Adding upstream version 6.1.76.upstream/6.1.76

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 2020 insertions, 0 deletions

diff --git a/kernel/resource.c b/kernel/resource.c
new file mode 100644
index 000000000..8f52f8800
--- /dev/null
+++ b/kernel/resource.c
@@ -0,0 +1,2020 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ *	linux/kernel/resource.c
+ *
+ * Copyright (C) 1999	Linus Torvalds
+ * Copyright (C) 1999	Martin Mares <mj@ucw.cz>
+ *
+ * Arbitrary resource management.
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/export.h>
+#include <linux/errno.h>
+#include <linux/ioport.h>
+#include <linux/init.h>
+#include <linux/slab.h>
+#include <linux/spinlock.h>
+#include <linux/fs.h>
+#include <linux/proc_fs.h>
+#include <linux/pseudo_fs.h>
+#include <linux/sched.h>
+#include <linux/seq_file.h>
+#include <linux/device.h>
+#include <linux/pfn.h>
+#include <linux/mm.h>
+#include <linux/mount.h>
+#include <linux/resource_ext.h>
+#include <uapi/linux/magic.h>
+#include <asm/io.h>
+
+
+struct resource ioport_resource = {
+	.name	= "PCI IO",
+	.start	= 0,
+	.end	= IO_SPACE_LIMIT,
+	.flags	= IORESOURCE_IO,
+};
+EXPORT_SYMBOL(ioport_resource);
+
+struct resource iomem_resource = {
+	.name	= "PCI mem",
+	.start	= 0,
+	.end	= -1,
+	.flags	= IORESOURCE_MEM,
+};
+EXPORT_SYMBOL(iomem_resource);
+
+/* constraints to be met while allocating resources */
+struct resource_constraint {
+	resource_size_t min, max, align;
+	resource_size_t (*alignf)(void *, const struct resource *,
+			resource_size_t, resource_size_t);
+	void *alignf_data;
+};
+
+static DEFINE_RWLOCK(resource_lock);
+
+static struct resource *next_resource(struct resource *p)
+{
+	if (p->child)
+		return p->child;
+	while (!p->sibling && p->parent)
+		p = p->parent;
+	return p->sibling;
+}
+
+static struct resource *next_resource_skip_children(struct resource *p)
+{
+	while (!p->sibling && p->parent)
+		p = p->parent;
+	return p->sibling;
+}
+
+#define for_each_resource(_root, _p, _skip_children) \
+	for ((_p) = (_root)->child; (_p); \
+	     (_p) = (_skip_children) ? next_resource_skip_children(_p) : \
+				       next_resource(_p))
+
+static void *r_next(struct seq_file *m, void *v, loff_t *pos)
+{
+	struct resource *p = v;
+	(*pos)++;
+	return (void *)next_resource(p);
+}
+
+#ifdef CONFIG_PROC_FS
+
+enum { MAX_IORES_LEVEL = 5 };
+
+static void *r_start(struct seq_file *m, loff_t *pos)
+	__acquires(resource_lock)
+{
+	struct resource *p = pde_data(file_inode(m->file));
+	loff_t l = 0;
+	read_lock(&resource_lock);
+	for (p = p->child; p && l < *pos; p = r_next(m, p, &l))
+		;
+	return p;
+}
+
+static void r_stop(struct seq_file *m, void *v)
+	__releases(resource_lock)
+{
+	read_unlock(&resource_lock);
+}
+
+static int r_show(struct seq_file *m, void *v)
+{
+	struct resource *root = pde_data(file_inode(m->file));
+	struct resource *r = v, *p;
+	unsigned long long start, end;
+	int width = root->end < 0x10000 ? 4 : 8;
+	int depth;
+
+	for (depth = 0, p = r; depth < MAX_IORES_LEVEL; depth++, p = p->parent)
+		if (p->parent == root)
+			break;
+
+	if (file_ns_capable(m->file, &init_user_ns, CAP_SYS_ADMIN)) {
+		start = r->start;
+		end = r->end;
+	} else {
+		start = end = 0;
+	}
+
+	seq_printf(m, "%*s%0*llx-%0*llx : %s\n",
+			depth * 2, "",
+			width, start,
+			width, end,
+			r->name ? r->name : "<BAD>");
+	return 0;
+}
+
+static const struct seq_operations resource_op = {
+	.start	= r_start,
+	.next	= r_next,
+	.stop	= r_stop,
+	.show	= r_show,
+};
+
+static int __init ioresources_init(void)
+{
+	proc_create_seq_data("ioports", 0, NULL, &resource_op,
+			&ioport_resource);
+	proc_create_seq_data("iomem", 0, NULL, &resource_op, &iomem_resource);
+	return 0;
+}
+__initcall(ioresources_init);
+
+#endif /* CONFIG_PROC_FS */
+
+static void free_resource(struct resource *res)
+{
+	/**
+	 * If the resource was allocated using memblock early during boot
+	 * we'll leak it here: we can only return full pages back to the
+	 * buddy and trying to be smart and reusing them eventually in
+	 * alloc_resource() overcomplicates resource handling.
+	 */
+	if (res && PageSlab(virt_to_head_page(res)))
+		kfree(res);
+}
+
+static struct resource *alloc_resource(gfp_t flags)
+{
+	return kzalloc(sizeof(struct resource), flags);
+}
+
+/* Return the conflict entry if you can't request it */
+static struct resource * __request_resource(struct resource *root, struct resource *new)
+{
+	resource_size_t start = new->start;
+	resource_size_t end = new->end;
+	struct resource *tmp, **p;
+
+	if (end < start)
+		return root;
+	if (start < root->start)
+		return root;
+	if (end > root->end)
+		return root;
+	p = &root->child;
+	for (;;) {
+		tmp = *p;
+		if (!tmp || tmp->start > end) {
+			new->sibling = tmp;
+			*p = new;
+			new->parent = root;
+			return NULL;
+		}
+		p = &tmp->sibling;
+		if (tmp->end < start)
+			continue;
+		return tmp;
+	}
+}
+
+static int __release_resource(struct resource *old, bool release_child)
+{
+	struct resource *tmp, **p, *chd;
+
+	p = &old->parent->child;
+	for (;;) {
+		tmp = *p;
+		if (!tmp)
+			break;
+		if (tmp == old) {
+			if (release_child || !(tmp->child)) {
+				*p = tmp->sibling;
+			} else {
+				for (chd = tmp->child;; chd = chd->sibling) {
+					chd->parent = tmp->parent;
+					if (!(chd->sibling))
+						break;
+				}
+				*p = tmp->child;
+				chd->sibling = tmp->sibling;
+			}
+			old->parent = NULL;
+			return 0;
+		}
+		p = &tmp->sibling;
+	}
+	return -EINVAL;
+}
+
+static void __release_child_resources(struct resource *r)
+{
+	struct resource *tmp, *p;
+	resource_size_t size;
+
+	p = r->child;
+	r->child = NULL;
+	while (p) {
+		tmp = p;
+		p = p->sibling;
+
+		tmp->parent = NULL;
+		tmp->sibling = NULL;
+		__release_child_resources(tmp);
+
+		printk(KERN_DEBUG "release child resource %pR\n", tmp);
+		/* need to restore size, and keep flags */
+		size = resource_size(tmp);
+		tmp->start = 0;
+		tmp->end = size - 1;
+	}
+}
+
+void release_child_resources(struct resource *r)
+{
+	write_lock(&resource_lock);
+	__release_child_resources(r);
+	write_unlock(&resource_lock);
+}
+
+/**
+ * request_resource_conflict - request and reserve an I/O or memory resource
+ * @root: root resource descriptor
+ * @new: resource descriptor desired by caller
+ *
+ * Returns 0 for success, conflict resource on error.
