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core.c

/*
 * drivers/base/core.c - core driver model code (device registration, etc)
 *
 * Copyright (c) 2002-3 Patrick Mochel
 * Copyright (c) 2002-3 Open Source Development Labs
 * Copyright (c) 2006 Greg Kroah-Hartman <gregkh@suse.de>
 * Copyright (c) 2006 Novell, Inc.
 *
 * This file is released under the GPLv2
 *
 */

#include <linux/device.h>
#include <linux/err.h>
#include <linux/init.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/string.h>
#include <linux/kdev_t.h>
#include <linux/notifier.h>

#include <asm/semaphore.h>

#include "base.h"
#include "power/power.h"

int (*platform_notify)(struct device * dev) = NULL;
int (*platform_notify_remove)(struct device * dev) = NULL;

/*
 * sysfs bindings for devices.
 */

/**
 * dev_driver_string - Return a device's driver name, if at all possible
 * @dev: struct device to get the name of
 *
 * Will return the device's driver's name if it is bound to a device.  If
 * the device is not bound to a device, it will return the name of the bus
 * it is attached to.  If it is not attached to a bus either, an empty
 * string will be returned.
 */
const char *dev_driver_string(struct device *dev)
{
      return dev->driver ? dev->driver->name :
                  (dev->bus ? dev->bus->name :
                  (dev->class ? dev->class->name : ""));
}
EXPORT_SYMBOL(dev_driver_string);

#define to_dev(obj) container_of(obj, struct device, kobj)
#define to_dev_attr(_attr) container_of(_attr, struct device_attribute, attr)

static ssize_t
dev_attr_show(struct kobject * kobj, struct attribute * attr, char * buf)
{
      struct device_attribute * dev_attr = to_dev_attr(attr);
      struct device * dev = to_dev(kobj);
      ssize_t ret = -EIO;

      if (dev_attr->show)
            ret = dev_attr->show(dev, dev_attr, buf);
      return ret;
}

static ssize_t
dev_attr_store(struct kobject * kobj, struct attribute * attr,
             const char * buf, size_t count)
{
      struct device_attribute * dev_attr = to_dev_attr(attr);
      struct device * dev = to_dev(kobj);
      ssize_t ret = -EIO;

      if (dev_attr->store)
            ret = dev_attr->store(dev, dev_attr, buf, count);
      return ret;
}

static struct sysfs_ops dev_sysfs_ops = {
      .show = dev_attr_show,
      .store      = dev_attr_store,
};


/**
 *    device_release - free device structure.
 *    @kobj:      device's kobject.
 *
 *    This is called once the reference count for the object
 *    reaches 0. We forward the call to the device's release
 *    method, which should handle actually freeing the structure.
 */
static void device_release(struct kobject * kobj)
{
      struct device * dev = to_dev(kobj);

      if (dev->release)
            dev->release(dev);
      else if (dev->type && dev->type->release)
            dev->type->release(dev);
      else if (dev->class && dev->class->dev_release)
            dev->class->dev_release(dev);
      else {
            printk(KERN_ERR "Device '%s' does not have a release() function, "
                  "it is broken and must be fixed.\n",
                  dev->bus_id);
            WARN_ON(1);
      }
}

static struct kobj_type device_ktype = {
      .release    = device_release,
      .sysfs_ops  = &dev_sysfs_ops,
};


static int dev_uevent_filter(struct kset *kset, struct kobject *kobj)
{
      struct kobj_type *ktype = get_ktype(kobj);

      if (ktype == &device_ktype) {
            struct device *dev = to_dev(kobj);
            if (dev->uevent_suppress)
                  return 0;
            if (dev->bus)
                  return 1;
            if (dev->class)
                  return 1;
      }
      return 0;
}

static const char *dev_uevent_name(struct kset *kset, struct kobject *kobj)
{
      struct device *dev = to_dev(kobj);

      if (dev->bus)
            return dev->bus->name;
      if (dev->class)
            return dev->class->name;
      return NULL;
}

static int dev_uevent(struct kset *kset, struct kobject *kobj,
                  struct kobj_uevent_env *env)
{
      struct device *dev = to_dev(kobj);
      int retval = 0;

