[PATCH v4 14/33] bootstd: Add the bootdev uclass

[Simon Glass <sjg@chromium.org>]

A 'bootdev' is a device which can be used to boot an operating system.
It is a child of the media device (e.g. MMC) which handles reading files
from that device, such as a bootflow file.

Add a uclass for bootdev and the various helpers needed to make it
work. Also add a binding file, empty for now.

Signed-off-by: Simon Glass <sjg@chromium.org>
---

Changes in v4:
- Use new Return style in function comments

Changes in v3:
- Add bootdev_get_from_blk() function
- Move bootdev ordering into the uclass
- Update for the new trailing_strtoln_end()
- Use blk_find_device() to find the block device for a media device

 MAINTAINERS                          |   4 +-
 boot/Makefile                        |   1 +
 boot/bootdev-uclass.c                | 640 +++++++++++++++++++++++++++
 doc/device-tree-bindings/bootdev.txt |   8 +
 include/bootdev.h                    | 275 ++++++++++++
 include/dm/uclass-id.h               |   1 +
 6 files changed, 928 insertions(+), 1 deletion(-)
 create mode 100644 boot/bootdev-uclass.c
 create mode 100644 doc/device-tree-bindings/bootdev.txt
 create mode 100644 include/bootdev.h

diff --git a/MAINTAINERS b/MAINTAINERS
index 9df9812978..a77ad1adb7 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -685,9 +685,11 @@ F:	tools/binman/
 BOOTDEVICE
 M:	Simon Glass <sjg@chromium.org>
 S:	Maintained
+F:	boot/bootdev*.c
 F:	boot/bootstd.c
-F:	include/bootstd.h
+F:	include/bootdev*.h
 F:	include/bootflow.h
+F:	include/bootstd.h
 
 BTRFS
 M:	Marek Behun <marek.behun@nic.cz>
diff --git a/boot/Makefile b/boot/Makefile
index 48031d1c2b..35abfd3765 100644
--- a/boot/Makefile
+++ b/boot/Makefile
@@ -23,6 +23,7 @@ obj-y += image.o image-board.o
 obj-$(CONFIG_ANDROID_AB) += android_ab.o
 obj-$(CONFIG_ANDROID_BOOT_IMAGE) += image-android.o image-android-dt.o
 
+obj-$(CONFIG_$(SPL_TPL_)BOOTSTD) += bootdev-uclass.o
 obj-$(CONFIG_$(SPL_TPL_)BOOTSTD) += bootstd-uclass.o
 
 obj-$(CONFIG_$(SPL_TPL_)OF_LIBFDT) += image-fdt.o
diff --git a/boot/bootdev-uclass.c b/boot/bootdev-uclass.c
new file mode 100644
index 0000000000..e0baeb82b1
--- /dev/null
+++ b/boot/bootdev-uclass.c
@@ -0,0 +1,640 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Copyright 2021 Google LLC
+ * Written by Simon Glass <sjg@chromium.org>
+ */
+
+#define LOG_CATEGORY UCLASS_BOOTSTD
+
+#include <common.h>
+#include <dm.h>
+#include <bootdev.h>
+#include <bootflow.h>
+#include <bootstd.h>
+#include <env.h>
+#include <fs.h>
+#include <log.h>
+#include <malloc.h>
+#include <part.h>
+#include <sort.h>
+#include <dm/device-internal.h>
+#include <dm/lists.h>
+#include <dm/uclass-internal.h>
+
+enum {
+	/*
+	 * Set some sort of limit on the number of partitions a bootdev can
+	 * have. Note that for disks this limits the partitions numbers that
+	 * are scanned to 1..MAX_BOOTFLOWS_PER_BOOTDEV
+	 */
+	MAX_PART_PER_BOOTDEV	= 30,
+
+	/* Maximum supported length of the "boot_targets" env string */
+	BOOT_TARGETS_MAX_LEN	= 100,
+};
+
+int bootdev_add_bootflow(struct bootflow *bflow)
+{
+	struct bootdev_uc_plat *ucp = dev_get_uclass_plat(bflow->dev);
+	struct bootstd_priv *std;
+	struct bootflow *new;
+	int ret;
+
+	assert(bflow->dev);
+	ret = bootstd_get_priv(&std);
+	if (ret)
+		return ret;
+
+	new = malloc(sizeof(*bflow));
+	if (!new)
+		return log_msg_ret("bflow", -ENOMEM);
