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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
@@ -21059,6 +21059,12 @@ 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 +1,636 @@
+// 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_t(size_t, 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 */
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