      /* add the major/minor if present */
      if (MAJOR(dev->devt)) {
            add_uevent_var(env, "MAJOR=%u", MAJOR(dev->devt));
            add_uevent_var(env, "MINOR=%u", MINOR(dev->devt));
      }

      if (dev->type && dev->type->name)
            add_uevent_var(env, "DEVTYPE=%s", dev->type->name);

      if (dev->driver)
            add_uevent_var(env, "DRIVER=%s", dev->driver->name);

#ifdef CONFIG_SYSFS_DEPRECATED
      if (dev->class) {
            struct device *parent = dev->parent;

            /* find first bus device in parent chain */
            while (parent && !parent->bus)
                  parent = parent->parent;
            if (parent && parent->bus) {
                  const char *path;

                  path = kobject_get_path(&parent->kobj, GFP_KERNEL);
                  if (path) {
                        add_uevent_var(env, "PHYSDEVPATH=%s", path);
                        kfree(path);
                  }

                  add_uevent_var(env, "PHYSDEVBUS=%s", parent->bus->name);

                  if (parent->driver)
                        add_uevent_var(env, "PHYSDEVDRIVER=%s",
                                     parent->driver->name);
            }
      } else if (dev->bus) {
            add_uevent_var(env, "PHYSDEVBUS=%s", dev->bus->name);

            if (dev->driver)
                  add_uevent_var(env, "PHYSDEVDRIVER=%s", dev->driver->name);
      }
#endif

      /* have the bus specific function add its stuff */
      if (dev->bus && dev->bus->uevent) {
            retval = dev->bus->uevent(dev, env);
            if (retval)
                  pr_debug ("%s: bus uevent() returned %d\n",
                          __FUNCTION__, retval);
      }

      /* have the class specific function add its stuff */
      if (dev->class && dev->class->dev_uevent) {
            retval = dev->class->dev_uevent(dev, env);
            if (retval)
                  pr_debug("%s: class uevent() returned %d\n",
                         __FUNCTION__, retval);
      }

      /* have the device type specific fuction add its stuff */
      if (dev->type && dev->type->uevent) {
            retval = dev->type->uevent(dev, env);
            if (retval)
                  pr_debug("%s: dev_type uevent() returned %d\n",
                         __FUNCTION__, retval);
      }

      return retval;
}

static struct kset_uevent_ops device_uevent_ops = {
      .filter =   dev_uevent_filter,
      .name =           dev_uevent_name,
      .uevent =   dev_uevent,
};

static ssize_t show_uevent(struct device *dev, struct device_attribute *attr,
                     char *buf)
{
      struct kobject *top_kobj;
      struct kset *kset;
      struct kobj_uevent_env *env = NULL;
      int i;
      size_t count = 0;
      int retval;

      /* search the kset, the device belongs to */
      top_kobj = &dev->kobj;
      while (!top_kobj->kset && top_kobj->parent)
            top_kobj = top_kobj->parent;
      if (!top_kobj->kset)
            goto out;

      kset = top_kobj->kset;
      if (!kset->uevent_ops || !kset->uevent_ops->uevent)
            goto out;

      /* respect filter */
      if (kset->uevent_ops && kset->uevent_ops->filter)
            if (!kset->uevent_ops->filter(kset, &dev->kobj))
                  goto out;

      env = kzalloc(sizeof(struct kobj_uevent_env), GFP_KERNEL);
      if (!env)
            return -ENOMEM;

      /* let the kset specific function add its keys */
      retval = kset->uevent_ops->uevent(kset, &dev->kobj, env);
      if (retval)
            goto out;