+	memcpy(new, bflow, sizeof(*bflow));
+
+	list_add_tail(&new->glob_node, &std->glob_head);
+	list_add_tail(&new->bm_node, &ucp->bootflow_head);
+
+	return 0;
+}
+
+int bootdev_first_bootflow(struct udevice *dev, struct bootflow **bflowp)
+{
+	struct bootdev_uc_plat *ucp = dev_get_uclass_plat(dev);
+
+	if (list_empty(&ucp->bootflow_head))
+		return -ENOENT;
+
+	*bflowp = list_first_entry(&ucp->bootflow_head, struct bootflow,
+				   bm_node);
+
+	return 0;
+}
+
+int bootdev_next_bootflow(struct bootflow **bflowp)
+{
+	struct bootflow *bflow = *bflowp;
+	struct bootdev_uc_plat *ucp = dev_get_uclass_plat(bflow->dev);
+
+	*bflowp = NULL;
+
+	if (list_is_last(&bflow->bm_node, &ucp->bootflow_head))
+		return -ENOENT;
+
+	*bflowp = list_entry(bflow->bm_node.next, struct bootflow, bm_node);
+
+	return 0;
+}
+
+int bootdev_bind(struct udevice *parent, const char *drv_name, const char *name,
+		 struct udevice **devp)
+{
+	struct udevice *dev;
+	char dev_name[30];
+	char *str;
+	int ret;
+
+	snprintf(dev_name, sizeof(dev_name), "%s.%s", parent->name, name);
+	str = strdup(dev_name);
+	if (!str)
+		return -ENOMEM;
+	ret = device_bind_driver(parent, drv_name, str, &dev);
+	if (ret)
+		return ret;
+	device_set_name_alloced(dev);
+	*devp = dev;
+
+	return 0;
+}
+
+int bootdev_find_in_blk(struct udevice *dev, struct udevice *blk,
+			struct bootflow_iter *iter, struct bootflow *bflow)
+{
+	struct blk_desc *desc = dev_get_uclass_plat(blk);
+	struct disk_partition info;
+	char partstr[20];
+	char name[60];
+	int ret;
+
+	/* Sanity check */
+	if (iter->part >= MAX_PART_PER_BOOTDEV)
+		return log_msg_ret("max", -ESHUTDOWN);
+
+	bflow->blk = blk;
+	if (iter->part)
+		snprintf(partstr, sizeof(partstr), "part_%x", iter->part);
+	else
+		strcpy(partstr, "whole");
+	snprintf(name, sizeof(name), "%s.%s", dev->name, partstr);
+	bflow->name = strdup(name);
+	if (!bflow->name)
+		return log_msg_ret("name", -ENOMEM);
+
+	bflow->part = iter->part;
+
+	/*
+	 * partition numbers start at 0 so this cannot succeed, but it can tell
+	 * us whether there is valid media there
+	 */
+	ret = part_get_info(desc, iter->part, &info);
+	if (!iter->part && ret == -ENOENT)
+		ret = 0;
+
+	/*
+	 * This error indicates the media is not present. Otherwise we just
+	 * blindly scan the next partition. We could be more intelligent here
+	 * and check which partition numbers actually exist.
+	 */
+	if (ret == -EOPNOTSUPP)
+		ret = -ESHUTDOWN;
+	else
+		bflow->state = BOOTFLOWST_MEDIA;
+	if (ret)
+		return log_msg_ret("part", ret);
+
+	/*
+	 * Currently we don't get the number of partitions, so just
+	 * assume a large number
+	 */
+	iter->max_part = MAX_PART_PER_BOOTDEV;
+
+	if (iter->part) {
+		ret = fs_set_blk_dev_with_part(desc, bflow->part);
+		bflow->state = BOOTFLOWST_PART;
+
+		/* Use an #ifdef due to info.sys_ind */
+#ifdef CONFIG_DOS_PARTITION
+		log_debug("%s: Found partition %x type %x fstype %d\n",
+			  blk->name, bflow->part, info.sys_ind,
+			  ret ? -1 : fs_get_type());
+#endif
+		if (ret)
+			return log_msg_ret("fs", ret);
+		bflow->state = BOOTFLOWST_FS;
+	}
+
+	return 0;
+}
+
+void bootdev_list(bool probe)
+{
+	struct udevice *dev;
+	int ret;
+	int i;
+
+	printf("Seq  Probed  Status  Uclass    Name\n");
+	printf("---  ------  ------  --------  ------------------\n");
+	if (probe)
+		ret = uclass_first_device_err(UCLASS_BOOTDEV, &dev);
+	else
+		ret = uclass_find_first_device(UCLASS_BOOTDEV, &dev);
