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class.c

/*
 * class.c - basic device class management
 *
 * Copyright (c) 2002-3 Patrick Mochel
 * Copyright (c) 2002-3 Open Source Development Labs
 * Copyright (c) 2003-2004 Greg Kroah-Hartman
 * Copyright (c) 2003-2004 IBM Corp.
 *
 * This file is released under the GPLv2
 *
 */

#include <linux/device.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/string.h>
#include <linux/kdev_t.h>
#include <linux/err.h>
#include <linux/slab.h>
#include <linux/genhd.h>
#include <linux/mutex.h>
#include "base.h"

#define to_class_attr(_attr) container_of(_attr, struct class_attribute, attr)

static ssize_t class_attr_show(struct kobject *kobj, struct attribute *attr,
                         char *buf)
{
      struct class_attribute *class_attr = to_class_attr(attr);
      struct class_private *cp = to_class(kobj);
      ssize_t ret = -EIO;

      if (class_attr->show)
            ret = class_attr->show(cp->class, buf);
      return ret;
}

static ssize_t class_attr_store(struct kobject *kobj, struct attribute *attr,
                        const char *buf, size_t count)
{
      struct class_attribute *class_attr = to_class_attr(attr);
      struct class_private *cp = to_class(kobj);
      ssize_t ret = -EIO;

      if (class_attr->store)
            ret = class_attr->store(cp->class, buf, count);
      return ret;
}

static void class_release(struct kobject *kobj)
{
      struct class_private *cp = to_class(kobj);
      struct class *class = cp->class;

      pr_debug("class '%s': release.\n", class->name);

      if (class->class_release)
            class->class_release(class);
      else
            pr_debug("class '%s' does not have a release() function, "
                   "be careful\n", class->name);
}

static struct sysfs_ops class_sysfs_ops = {
      .show = class_attr_show,
      .store      = class_attr_store,
};

static struct kobj_type class_ktype = {
      .sysfs_ops  = &class_sysfs_ops,
      .release    = class_release,
};

/* Hotplug events for classes go to the class class_subsys */
static struct kset *class_kset;


int class_create_file(struct class *cls, const struct class_attribute *attr)
{
      int error;
      if (cls)
            error = sysfs_create_file(&cls->p->class_subsys.kobj,
                                &attr->attr);
      else
            error = -EINVAL;
      return error;
}

void class_remove_file(struct class *cls, const struct class_attribute *attr)
{
      if (cls)
            sysfs_remove_file(&cls->p->class_subsys.kobj, &attr->attr);
}

static struct class *class_get(struct class *cls)
{
      if (cls)
            kset_get(&cls->p->class_subsys);
      return cls;
}

static void class_put(struct class *cls)
{
      if (cls)
            kset_put(&cls->p->class_subsys);
}

static int add_class_attrs(struct class *cls)
{
      int i;
      int error = 0;

      if (cls->class_attrs) {
            for (i = 0; attr_name(cls->class_attrs[i]); i++) {
                  error = class_create_file(cls, &cls->class_attrs[i]);
                  if (error)
                        goto error;
            }
      }
done:
      return error;
error:
      while (--i >= 0)
            class_remove_file(cls, &cls->class_attrs[i]);
      goto done;
}

static void remove_class_attrs(struct class *cls)
{
      int i;

      if (cls->class_attrs) {
            for (i = 0; attr_name(cls->class_attrs[i]); i++)
                  class_remove_file(cls, &cls->class_attrs[i]);
      }
}

static void klist_class_dev_get(struct klist_node *n)
{
      struct device *dev = container_of(n, struct device, knode_class);

      get_device(dev);
}

static void klist_class_dev_put(struct klist_node *n)
{
      struct device *dev = container_of(n, struct device, knode_class);

      put_device(dev);
}

int __class_register(struct class *cls, struct lock_class_key *key)
{
      struct class_private *cp;
      int error;

      pr_debug("device class '%s': registering\n", cls->name);

      cp = kzalloc(sizeof(*cp), GFP_KERNEL);
      if (!cp)
            return -ENOMEM;
      klist_init(&cp->class_devices, klist_class_dev_get, klist_class_dev_put);
      INIT_LIST_HEAD(&cp->class_interfaces);
      kset_init(&cp->class_dirs);
      __mutex_init(&cp->class_mutex, "struct class mutex", key);
      error = kobject_set_name(&cp->class_subsys.kobj, "%s", cls->name);
      if (error) {
            kfree(cp);
            return error;
      }

      /* set the default /sys/dev directory for devices of this class */
      if (!cls->dev_kobj)
            cls->dev_kobj = sysfs_dev_char_kobj;