+ */
+struct resource *request_resource_conflict(struct resource *root, struct resource *new)
+{
+	struct resource *conflict;
+
+	write_lock(&resource_lock);
+	conflict = __request_resource(root, new);
+	write_unlock(&resource_lock);
+	return conflict;
+}
+
+/**
+ * request_resource - request and reserve an I/O or memory resource
+ * @root: root resource descriptor
+ * @new: resource descriptor desired by caller
+ *
+ * Returns 0 for success, negative error code on error.
+ */
+int request_resource(struct resource *root, struct resource *new)
+{
+	struct resource *conflict;
+
+	conflict = request_resource_conflict(root, new);
+	return conflict ? -EBUSY : 0;
+}
+
+EXPORT_SYMBOL(request_resource);
+
+/**
+ * release_resource - release a previously reserved resource
+ * @old: resource pointer
+ */
+int release_resource(struct resource *old)
+{
+	int retval;
+
+	write_lock(&resource_lock);
+	retval = __release_resource(old, true);
+	write_unlock(&resource_lock);
+	return retval;
+}
+
+EXPORT_SYMBOL(release_resource);
+
+/**
+ * find_next_iomem_res - Finds the lowest iomem resource that covers part of
+ *			 [@start..@end].
+ *
+ * If a resource is found, returns 0 and @*res is overwritten with the part
+ * of the resource that's within [@start..@end]; if none is found, returns
+ * -ENODEV.  Returns -EINVAL for invalid parameters.
+ *
+ * @start:	start address of the resource searched for
+ * @end:	end address of same resource
+ * @flags:	flags which the resource must have
+ * @desc:	descriptor the resource must have
+ * @res:	return ptr, if resource found
+ *
+ * The caller must specify @start, @end, @flags, and @desc
+ * (which may be IORES_DESC_NONE).
+ */
+static int find_next_iomem_res(resource_size_t start, resource_size_t end,
+			       unsigned long flags, unsigned long desc,
+			       struct resource *res)
+{
+	struct resource *p;
+
+	if (!res)
+		return -EINVAL;
+
+	if (start >= end)
+		return -EINVAL;
+
+	read_lock(&resource_lock);
+
+	for (p = iomem_resource.child; p; p = next_resource(p)) {
+		/* If we passed the resource we are looking for, stop */
+		if (p->start > end) {
+			p = NULL;
+			break;
+		}
+
+		/* Skip until we find a range that matches what we look for */
+		if (p->end < start)
+			continue;
+
+		if ((p->flags & flags) != flags)
+			continue;
+		if ((desc != IORES_DESC_NONE) && (desc != p->desc))
+			continue;
+
+		/* Found a match, break */
+		break;
+	}
+
+	if (p) {
+		/* copy data */
+		*res = (struct resource) {
+			.start = max(start, p->start),
+			.end = min(end, p->end),
+			.flags = p->flags,
+			.desc = p->desc,
+			.parent = p->parent,
+		};
+	}
+
+	read_unlock(&resource_lock);
+	return p ? 0 : -ENODEV;
+}
+
+static int __walk_iomem_res_desc(resource_size_t start, resource_size_t end,
+				 unsigned long flags, unsigned long desc,
+				 void *arg,
+				 int (*func)(struct resource *, void *))
+{
+	struct resource res;
+	int ret = -EINVAL;
+
+	while (start < end &&
+	       !find_next_iomem_res(start, end, flags, desc, &res)) {
+		ret = (*func)(&res, arg);
+		if (ret)
+			break;
+
+		start = res.end + 1;
+	}
+
+	return ret;
+}
+
+/**
+ * walk_iomem_res_desc - Walks through iomem resources and calls func()
+ *			 with matching resource ranges.
+ * *
+ * @desc: I/O resource descriptor. Use IORES_DESC_NONE to skip @desc check.
+ * @flags: I/O resource flags
+ * @start: start addr
+ * @end: end addr
+ * @arg: function argument for the callback @func
+ * @func: callback function that is called for each qualifying resource area
+ *
+ * All the memory ranges which overlap start,end and also match flags and
+ * desc are valid candidates.
+ *
+ * NOTE: For a new descriptor search, define a new IORES_DESC in
+ * <linux/ioport.h> and set it in 'desc' of a target resource entry.
+ */
+int walk_iomem_res_desc(unsigned long desc, unsigned long flags, u64 start,
+		u64 end, void *arg, int (*func)(struct resource *, void *))
+{
+	return __walk_iomem_res_desc(start, end, flags, desc, arg, func);
+}
+EXPORT_SYMBOL_GPL(walk_iomem_res_desc);
+
+/*
+ * This function calls the @func callback against all memory ranges of type
+ * System RAM which are marked as IORESOURCE_SYSTEM_RAM and IORESOUCE_BUSY.
+ * Now, this function is only for System RAM, it deals with full ranges and
+ * not PFNs. If resources are not PFN-aligned, dealing with PFNs can truncate
+ * ranges.
+ */
+int walk_system_ram_res(u64 start, u64 end, void *arg,
+			int (*func)(struct resource *, void *))
+{
+	unsigned long flags = IORESOURCE_SYSTEM_RAM | IORESOURCE_BUSY;
+
+	return __walk_iomem_res_desc(start, end, flags, IORES_DESC_NONE, arg,
+				     func);
+}
+
+/*
+ * This function calls the @func callback against all memory ranges, which
+ * are ranges marked as IORESOURCE_MEM and IORESOUCE_BUSY.
+ */
+int walk_mem_res(u64 start, u64 end, void *arg,
+		 int (*func)(struct resource *, void *))
+{
+	unsigned long flags = IORESOURCE_MEM | IORESOURCE_BUSY;
+
+	return __walk_iomem_res_desc(start, end, flags, IORES_DESC_NONE, arg,
+				     func);
+}
+
+/*
+ * This function calls the @func callback against all memory ranges of type
+ * System RAM which are marked as IORESOURCE_SYSTEM_RAM and IORESOUCE_BUSY.
+ * It is to be used only for System RAM.
+ */
+int walk_system_ram_range(unsigned long start_pfn, unsigned long nr_pages,
+			  void *arg, int (*func)(unsigned long, unsigned long, void *))
+{
+	resource_size_t start, end;
+	unsigned long flags;
+	struct resource res;
+	unsigned long pfn, end_pfn;
+	int ret = -EINVAL;
+
+	start = (u64) start_pfn << PAGE_SHIFT;
+	end = ((u64)(start_pfn + nr_pages) << PAGE_SHIFT) - 1;
+	flags = IORESOURCE_SYSTEM_RAM | IORESOURCE_BUSY;
+	while (start < end &&
+	       !find_next_iomem_res(start, end, flags, IORES_DESC_NONE, &res)) {
+		pfn = PFN_UP(res.start);
+		end_pfn = PFN_DOWN(res.end + 1);
+		if (end_pfn > pfn)
+			ret = (*func)(pfn, end_pfn - pfn, arg);
+		if (ret)
+			break;
+		start = res.end + 1;
+	}
+	return ret;
+}
+
+static int __is_ram(unsigned long pfn, unsigned long nr_pages, void *arg)
+{
+	return 1;
+}
+
+/*
+ * This generic page_is_ram() returns true if specified address is
+ * registered as System RAM in iomem_resource list.
+ */
+int __weak page_is_ram(unsigned long pfn)
+{
+	return walk_system_ram_range(pfn, 1, NULL, __is_ram) == 1;
+}
+EXPORT_SYMBOL_GPL(page_is_ram);
+
+static int __region_intersects(struct resource *parent, resource_size_t start,
+			       size_t size, unsigned long flags,
+			       unsigned long desc)
+{
+	struct resource res;
+	int type = 0; int other = 0;
+	struct resource *p;
+
+	res.start = start;
+	res.end = start + size - 1;
+
+	for (p = parent->child; p ; p = p->sibling) {
+		bool is_type = (((p->flags & flags) == flags) &&
+				((desc == IORES_DESC_NONE) ||
+				 (desc == p->desc)));
+
+		if (resource_overlaps(p, &res))
+			is_type ? type++ : other++;
+	}
+
+	if (type == 0)
+		return REGION_DISJOINT;
+
+	if (other == 0)
+		return REGION_INTERSECTS;
+
+	return REGION_MIXED;
+}
+
+/**
+ * region_intersects() - determine intersection of region with known resources
+ * @start: region start address
+ * @size: size of region
+ * @flags: flags of resource (in iomem_resource)
+ * @desc: descriptor of resource (in iomem_resource) or IORES_DESC_NONE
+ *
+ * Check if the specified region partially overlaps or fully eclipses a
+ * resource identified by @flags and @desc (optional with IORES_DESC_NONE).