+	for (i = 0; dev; i++) {
+		printf("%3x   [ %c ]  %6s  %-9.9s %s\n", dev_seq(dev),
+		       device_active(dev) ? '+' : ' ',
+		       ret ? simple_itoa(ret) : "OK",
+		       dev_get_uclass_name(dev_get_parent(dev)), dev->name);
+		if (probe)
+			ret = uclass_next_device_err(&dev);
+		else
+			ret = uclass_find_next_device(&dev);
+	}
+	printf("---  ------  ------  --------  ------------------\n");
+	printf("(%d bootdev%s)\n", i, i != 1 ? "s" : "");
+}
+
+int bootdev_setup_for_dev(struct udevice *parent, const char *drv_name)
+{
+	struct udevice *bdev;
+	int ret;
+
+	ret = device_find_first_child_by_uclass(parent, UCLASS_BOOTDEV,
+						&bdev);
+	if (ret) {
+		if (ret != -ENODEV) {
+			log_debug("Cannot access bootdev device\n");
+			return ret;
+		}
+
+		ret = bootdev_bind(parent, drv_name, "bootdev", &bdev);
+		if (ret) {
+			log_debug("Cannot create bootdev device\n");
+			return ret;
+		}
+	}
+
+	return 0;
+}
+
+int bootdev_setup_sibling_blk(struct udevice *blk, const char *drv_name)
+{
+	struct udevice *parent, *dev;
+	char dev_name[50];
+	int ret;
+
+	snprintf(dev_name, sizeof(dev_name), "%s.%s", blk->name, "bootdev");
+
+	parent = dev_get_parent(blk);
+	ret = device_find_child_by_name(parent, dev_name, &dev);
+	if (ret) {
+		char *str;
+
+		if (ret != -ENODEV) {
+			log_debug("Cannot access bootdev device\n");
+			return ret;
+		}
+		str = strdup(dev_name);
+		if (!str)
+			return -ENOMEM;
+
+		ret = device_bind_driver(parent, drv_name, str, &dev);
+		if (ret) {
+			log_debug("Cannot create bootdev device\n");
+			return ret;
+		}
+		device_set_name_alloced(dev);
+	}
+
+	return 0;
+}
+
+int bootdev_get_sibling_blk(struct udevice *dev, struct udevice **blkp)
+{
+	struct udevice *parent = dev_get_parent(dev);
+	struct udevice *blk;
+	int ret, len;
+	char *p;
+
+	if (device_get_uclass_id(dev) != UCLASS_BOOTDEV)
+		return -EINVAL;
+
+	/* This should always work if bootdev_setup_sibling_blk() was used */
+	p = strstr(dev->name, ".bootdev");
+	if (!p)
+		return log_msg_ret("str", -EINVAL);
+
+	len = p - dev->name;
+	ret = device_find_child_by_namelen(parent, dev->name, len, &blk);
+	if (ret)
+		return log_msg_ret("find", ret);
+	*blkp = blk;
+
+	return 0;
+}
+
+static int bootdev_get_from_blk(struct udevice *blk, struct udevice **bootdevp)
+{
+	struct udevice *parent = dev_get_parent(blk);
+	struct udevice *bootdev;
+	char dev_name[50];
+	int ret;
+
+	if (device_get_uclass_id(blk) != UCLASS_BLK)
+		return -EINVAL;
+
+	/* This should always work if bootdev_setup_sibling_blk() was used */
+	snprintf(dev_name, sizeof(dev_name), "%s.%s", blk->name, "bootdev");
+	ret = device_find_child_by_name(parent, dev_name, &bootdev);
+	if (ret)
+		return log_msg_ret("find", ret);
+	*bootdevp = bootdev;
+
+	return 0;
+}
+
+int bootdev_unbind_dev(struct udevice *parent)
+{
+	struct udevice *dev;
+	int ret;
+
+	ret = device_find_first_child_by_uclass(parent, UCLASS_BOOTDEV, &dev);
+	if (!ret) {
+		ret = device_remove(dev, DM_REMOVE_NORMAL);
+		if (ret)
+			return log_msg_ret("rem", ret);
+		ret = device_unbind(dev);
+		if (ret)
+			return log_msg_ret("unb", ret);
+	}
+
+	return 0;
+}
+
+/**
+ * bootdev_find_by_label() - Convert a label string to a bootdev device
+ *
+ * Looks up a label name to find the associated bootdev. For example, if the
+ * label name is "mmc2", this will find a bootdev for an mmc device whose
+ * sequence number is 2.
