[PATCH] Kobject: provide better warning messages when people do stupid things

[linux-2.6/x86.git] / lib / kobject.c

/*
 * kobject.c - library routines for handling generic kernel objects
 *
 * Copyright (c) 2002-2003 Patrick Mochel <mochel@osdl.org>
 *
 * This file is released under the GPLv2.
 *
 *
 * Please see the file Documentation/kobject.txt for critical information
 * about using the kobject interface.
 */

#include <linux/kobject.h>
#include <linux/string.h>
#include <linux/module.h>
#include <linux/stat.h>
#include <linux/slab.h>

/**
 *      populate_dir - populate directory with attributes.
 *      @kobj:  object we're working on.
 *
 *      Most subsystems have a set of default attributes that 
 *      are associated with an object that registers with them.
 *      This is a helper called during object registration that 
 *      loops through the default attributes of the subsystem 
 *      and creates attributes files for them in sysfs.
 *
 */

static int populate_dir(struct kobject * kobj)
{
        struct kobj_type * t = get_ktype(kobj);
        struct attribute * attr;
        int error = 0;
        int i;
        
        if (t && t->default_attrs) {
                for (i = 0; (attr = t->default_attrs[i]) != NULL; i++) {
                        if ((error = sysfs_create_file(kobj,attr)))
                                break;
                }
        }
        return error;
}

static int create_dir(struct kobject * kobj)
{
        int error = 0;
        if (kobject_name(kobj)) {
                error = sysfs_create_dir(kobj);
                if (!error) {
                        if ((error = populate_dir(kobj)))
                                sysfs_remove_dir(kobj);
                }
        }
        return error;
}

static inline struct kobject * to_kobj(struct list_head * entry)
{
        return container_of(entry,struct kobject,entry);
}

static int get_kobj_path_length(struct kobject *kobj)
{
        int length = 1;
        struct kobject * parent = kobj;

        /* walk up the ancestors until we hit the one pointing to the 
         * root.
         * Add 1 to strlen for leading '/' of each level.
         */
        do {
                if (kobject_name(parent) == NULL)
                        return 0;
                length += strlen(kobject_name(parent)) + 1;
                parent = parent->parent;
        } while (parent);
        return length;
}

static void fill_kobj_path(struct kobject *kobj, char *path, int length)
{
        struct kobject * parent;

        --length;
        for (parent = kobj; parent; parent = parent->parent) {
                int cur = strlen(kobject_name(parent));
                /* back up enough to print this name with '/' */
                length -= cur;
                strncpy (path + length, kobject_name(parent), cur);
                *(path + --length) = '/';
        }

        pr_debug("%s: path = '%s'\n",__FUNCTION__,path);
}

/**
 * kobject_get_path - generate and return the path associated with a given kobj
 * and kset pair.  The result must be freed by the caller with kfree().
 *
 * @kobj:       kobject in question, with which to build the path
 * @gfp_mask:   the allocation type used to allocate the path
 */
char *kobject_get_path(struct kobject *kobj, gfp_t gfp_mask)
{
        char *path;
        int len;

        len = get_kobj_path_length(kobj);
        if (len == 0)
                return NULL;
        path = kmalloc(len, gfp_mask);
        if (!path)
                return NULL;
        memset(path, 0x00, len);
        fill_kobj_path(kobj, path, len);

        return path;
}

/**
 *      kobject_init - initialize object.
 *      @kobj:  object in question.
 */
void kobject_init(struct kobject * kobj)
{
        kref_init(&kobj->kref);
        INIT_LIST_HEAD(&kobj->entry);
        kobj->kset = kset_get(kobj->kset);
}


/**
 *      unlink - remove kobject from kset list.
 *      @kobj:  kobject.
 *
 *      Remove the kobject from the kset list and decrement
 *      its parent's refcount.
 *      This is separated out, so we can use it in both 
 *      kobject_del() and kobject_add() on error.
 */

static void unlink(struct kobject * kobj)
{
        if (kobj->kset) {
                spin_lock(&kobj->kset->list_lock);
                list_del_init(&kobj->entry);
                spin_unlock(&kobj->kset->list_lock);
        }
        kobject_put(kobj);
}

/**
 *      kobject_add - add an object to the hierarchy.
 *      @kobj:  object.
 */

int kobject_add(struct kobject * kobj)
{
        int error = 0;
        struct kobject * parent;

        if (!(kobj = kobject_get(kobj)))
                return -ENOENT;
        if (!kobj->k_name)
                kobj->k_name = kobj->name;
        if (!kobj->k_name) {
                pr_debug("kobject attempted to be registered with no name!\n");
                WARN_ON(1);
                return -EINVAL;
        }
        parent = kobject_get(kobj->parent);

        pr_debug("kobject %s: registering. parent: %s, set: %s\n",
                 kobject_name(kobj), parent ? kobject_name(parent) : "<NULL>", 
                 kobj->kset ? kobj->kset->kobj.name : "<NULL>" );

        if (kobj->kset) {
                spin_lock(&kobj->kset->list_lock);

                if (!parent)
                        parent = kobject_get(&kobj->kset->kobj);

                list_add_tail(&kobj->entry,&kobj->kset->list);
                spin_unlock(&kobj->kset->list_lock);
        }
        kobj->parent = parent;

        error = create_dir(kobj);
        if (error) {
                /* unlink does the kobject_put() for us */
                unlink(kobj);
                if (parent)
                        kobject_put(parent);