      /* copy keys to file */
      for (i = 0; i < env->envp_idx; i++)
            count += sprintf(&buf[count], "%s\n", env->envp[i]);
out:
      kfree(env);
      return count;
}

static ssize_t store_uevent(struct device *dev, struct device_attribute *attr,
                      const char *buf, size_t count)
{
      enum kobject_action action;

      if (kobject_action_type(buf, count, &action) == 0) {
            kobject_uevent(&dev->kobj, action);
            goto out;
      }

      dev_err(dev, "uevent: unsupported action-string; this will "
                 "be ignored in a future kernel version\n");
      kobject_uevent(&dev->kobj, KOBJ_ADD);
out:
      return count;
}

static struct device_attribute uevent_attr =
      __ATTR(uevent, S_IRUGO | S_IWUSR, show_uevent, store_uevent);

static int device_add_attributes(struct device *dev,
                         struct device_attribute *attrs)
{
      int error = 0;
      int i;

      if (attrs) {
            for (i = 0; attr_name(attrs[i]); i++) {
                  error = device_create_file(dev, &attrs[i]);
                  if (error)
                        break;
            }
            if (error)
                  while (--i >= 0)
                        device_remove_file(dev, &attrs[i]);
      }
      return error;
}

static void device_remove_attributes(struct device *dev,
                             struct device_attribute *attrs)
{
      int i;

      if (attrs)
            for (i = 0; attr_name(attrs[i]); i++)
                  device_remove_file(dev, &attrs[i]);
}

static int device_add_groups(struct device *dev,
                       struct attribute_group **groups)
{
      int error = 0;
      int i;

      if (groups) {
            for (i = 0; groups[i]; i++) {
                  error = sysfs_create_group(&dev->kobj, groups[i]);
                  if (error) {
                        while (--i >= 0)
                              sysfs_remove_group(&dev->kobj, groups[i]);
                        break;
                  }
            }
      }
      return error;
}

static void device_remove_groups(struct device *dev,
                         struct attribute_group **groups)
{
      int i;

      if (groups)
            for (i = 0; groups[i]; i++)
                  sysfs_remove_group(&dev->kobj, groups[i]);
}

static int device_add_attrs(struct device *dev)
{
      struct class *class = dev->class;
      struct device_type *type = dev->type;
      int error;

      if (class) {
            error = device_add_attributes(dev, class->dev_attrs);
            if (error)
                  return error;
      }

      if (type) {
            error = device_add_groups(dev, type->groups);
            if (error)
                  goto err_remove_class_attrs;
      }

      error = device_add_groups(dev, dev->groups);
      if (error)
            goto err_remove_type_groups;

      return 0;

 err_remove_type_groups:
      if (type)
            device_remove_groups(dev, type->groups);
 err_remove_class_attrs:
      if (class)
            device_remove_attributes(dev, class->dev_attrs);

      return error;
}

static void device_remove_attrs(struct device *dev)
{
      struct class *class = dev->class;
      struct device_type *type = dev->type;

      device_remove_groups(dev, dev->groups);

      if (type)
            device_remove_groups(dev, type->groups);

      if (class)
            device_remove_attributes(dev, class->dev_attrs);
}


static ssize_t show_dev(struct device *dev, struct device_attribute *attr,
                  char *buf)
{
      return print_dev_t(buf, dev->devt);
}

static struct device_attribute devt_attr =
      __ATTR(dev, S_IRUGO, show_dev, NULL);

/*
 *    devices_subsys - structure to be registered with kobject core.
 */

decl_subsys(devices, &device_ktype, &device_uevent_ops);


/**
 *    device_create_file - create sysfs attribute file for device.
 *    @dev: device.
 *    @attr:      device attribute descriptor.
 */

int device_create_file(struct device * dev, struct device_attribute * attr)
{
      int error = 0;
      if (get_device(dev)) {
            error = sysfs_create_file(&dev->kobj, &attr->attr);
            put_device(dev);
      }
      return error;
}

/**
 *    device_remove_file - remove sysfs attribute file.
 *    @dev: device.
 *    @attr:      device attribute descriptor.
 */

void device_remove_file(struct device * dev, struct device_attribute * attr)
{
      if (get_device(dev)) {
            sysfs_remove_file(&dev->kobj, &attr->attr);
            put_device(dev);
      }
}

/**
 * device_create_bin_file - create sysfs binary attribute file for device.
 * @dev: device.
 * @attr: device binary attribute descriptor.
 */
int device_create_bin_file(struct device *dev, struct bin_attribute *attr)
{
      int error = -EINVAL;
      if (dev)
            error = sysfs_create_bin_file(&dev->kobj, attr);
      return error;
}
EXPORT_SYMBOL_GPL(device_create_bin_file);