+ *
+ * @label: Label string to convert, e.g. "mmc2"
+ * @devp: Returns bootdev device corresponding to that boot label
+ * Return: 0 if OK, -EINVAL if the label name (e.g. "mmc") does not refer to a
+ *	uclass, -ENOENT if no bootdev for that media has the sequence number
+ *	(e.g. 2)
+ */
+int bootdev_find_by_label(const char *label, struct udevice **devp)
+{
+	struct udevice *media;
+	struct uclass *uc;
+	enum uclass_id id;
+	const char *end;
+	int seq;
+
+	seq = trailing_strtoln_end(label, NULL, &end);
+	id = uclass_get_by_namelen(label, end - label);
+	log_debug("find %s: seq=%d, id=%d/%s\n", label, seq, id,
+		  uclass_get_name(id));
+	if (id == UCLASS_INVALID) {
+		log_warning("Unknown uclass '%s' in label\n", label);
+		return -EINVAL;
+	}
+	if (id == UCLASS_USB)
+		id = UCLASS_MASS_STORAGE;
+
+	/* Iterate through devices in the media uclass (e.g. UCLASS_MMC) */
+	uclass_id_foreach_dev(id, media, uc) {
+		struct udevice *bdev, *blk;
+		int ret;
+
+		/* if there is no seq, match anything */
+		if (seq != -1 && dev_seq(media) != seq) {
+			log_debug("- skip, media seq=%d\n", dev_seq(media));
+			continue;
+		}
+
+		ret = device_find_first_child_by_uclass(media, UCLASS_BOOTDEV,
+							&bdev);
+		if (ret) {
+			log_debug("- looking via blk, seq=%d, id=%d\n", seq,
+				  id);
+			ret = blk_find_device(id, seq, &blk);
+			if (!ret) {
+				log_debug("- get from blk %s\n", blk->name);
+				ret = bootdev_get_from_blk(blk, &bdev);
+			}
+		}
+		if (!ret) {
+			log_debug("- found %s\n", bdev->name);
+			*devp = bdev;
+			return 0;
+		}
+		log_debug("- no device in %s\n", media->name);
+	}
+	log_warning("Unknown seq %d for label '%s'\n", seq, label);
+
+	return -ENOENT;
+}
+
+int bootdev_find_by_any(const char *name, struct udevice **devp)
+{
+	struct udevice *dev;
+	int ret, seq;
+	char *endp;
+
+	seq = simple_strtol(name, &endp, 16);
+
+	/* Select by name, label or number */
+	if (*endp) {
+		ret = uclass_get_device_by_name(UCLASS_BOOTDEV, name, &dev);
+		if (ret == -ENODEV) {
+			ret = bootdev_find_by_label(name, &dev);
+			if (ret) {
+				printf("Cannot find bootdev '%s' (err=%d)\n",
+				       name, ret);
+				return ret;
+			}
+			ret = device_probe(dev);
+		}
+		if (ret) {
+			printf("Cannot probe bootdev '%s' (err=%d)\n", name,
+			       ret);
+			return ret;
+		}
+	} else {
+		ret = uclass_get_device_by_seq(UCLASS_BOOTDEV, seq, &dev);
+	}
+	if (ret) {
+		printf("Cannot find '%s' (err=%d)\n", name, ret);
+		return ret;
+	}
+
+	*devp = dev;
+
+	return 0;
+}
+
+int bootdev_get_bootflow(struct udevice *dev, struct bootflow_iter *iter,
+			 struct bootflow *bflow)
+{
+	const struct bootdev_ops *ops = bootdev_get_ops(dev);
+
+	if (!ops->get_bootflow)
+		return -ENOSYS;
+	memset(bflow, '\0', sizeof(*bflow));
+	bflow->dev = dev;
+	bflow->method = iter->method;
+	bflow->state = BOOTFLOWST_BASE;
+
+	return ops->get_bootflow(dev, iter, bflow);
+}
+
+void bootdev_clear_bootflows(struct udevice *dev)
+{
+	struct bootdev_uc_plat *ucp = dev_get_uclass_plat(dev);
+
+	while (!list_empty(&ucp->bootflow_head)) {
+		struct bootflow *bflow;
+
+		bflow = list_first_entry(&ucp->bootflow_head, struct bootflow,
+					 bm_node);
+		/* later bootflow_remove(bflow); */
+	}
+}
+
+/**
+ * h_cmp_bootdev() - Compare two bootdevs to find out which should go first
+ *
+ * @v1: struct udevice * of first bootdev device
+ * @v2: struct udevice * of second bootdev device
+ * Return: sort order (<0 if dev1 < dev2, ==0 if equal, >0 if dev1 > dev2)
