PROP, &config_description_len);
++	config_loadables = fdt_getprop(fit, node, FIT_LOADABLE_PROP,
++				       &config_loadables_len);
++
++	pr_info("FIT: %s configuration: \"%.*s\"%s%.*s%s\n",
++		bootconf ? "Selected" : "Default",
++		bootconf ? bootconf_len : config_default_len,
++		bootconf ?: config_default,
++		config_description ? " (" : "",
++		config_description ? config_description_len : 0,
++		config_description ?: "",
++		config_description ? ")" : "");
++
++	if (!config_loadables || !config_loadables_len) {
++		pr_err("FIT: No loadables configured in \"%s\"\n",
++			bootconf ?: config_default);
++		ret = -ENOENT;
++		goto out_bootconf;
++	}
++
++	/* get images path in uImage.FIT */
++	images = fdt_path_offset(fit, FIT_IMAGES_PATH);
++	if (images < 0) {
++		pr_err("FIT: Cannot find %s node: %d\n", FIT_IMAGES_PATH, images);
++		ret = -EINVAL;
++		goto out_bootconf;
++	}
++
++	/* iterate over images in uImage.FIT */
++	fdt_for_each_subnode(node, fit, images) {
++		image_name = fdt_get_name(fit, node, &image_name_len);
++		image_type = fdt_getprop(fit, node, FIT_TYPE_PROP, &image_type_len);
++		image_offset_be = fdt_getprop(fit, node, FIT_DATA_OFFSET_PROP, NULL);
++		image_pos_be = fdt_getprop(fit, node, FIT_DATA_POSITION_PROP, NULL);
++		image_len_be = fdt_getprop(fit, node, FIT_DATA_SIZE_PROP, NULL);
++
++		if (!image_name || !image_type || !image_len_be ||
++		    !image_name_len || !image_type_len)
++			continue;
++
++		image_len = be32_to_cpu(*image_len_be);
++		if (!image_len)
++			continue;
++
++		if (image_offset_be)
++			image_pos = be32_to_cpu(*image_offset_be) + size;
++		else if (image_pos_be)
++			image_pos = be32_to_cpu(*image_pos_be);
++		else
++			continue;
++
++		image_description = fdt_getprop(fit, node, FIT_DESC_PROP,
++						&image_description_len);
++
++		pr_info("FIT: %16s sub-image 0x%08x..0x%08x \"%.*s\"%s%.*s%s\n",
++			image_type, image_pos, image_pos + image_len - 1,
++			image_name_len, image_name, image_description ? " (" : "",
++			image_description ? image_description_len : 0,
++			image_description ?: "", image_description ? ") " : "");
++
++		/* only 'filesystem' images should be mapped as partitions */
++		if (strncmp(image_type, FIT_FILESYSTEM_PROP, image_type_len))
++			continue;
++
++		/* check if sub-image is part of configured loadables */
++		found = false;
++		loadable = config_loadables;
++		loadables_rem_len = config_loadables_len;
++		for (loadcnt = 0; loadables_rem_len > 1 &&
++				  loadcnt < MAX_FIT_LOADABLES; ++loadcnt) {
++			loadable_len =
++				strnlen(loadable, loadables_rem_len - 1) + 1;
++			loadables_rem_len -= loadable_len;
++			if (!strncmp(image_name, loadable, loadable_len)) {
++				found = true;
++				break;
++			}
++			loadable += loadable_len;
++		}
++		if (!found)
++			continue;
++
++		if (image_pos % (1 << PAGE_SHIFT)) {
++			dev_err(dev, "FIT: image %.*s start not aligned to page boundaries, skipping\n",
++				image_name_len, image_name);
++			continue;
++		}
++
++		if (image_len % (1 << PAGE_SHIFT)) {
++			dev_err(dev, "FIT: sub-image %.*s end not aligned to page boundaries, skipping\n",
++				image_name_len, image_name);
++			continue;
++		}
++
++		start_sect = image_pos >> SECTOR_SHIFT;
++		nr_sects = image_len >> SECTOR_SHIFT;
++		imgmaxsect = max_t(sector_t, imgmaxsect, start_sect + nr_sects);
++
++		if (start_sect + nr_sects > dsectors) {
++			dev_err(dev, "FIT: sub-image %.*s disk access beyond EOD\n",
++				image_name_len, image_name);
++			continue;
++		}
++
++		if (!slot) {
++			ret = sysfs_create_link_nowarn(&pdev->dev.kobj, bdev_kobj(bdev), "lower_dev");
++			if (ret && ret != -EEXIST)
++				goto out_bootconf;
++
++			ret = 0;
++		}
++
++		add_fit_subimage_device(bdev, slot++, start_sect, nr_sects, true);