+ * Return REGION_DISJOINT if the region does not overlap @flags/@desc,
+ * return REGION_MIXED if the region overlaps @flags/@desc and another
+ * resource, and return REGION_INTERSECTS if the region overlaps @flags/@desc
+ * and no other defined resource. Note that REGION_INTERSECTS is also
+ * returned in the case when the specified region overlaps RAM and undefined
+ * memory holes.
+ *
+ * region_intersect() is used by memory remapping functions to ensure
+ * the user is not remapping RAM and is a vast speed up over walking
+ * through the resource table page by page.
+ */
+int region_intersects(resource_size_t start, size_t size, unsigned long flags,
+		      unsigned long desc)
+{
+	int ret;
+
+	read_lock(&resource_lock);
+	ret = __region_intersects(&iomem_resource, start, size, flags, desc);
+	read_unlock(&resource_lock);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(region_intersects);
+
+void __weak arch_remove_reservations(struct resource *avail)
+{
+}
+
+static resource_size_t simple_align_resource(void *data,
+					     const struct resource *avail,
+					     resource_size_t size,
+					     resource_size_t align)
+{
+	return avail->start;
+}
+
+static void resource_clip(struct resource *res, resource_size_t min,
+			  resource_size_t max)
+{
+	if (res->start < min)
+		res->start = min;
+	if (res->end > max)
+		res->end = max;
+}
+
+/*
+ * Find empty slot in the resource tree with the given range and
+ * alignment constraints
+ */
+static int __find_resource(struct resource *root, struct resource *old,
+			 struct resource *new,
+			 resource_size_t  size,
+			 struct resource_constraint *constraint)
+{
+	struct resource *this = root->child;
+	struct resource tmp = *new, avail, alloc;
+
+	tmp.start = root->start;
+	/*
+	 * Skip past an allocated resource that starts at 0, since the assignment
+	 * of this->start - 1 to tmp->end below would cause an underflow.
+	 */
+	if (this && this->start == root->start) {
+		tmp.start = (this == old) ? old->start : this->end + 1;
+		this = this->sibling;
+	}
+	for(;;) {
+		if (this)
+			tmp.end = (this == old) ?  this->end : this->start - 1;
+		else
+			tmp.end = root->end;
+
+		if (tmp.end < tmp.start)
+			goto next;
+
+		resource_clip(&tmp, constraint->min, constraint->max);
+		arch_remove_reservations(&tmp);
+
+		/* Check for overflow after ALIGN() */
+		avail.start = ALIGN(tmp.start, constraint->align);
+		avail.end = tmp.end;
+		avail.flags = new->flags & ~IORESOURCE_UNSET;
+		if (avail.start >= tmp.start) {
+			alloc.flags = avail.flags;
+			alloc.start = constraint->alignf(constraint->alignf_data, &avail,
+					size, constraint->align);
+			alloc.end = alloc.start + size - 1;
+			if (alloc.start <= alloc.end &&
+			    resource_contains(&avail, &alloc)) {
+				new->start = alloc.start;
+				new->end = alloc.end;
+				return 0;
+			}
+		}
+
+next:		if (!this || this->end == root->end)
+			break;
+
+		if (this != old)
+			tmp.start = this->end + 1;
+		this = this->sibling;
+	}
+	return -EBUSY;
+}
+
+/*
+ * Find empty slot in the resource tree given range and alignment.
+ */
+static int find_resource(struct resource *root, struct resource *new,
+			resource_size_t size,
+			struct resource_constraint  *constraint)
+{
+	return  __find_resource(root, NULL, new, size, constraint);
+}
+
+/**
+ * reallocate_resource - allocate a slot in the resource tree given range & alignment.
+ *	The resource will be relocated if the new size cannot be reallocated in the
+ *	current location.
+ *
+ * @root: root resource descriptor
+ * @old:  resource descriptor desired by caller
+ * @newsize: new size of the resource descriptor
+ * @constraint: the size and alignment constraints to be met.
+ */
+static int reallocate_resource(struct resource *root, struct resource *old,
+			       resource_size_t newsize,
+			       struct resource_constraint *constraint)
+{
+	int err=0;
+	struct resource new = *old;
+	struct resource *conflict;
+
+	write_lock(&resource_lock);
+
+	if ((err = __find_resource(root, old, &new, newsize, constraint)))
+		goto out;
+
+	if (resource_contains(&new, old)) {
+		old->start = new.start;
+		old->end = new.end;
+		goto out;
+	}
+
+	if (old->child) {
+		err = -EBUSY;
+		goto out;
+	}
+
+	if (resource_contains(old, &new)) {
+		old->start = new.start;
+		old->end = new.end;
+	} else {
+		__release_resource(old, true);
+		*old = new;
+		conflict = __request_resource(root, old);
+		BUG_ON(conflict);
+	}
+out:
+	write_unlock(&resource_lock);
+	return err;
+}
+
+
+/**
+ * allocate_resource - allocate empty slot in the resource tree given range & alignment.
+ * 	The resource will be reallocated with a new size if it was already allocated
+ * @root: root resource descriptor
+ * @new: resource descriptor desired by caller
+ * @size: requested resource region size
+ * @min: minimum boundary to allocate
+ * @max: maximum boundary to allocate
+ * @align: alignment requested, in bytes
+ * @alignf: alignment function, optional, called if not NULL
+ * @alignf_data: arbitrary data to pass to the @alignf function
+ */
+int allocate_resource(struct resource *root, struct resource *new,
+		      resource_size_t size, resource_size_t min,
+		      resource_size_t max, resource_size_t align,
+		      resource_size_t (*alignf)(void *,
+						const struct resource *,
+						resource_size_t,
+						resource_size_t),
+		      void *alignf_data)
+{
+	int err;
+	struct resource_constraint constraint;
+
+	if (!alignf)
+		alignf = simple_align_resource;
+
+	constraint.min = min;
+	constraint.max = max;
+	constraint.align = align;
+	constraint.alignf = alignf;
+	constraint.alignf_data = alignf_data;
+
+	if ( new->parent ) {
+		/* resource is already allocated, try reallocating with
+		   the new constraints */
+		return reallocate_resource(root, new, size, &constraint);
+	}
+
+	write_lock(&resource_lock);
+	err = find_resource(root, new, size, &constraint);
+	if (err >= 0 && __request_resource(root, new))
+		err = -EBUSY;
+	write_unlock(&resource_lock);
+	return err;
+}
+
+EXPORT_SYMBOL(allocate_resource);
+
+/**
+ * lookup_resource - find an existing resource by a resource start address
+ * @root: root resource descriptor
+ * @start: resource start address
+ *
+ * Returns a pointer to the resource if found, NULL otherwise
+ */
+struct resource *lookup_resource(struct resource *root, resource_size_t start)
+{
+	struct resource *res;
+
+	read_lock(&resource_lock);
+	for (res = root->child; res; res = res->sibling) {
+		if (res->start == start)
+			break;
+	}
+	read_unlock(&resource_lock);
+
+	return res;
+}
+
+/*
+ * Insert a resource into the resource tree. If successful, return NULL,
+ * otherwise return the conflicting resource (compare to __request_resource())
+ */
+static struct resource * __insert_resource(struct resource *parent, struct resource *new)
+{
+	struct resource *first, *next;
+
+	for (;; parent = first) {
+		first = __request_resource(parent, new);
+		if (!first)
+			return first;
+
+		if (first == parent)
+			return first;
+		if (WARN_ON(first == new))	/* duplicated insertion */
+			return first;
+
+		if ((first->start > new->start) || (first->end < new->end))
+			break;
+		if ((first->start == new->start) && (first->end == new->end))
+			break;
+	}
+
+	for (next = first; ; next = next->sibling) {
+		/* Partial overlap? Bad, and unfixable */
+		if (next->start < new->start || next->end > new->end)
+			return next;
+		if (!next->sibling)
+			break;
+		if (next->sibling->start > new->end)
+			break;
+	}
+
+	new->parent = parent;
+	new->sibling = next->sibling;
+	new->child = first;
+
+	next->sibling = NULL;
+	for (next = first; next; next = next->sibling)
+		next->parent = new;
+
+	if (parent->child == first) {
+		parent->child = new;
+	} else {
+		next = parent->child;
+		while (next->sibling != first)
+			next = next->sibling;
+		next->sibling = new;
+	}
+	return NULL;
+}
+
+/**
+ * insert_resource_conflict - Inserts resource in the resource tree
+ * @parent: parent of the new resource
+ * @new: new resource to insert
+ *
+ * Returns 0 on success, conflict resource if the resource can't be inserted.