+ */
+static int h_cmp_bootdev(const void *v1, const void *v2)
+{
+	const struct udevice *dev1 = *(struct udevice **)v1;
+	const struct udevice *dev2 = *(struct udevice **)v2;
+	const struct bootdev_uc_plat *ucp1 = dev_get_uclass_plat(dev1);
+	const struct bootdev_uc_plat *ucp2 = dev_get_uclass_plat(dev2);
+	int diff;
+
+	/* Use priority first */
+	diff = ucp1->prio - ucp2->prio;
+	if (diff)
+		return diff;
+
+	/* Fall back to seq for devices of the same priority */
+	diff = dev_seq(dev1) - dev_seq(dev2);
+
+	return diff;
+}
+
+/**
+ * build_order() - Build the ordered list of bootdevs to use
+ *
+ * This builds an ordered list of devices by one of three methods:
+ * - using the boot_targets environment variable, if non-empty
+ * - using the bootdev-order devicetree property, if present
+ * - sorted by priority and sequence number
+ *
+ * @bootstd: BOOTSTD device to use
+ * @order: Bootdevs listed in default order
+ * @max_count: Number of entries in @order
+ * Return: number of bootdevs found in the ordering, or -E2BIG if the
+ * boot_targets string is too long, or -EXDEV if the ordering produced 0 results
+ */
+static int build_order(struct udevice *bootstd, struct udevice **order,
+		       int max_count)
+{
+	const char *overflow_target = NULL;
+	const char *const *labels;
+	struct udevice *dev;
+	const char *targets;
+	int i, ret, count;
+
+	targets = env_get("boot_targets");
+	labels = IS_ENABLED(CONFIG_BOOTSTD_FULL) ?
+		bootstd_get_bootdev_order(bootstd) : NULL;
+	if (targets) {
+		char str[BOOT_TARGETS_MAX_LEN];
+		char *target;
+
+		if (strlen(targets) >= BOOT_TARGETS_MAX_LEN)
+			return log_msg_ret("len", -E2BIG);
+
+		/* make a copy of the string, since strok() will change it */
+		strcpy(str, targets);
+		for (i = 0, target = strtok(str, " "); target;
+		     target = strtok(NULL, " ")) {
+			ret = bootdev_find_by_label(target, &dev);
+			if (!ret) {
+				if (i == max_count) {
+					overflow_target = target;
+					break;
+				}
+				order[i++] = dev;
+			}
+		}
+		count = i;
+	} else if (labels) {
+		int upto;
+
+		upto = 0;
+		for (i = 0; labels[i]; i++) {
+			ret = bootdev_find_by_label(labels[i], &dev);
+			if (!ret) {
+				if (upto == max_count) {
+					overflow_target = labels[i];
+					break;
+				}
+				order[upto++] = dev;
+			}
+		}
+		count = upto;
+	} else {
+		/* sort them into priority order */
+		count = max_count;
+		qsort(order, count, sizeof(struct udevice *), h_cmp_bootdev);
+	}
+
+	if (overflow_target) {
+		log_warning("Expected at most %d bootdevs, but overflowed with boot_target '%s'\n",
+			    max_count, overflow_target);
+	}
+
+	if (!count)
+		return log_msg_ret("targ", -EXDEV);
+
+	return count;
+}
+
+int bootdev_setup_iter_order(struct bootflow_iter *iter, struct udevice **devp)
+{
+	struct udevice *bootstd, *dev = *devp, **order;
+	int upto, i;
+	int count;
+	int ret;
+
+	ret = uclass_first_device_err(UCLASS_BOOTSTD, &bootstd);
+	if (ret) {
+		log_err("Missing bootstd device\n");
+		return log_msg_ret("std", ret);
+	}
+
+	/* Handle scanning a single device */
+	if (dev) {
+		iter->flags |= BOOTFLOWF_SINGLE_DEV;
+		return 0;
+	}
+
+	count = uclass_id_count(UCLASS_BOOTDEV);
+	if (!count)
+		return log_msg_ret("count", -ENOENT);
+
+	order = calloc(count, sizeof(struct udevice *));
+	if (!order)
+		return log_msg_ret("order", -ENOMEM);
+
+	/*
+	 * Get a list of bootdevs, in seq order (i.e. using aliases). There may
+	 * be gaps so try to count up high enough to find them all.