++	}
++
++	if (!found || !slot)
++		goto out_bootconf;
++
++	dev_info(dev, "mapped %u uImage.FIT filesystem sub-image%s as /dev/fit%s%u%s\n",
++		 slot, (slot > 1)?"s":"", (slot > 1)?"[0...":"", slot - 1,
++		 (slot > 1)?"]":"");
++
++	/* in case uImage.FIT is stored in a partition, map the remaining space */
++	if (!bdev->bd_read_only && bdev_is_partition(bdev) &&
++	    (imgmaxsect + MIN_FREE_SECT) < dsectors) {
++		add_fit_subimage_device(bdev, slot++, imgmaxsect,
++					dsectors - imgmaxsect, false);
++		dev_info(dev, "mapped remaing space as /dev/fitrw\n");
++	}
++
++out_bootconf:
++	kfree(bootconf);
++	kfree(fit);
++out_blkdev:
++	if (!found || ret)
++		blkdev_put(bdev, FMODE_READ | FMODE_EXCL);
++
++	return ret;
++}
++
++static int fitblk_match_of_node(struct device *dev, const void *np)
++{
++	int ret;
++
++	ret = device_match_of_node(dev, np);
++	if (ret)
++		return ret;
++
++	/*
++	 * To match ubiblock and mtdblock devices by their parent ubi
++	 * or mtd device, also consider block device parent
++	 */
++	if (!dev->parent)
++		return 0;
++
++	return device_match_of_node(dev->parent, np);
++}
++
++static int fitblk_probe(struct platform_device *pdev)
++{
++	struct device *dev;
++
++	dev = class_find_device(&block_class, NULL, rootdisk, fitblk_match_of_node);
++	if (!dev)
++		return -EPROBE_DEFER;
++
++	return parse_fit_on_dev(dev);
++}
++
++static struct platform_driver fitblk_driver = {
++	.probe		= fitblk_probe,
++	.driver		= {
++		.name   = "fitblk",
++		.owner   = THIS_MODULE,
++	},
++};
++
++static int __init fitblk_init(void)
++{
++	/* detect U-Boot firmware */
++	ubootver = of_get_property(of_chosen, "u-boot,version", NULL);
++	if (!ubootver)
++		return 0;
++
++	/* parse 'rootdisk' property phandle */
++	rootdisk = of_parse_phandle(of_chosen, "rootdisk", 0);
++	if (!rootdisk)
++		return 0;
++
++	if (platform_driver_register(&fitblk_driver))
++		return -ENODEV;
++
++	refcount_set(&num_devs, 1);
++	pdev = platform_device_register_simple("fitblk", -1, NULL, 0);
++	if (IS_ERR(pdev))
++		return PTR_ERR(pdev);
++
++	return 0;
++}
++device_initcall(fitblk_init);
+--- /dev/null
++++ b/include/uapi/linux/fitblk.h
+@@ -0,0 +1,10 @@
++/* SPDX-License-Identifier: GPL-2.0+ WITH Linux-syscall-note */
++#ifndef _UAPI_LINUX_FITBLK_H
++#define _UAPI_LINUX_FITBLK_H
++
++/*
++ * IOCTL commands --- we will commandeer 0x46 ('F')
++ */
++#define FITBLK_RELEASE             0x4600
++
++#endif /* _UAPI_LINUX_FITBLK_H */
diff --git a/target/linux/generic/pending-6.1/511-init-bypass-device-lookup-for-dev-fit-rootfs.patch b/target/linux/generic/pending-6.1/511-init-bypass-device-lookup-for-dev-fit-rootfs.patch
new file mode 100644
index 0000000000..685a5f9da5
--- /dev/null
+++ b/target/linux/generic/pending-6.1/511-init-bypass-device-lookup-for-dev-fit-rootfs.patch
@@ -0,0 +1,25 @@
+From 5ede3f8aed9a1a579bf7304142600d1f3500add9 Mon Sep 17 00:00:00 2001
+From: Daniel Golle <daniel@makrotopia.org>
+Date: Mon, 12 Jun 2023 03:58:42 +0100
+Subject: [PATCH 2/2] init: bypass device lookup for /dev/fit* rootfs
+
+Allow 'rootwait' as /dev/fit* can show up late if the underlaying
+device is probed late.
+
+Signed-off-by: Daniel Golle <daniel@makrotopia.org>
+---
+ init/do_mounts.c | 3 ++-
+ 1 file changed, 2 insertions(+), 1 deletion(-)
+
+--- a/init/do_mounts.c
++++ b/init/do_mounts.c
+@@ -645,7 +645,8 @@ void __init prepare_namespace(void)
+ 
+ 	if (saved_root_name[0]) {
+ 		root_device_name = saved_root_name;
+-		if (!strncmp(root_device_name, "mtd", 3) ||
++		if (!strncmp(root_device_name, "fit", 3) ||
++		    !strncmp(root_device_name, "mtd", 3) ||
+ 		    !strncmp(root_device_name, "ubi", 3)) {
+ 			mount_block_root(root_device_name, root_mountflags);
+ 			goto out;