root/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.
 */

#undef DEBUG

#include <linux/kobject.h>
#include <linux/string.h>
#include <linux/module.h>
#include <linux/stat.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]); 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);
}


#ifdef CONFIG_HOTPLUG
static int get_kobj_path_length(struct kset *kset, 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 {
                length += strlen(kobject_name(parent)) + 1;
                parent = parent->parent;
        } while (parent);
        return length;
}

static void fill_kobj_path(struct kset *kset, 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);
}

#define BUFFER_SIZE     1024    /* should be enough memory for the env */
#define NUM_ENVP        32      /* number of env pointers */
static unsigned long sequence_num;
static spinlock_t sequence_lock = SPIN_LOCK_UNLOCKED;

static void kset_hotplug(const char *action, struct kset *kset,
                         struct kobject *kobj)
{
        char *argv [3];
        char **envp = NULL;
        char *buffer = NULL;
        char *scratch;
        int i = 0;
        int retval;
        int kobj_path_length;
        char *kobj_path = NULL;
        char *name = NULL;
        unsigned long seq;

        /* If the kset has a filter operation, call it. If it returns
           failure, no hotplug event is required. */
        if (kset->hotplug_ops->filter) {
                if (!kset->hotplug_ops->filter(kset, kobj))
                        return;
        }

        pr_debug ("%s\n", __FUNCTION__);

        if (!hotplug_path[0])
                return;

        envp = kmalloc(NUM_ENVP * sizeof (char *), GFP_KERNEL);
        if (!envp)
                return;
        memset (envp, 0x00, NUM_ENVP * sizeof (char *));

        buffer = kmalloc(BUFFER_SIZE, GFP_KERNEL);
        if (!buffer)
                goto exit;

        if (kset->hotplug_ops->name)
                name = kset->hotplug_ops->name(kset, kobj);
        if (name == NULL)
                name = kset->kobj.name;

        argv [0] = hotplug_path;
        argv [1] = name;
        argv [2] = 0;

        /* minimal command environment */
        envp [i++] = "HOME=/";
        envp [i++] = "PATH=/sbin:/bin:/usr/sbin:/usr/bin";

        scratch = buffer;

        envp [i++] = scratch;
        scratch += sprintf(scratch, "ACTION=%s", action) + 1;

        spin_lock(&sequence_lock);
        seq = sequence_num++;
        spin_unlock(&sequence_lock);

        envp [i++] = scratch;
        scratch += sprintf(scratch, "SEQNUM=%ld", seq) + 1;

        kobj_path_length = get_kobj_path_length (kset, kobj);
        kobj_path = kmalloc (kobj_path_length, GFP_KERNEL);
        if (!kobj_path)
                goto exit;
        memset (kobj_path, 0x00, kobj_path_length);
        fill_kobj_path (kset, kobj, kobj_path, kobj_path_length);

        envp [i++] = scratch;
        scratch += sprintf (scratch, "DEVPATH=%s", kobj_path) + 1;

        if (kset->hotplug_ops->hotplug) {
                /* have the kset specific function add its stuff */
                retval = kset->hotplug_ops->hotplug (kset, kobj,
                                  &envp[i], NUM_ENVP - i, scratch,
                                  BUFFER_SIZE - (scratch - buffer));
                if (retval) {
                        pr_debug ("%s - hotplug() returned %d\n",
                                  __FUNCTION__, retval);
                        goto exit;
                }
        }

        pr_debug ("%s: %s %s %s %s %s %s %s\n", __FUNCTION__, argv[0], argv[1],
                  envp[0], envp[1], envp[2], envp[3], envp[4]);
        retval = call_usermodehelper (argv[0], argv, envp, 0);
        if (retval)
                pr_debug ("%s - call_usermodehelper returned %d\n",
                          __FUNCTION__, retval);

exit:
        kfree(kobj_path);
        kfree(buffer);
        kfree(envp);
        return;
}

void kobject_hotplug(const char *action, struct kobject *kobj)
{
        struct kobject * top_kobj = kobj;

        /* If this kobj does not belong to a kset,
           try to find a parent that does. */
        if (!top_kobj->kset && top_kobj->parent) {
                do {
                        top_kobj = top_kobj->parent;
                } while (!top_kobj->kset && top_kobj->parent);
        }

        if (top_kobj->kset && top_kobj->kset->hotplug_ops)
                kset_hotplug(action, top_kobj->kset, kobj);
}
#else
void kobject_hotplug(const char *action, struct kobject *kobj)
{
        return;
}
#endif  /* CONFIG_HOTPLUG */

/**
 *      kobject_init - initialize object.
 *      @kobj:  object in question.
 */

void kobject_init(struct kobject * kobj)
{
        atomic_set(&kobj->refcount,1);
        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) {
                down_write(&kobj->kset->subsys->rwsem);
                list_del_init(&kobj->entry);
                up_write(&kobj->kset->subsys->rwsem);
        }
        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;
        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) {
                down_write(&kobj->kset->subsys->rwsem);

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

                list_add_tail(&kobj->entry,&kobj->kset->list);
                up_write(&kobj->kset->subsys->rwsem);
        }
        kobj->parent = parent;

        error = create_dir(kobj);
        if (error) {
                unlink(kobj);
                if (parent)
                        kobject_put(parent);
        } else {
                kobject_hotplug("add", kobj);
        }

        return error;
}


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

int kobject_register(struct kobject * kobj)
{
        int error = 0;
        if (kobj) {
                kobject_init(kobj);
                error = kobject_add(kobj);
                if (error) {
                        printk("kobject_register failed for %s (%d)\n",
                               kobject_name(kobj),error);
                        dump_stack();
                }
        } else
                error = -EINVAL;
        return error;
}


/**
 *      kobject_set_name - Set the name of an object
 *      @kobj:  object.
 *      @name:  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;

        va_start(args,fmt);
        /* 
         * First, try the static array 
         */
        need = vsnprintf(kobj->name,limit,fmt,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;
                }
                need = vsnprintf(name,limit,fmt,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:
        va_end(args);
        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, 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)
{
        kobject_hotplug("remove", 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_del(kobj);
        kobject_put(kobj);
}

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

struct kobject * kobject_get(struct kobject * kobj)
{
        if (kobj) {
                WARN_ON(!atomic_read(&kobj->refcount));
                atomic_inc(&kobj->refcount);
        }
        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);
}

/**
 *      kobject_put - decrement refcount for object.
 *      @kobj:  object.
 *
 *      Decrement the refcount, and if 0, call kobject_cleanup().
 */

void kobject_put(struct kobject * kobj)
{
        if (atomic_dec_and_test(&kobj->refcount))
                kobject_cleanup(kobj);
}


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

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


/**
 *      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. Return object if found.
 */

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

        down_read(&kset->subsys->rwsem);
        list_for_each(entry,&kset->list) {
                struct kobject * k = to_kobj(entry);
                if (kobject_name(k) && (!strcmp(kobject_name(k),name))) {
                        ret = k;
                        break;
                }
        }
        up_read(&kset->subsys->rwsem);
        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(kobject_rename);
EXPORT_SYMBOL(kobject_hotplug);

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);