+	 */
+	for (i = 0, upto = 0; upto < count && i < 20 + count * 2; i++) {
+		ret = uclass_find_device_by_seq(UCLASS_BOOTDEV, i, &dev);
+		if (!ret)
+			order[upto++] = dev;
+	}
+	log_debug("Found %d bootdevs\n", count);
+	if (upto != count)
+		log_debug("Expected %d bootdevs, found %d using aliases\n",
+			  count, upto);
+
+	count = build_order(bootstd, order, upto);
+	if (count < 0) {
+		free(order);
+		return log_msg_ret("build", count);
+	}
+
+	iter->dev_order = order;
+	iter->num_devs = count;
+	iter->cur_dev = 0;
+
+	dev = *order;
+	ret = device_probe(dev);
+	if (ret)
+		return log_msg_ret("probe", ret);
+	*devp = dev;
+
+	return 0;
+}
+
+static int bootdev_post_bind(struct udevice *dev)
+{
+	struct bootdev_uc_plat *ucp = dev_get_uclass_plat(dev);
+
+	INIT_LIST_HEAD(&ucp->bootflow_head);
+
+	return 0;
+}
+
+static int bootdev_pre_unbind(struct udevice *dev)
+{
+	bootdev_clear_bootflows(dev);
+
+	return 0;
+}
+
+UCLASS_DRIVER(bootdev) = {
+	.id		= UCLASS_BOOTDEV,
+	.name		= "bootdev",
+	.flags		= DM_UC_FLAG_SEQ_ALIAS,
+	.per_device_plat_auto	= sizeof(struct bootdev_uc_plat),
+	.post_bind	= bootdev_post_bind,
+	.pre_unbind	= bootdev_pre_unbind,
+};
diff --git a/doc/device-tree-bindings/bootdev.txt b/doc/device-tree-bindings/bootdev.txt
new file mode 100644
index 0000000000..95b7fec821
--- /dev/null
+++ b/doc/device-tree-bindings/bootdev.txt
@@ -0,0 +1,8 @@
+U-Boot boot device (bootdev)
+============================
+
+A bootdev provides a way to obtain a bootflow file from a device. It is a
+child of the media device (UCLASS_MMC, UCLASS_SPI_FLASH, etc.)
+
+The bootdev driver is provided by the media devices. The bindings for each
+are described in this file (to come).
diff --git a/include/bootdev.h b/include/bootdev.h
new file mode 100644
index 0000000000..9fc219839f
--- /dev/null
+++ b/include/bootdev.h
@@ -0,0 +1,275 @@
+/* SPDX-License-Identifier: GPL-2.0+ */
+/*
+ * Copyright 2021 Google LLC
+ * Written by Simon Glass <sjg@chromium.org>
+ */
+
+#ifndef __bootdev_h
+#define __bootdev_h
+
+#include <linux/list.h>
+
+struct bootflow;
+struct bootflow_iter;
+struct udevice;
+
+/**
+ * enum bootdev_prio_t - priority of each bootdev
+ *
+ * These values are associated with each bootdev and set up by the driver.
+ *
+ * Smallest value is the highest priority. By default, bootdevs are scanned from
+ * highest to lowest priority
+ */
+enum bootdev_prio_t {
+	BOOTDEVP_0_INTERNAL_FAST	= 10,
+	BOOTDEVP_1_INTERNAL_SLOW	= 20,
+	BOOTDEVP_2_SCAN_FAST		= 30,
+	BOOTDEVP_3_SCAN_SLOW		= 40,
+	BOOTDEVP_4_NET_BASE		= 50,
+	BOOTDEVP_5_NET_FALLBACK		= 60,
+	BOOTDEVP_6_SYSTEM		= 70,
+
+	BOOTDEVP_COUNT,
+};
+
+/**
+ * struct bootdev_uc_plat - uclass information about a bootdev
+ *
+ * This is attached to each device in the bootdev uclass and accessible via
+ * dev_get_uclass_plat(dev)
+ *
+ * @bootflows: List of available bootflows for this bootdev
+ * @piro: Priority of this bootdev
+ */
+struct bootdev_uc_plat {
+	struct list_head bootflow_head;
+	enum bootdev_prio_t prio;
+};
+
+/** struct bootdev_ops - Operations for the bootdev uclass */
+struct bootdev_ops {
+	/**
+	 * get_bootflow() - get a bootflow
+	 *
+	 * @dev:	Bootflow device to check
+	 * @iter:	Provides current dev, part, method to get. Should update
+	 *	max_part if there is a partition table. Should update state,
+	 *	subdir, fname, buf, size according to progress
+	 * @bflow:	Updated bootflow if found
+	 * Return: 0 if OK, -ESHUTDOWN if there are no more bootflows on this
+	 *	device, -ENOSYS if this device doesn't support bootflows,
+	 *	other -ve value on other error
+	 */
+	int (*get_bootflow)(struct udevice *dev, struct bootflow_iter *iter,
+			    struct bootflow *bflow);
+};
+