                /* be noisy on error issues */
                if (error == -EEXIST)
                        printk("kobject_add failed for %s with -EEXIST, "
                               "don't try to register things with the "
                               "same name in the same directory.\n",
                               kobject_name(kobj));
                else
                        printk("kobject_add failed for %s (%d)\n",
                               kobject_name(kobj), error);
                dump_stack();
        }

        return error;
}


/**
 *      kobject_register - initialize and add an object.
 *      @kobj:  object in question.
 */

int kobject_register(struct kobject * kobj)
{
        int error = -EINVAL;
        if (kobj) {
                kobject_init(kobj);
                error = kobject_add(kobj);
                if (!error)
                        kobject_uevent(kobj, KOBJ_ADD);
        }
        return error;
}


/**
 *      kobject_set_name - Set the name of an object
 *      @kobj:  object.
 *      @fmt:   format string used to build the name
 *
 *      If strlen(name) >= KOBJ_NAME_LEN, then use a dynamically allocated
 *      string that @kobj->k_name points to. Otherwise, use the static 
 *      @kobj->name array.
 */
int kobject_set_name(struct kobject * kobj, const char * fmt, ...)
{
        int error = 0;
        int limit = KOBJ_NAME_LEN;
        int need;
        va_list args;
        char * name;

        /* 
         * First, try the static array 
         */
        va_start(args,fmt);
        need = vsnprintf(kobj->name,limit,fmt,args);
        va_end(args);
        if (need < limit) 
                name = kobj->name;
        else {
                /* 
                 * Need more space? Allocate it and try again 
                 */
                limit = need + 1;
                name = kmalloc(limit,GFP_KERNEL);
                if (!name) {
                        error = -ENOMEM;
                        goto Done;
                }
                va_start(args,fmt);
                need = vsnprintf(name,limit,fmt,args);
                va_end(args);

                /* Still? Give up. */
                if (need >= limit) {
                        kfree(name);
                        error = -EFAULT;
                        goto Done;
                }
        }

        /* Free the old name, if necessary. */
        if (kobj->k_name && kobj->k_name != kobj->name)
                kfree(kobj->k_name);

        /* Now, set the new name */
        kobj->k_name = name;
 Done:
        return error;
}

EXPORT_SYMBOL(kobject_set_name);


/**
 *      kobject_rename - change the name of an object
 *      @kobj:  object in question.
 *      @new_name: object's new name
 */

int kobject_rename(struct kobject * kobj, const char *new_name)
{
        int error = 0;

        kobj = kobject_get(kobj);
        if (!kobj)
                return -EINVAL;
        error = sysfs_rename_dir(kobj, new_name);
        kobject_put(kobj);

        return error;
}

/**
 *      kobject_del - unlink kobject from hierarchy.
 *      @kobj:  object.
 */

void kobject_del(struct kobject * kobj)
{
        sysfs_remove_dir(kobj);
        unlink(kobj);
}

/**
 *      kobject_unregister - remove object from hierarchy and decrement refcount.
 *      @kobj:  object going away.
 */

void kobject_unregister(struct kobject * kobj)
{
        pr_debug("kobject %s: unregistering\n",kobject_name(kobj));
        kobject_uevent(kobj, KOBJ_REMOVE);
        kobject_del(kobj);
        kobject_put(kobj);
}

/**
 *      kobject_get - increment refcount for object.
 *      @kobj:  object.
 */

struct kobject * kobject_get(struct kobject * kobj)
{
        if (kobj)
                kref_get(&kobj->kref);
        return kobj;
}

/**
 *      kobject_cleanup - free kobject resources. 
 *      @kobj:  object.
 */

void kobject_cleanup(struct kobject * kobj)
{
        struct kobj_type * t = get_ktype(kobj);
        struct kset * s = kobj->kset;
        struct kobject * parent = kobj->parent;

        pr_debug("kobject %s: cleaning up\n",kobject_name(kobj));
        if (kobj->k_name != kobj->name)
                kfree(kobj->k_name);
        kobj->k_name = NULL;
        if (t && t->release)
                t->release(kobj);
        if (s)
                kset_put(s);
        if (parent) 
                kobject_put(parent);
}

static void kobject_release(struct kref *kref)
{
        kobject_cleanup(container_of(kref, struct kobject, kref));
}

