resource.c

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/*
 *  linux/kernel/resource.c
 *
 * Copyright (C) 1999   Linus Torvalds
 * Copyright (C) 1999   Martin Mares <[email protected]>
 *
 * 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/sched.h>
#include <linux/seq_file.h>
#include <linux/device.h>
#include <linux/pfn.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 void *r_next(struct seq_file *m, void *v, loff_t *pos)
{
    struct resource *p = v;
    (*pos)++;
    if (p->child)
        return p->child;
    while (!p->sibling && p->parent)
        p = p->parent;
    return p->sibling;
}

#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 = m->private;
    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 = m->private;
    struct resource *r = v, *p;
    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;
    seq_printf(m, "%*s%0*llx-%0*llx : %s\n",
            depth * 2, "",
            width, (unsigned long long) r->start,
            width, (unsigned long long) r->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 ioports_open(struct inode *inode, struct file *file)
{
    int res = seq_open(file, &resource_op);
    if (!res) {
        struct seq_file *m = file->private_data;
        m->private = &ioport_resource;
    }
    return res;
}

static int iomem_open(struct inode *inode, struct file *file)
{
    int res = seq_open(file, &resource_op);
    if (!res) {
        struct seq_file *m = file->private_data;
        m->private = &iomem_resource;
    }
    return res;
}

static const struct file_operations proc_ioports_operations = {
    .open       = ioports_open,
    .read       = seq_read,
    .llseek     = seq_lseek,
    .release    = seq_release,
};

static const struct file_operations proc_iomem_operations = {
    .open       = iomem_open,
    .read       = seq_read,
    .llseek     = seq_lseek,
    .release    = seq_release,
};

static int __init ioresources_init(void)
{
    proc_create("ioports", 0, NULL, &proc_ioports_operations);
    proc_create("iomem", 0, NULL, &proc_iomem_operations);
    return 0;
}
__initcall(ioresources_init);

#endif /* CONFIG_PROC_FS */

/* 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)
{
    struct resource *tmp, **p;

    p = &old->parent->child;
    for (;;) {
        tmp = *p;
        if (!tmp)
            break;
        if (tmp == old) {
            *p = 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);
}

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;
}

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);

int release_resource(struct resource *old)
{
    int retval;

    write_lock(&resource_lock);
    retval = __release_resource(old);
    write_unlock(&resource_lock);
    return retval;
}

EXPORT_SYMBOL(release_resource);

#if !defined(CONFIG_ARCH_HAS_WALK_MEMORY)
/*
 * Finds the lowest memory reosurce exists within [res->start.res->end)
 * the caller must specify res->start, res->end, res->flags and "name".
 * If found, returns 0, res is overwritten, if not found, returns -1.
 */
static int find_next_system_ram(struct resource *res, char *name)
{
    resource_size_t start, end;
    struct resource *p;

    BUG_ON(!res);

    start = res->start;
    end = res->end;
    BUG_ON(start >= end);

    read_lock(&resource_lock);
    for (p = iomem_resource.child; p ; p = p->sibling) {
        /* system ram is just marked as IORESOURCE_MEM */
        if (p->flags != res->flags)
            continue;
        if (name && strcmp(p->name, name))
            continue;
        if (p->start > end) {
            p = NULL;
            break;
        }
        if ((p->end >= start) && (p->start < end))
            break;
    }
    read_unlock(&resource_lock);
    if (!p)
        return -1;
    /* copy data */
    if (res->start < p->start)
        res->start = p->start;
    if (res->end > p->end)
        res->end = p->end;
    return 0;
}

/*
 * This function calls callback against all memory range of "System RAM"
 * which are marked as IORESOURCE_MEM and IORESOUCE_BUSY.
 * Now, this function is 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 *))
{
    struct resource res;
    unsigned long pfn, end_pfn;
    u64 orig_end;
    int ret = -1;

    res.start = (u64) start_pfn << PAGE_SHIFT;
    res.end = ((u64)(start_pfn + nr_pages) << PAGE_SHIFT) - 1;
    res.flags = IORESOURCE_MEM | IORESOURCE_BUSY;
    orig_end = res.end;
    while ((res.start < res.end) &&
        (find_next_system_ram(&res, "System RAM") >= 0)) {
        pfn = (res.start + PAGE_SIZE - 1) >> PAGE_SHIFT;
        end_pfn = (res.end + 1) >> PAGE_SHIFT;
        if (end_pfn > pfn)
            ret = (*func)(pfn, end_pfn - pfn, arg);
        if (ret)
            break;
        res.start = res.end + 1;
        res.end = orig_end;
    }
    return ret;
}