+#define bootdev_get_ops(dev)  ((struct bootdev_ops *)(dev)->driver->ops)
+
+/**
+ * bootdev_get_bootflow() - get a bootflow
+ *
+ * @dev:	Bootflow device to check
+ * @iter:	Provides current  part, method to get
+ * @bflow:	Returns bootflow if found
+ * Return: 0 if OK, -ESHUTDOWN if there are no more bootflows on this device,
+ *	-ENOSYS if this device doesn't support bootflows, other -ve value on
+ *	other error
+ */
+int bootdev_get_bootflow(struct udevice *dev, struct bootflow_iter *iter,
+			 struct bootflow *bflow);
+
+/**
+ * bootdev_bind() - Bind a new named bootdev device
+ *
+ * @parent:	Parent of the new device
+ * @drv_name:	Driver name to use for the bootdev device
+ * @name:	Name for the device (parent name is prepended)
+ * @devp:	the new device (which has not been probed)
+ */
+int bootdev_bind(struct udevice *parent, const char *drv_name, const char *name,
+		 struct udevice **devp);
+
+/**
+ * bootdev_find_in_blk() - Find a bootdev in a block device
+ *
+ * @dev: Bootflow device associated with this block device
+ * @blk: Block device to search
+ * @iter:	Provides current dev, part, method to get. Should update
+ *	max_part if there is a partition table
+ * @bflow: On entry, provides information about the partition and device to
+ *	check. On exit, returns bootflow if found
+ * Return: 0 if found, -ESHUTDOWN if no more bootflows, other -ve on error
+ */
+int bootdev_find_in_blk(struct udevice *dev, struct udevice *blk,
+			struct bootflow_iter *iter, struct bootflow *bflow);
+
+/**
+ * bootdev_list() - List all available bootdevs
+ *
+ * @probe: true to probe devices, false to leave them as is
+ */
+void bootdev_list(bool probe);
+
+/**
+ * bootdev_clear_bootflows() - Clear bootflows from a bootdev
+ *
+ * Each bootdev maintains a list of discovered bootflows. This provides a
+ * way to clear it. These bootflows are removed from the global list too.
+ *
+ * @dev: bootdev device to update
+ */
+void bootdev_clear_bootflows(struct udevice *dev);
+
+/**
+ * bootdev_add_bootflow() - Add a bootflow to the bootdev's list
+ *
+ * All fields in @bflow must be set up. Note that @bflow->dev is used to add the
+ * bootflow to that device.
+ *
+ * @dev: Bootdevice device to add to
+ * @bflow: Bootflow to add. Note that fields within bflow must be allocated
+ *	since this function takes over ownership of these. This functions makes
+ *	a copy of @bflow itself (without allocating its fields again), so the
+ *	caller must dispose of the memory used by the @bflow pointer itself
+ * Return: 0 if OK, -ENOMEM if out of memory
+ */
+int bootdev_add_bootflow(struct bootflow *bflow);
+
+/**
+ * bootdev_first_bootflow() - Get the first bootflow from a bootdev
+ *
+ * Returns the first bootflow attached to a bootdev
+ *
+ * @dev: bootdev device
+ * @bflowp: Returns a pointer to the bootflow
+ * Return: 0 if found, -ENOENT if there are no bootflows
+ */
+int bootdev_first_bootflow(struct udevice *dev, struct bootflow **bflowp);
+
+/**
+ * bootdev_next_bootflow() - Get the next bootflow from a bootdev
+ *
+ * Returns the next bootflow attached to a bootdev
+ *
+ * @bflowp: On entry, the last bootflow returned , e.g. from
+ *	bootdev_first_bootflow()
+ * Return: 0 if found, -ENOENT if there are no more bootflows
+ */
+int bootdev_next_bootflow(struct bootflow **bflowp);
+
+/**
+ * bootdev_find_by_label() - Look up a bootdev by label
+ *
+ * Each bootdev has a label which contains the media-uclass name and a number,
+ * e.g. 'mmc2'. This looks up the label and returns the associated bootdev
+ *
+ * The lookup is performed based on the media device's sequence number. So for
+ * 'mmc2' this looks for a device in UCLASS_MMC with a dev_seq() of 2.