#if defined(CONFIG_SYSFS_DEPRECATED) && defined(CONFIG_BLOCK)
      /* let the block class directory show up in the root of sysfs */
      if (cls != &block_class)
            cp->class_subsys.kobj.kset = class_kset;
#else
      cp->class_subsys.kobj.kset = class_kset;
#endif
      cp->class_subsys.kobj.ktype = &class_ktype;
      cp->class = cls;
      cls->p = cp;

      error = kset_register(&cp->class_subsys);
      if (error) {
            kfree(cp);
            return error;
      }
      error = add_class_attrs(class_get(cls));
      class_put(cls);
      return error;
}
EXPORT_SYMBOL_GPL(__class_register);

void class_unregister(struct class *cls)
{
      pr_debug("device class '%s': unregistering\n", cls->name);
      remove_class_attrs(cls);
      kset_unregister(&cls->p->class_subsys);
}

static void class_create_release(struct class *cls)
{
      pr_debug("%s called for %s\n", __func__, cls->name);
      kfree(cls);
}

/**
 * class_create - create a struct class structure
 * @owner: pointer to the module that is to "own" this struct class
 * @name: pointer to a string for the name of this class.
 * @key: the lock_class_key for this class; used by mutex lock debugging
 *
 * This is used to create a struct class pointer that can then be used
 * in calls to device_create().
 *
 * Note, the pointer created here is to be destroyed when finished by
 * making a call to class_destroy().
 */
struct class *__class_create(struct module *owner, const char *name,
                       struct lock_class_key *key)
{
      struct class *cls;
      int retval;

      cls = kzalloc(sizeof(*cls), GFP_KERNEL);
      if (!cls) {
            retval = -ENOMEM;
            goto error;
      }

      cls->name = name;
      cls->owner = owner;
      cls->class_release = class_create_release;

      retval = __class_register(cls, key);
      if (retval)
            goto error;

      return cls;

error:
      kfree(cls);
      return ERR_PTR(retval);
}
EXPORT_SYMBOL_GPL(__class_create);

/**
 * class_destroy - destroys a struct class structure
 * @cls: pointer to the struct class that is to be destroyed
 *
 * Note, the pointer to be destroyed must have been created with a call
 * to class_create().
 */
void class_destroy(struct class *cls)
{
      if ((cls == NULL) || (IS_ERR(cls)))
            return;

      class_unregister(cls);
}

#ifdef CONFIG_SYSFS_DEPRECATED
char *make_class_name(const char *name, struct kobject *kobj)
{
      char *class_name;
      int size;

      size = strlen(name) + strlen(kobject_name(kobj)) + 2;

      class_name = kmalloc(size, GFP_KERNEL);
      if (!class_name)
            return NULL;

      strcpy(class_name, name);
      strcat(class_name, ":");
      strcat(class_name, kobject_name(kobj));
      return class_name;
}
#endif

/**
 * class_dev_iter_init - initialize class device iterator
 * @iter: class iterator to initialize
 * @class: the class we wanna iterate over
 * @start: the device to start iterating from, if any
 * @type: device_type of the devices to iterate over, NULL for all
 *
 * Initialize class iterator @iter such that it iterates over devices
 * of @class.  If @start is set, the list iteration will start there,
 * otherwise if it is NULL, the iteration starts at the beginning of
 * the list.
 */
void class_dev_iter_init(struct class_dev_iter *iter, struct class *class,
                   struct device *start, const struct device_type *type)
{
      struct klist_node *start_knode = NULL;

      if (start)
            start_knode = &start->knode_class;
      klist_iter_init_node(&class->p->class_devices, &iter->ki, start_knode);
      iter->type = type;
}
EXPORT_SYMBOL_GPL(class_dev_iter_init);

/**
 * class_dev_iter_next - iterate to the next device
 * @iter: class iterator to proceed
 *
 * Proceed @iter to the next device and return it.  Returns NULL if
 * iteration is complete.
 *
 * The returned device is referenced and won't be released till
 * iterator is proceed to the next device or exited.  The caller is
 * free to do whatever it wants to do with the device including
 * calling back into class code.
 */
struct device *class_dev_iter_next(struct class_dev_iter *iter)
{
      struct klist_node *knode;
      struct device *dev;

      while (1) {
            knode = klist_next(&iter->ki);
            if (!knode)
                  return NULL;
            dev = container_of(knode, struct device, knode_class);
            if (!iter->type || iter->type == dev->type)
                  return dev;
      }
}
EXPORT_SYMBOL_GPL(class_dev_iter_next);

/**
 * class_dev_iter_exit - finish iteration
 * @iter: class iterator to finish
 *
 * Finish an iteration.  Always call this function after iteration is
 * complete whether the iteration ran till the end or not.
 */
void class_dev_iter_exit(struct class_dev_iter *iter)
{
      klist_iter_exit(&iter->ki);
}
EXPORT_SYMBOL_GPL(class_dev_iter_exit);