#endif

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;
}

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;
}

static bool resource_contains(struct resource *res1, struct resource *res2)
{
    return res1->start <= res2->start && res1->end >= res2->end;
}

/*
 * 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.flags = new->flags;
    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 = *new;
        avail.start = ALIGN(tmp.start, constraint->align);
        avail.end = tmp.end;
        if (avail.start >= tmp.start) {
            alloc.start = constraint->alignf(constraint->alignf_data, &avail,
                    size, constraint->align);
            alloc.end = alloc.start + size - 1;
            if (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);
}

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);
        *old = new;
        conflict = __request_resource(root, old);
        BUG_ON(conflict);
    }
out:
    write_unlock(&resource_lock);
    return err;
}


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);

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;
}

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;
}

int insert_resource(struct resource *parent, struct resource *new)
{
    struct resource *conflict;

    conflict = insert_resource_conflict(parent, new);
    return conflict ? -EBUSY : 0;
}

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);
}

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;

    write_lock(&resource_lock);

    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:
    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 = kzalloc(sizeof(*res), GFP_ATOMIC);
    struct resource *next_res = NULL;

    if (!res)
        return;

    res->name = name;
    res->start = start;
    res->end = end;
    res->flags = IORESOURCE_BUSY;

    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) {
            kfree(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 = kzalloc(sizeof(*next_res),
                        GFP_ATOMIC);
                if (!next_res) {
                    kfree(res);
                    break;
                }
                next_res->name = name;
                next_res->start = conflict->end + 1;
                next_res->end = end;
                next_res->flags = IORESOURCE_BUSY;
            }
        } 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_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.
 *
 * check_region returns non-zero if the area is already busy.
 *
 * release_region releases a matching busy region.
 */

static DECLARE_WAIT_QUEUE_HEAD(muxed_resource_wait);

struct resource * __request_region(struct resource *parent,
                   resource_size_t start, resource_size_t n,
                   const char *name, int flags)
{
    DECLARE_WAITQUEUE(wait, current);
    struct resource *res = kzalloc(sizeof(*res), GFP_KERNEL);

    if (!res)
        return NULL;

    res->name = name;
    res->start = start;
    res->end = start + n - 1;
    res->flags = IORESOURCE_BUSY;
    res->flags |= flags;

    write_lock(&resource_lock);

    for (;;) {
        struct resource *conflict;

        conflict = __request_resource(parent, res);
        if (!conflict)
            break;
        if (conflict != parent) {
            parent = conflict;
            if (!(conflict->flags & IORESOURCE_BUSY))
                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.. */
        kfree(res);
        res = NULL;
        break;
    }
    write_unlock(&resource_lock);
    return res;
}
EXPORT_SYMBOL(__request_region);

int __check_region(struct resource *parent, resource_size_t start,
            resource_size_t n)
{
    struct resource * res;

    res = __request_region(parent, start, n, "check-region", 0);
    if (!res)
        return -EBUSY;

    release_resource(res);
    kfree(res);
    return 0;
}
EXPORT_SYMBOL(__check_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);
            kfree(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);

/*
 * Managed region 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);

/*
 * Called from init/main.c to reserve IO ports.
 */
#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;

        if (get_option (&str, &io_start) != 2)
            break;
        if (get_option (&str, &io_num)   == 0)
            break;
        if (x < MAXRESERVE) {
            struct resource *res = reserve + x;
            res->name = "reserved";
            res->start = io_start;
            res->end = io_start + io_num - 1;
            res->flags = IORESOURCE_BUSY;
            res->child = NULL;
            if (request_resource(res->start >= 0x10000 ? &iomem_resource : &ioport_resource, 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 map sanity check conflict: "
               "0x%llx 0x%llx 0x%llx 0x%llx %s\n",
               (unsigned long long)addr,
               (unsigned long long)(addr + size - 1),
               (unsigned long long)p->start,
               (unsigned long long)p->end,
               p->name);
        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 reserved in the iomem resource tree
 * returns 1 if reserved, 0 if not reserved.
 */
int iomem_is_exclusive(u64 addr)
{
    struct resource *p = &iomem_resource;
    int err = 0;
    loff_t l;
    int size = PAGE_SIZE;

    if (!strict_iomem_checks)
        return 0;

    addr = addr & PAGE_MASK;

    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)
            break;
        if (p->end < addr)
            continue;
        if (p->flags & IORESOURCE_BUSY &&
             p->flags & IORESOURCE_EXCLUSIVE) {
            err = 1;
            break;
        }
    }
    read_unlock(&resource_lock);

    return err;
}

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;
}

__setup("iomem=", strict_iomem);