/**
 *      kobject_put - decrement refcount for object.
 *      @kobj:  object.
 *
 *      Decrement the refcount, and if 0, call kobject_cleanup().
 */
void kobject_put(struct kobject * kobj)
{
        if (kobj)
                kref_put(&kobj->kref, kobject_release);
}


/**
 *      kset_init - initialize a kset for use
 *      @k:     kset 
 */

void kset_init(struct kset * k)
{
        kobject_init(&k->kobj);
        INIT_LIST_HEAD(&k->list);
        spin_lock_init(&k->list_lock);
}


/**
 *      kset_add - add a kset object to the hierarchy.
 *      @k:     kset.
 *
 *      Simply, this adds the kset's embedded kobject to the 
 *      hierarchy. 
 *      We also try to make sure that the kset's embedded kobject
 *      has a parent before it is added. We only care if the embedded
 *      kobject is not part of a kset itself, since kobject_add()
 *      assigns a parent in that case. 
 *      If that is the case, and the kset has a controlling subsystem,
 *      then we set the kset's parent to be said subsystem. 
 */

int kset_add(struct kset * k)
{
        if (!k->kobj.parent && !k->kobj.kset && k->subsys)
                k->kobj.parent = &k->subsys->kset.kobj;

        return kobject_add(&k->kobj);
}


/**
 *      kset_register - initialize and add a kset.
 *      @k:     kset.
 */

int kset_register(struct kset * k)
{
        kset_init(k);
        return kset_add(k);
}


/**
 *      kset_unregister - remove a kset.
 *      @k:     kset.
 */

void kset_unregister(struct kset * k)
{
        kobject_unregister(&k->kobj);
}


/**
 *      kset_find_obj - search for object in kset.
 *      @kset:  kset we're looking in.
 *      @name:  object's name.
 *
 *      Lock kset via @kset->subsys, and iterate over @kset->list,
 *      looking for a matching kobject. If matching object is found
 *      take a reference and return the object.
 */

struct kobject * kset_find_obj(struct kset * kset, const char * name)
{
        struct list_head * entry;
        struct kobject * ret = NULL;

        spin_lock(&kset->list_lock);
        list_for_each(entry,&kset->list) {
                struct kobject * k = to_kobj(entry);
                if (kobject_name(k) && !strcmp(kobject_name(k),name)) {
                        ret = kobject_get(k);
                        break;
                }
        }
        spin_unlock(&kset->list_lock);
        return ret;
}


void subsystem_init(struct subsystem * s)
{
        init_rwsem(&s->rwsem);
        kset_init(&s->kset);
}

/**
 *      subsystem_register - register a subsystem.
 *      @s:     the subsystem we're registering.
 *
 *      Once we register the subsystem, we want to make sure that 
 *      the kset points back to this subsystem for correct usage of 
 *      the rwsem. 
 */

int subsystem_register(struct subsystem * s)
{
        int error;

        subsystem_init(s);
        pr_debug("subsystem %s: registering\n",s->kset.kobj.name);

        if (!(error = kset_add(&s->kset))) {
                if (!s->kset.subsys)
                        s->kset.subsys = s;
        }
        return error;
}

void subsystem_unregister(struct subsystem * s)
{
        pr_debug("subsystem %s: unregistering\n",s->kset.kobj.name);
        kset_unregister(&s->kset);
}


/**
 *      subsystem_create_file - export sysfs attribute file.
 *      @s:     subsystem.
 *      @a:     subsystem attribute descriptor.
 */

int subsys_create_file(struct subsystem * s, struct subsys_attribute * a)
{
        int error = 0;
        if (subsys_get(s)) {
                error = sysfs_create_file(&s->kset.kobj,&a->attr);
                subsys_put(s);
        }
        return error;
}


/**
 *      subsystem_remove_file - remove sysfs attribute file.
 *      @s:     subsystem.
 *      @a:     attribute desciptor.
 */

void subsys_remove_file(struct subsystem * s, struct subsys_attribute * a)
{
        if (subsys_get(s)) {
                sysfs_remove_file(&s->kset.kobj,&a->attr);
                subsys_put(s);
        }
}

EXPORT_SYMBOL(kobject_init);
EXPORT_SYMBOL(kobject_register);
EXPORT_SYMBOL(kobject_unregister);
EXPORT_SYMBOL(kobject_get);
EXPORT_SYMBOL(kobject_put);
EXPORT_SYMBOL(kobject_add);
EXPORT_SYMBOL(kobject_del);

EXPORT_SYMBOL(kset_register);
EXPORT_SYMBOL(kset_unregister);
EXPORT_SYMBOL(kset_find_obj);

EXPORT_SYMBOL(subsystem_init);
EXPORT_SYMBOL(subsystem_register);
EXPORT_SYMBOL(subsystem_unregister);
EXPORT_SYMBOL(subsys_create_file);
EXPORT_SYMBOL(subsys_remove_file);