+ *
+ * This function is equivalent to request_resource_conflict when no conflict
+ * happens. If a conflict happens, and the conflicting resources
+ * entirely fit within the range of the new resource, then the new
+ * resource is inserted and the conflicting resources become children of
+ * the new resource.
+ *
+ * This function is intended for producers of resources, such as FW modules
+ * and bus drivers.
+ */
+struct resource *insert_resource_conflict(struct resource *parent, struct resource *new)
+{
+	struct resource *conflict;
+
+	write_lock(&resource_lock);
+	conflict = __insert_resource(parent, new);
+	write_unlock(&resource_lock);
+	return conflict;
+}
+
+/**
+ * insert_resource - Inserts a resource in the resource tree
+ * @parent: parent of the new resource
+ * @new: new resource to insert
+ *
+ * Returns 0 on success, -EBUSY if the resource can't be inserted.
+ *
+ * This function is intended for producers of resources, such as FW modules
+ * and bus drivers.
+ */
+int insert_resource(struct resource *parent, struct resource *new)
+{
+	struct resource *conflict;
+
+	conflict = insert_resource_conflict(parent, new);
+	return conflict ? -EBUSY : 0;
+}
+EXPORT_SYMBOL_GPL(insert_resource);
+
+/**
+ * insert_resource_expand_to_fit - Insert a resource into the resource tree
+ * @root: root resource descriptor
+ * @new: new resource to insert
+ *
+ * Insert a resource into the resource tree, possibly expanding it in order
+ * to make it encompass any conflicting resources.
+ */
+void insert_resource_expand_to_fit(struct resource *root, struct resource *new)
+{
+	if (new->parent)
+		return;
+
+	write_lock(&resource_lock);
+	for (;;) {
+		struct resource *conflict;
+
+		conflict = __insert_resource(root, new);
+		if (!conflict)
+			break;
+		if (conflict == root)
+			break;
+
+		/* Ok, expand resource to cover the conflict, then try again .. */
+		if (conflict->start < new->start)
+			new->start = conflict->start;
+		if (conflict->end > new->end)
+			new->end = conflict->end;
+
+		printk("Expanded resource %s due to conflict with %s\n", new->name, conflict->name);
+	}
+	write_unlock(&resource_lock);
+}
+/*
+ * Not for general consumption, only early boot memory map parsing, PCI
+ * resource discovery, and late discovery of CXL resources are expected
+ * to use this interface. The former are built-in and only the latter,
+ * CXL, is a module.
+ */
+EXPORT_SYMBOL_NS_GPL(insert_resource_expand_to_fit, CXL);
+
+/**
+ * remove_resource - Remove a resource in the resource tree
+ * @old: resource to remove
+ *
+ * Returns 0 on success, -EINVAL if the resource is not valid.
+ *
+ * This function removes a resource previously inserted by insert_resource()
+ * or insert_resource_conflict(), and moves the children (if any) up to
+ * where they were before.  insert_resource() and insert_resource_conflict()
+ * insert a new resource, and move any conflicting resources down to the
+ * children of the new resource.
+ *
+ * insert_resource(), insert_resource_conflict() and remove_resource() are
+ * intended for producers of resources, such as FW modules and bus drivers.
+ */
+int remove_resource(struct resource *old)
+{
+	int retval;
+
+	write_lock(&resource_lock);
+	retval = __release_resource(old, false);
+	write_unlock(&resource_lock);
+	return retval;
+}
+EXPORT_SYMBOL_GPL(remove_resource);
+
+static int __adjust_resource(struct resource *res, resource_size_t start,
+				resource_size_t size)
+{
+	struct resource *tmp, *parent = res->parent;
+	resource_size_t end = start + size - 1;
+	int result = -EBUSY;
+
+	if (!parent)
+		goto skip;
+
+	if ((start < parent->start) || (end > parent->end))
+		goto out;
+
+	if (res->sibling && (res->sibling->start <= end))
+		goto out;
+
+	tmp = parent->child;
+	if (tmp != res) {
+		while (tmp->sibling != res)
+			tmp = tmp->sibling;
+		if (start <= tmp->end)
+			goto out;
+	}
+
+skip:
+	for (tmp = res->child; tmp; tmp = tmp->sibling)
+		if ((tmp->start < start) || (tmp->end > end))
+			goto out;
+
+	res->start = start;
+	res->end = end;
+	result = 0;
+
+ out:
+	return result;
+}
+
+/**
+ * adjust_resource - modify a resource's start and size
+ * @res: resource to modify
+ * @start: new start value
+ * @size: new size
+ *
+ * Given an existing resource, change its start and size to match the
+ * arguments.  Returns 0 on success, -EBUSY if it can't fit.
+ * Existing children of the resource are assumed to be immutable.
+ */
+int adjust_resource(struct resource *res, resource_size_t start,
+		    resource_size_t size)
+{
+	int result;
+
+	write_lock(&resource_lock);
+	result = __adjust_resource(res, start, size);
+	write_unlock(&resource_lock);
+	return result;
+}
+EXPORT_SYMBOL(adjust_resource);
+
+static void __init
+__reserve_region_with_split(struct resource *root, resource_size_t start,
+			    resource_size_t end, const char *name)
+{
+	struct resource *parent = root;
+	struct resource *conflict;
+	struct resource *res = alloc_resource(GFP_ATOMIC);
+	struct resource *next_res = NULL;
+	int type = resource_type(root);
+
+	if (!res)
+		return;
+
+	res->name = name;
+	res->start = start;
+	res->end = end;
+	res->flags = type | IORESOURCE_BUSY;
+	res->desc = IORES_DESC_NONE;
+
+	while (1) {
+
+		conflict = __request_resource(parent, res);
+		if (!conflict) {
+			if (!next_res)
+				break;
+			res = next_res;
+			next_res = NULL;
+			continue;
+		}
+
+		/* conflict covered whole area */
+		if (conflict->start <= res->start &&
+				conflict->end >= res->end) {
+			free_resource(res);
+			WARN_ON(next_res);
+			break;
+		}
+
+		/* failed, split and try again */
+		if (conflict->start > res->start) {
+			end = res->end;
+			res->end = conflict->start - 1;
+			if (conflict->end < end) {
+				next_res = alloc_resource(GFP_ATOMIC);
+				if (!next_res) {
+					free_resource(res);
+					break;
+				}
+				next_res->name = name;
+				next_res->start = conflict->end + 1;
+				next_res->end = end;
+				next_res->flags = type | IORESOURCE_BUSY;
+				next_res->desc = IORES_DESC_NONE;
+			}
+		} else {
+			res->start = conflict->end + 1;
+		}
+	}
+
+}
+
+void __init
+reserve_region_with_split(struct resource *root, resource_size_t start,
+			  resource_size_t end, const char *name)
+{
+	int abort = 0;
+
+	write_lock(&resource_lock);
+	if (root->start > start || root->end < end) {
+		pr_err("requested range [0x%llx-0x%llx] not in root %pr\n",
+		       (unsigned long long)start, (unsigned long long)end,
+		       root);
+		if (start > root->end || end < root->start)
+			abort = 1;
+		else {
+			if (end > root->end)
+				end = root->end;
+			if (start < root->start)
+				start = root->start;
+			pr_err("fixing request to [0x%llx-0x%llx]\n",
+			       (unsigned long long)start,
+			       (unsigned long long)end);
+		}
+		dump_stack();
+	}
+	if (!abort)
+		__reserve_region_with_split(root, start, end, name);
+	write_unlock(&resource_lock);
+}
+
+/**
+ * resource_alignment - calculate resource's alignment
+ * @res: resource pointer
+ *
+ * Returns alignment on success, 0 (invalid alignment) on failure.