/**
 * class_for_each_device - device iterator
 * @class: the class we're iterating
 * @start: the device to start with in the list, if any.
 * @data: data for the callback
 * @fn: function to be called for each device
 *
 * Iterate over @class's list of devices, and call @fn for each,
 * passing it @data.  If @start is set, the list iteration will start
 * there, otherwise if it is NULL, the iteration starts at the
 * beginning of the list.
 *
 * We check the return of @fn each time. If it returns anything
 * other than 0, we break out and return that value.
 *
 * @fn is allowed to do anything including calling back into class
 * code.  There's no locking restriction.
 */
int class_for_each_device(struct class *class, struct device *start,
                    void *data, int (*fn)(struct device *, void *))
{
      struct class_dev_iter iter;
      struct device *dev;
      int error = 0;

      if (!class)
            return -EINVAL;
      if (!class->p) {
            WARN(1, "%s called for class '%s' before it was initialized",
                 __func__, class->name);
            return -EINVAL;
      }

      class_dev_iter_init(&iter, class, start, NULL);
      while ((dev = class_dev_iter_next(&iter))) {
            error = fn(dev, data);
            if (error)
                  break;
      }
      class_dev_iter_exit(&iter);

      return error;
}
EXPORT_SYMBOL_GPL(class_for_each_device);

/**
 * class_find_device - device iterator for locating a particular device
 * @class: the class we're iterating
 * @start: Device to begin with
 * @data: data for the match function
 * @match: function to check device
 *
 * This is similar to the class_for_each_dev() function above, but it
 * returns a reference to a device that is 'found' for later use, as
 * determined by the @match callback.
 *
 * The callback should return 0 if the device doesn't match and non-zero
 * if it does.  If the callback returns non-zero, this function will
 * return to the caller and not iterate over any more devices.
 *
 * Note, you will need to drop the reference with put_device() after use.
 *
 * @fn is allowed to do anything including calling back into class
 * code.  There's no locking restriction.
 */
struct device *class_find_device(struct class *class, struct device *start,
                         void *data,
                         int (*match)(struct device *, void *))
{
      struct class_dev_iter iter;
      struct device *dev;

      if (!class)
            return NULL;
      if (!class->p) {
            WARN(1, "%s called for class '%s' before it was initialized",
                 __func__, class->name);
            return NULL;
      }

      class_dev_iter_init(&iter, class, start, NULL);
      while ((dev = class_dev_iter_next(&iter))) {
            if (match(dev, data)) {
                  get_device(dev);
                  break;
            }
      }
      class_dev_iter_exit(&iter);

      return dev;
}
EXPORT_SYMBOL_GPL(class_find_device);

int class_interface_register(struct class_interface *class_intf)
{
      struct class *parent;
      struct class_dev_iter iter;
      struct device *dev;

      if (!class_intf || !class_intf->class)
            return -ENODEV;

      parent = class_get(class_intf->class);
      if (!parent)
            return -EINVAL;

      mutex_lock(&parent->p->class_mutex);
      list_add_tail(&class_intf->node, &parent->p->class_interfaces);
      if (class_intf->add_dev) {
            class_dev_iter_init(&iter, parent, NULL, NULL);
            while ((dev = class_dev_iter_next(&iter)))
                  class_intf->add_dev(dev, class_intf);
            class_dev_iter_exit(&iter);
      }
      mutex_unlock(&parent->p->class_mutex);

      return 0;
}

void class_interface_unregister(struct class_interface *class_intf)
{
      struct class *parent = class_intf->class;
      struct class_dev_iter iter;
      struct device *dev;

      if (!parent)
            return;

      mutex_lock(&parent->p->class_mutex);
      list_del_init(&class_intf->node);
      if (class_intf->remove_dev) {
            class_dev_iter_init(&iter, parent, NULL, NULL);
            while ((dev = class_dev_iter_next(&iter)))
                  class_intf->remove_dev(dev, class_intf);
            class_dev_iter_exit(&iter);
      }
      mutex_unlock(&parent->p->class_mutex);

      class_put(parent);
}

int __init classes_init(void)
{
      class_kset = kset_create_and_add("class", NULL, NULL);
      if (!class_kset)
            return -ENOMEM;
      return 0;
}

EXPORT_SYMBOL_GPL(class_create_file);
EXPORT_SYMBOL_GPL(class_remove_file);
EXPORT_SYMBOL_GPL(class_unregister);
EXPORT_SYMBOL_GPL(class_destroy);

EXPORT_SYMBOL_GPL(class_interface_register);
EXPORT_SYMBOL_GPL(class_interface_unregister);

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