+ *
+ * @label: Label to look up (e.g. "mmc1" or "mmc0")
+ * @devp: Returns the bootdev device found, or NULL if none (note it does not
+ *	return the media device, but its bootdev child)
+ * Return: 0 if OK, -EINVAL if the uclass is not supported by this board,
+ *	-ENOENT if there is no device with that number
+ */
+int bootdev_find_by_label(const char *label, struct udevice **devp);
+
+/**
+ * bootdev_find_by_any() - Find a bootdev by name, label or sequence
+ *
+ * @name: name (e.g. "mmc2.bootdev"), label ("mmc2"), or sequence ("2") to find
+ * @devp: returns the device found, on success
+ * Return: 0 if OK, -ve on error
+ */
+int bootdev_find_by_any(const char *name, struct udevice **devp);
+
+/**
+ * bootdev_setup_iter_order() - Set up the ordering of bootdevs to scan
+ *
+ * This sets up the ordering information in @iter, based on the priority of each
+ * bootdev and the bootdev-order property in the bootstd node
+ *
+ * If a single device is requested, no ordering is needed
+ *
+ * @iter: Iterator to update with the order
+ * @devp: On entry, *devp is NULL to scan all, otherwise this is the (single)
+ *	device to scan. Returns the first device to use, which is the passed-in
+ *	@devp if it was non-NULL
+ * Return: 0 if OK, -ENOENT if no bootdevs, -ENOMEM if out of memory, other -ve
+ *	on other error
+ */
+int bootdev_setup_iter_order(struct bootflow_iter *iter, struct udevice **devp);
+
+#if CONFIG_IS_ENABLED(BOOTSTD)
+/**
+ * bootdev_setup_for_dev() - Bind a new bootdev device
+ *
+ * Creates a bootdev device as a child of @parent. This should be called from
+ * the driver's bind() method or its uclass' post_bind() method.
+ *
+ * If a child bootdev already exists, this function does nothing
+ *
+ * @parent: Parent device (e.g. MMC or Ethernet)
+ * @drv_name: Name of bootdev driver to bind
+ * Return: 0 if OK, -ve on error
+ */
+int bootdev_setup_for_dev(struct udevice *parent, const char *drv_name);
+
+/**
+ * bootdev_setup_for_blk() - Bind a new bootdev device for a blk device
+ *
+ * Creates a bootdev device as a sibling of @blk. This should be called from
+ * the driver's bind() method or its uclass' post_bind() method, at the same
+ * time as the bould device is bound
+ *
+ * If a device of the same name already exists, this function does nothing
+ *
+ * @parent: Parent device (e.g. MMC or Ethernet)
+ * @drv_name: Name of bootdev driver to bind
+ * Return: 0 if OK, -ve on error
+ */
+int bootdev_setup_sibling_blk(struct udevice *blk, const char *drv_name);
+
+/**
+ * bootdev_get_sibling_blk() - Locate the block device for a bootdev
+ *
+ * @dev: bootdev to check
+ * @blkp: returns associated block device
+ * Return: 0 if OK, -EINVAL if @dev is not a bootdev device, other -ve on other
+ *	error
+ */
+int bootdev_get_sibling_blk(struct udevice *dev, struct udevice **blkp);
+
+/**
+ * bootdev_unbind_dev() - Unbind a bootdev device
+ *
+ * Remove and unbind a bootdev device which is a child of @parent. This should
+ * be called from the driver's unbind() method or its uclass' post_bind()
+ * method.
+ *
+ * @parent: Parent device (e.g. MMC or Ethernet)
+ * Return: 0 if OK, -ve on error
+ */
+int bootdev_unbind_dev(struct udevice *parent);
+#else
+static inline int bootdev_setup_for_dev(struct udevice *parent,
+					const char *drv_name)
+{
+	return 0;
+}
+
+static inline int bootdev_setup_sibling_blk(struct udevice *blk,
+					    const char *drv_name)
+{
+	return 0;
+}
+
+static inline int bootdev_unbind_dev(struct udevice *parent)
+{
+	return 0;
+}
+#endif
+
+#endif
diff --git a/include/dm/uclass-id.h b/include/dm/uclass-id.h
index cece0626a1..97ba4c02c4 100644
--- a/include/dm/uclass-id.h
+++ b/include/dm/uclass-id.h
@@ -38,6 +38,7 @@ enum uclass_id {
 	UCLASS_AXI,		/* AXI bus */
 	UCLASS_BLK,		/* Block device */
 	UCLASS_BOOTCOUNT,       /* Bootcount backing store */
+	UCLASS_BOOTDEV,		/* Boot device for locating an OS to boot */
 	UCLASS_BOOTSTD,		/* Standard boot driver */
 	UCLASS_BUTTON,		/* Button */
 	UCLASS_CACHE,		/* Cache controller */
-- 
2.35.1.616.g0bdcbb4464-goog