+ */
+resource_size_t resource_alignment(struct resource *res)
+{
+	switch (res->flags & (IORESOURCE_SIZEALIGN | IORESOURCE_STARTALIGN)) {
+	case IORESOURCE_SIZEALIGN:
+		return resource_size(res);
+	case IORESOURCE_STARTALIGN:
+		return res->start;
+	default:
+		return 0;
+	}
+}
+
+/*
+ * This is compatibility stuff for IO resources.
+ *
+ * Note how this, unlike the above, knows about
+ * the IO flag meanings (busy etc).
+ *
+ * request_region creates a new busy region.
+ *
+ * release_region releases a matching busy region.
+ */
+
+static DECLARE_WAIT_QUEUE_HEAD(muxed_resource_wait);
+
+static struct inode *iomem_inode;
+
+#ifdef CONFIG_IO_STRICT_DEVMEM
+static void revoke_iomem(struct resource *res)
+{
+	/* pairs with smp_store_release() in iomem_init_inode() */
+	struct inode *inode = smp_load_acquire(&iomem_inode);
+
+	/*
+	 * Check that the initialization has completed. Losing the race
+	 * is ok because it means drivers are claiming resources before
+	 * the fs_initcall level of init and prevent iomem_get_mapping users
+	 * from establishing mappings.
+	 */
+	if (!inode)
+		return;
+
+	/*
+	 * The expectation is that the driver has successfully marked
+	 * the resource busy by this point, so devmem_is_allowed()
+	 * should start returning false, however for performance this
+	 * does not iterate the entire resource range.
+	 */
+	if (devmem_is_allowed(PHYS_PFN(res->start)) &&
+	    devmem_is_allowed(PHYS_PFN(res->end))) {
+		/*
+		 * *cringe* iomem=relaxed says "go ahead, what's the
+		 * worst that can happen?"
+		 */
+		return;
+	}
+
+	unmap_mapping_range(inode->i_mapping, res->start, resource_size(res), 1);
+}
+#else
+static void revoke_iomem(struct resource *res) {}
+#endif
+
+struct address_space *iomem_get_mapping(void)
+{
+	/*
+	 * This function is only called from file open paths, hence guaranteed
+	 * that fs_initcalls have completed and no need to check for NULL. But
+	 * since revoke_iomem can be called before the initcall we still need
+	 * the barrier to appease checkers.
+	 */
+	return smp_load_acquire(&iomem_inode)->i_mapping;
+}
+
+static int __request_region_locked(struct resource *res, struct resource *parent,
+				   resource_size_t start, resource_size_t n,
+				   const char *name, int flags)
+{
+	DECLARE_WAITQUEUE(wait, current);
+
+	res->name = name;
+	res->start = start;
+	res->end = start + n - 1;
+
+	for (;;) {
+		struct resource *conflict;
+
+		res->flags = resource_type(parent) | resource_ext_type(parent);
+		res->flags |= IORESOURCE_BUSY | flags;
+		res->desc = parent->desc;
+
+		conflict = __request_resource(parent, res);
+		if (!conflict)
+			break;
+		/*
+		 * mm/hmm.c reserves physical addresses which then
+		 * become unavailable to other users.  Conflicts are
+		 * not expected.  Warn to aid debugging if encountered.
+		 */
+		if (conflict->desc == IORES_DESC_DEVICE_PRIVATE_MEMORY) {
+			pr_warn("Unaddressable device %s %pR conflicts with %pR",
+				conflict->name, conflict, res);
+		}
+		if (conflict != parent) {
+			if (!(conflict->flags & IORESOURCE_BUSY)) {
+				parent = conflict;
+				continue;
+			}
+		}
+		if (conflict->flags & flags & IORESOURCE_MUXED) {
+			add_wait_queue(&muxed_resource_wait, &wait);
+			write_unlock(&resource_lock);
+			set_current_state(TASK_UNINTERRUPTIBLE);
+			schedule();
+			remove_wait_queue(&muxed_resource_wait, &wait);
+			write_lock(&resource_lock);
+			continue;
+		}
+		/* Uhhuh, that didn't work out.. */
+		return -EBUSY;
+	}
+
+	return 0;
+}
+
+/**
+ * __request_region - create a new busy resource region
+ * @parent: parent resource descriptor
+ * @start: resource start address
+ * @n: resource region size
+ * @name: reserving caller's ID string
+ * @flags: IO resource flags
+ */
+struct resource *__request_region(struct resource *parent,
+				  resource_size_t start, resource_size_t n,
+				  const char *name, int flags)
+{
+	struct resource *res = alloc_resource(GFP_KERNEL);
+	int ret;
+
+	if (!res)
+		return NULL;
+
+	write_lock(&resource_lock);
+	ret = __request_region_locked(res, parent, start, n, name, flags);
+	write_unlock(&resource_lock);
+
+	if (ret) {
+		free_resource(res);
+		return NULL;
+	}
+
+	if (parent == &iomem_resource)
+		revoke_iomem(res);
+
+	return res;
+}
+EXPORT_SYMBOL(__request_region);
+
+/**
+ * __release_region - release a previously reserved resource region
+ * @parent: parent resource descriptor
+ * @start: resource start address
+ * @n: resource region size
+ *
+ * The described resource region must match a currently busy region.
+ */
+void __release_region(struct resource *parent, resource_size_t start,
+		      resource_size_t n)
+{
+	struct resource **p;
+	resource_size_t end;
+
+	p = &parent->child;
+	end = start + n - 1;
+
+	write_lock(&resource_lock);
+
+	for (;;) {
+		struct resource *res = *p;
+
+		if (!res)
+			break;
+		if (res->start <= start && res->end >= end) {
+			if (!(res->flags & IORESOURCE_BUSY)) {
+				p = &res->child;
+				continue;
+			}
+			if (res->start != start || res->end != end)
+				break;
+			*p = res->sibling;
+			write_unlock(&resource_lock);
+			if (res->flags & IORESOURCE_MUXED)
+				wake_up(&muxed_resource_wait);
+			free_resource(res);
+			return;
+		}
+		p = &res->sibling;
+	}
+
+	write_unlock(&resource_lock);
+
+	printk(KERN_WARNING "Trying to free nonexistent resource "
+		"<%016llx-%016llx>\n", (unsigned long long)start,
+		(unsigned long long)end);
+}
+EXPORT_SYMBOL(__release_region);
+
+#ifdef CONFIG_MEMORY_HOTREMOVE
+/**
+ * release_mem_region_adjustable - release a previously reserved memory region
+ * @start: resource start address
+ * @size: resource region size
+ *
+ * This interface is intended for memory hot-delete.  The requested region
+ * is released from a currently busy memory resource.  The requested region
+ * must either match exactly or fit into a single busy resource entry.  In
+ * the latter case, the remaining resource is adjusted accordingly.
