// SPDX-License-Identifier: GPL-2.0
/*
 *  linux/drivers/base/map.c
 *
 * (C) Copyright Al Viro 2002,2003
 *
 * NOTE: data structure needs to be changed.  It works, but for large dev_t
 * it will be too slow.  It is isolated, though, so these changes will be
 * local to that file.
 */

#include <linux/module.h>
#include <linux/slab.h>
#include <linux/mutex.h>
#include <linux/kdev_t.h>
#include <linux/kobject.h>
#include <linux/kobj_map.h>

struct kobj_map {
        struct probe {
                struct probe *next;
                dev_t dev;
                unsigned long range;
                struct module *owner;
                kobj_probe_t *get;
                int (*lock)(dev_t, void *);
                void *data;
        } *probes[255];
        struct mutex *lock;
};

int kobj_map(struct kobj_map *domain, dev_t dev, unsigned long range,
             struct module *module, kobj_probe_t *probe,
             int (*lock)(dev_t, void *), void *data)
{
        unsigned int n = MAJOR(dev + range - 1) - MAJOR(dev) + 1;
        unsigned int index = MAJOR(dev);
        unsigned int i;
        struct probe *p;

        if (n > 255)
                n = 255;

        p = kmalloc_objs(struct probe, n);
        if (p == NULL)
                return -ENOMEM;

        for (i = 0; i < n; i++, p++) {
                p->owner = module;
                p->get = probe;
                p->lock = lock;
                p->dev = dev;
                p->range = range;
                p->data = data;
        }
        mutex_lock(domain->lock);
        for (i = 0, p -= n; i < n; i++, p++, index++) {
                struct probe **s = &domain->probes[index % 255];
                while (*s && (*s)->range < range)
                        s = &(*s)->next;
                p->next = *s;
                *s = p;
        }
        mutex_unlock(domain->lock);
        return 0;
}

void kobj_unmap(struct kobj_map *domain, dev_t dev, unsigned long range)
{
        unsigned int n = MAJOR(dev + range - 1) - MAJOR(dev) + 1;
        unsigned int index = MAJOR(dev);
        unsigned int i;
        struct probe *found = NULL;

        if (n > 255)
                n = 255;

        mutex_lock(domain->lock);
        for (i = 0; i < n; i++, index++) {
                struct probe **s;
                for (s = &domain->probes[index % 255]; *s; s = &(*s)->next) {
                        struct probe *p = *s;
                        if (p->dev == dev && p->range == range) {
                                *s = p->next;
                                if (!found)
                                        found = p;
                                break;
                        }
                }
        }
        mutex_unlock(domain->lock);
        kfree(found);
}

struct kobject *kobj_lookup(struct kobj_map *domain, dev_t dev, int *index)
{
        struct kobject *kobj;
        struct probe *p;
        unsigned long best = ~0UL;

retry:
        mutex_lock(domain->lock);
        for (p = domain->probes[MAJOR(dev) % 255]; p; p = p->next) {
                struct kobject *(*probe)(dev_t, int *, void *);
                struct module *owner;
                void *data;

                if (p->dev > dev || p->dev + p->range - 1 < dev)
                        continue;
                if (p->range - 1 >= best)
                        break;
                if (!try_module_get(p->owner))
                        continue;
                owner = p->owner;
                data = p->data;
                probe = p->get;
                best = p->range - 1;
                *index = dev - p->dev;
                if (p->lock && p->lock(dev, data) < 0) {
                        module_put(owner);
                        continue;
                }
                mutex_unlock(domain->lock);
                kobj = probe(dev, index, data);
                /* Currently ->owner protects _only_ ->probe() itself. */
                module_put(owner);
                if (kobj)
                        return kobj;
                goto retry;
        }
        mutex_unlock(domain->lock);
        return NULL;
}

struct kobj_map *kobj_map_init(kobj_probe_t *base_probe, struct mutex *lock)
{
        struct kobj_map *p = kmalloc_obj(struct kobj_map);
        struct probe *base = kzalloc_obj(*base);
        int i;

        if ((p == NULL) || (base == NULL)) {
                kfree(p);
                kfree(base);
                return NULL;
        }

        base->dev = 1;
        base->range = ~0;
        base->get = base_probe;
        for (i = 0; i < 255; i++)
                p->probes[i] = base;
        p->lock = lock;
        return p;
}