/**
 * device_remove_bin_file - remove sysfs binary attribute file
 * @dev: device.
 * @attr: device binary attribute descriptor.
 */
void device_remove_bin_file(struct device *dev, struct bin_attribute *attr)
{
      if (dev)
            sysfs_remove_bin_file(&dev->kobj, attr);
}
EXPORT_SYMBOL_GPL(device_remove_bin_file);

/**
 * device_schedule_callback_owner - helper to schedule a callback for a device
 * @dev: device.
 * @func: callback function to invoke later.
 * @owner: module owning the callback routine
 *
 * Attribute methods must not unregister themselves or their parent device
 * (which would amount to the same thing).  Attempts to do so will deadlock,
 * since unregistration is mutually exclusive with driver callbacks.
 *
 * Instead methods can call this routine, which will attempt to allocate
 * and schedule a workqueue request to call back @func with @dev as its
 * argument in the workqueue's process context.  @dev will be pinned until
 * @func returns.
 *
 * This routine is usually called via the inline device_schedule_callback(),
 * which automatically sets @owner to THIS_MODULE.
 *
 * Returns 0 if the request was submitted, -ENOMEM if storage could not
 * be allocated, -ENODEV if a reference to @owner isn't available.
 *
 * NOTE: This routine won't work if CONFIG_SYSFS isn't set!  It uses an
 * underlying sysfs routine (since it is intended for use by attribute
 * methods), and if sysfs isn't available you'll get nothing but -ENOSYS.
 */
int device_schedule_callback_owner(struct device *dev,
            void (*func)(struct device *), struct module *owner)
{
      return sysfs_schedule_callback(&dev->kobj,
                  (void (*)(void *)) func, dev, owner);
}
EXPORT_SYMBOL_GPL(device_schedule_callback_owner);

static void klist_children_get(struct klist_node *n)
{
      struct device *dev = container_of(n, struct device, knode_parent);

      get_device(dev);
}

static void klist_children_put(struct klist_node *n)
{
      struct device *dev = container_of(n, struct device, knode_parent);

      put_device(dev);
}


/**
 *    device_initialize - init device structure.
 *    @dev: device.
 *
 *    This prepares the device for use by other layers,
 *    including adding it to the device hierarchy.
 *    It is the first half of device_register(), if called by
 *    that, though it can also be called separately, so one
 *    may use @dev's fields (e.g. the refcount).
 */

void device_initialize(struct device *dev)
{
      kobj_set_kset_s(dev, devices_subsys);
      kobject_init(&dev->kobj);
      klist_init(&dev->klist_children, klist_children_get,
               klist_children_put);
      INIT_LIST_HEAD(&dev->dma_pools);
      INIT_LIST_HEAD(&dev->node);
      init_MUTEX(&dev->sem);
      spin_lock_init(&dev->devres_lock);
      INIT_LIST_HEAD(&dev->devres_head);
      device_init_wakeup(dev, 0);
      set_dev_node(dev, -1);
}

#ifdef CONFIG_SYSFS_DEPRECATED
static struct kobject * get_device_parent(struct device *dev,
                                struct device *parent)
{
      /*
       * Set the parent to the class, not the parent device
       * for topmost devices in class hierarchy.
       * This keeps sysfs from having a symlink to make old
       * udevs happy
       */
      if (dev->class && (!parent || parent->class != dev->class))
            return &dev->class->subsys.kobj;
      else if (parent)
            return &parent->kobj;

      return NULL;
}
#else
static struct kobject *virtual_device_parent(struct device *dev)
{
      static struct kobject *virtual_dir = NULL;

      if (!virtual_dir)
            virtual_dir = kobject_add_dir(&devices_subsys.kobj, "virtual");

      return virtual_dir;
}

static struct kobject * get_device_parent(struct device *dev,
                                struct device *parent)
{
      if (dev->class) {
            struct kobject *kobj = NULL;
            struct kobject *parent_kobj;
            struct kobject *k;