+ * Existing children of the busy memory resource must be immutable in the
+ * request.
+ *
+ * Note:
+ * - Additional release conditions, such as overlapping region, can be
+ *   supported after they are confirmed as valid cases.
+ * - When a busy memory resource gets split into two entries, the code
+ *   assumes that all children remain in the lower address entry for
+ *   simplicity.  Enhance this logic when necessary.
+ */
+void release_mem_region_adjustable(resource_size_t start, resource_size_t size)
+{
+	struct resource *parent = &iomem_resource;
+	struct resource *new_res = NULL;
+	bool alloc_nofail = false;
+	struct resource **p;
+	struct resource *res;
+	resource_size_t end;
+
+	end = start + size - 1;
+	if (WARN_ON_ONCE((start < parent->start) || (end > parent->end)))
+		return;
+
+	/*
+	 * We free up quite a lot of memory on memory hotunplug (esp., memap),
+	 * just before releasing the region. This is highly unlikely to
+	 * fail - let's play save and make it never fail as the caller cannot
+	 * perform any error handling (e.g., trying to re-add memory will fail
+	 * similarly).
+	 */
+retry:
+	new_res = alloc_resource(GFP_KERNEL | (alloc_nofail ? __GFP_NOFAIL : 0));
+
+	p = &parent->child;
+	write_lock(&resource_lock);
+
+	while ((res = *p)) {
+		if (res->start >= end)
+			break;
+
+		/* look for the next resource if it does not fit into */
+		if (res->start > start || res->end < end) {
+			p = &res->sibling;
+			continue;
+		}
+
+		if (!(res->flags & IORESOURCE_MEM))
+			break;
+
+		if (!(res->flags & IORESOURCE_BUSY)) {
+			p = &res->child;
+			continue;
+		}
+
+		/* found the target resource; let's adjust accordingly */
+		if (res->start == start && res->end == end) {
+			/* free the whole entry */
+			*p = res->sibling;
+			free_resource(res);
+		} else if (res->start == start && res->end != end) {
+			/* adjust the start */
+			WARN_ON_ONCE(__adjust_resource(res, end + 1,
+						       res->end - end));
+		} else if (res->start != start && res->end == end) {
+			/* adjust the end */
+			WARN_ON_ONCE(__adjust_resource(res, res->start,
+						       start - res->start));
+		} else {
+			/* split into two entries - we need a new resource */
+			if (!new_res) {
+				new_res = alloc_resource(GFP_ATOMIC);
+				if (!new_res) {
+					alloc_nofail = true;
+					write_unlock(&resource_lock);
+					goto retry;
+				}
+			}
+			new_res->name = res->name;
+			new_res->start = end + 1;
+			new_res->end = res->end;
+			new_res->flags = res->flags;
+			new_res->desc = res->desc;
+			new_res->parent = res->parent;
+			new_res->sibling = res->sibling;
+			new_res->child = NULL;
+
+			if (WARN_ON_ONCE(__adjust_resource(res, res->start,
+							   start - res->start)))
+				break;
+			res->sibling = new_res;
+			new_res = NULL;
+		}
+
+		break;
+	}
+
+	write_unlock(&resource_lock);
+	free_resource(new_res);
+}
+#endif	/* CONFIG_MEMORY_HOTREMOVE */
+
+#ifdef CONFIG_MEMORY_HOTPLUG
+static bool system_ram_resources_mergeable(struct resource *r1,
+					   struct resource *r2)
+{
+	/* We assume either r1 or r2 is IORESOURCE_SYSRAM_MERGEABLE. */
+	return r1->flags == r2->flags && r1->end + 1 == r2->start &&
+	       r1->name == r2->name && r1->desc == r2->desc &&
+	       !r1->child && !r2->child;
+}
+
+/**
+ * merge_system_ram_resource - mark the System RAM resource mergeable and try to
+ *	merge it with adjacent, mergeable resources
+ * @res: resource descriptor
+ *
+ * This interface is intended for memory hotplug, whereby lots of contiguous
+ * system ram resources are added (e.g., via add_memory*()) by a driver, and
+ * the actual resource boundaries are not of interest (e.g., it might be
+ * relevant for DIMMs). Only resources that are marked mergeable, that have the
+ * same parent, and that don't have any children are considered. All mergeable
+ * resources must be immutable during the request.
+ *
+ * Note:
+ * - The caller has to make sure that no pointers to resources that are
+ *   marked mergeable are used anymore after this call - the resource might
+ *   be freed and the pointer might be stale!
+ * - release_mem_region_adjustable() will split on demand on memory hotunplug
+ */
+void merge_system_ram_resource(struct resource *res)
+{
+	const unsigned long flags = IORESOURCE_SYSTEM_RAM | IORESOURCE_BUSY;
+	struct resource *cur;
+
+	if (WARN_ON_ONCE((res->flags & flags) != flags))
+		return;
+
+	write_lock(&resource_lock);
+	res->flags |= IORESOURCE_SYSRAM_MERGEABLE;
+
+	/* Try to merge with next item in the list. */
+	cur = res->sibling;
+	if (cur && system_ram_resources_mergeable(res, cur)) {
+		res->end = cur->end;
+		res->sibling = cur->sibling;
+		free_resource(cur);
+	}
+
+	/* Try to merge with previous item in the list. */
+	cur = res->parent->child;
+	while (cur && cur->sibling != res)
+		cur = cur->sibling;
+	if (cur && system_ram_resources_mergeable(cur, res)) {
+		cur->end = res->end;
+		cur->sibling = res->sibling;
+		free_resource(res);
+	}
+	write_unlock(&resource_lock);
+}
+#endif	/* CONFIG_MEMORY_HOTPLUG */
+
+/*
+ * Managed region resource
+ */
+static void devm_resource_release(struct device *dev, void *ptr)
+{
+	struct resource **r = ptr;
+
+	release_resource(*r);
+}
+
+/**
+ * devm_request_resource() - request and reserve an I/O or memory resource
+ * @dev: device for which to request the resource
+ * @root: root of the resource tree from which to request the resource
+ * @new: descriptor of the resource to request
+ *
+ * This is a device-managed version of request_resource(). There is usually
+ * no need to release resources requested by this function explicitly since
+ * that will be taken care of when the device is unbound from its driver.
+ * If for some reason the resource needs to be released explicitly, because
+ * of ordering issues for example, drivers must call devm_release_resource()
+ * rather than the regular release_resource().
+ *
+ * When a conflict is detected between any existing resources and the newly
+ * requested resource, an error message will be printed.
+ *
+ * Returns 0 on success or a negative error code on failure.
+ */
+int devm_request_resource(struct device *dev, struct resource *root,
+			  struct resource *new)
+{
+	struct resource *conflict, **ptr;
+
+	ptr = devres_alloc(devm_resource_release, sizeof(*ptr), GFP_KERNEL);
+	if (!ptr)
+		return -ENOMEM;
+
+	*ptr = new;
+
+	conflict = request_resource_conflict(root, new);
+	if (conflict) {
+		dev_err(dev, "resource collision: %pR conflicts with %s %pR\n",
+			new, conflict->name, conflict);
+		devres_free(ptr);
+		return -EBUSY;
+	}
+
+	devres_add(dev, ptr);
+	return 0;
+}
+EXPORT_SYMBOL(devm_request_resource);
+
+static int devm_resource_match(struct device *dev, void *res, void *data)
+{
+	struct resource **ptr = res;
+
+	return *ptr == data;
+}
+
+/**
+ * devm_release_resource() - release a previously requested resource
+ * @dev: device for which to release the resource
+ * @new: descriptor of the resource to release
+ *
+ * Releases a resource previously requested using devm_request_resource().
+ */
+void devm_release_resource(struct device *dev, struct resource *new)
+{
+	WARN_ON(devres_release(dev, devm_resource_release, devm_resource_match,
+			       new));
+}
+EXPORT_SYMBOL(devm_release_resource);
+
+struct region_devres {
+	struct resource *parent;
+	resource_size_t start;
+	resource_size_t n;
+};
+
+static void devm_region_release(struct device *dev, void *res)
+{
+	struct region_devres *this = res;
+
+	__release_region(this->parent, this->start, this->n);
+}
+
+static int devm_region_match(struct device *dev, void *res, void *match_data)
+{
+	struct region_devres *this = res, *match = match_data;
+
+	return this->parent == match->parent &&
+		this->start == match->start && this->n == match->n;
+}
+
+struct resource *
+__devm_request_region(struct device *dev, struct resource *parent,
+		      resource_size_t start, resource_size_t n, const char *name)
+{
+	struct region_devres *dr = NULL;
+	struct resource *res;
+
+	dr = devres_alloc(devm_region_release, sizeof(struct region_devres),
+			  GFP_KERNEL);
+	if (!dr)
+		return NULL;
+
+	dr->parent = parent;
+	dr->start = start;
+	dr->n = n;
+
+	res = __request_region(parent, start, n, name, 0);
+	if (res)
+		devres_add(dev, dr);
+	else
+		devres_free(dr);
+
+	return res;
+}
+EXPORT_SYMBOL(__devm_request_region);
+
+void __devm_release_region(struct device *dev, struct resource *parent,
+			   resource_size_t start, resource_size_t n)
+{
+	struct region_devres match_data = { parent, start, n };
+
+	__release_region(parent, start, n);
+	WARN_ON(devres_destroy(dev, devm_region_release, devm_region_match,
+			       &match_data));
+}
+EXPORT_SYMBOL(__devm_release_region);
+
+/*
+ * Reserve I/O ports or memory based on "reserve=" kernel parameter.
+ */
+#define MAXRESERVE 4
+static int __init reserve_setup(char *str)
+{
+	static int reserved;
+	static struct resource reserve[MAXRESERVE];
+
+	for (;;) {
+		unsigned int io_start, io_num;
+		int x = reserved;
+		struct resource *parent;
+
+		if (get_option(&str, &io_start) != 2)
+			break;
+		if (get_option(&str, &io_num) == 0)
+			break;
+		if (x < MAXRESERVE) {
+			struct resource *res = reserve + x;
+
+			/*
+			 * If the region starts below 0x10000, we assume it's
+			 * I/O port space; otherwise assume it's memory.
+			 */
+			if (io_start < 0x10000) {
+				res->flags = IORESOURCE_IO;
+				parent = &ioport_resource;
+			} else {
+				res->flags = IORESOURCE_MEM;
+				parent = &iomem_resource;
+			}
+			res->name = "reserved";
+			res->start = io_start;
+			res->end = io_start + io_num - 1;
+			res->flags |= IORESOURCE_BUSY;
+			res->desc = IORES_DESC_NONE;
+			res->child = NULL;
+			if (request_resource(parent, res) == 0)
+				reserved = x+1;
+		}
+	}
+	return 1;
+}
+__setup("reserve=", reserve_setup);
+
+/*
+ * Check if the requested addr and size spans more than any slot in the
+ * iomem resource tree.
+ */
+int iomem_map_sanity_check(resource_size_t addr, unsigned long size)
+{
+	struct resource *p = &iomem_resource;
+	int err = 0;
+	loff_t l;
+
+	read_lock(&resource_lock);
+	for (p = p->child; p ; p = r_next(NULL, p, &l)) {
+		/*
+		 * We can probably skip the resources without
+		 * IORESOURCE_IO attribute?
+		 */
+		if (p->start >= addr + size)
+			continue;
+		if (p->end < addr)
+			continue;
+		if (PFN_DOWN(p->start) <= PFN_DOWN(addr) &&
+		    PFN_DOWN(p->end) >= PFN_DOWN(addr + size - 1))
+			continue;
+		/*
+		 * if a resource is "BUSY", it's not a hardware resource
+		 * but a driver mapping of such a resource; we don't want
+		 * to warn for those; some drivers legitimately map only
+		 * partial hardware resources. (example: vesafb)
+		 */
+		if (p->flags & IORESOURCE_BUSY)
+			continue;
+
+		printk(KERN_WARNING "resource sanity check: requesting [mem %#010llx-%#010llx], which spans more than %s %pR\n",
+		       (unsigned long long)addr,
+		       (unsigned long long)(addr + size - 1),
+		       p->name, p);
+		err = -1;
+		break;
+	}
+	read_unlock(&resource_lock);
+
+	return err;
+}
+
+#ifdef CONFIG_STRICT_DEVMEM
+static int strict_iomem_checks = 1;
+#else
+static int strict_iomem_checks;
+#endif
+
+/*
+ * Check if an address is exclusive to the kernel and must not be mapped to
+ * user space, for example, via /dev/mem.
+ *
+ * Returns true if exclusive to the kernel, otherwise returns false.
+ */
+bool resource_is_exclusive(struct resource *root, u64 addr, resource_size_t size)
+{
+	const unsigned int exclusive_system_ram = IORESOURCE_SYSTEM_RAM |
+						  IORESOURCE_EXCLUSIVE;
+	bool skip_children = false, err = false;
+	struct resource *p;
+
+	read_lock(&resource_lock);
+	for_each_resource(root, p, skip_children) {
+		if (p->start >= addr + size)
+			break;
+		if (p->end < addr) {
+			skip_children = true;
+			continue;
+		}
+		skip_children = false;
+
+		/*
+		 * IORESOURCE_SYSTEM_RAM resources are exclusive if
+		 * IORESOURCE_EXCLUSIVE is set, even if they
+		 * are not busy and even if "iomem=relaxed" is set. The
+		 * responsible driver dynamically adds/removes system RAM within
+		 * such an area and uncontrolled access is dangerous.
+		 */
+		if ((p->flags & exclusive_system_ram) == exclusive_system_ram) {
+			err = true;
+			break;
+		}
+
+		/*
+		 * A resource is exclusive if IORESOURCE_EXCLUSIVE is set
+		 * or CONFIG_IO_STRICT_DEVMEM is enabled and the
+		 * resource is busy.
+		 */
+		if (!strict_iomem_checks || !(p->flags & IORESOURCE_BUSY))
+			continue;
+		if (IS_ENABLED(CONFIG_IO_STRICT_DEVMEM)
+				|| p->flags & IORESOURCE_EXCLUSIVE) {
+			err = true;
+			break;
+		}
+	}
+	read_unlock(&resource_lock);
+
+	return err;
+}
+
+bool iomem_is_exclusive(u64 addr)
+{
+	return resource_is_exclusive(&iomem_resource, addr & PAGE_MASK,
+				     PAGE_SIZE);
+}
+
+struct resource_entry *resource_list_create_entry(struct resource *res,
+						  size_t extra_size)
+{
+	struct resource_entry *entry;
+
+	entry = kzalloc(sizeof(*entry) + extra_size, GFP_KERNEL);
+	if (entry) {
+		INIT_LIST_HEAD(&entry->node);
+		entry->res = res ? res : &entry->__res;
+	}
+
+	return entry;
+}
+EXPORT_SYMBOL(resource_list_create_entry);
+
+void resource_list_free(struct list_head *head)
+{
+	struct resource_entry *entry, *tmp;
+
+	list_for_each_entry_safe(entry, tmp, head, node)
+		resource_list_destroy_entry(entry);
+}
+EXPORT_SYMBOL(resource_list_free);
+
+#ifdef CONFIG_GET_FREE_REGION
+#define GFR_DESCENDING		(1UL << 0)
+#define GFR_REQUEST_REGION	(1UL << 1)
+#define GFR_DEFAULT_ALIGN (1UL << PA_SECTION_SHIFT)
+
+static resource_size_t gfr_start(struct resource *base, resource_size_t size,
+				 resource_size_t align, unsigned long flags)
+{
+	if (flags & GFR_DESCENDING) {
+		resource_size_t end;
+
+		end = min_t(resource_size_t, base->end,
+			    (1ULL << MAX_PHYSMEM_BITS) - 1);
+		return end - size + 1;
+	}
+
+	return ALIGN(base->start, align);
+}
+
+static bool gfr_continue(struct resource *base, resource_size_t addr,
+			 resource_size_t size, unsigned long flags)
+{
+	if (flags & GFR_DESCENDING)
+		return addr > size && addr >= base->start;
+	/*
+	 * In the ascend case be careful that the last increment by
+	 * @size did not wrap 0.