            /*
             * If we have no parent, we live in "virtual".
             * Class-devices with a bus-device as parent, live
             * in a class-directory to prevent namespace collisions.
             */
            if (parent == NULL)
                  parent_kobj = virtual_device_parent(dev);
            else if (parent->class)
                  return &parent->kobj;
            else
                  parent_kobj = &parent->kobj;

            /* find our class-directory at the parent and reference it */
            spin_lock(&dev->class->class_dirs.list_lock);
            list_for_each_entry(k, &dev->class->class_dirs.list, entry)
                  if (k->parent == parent_kobj) {
                        kobj = kobject_get(k);
                        break;
                  }
            spin_unlock(&dev->class->class_dirs.list_lock);
            if (kobj)
                  return kobj;

            /* or create a new class-directory at the parent device */
            return kobject_kset_add_dir(&dev->class->class_dirs,
                                  parent_kobj, dev->class->name);
      }

      if (parent)
            return &parent->kobj;
      return NULL;
}
#endif

static int setup_parent(struct device *dev, struct device *parent)
{
      struct kobject *kobj;
      kobj = get_device_parent(dev, parent);
      if (IS_ERR(kobj))
            return PTR_ERR(kobj);
      if (kobj)
            dev->kobj.parent = kobj;
      return 0;
}

static int device_add_class_symlinks(struct device *dev)
{
      int error;

      if (!dev->class)
            return 0;
      error = sysfs_create_link(&dev->kobj, &dev->class->subsys.kobj,
                          "subsystem");
      if (error)
            goto out;
      /*
       * If this is not a "fake" compatible device, then create the
       * symlink from the class to the device.
       */
      if (dev->kobj.parent != &dev->class->subsys.kobj) {
            error = sysfs_create_link(&dev->class->subsys.kobj, &dev->kobj,
                                dev->bus_id);
            if (error)
                  goto out_subsys;
      }
      if (dev->parent) {
#ifdef CONFIG_SYSFS_DEPRECATED
            {
                  struct device *parent = dev->parent;
                  char *class_name;

                  /*
                   * In old sysfs stacked class devices had 'device'
                   * link pointing to real device instead of parent
                   */
                  while (parent->class && !parent->bus && parent->parent)
                        parent = parent->parent;

                  error = sysfs_create_link(&dev->kobj,
                                      &parent->kobj,
                                      "device");
                  if (error)
                        goto out_busid;

                  class_name = make_class_name(dev->class->name,
                                          &dev->kobj);
                  if (class_name)
                        error = sysfs_create_link(&dev->parent->kobj,
                                          &dev->kobj, class_name);
                  kfree(class_name);
                  if (error)
                        goto out_device;
            }
#else
            error = sysfs_create_link(&dev->kobj, &dev->parent->kobj,
                                "device");
            if (error)
                  goto out_busid;
#endif
      }
      return 0;

#ifdef CONFIG_SYSFS_DEPRECATED
out_device:
      if (dev->parent)
            sysfs_remove_link(&dev->kobj, "device");
#endif
out_busid:
      if (dev->kobj.parent != &dev->class->subsys.kobj)
            sysfs_remove_link(&dev->class->subsys.kobj, dev->bus_id);
out_subsys:
      sysfs_remove_link(&dev->kobj, "subsystem");
out:
      return error;
}

static void device_remove_class_symlinks(struct device *dev)
{
      if (!dev->class)
            return;
      if (dev->parent) {
#ifdef CONFIG_SYSFS_DEPRECATED
            char *class_name;

            class_name = make_class_name(dev->class->name, &dev->kobj);
            if (class_name) {
                  sysfs_remove_link(&dev->parent->kobj, class_name);
                  kfree(class_name);
            }
#endif
            sysfs_remove_link(&dev->kobj, "device");
      }
      if (dev->kobj.parent != &dev->class->subsys.kobj)
            sysfs_remove_link(&dev->class->subsys.kobj, dev->bus_id);
      sysfs_remove_link(&dev->kobj, "subsystem");
}