+	 */
+	return addr > addr - size &&
+	       addr <= min_t(resource_size_t, base->end,
+			     (1ULL << MAX_PHYSMEM_BITS) - 1);
+}
+
+static resource_size_t gfr_next(resource_size_t addr, resource_size_t size,
+				unsigned long flags)
+{
+	if (flags & GFR_DESCENDING)
+		return addr - size;
+	return addr + size;
+}
+
+static void remove_free_mem_region(void *_res)
+{
+	struct resource *res = _res;
+
+	if (res->parent)
+		remove_resource(res);
+	free_resource(res);
+}
+
+static struct resource *
+get_free_mem_region(struct device *dev, struct resource *base,
+		    resource_size_t size, const unsigned long align,
+		    const char *name, const unsigned long desc,
+		    const unsigned long flags)
+{
+	resource_size_t addr;
+	struct resource *res;
+	struct region_devres *dr = NULL;
+
+	size = ALIGN(size, align);
+
+	res = alloc_resource(GFP_KERNEL);
+	if (!res)
+		return ERR_PTR(-ENOMEM);
+
+	if (dev && (flags & GFR_REQUEST_REGION)) {
+		dr = devres_alloc(devm_region_release,
+				sizeof(struct region_devres), GFP_KERNEL);
+		if (!dr) {
+			free_resource(res);
+			return ERR_PTR(-ENOMEM);
+		}
+	} else if (dev) {
+		if (devm_add_action_or_reset(dev, remove_free_mem_region, res))
+			return ERR_PTR(-ENOMEM);
+	}
+
+	write_lock(&resource_lock);
+	for (addr = gfr_start(base, size, align, flags);
+	     gfr_continue(base, addr, size, flags);
+	     addr = gfr_next(addr, size, flags)) {
+		if (__region_intersects(base, addr, size, 0, IORES_DESC_NONE) !=
+		    REGION_DISJOINT)
+			continue;
+
+		if (flags & GFR_REQUEST_REGION) {
+			if (__request_region_locked(res, &iomem_resource, addr,
+						    size, name, 0))
+				break;
+
+			if (dev) {
+				dr->parent = &iomem_resource;
+				dr->start = addr;
+				dr->n = size;
+				devres_add(dev, dr);
+			}
+
+			res->desc = desc;
+			write_unlock(&resource_lock);
+
+
+			/*
+			 * A driver is claiming this region so revoke any
+			 * mappings.
+			 */
+			revoke_iomem(res);
+		} else {
+			res->start = addr;
+			res->end = addr + size - 1;
+			res->name = name;
+			res->desc = desc;
+			res->flags = IORESOURCE_MEM;
+
+			/*
+			 * Only succeed if the resource hosts an exclusive
+			 * range after the insert
+			 */
+			if (__insert_resource(base, res) || res->child)
+				break;
+
+			write_unlock(&resource_lock);
+		}
+
+		return res;
+	}
+	write_unlock(&resource_lock);
+
+	if (flags & GFR_REQUEST_REGION) {
+		free_resource(res);
+		devres_free(dr);
+	} else if (dev)
+		devm_release_action(dev, remove_free_mem_region, res);
+
+	return ERR_PTR(-ERANGE);
+}
+
+/**
+ * devm_request_free_mem_region - find free region for device private memory
+ *
+ * @dev: device struct to bind the resource to
+ * @size: size in bytes of the device memory to add
+ * @base: resource tree to look in
+ *
+ * This function tries to find an empty range of physical address big enough to
+ * contain the new resource, so that it can later be hotplugged as ZONE_DEVICE
+ * memory, which in turn allocates struct pages.
+ */
+struct resource *devm_request_free_mem_region(struct device *dev,
+		struct resource *base, unsigned long size)
+{
+	unsigned long flags = GFR_DESCENDING | GFR_REQUEST_REGION;
+
+	return get_free_mem_region(dev, base, size, GFR_DEFAULT_ALIGN,
+				   dev_name(dev),
+				   IORES_DESC_DEVICE_PRIVATE_MEMORY, flags);
+}
+EXPORT_SYMBOL_GPL(devm_request_free_mem_region);
+
+struct resource *request_free_mem_region(struct resource *base,
+		unsigned long size, const char *name)
+{
+	unsigned long flags = GFR_DESCENDING | GFR_REQUEST_REGION;
+
+	return get_free_mem_region(NULL, base, size, GFR_DEFAULT_ALIGN, name,
+				   IORES_DESC_DEVICE_PRIVATE_MEMORY, flags);
+}
+EXPORT_SYMBOL_GPL(request_free_mem_region);
+
+/**
+ * alloc_free_mem_region - find a free region relative to @base
+ * @base: resource that will parent the new resource
+ * @size: size in bytes of memory to allocate from @base
+ * @align: alignment requirements for the allocation
+ * @name: resource name
+ *
+ * Buses like CXL, that can dynamically instantiate new memory regions,
+ * need a method to allocate physical address space for those regions.
+ * Allocate and insert a new resource to cover a free, unclaimed by a
+ * descendant of @base, range in the span of @base.
+ */
+struct resource *alloc_free_mem_region(struct resource *base,
+				       unsigned long size, unsigned long align,
+				       const char *name)
+{
+	/* Default of ascending direction and insert resource */
+	unsigned long flags = 0;
+
+	return get_free_mem_region(NULL, base, size, align, name,
+				   IORES_DESC_NONE, flags);
+}
+EXPORT_SYMBOL_NS_GPL(alloc_free_mem_region, CXL);
+#endif /* CONFIG_GET_FREE_REGION */
+
+static int __init strict_iomem(char *str)
+{
+	if (strstr(str, "relaxed"))
+		strict_iomem_checks = 0;
+	if (strstr(str, "strict"))
+		strict_iomem_checks = 1;
+	return 1;
+}
+
+static int iomem_fs_init_fs_context(struct fs_context *fc)
+{
+	return init_pseudo(fc, DEVMEM_MAGIC) ? 0 : -ENOMEM;
+}
+
+static struct file_system_type iomem_fs_type = {
+	.name		= "iomem",
+	.owner		= THIS_MODULE,
+	.init_fs_context = iomem_fs_init_fs_context,
+	.kill_sb	= kill_anon_super,
+};
+
+static int __init iomem_init_inode(void)
+{
+	static struct vfsmount *iomem_vfs_mount;
+	static int iomem_fs_cnt;
+	struct inode *inode;
+	int rc;
+
+	rc = simple_pin_fs(&iomem_fs_type, &iomem_vfs_mount, &iomem_fs_cnt);
+	if (rc < 0) {
+		pr_err("Cannot mount iomem pseudo filesystem: %d\n", rc);
+		return rc;
+	}
+
+	inode = alloc_anon_inode(iomem_vfs_mount->mnt_sb);
+	if (IS_ERR(inode)) {
+		rc = PTR_ERR(inode);
+		pr_err("Cannot allocate inode for iomem: %d\n", rc);
+		simple_release_fs(&iomem_vfs_mount, &iomem_fs_cnt);
+		return rc;
+	}
+
+	/*
+	 * Publish iomem revocation inode initialized.
+	 * Pairs with smp_load_acquire() in revoke_iomem().
+	 */
+	smp_store_release(&iomem_inode, inode);
+
+	return 0;
+}
+
+fs_initcall(iomem_init_inode);
+
+__setup("iomem=", strict_iomem);