/**
 *    device_add - add device to device hierarchy.
 *    @dev: device.
 *
 *    This is part 2 of device_register(), though may be called
 *    separately _iff_ device_initialize() has been called separately.
 *
 *    This adds it to the kobject hierarchy via kobject_add(), adds it
 *    to the global and sibling lists for the device, then
 *    adds it to the other relevant subsystems of the driver model.
 */
int device_add(struct device *dev)
{
      struct device *parent = NULL;
      struct class_interface *class_intf;
      int error = -EINVAL;

      dev = get_device(dev);
      if (!dev || !strlen(dev->bus_id))
            goto Error;

      pr_debug("DEV: registering device: ID = '%s'\n", dev->bus_id);

      parent = get_device(dev->parent);
      error = setup_parent(dev, parent);
      if (error)
            goto Error;

      /* first, register with generic layer. */
      kobject_set_name(&dev->kobj, "%s", dev->bus_id);
      error = kobject_add(&dev->kobj);
      if (error)
            goto Error;

      /* notify platform of device entry */
      if (platform_notify)
            platform_notify(dev);

      /* notify clients of device entry (new way) */
      if (dev->bus)
            blocking_notifier_call_chain(&dev->bus->bus_notifier,
                                   BUS_NOTIFY_ADD_DEVICE, dev);

      error = device_create_file(dev, &uevent_attr);
      if (error)
            goto attrError;

      if (MAJOR(dev->devt)) {
            error = device_create_file(dev, &devt_attr);
            if (error)
                  goto ueventattrError;
      }

      error = device_add_class_symlinks(dev);
      if (error)
            goto SymlinkError;
      error = device_add_attrs(dev);
      if (error)
            goto AttrsError;
      error = dpm_sysfs_add(dev);
      if (error)
            goto PMError;
      device_pm_add(dev);
      error = bus_add_device(dev);
      if (error)
            goto BusError;
      kobject_uevent(&dev->kobj, KOBJ_ADD);
      bus_attach_device(dev);
      if (parent)
            klist_add_tail(&dev->knode_parent, &parent->klist_children);

      if (dev->class) {
            down(&dev->class->sem);
            /* tie the class to the device */
            list_add_tail(&dev->node, &dev->class->devices);

            /* notify any interfaces that the device is here */
            list_for_each_entry(class_intf, &dev->class->interfaces, node)
                  if (class_intf->add_dev)
                        class_intf->add_dev(dev, class_intf);
            up(&dev->class->sem);
      }
 Done:
      put_device(dev);
      return error;
 BusError:
      device_pm_remove(dev);
      dpm_sysfs_remove(dev);
 PMError:
      if (dev->bus)
            blocking_notifier_call_chain(&dev->bus->bus_notifier,
                                   BUS_NOTIFY_DEL_DEVICE, dev);
      device_remove_attrs(dev);
 AttrsError:
      device_remove_class_symlinks(dev);
 SymlinkError:
      if (MAJOR(dev->devt))
            device_remove_file(dev, &devt_attr);

      if (dev->class) {
            sysfs_remove_link(&dev->kobj, "subsystem");
            /* If this is not a "fake" compatible device, remove the
             * symlink from the class to the device. */
            if (dev->kobj.parent != &dev->class->subsys.kobj)
                  sysfs_remove_link(&dev->class->subsys.kobj,
                                dev->bus_id);
            if (parent) {
#ifdef CONFIG_SYSFS_DEPRECATED
                  char *class_name = make_class_name(dev->class->name,
                                             &dev->kobj);
                  if (class_name)
                        sysfs_remove_link(&dev->parent->kobj,
                                      class_name);
                  kfree(class_name);
#endif
                  sysfs_remove_link(&dev->kobj, "device");
            }
      }
 ueventattrError:
      device_remove_file(dev, &uevent_attr);
 attrError:
      kobject_uevent(&dev->kobj, KOBJ_REMOVE);
      kobject_del(&dev->kobj);
 Error:
      if (parent)
            put_device(parent);
      goto Done;
}


/**
 *    device_register - register a device with the system.
 *    @dev: pointer to the device structure
 *
 *    This happens in two clean steps - initialize the device
 *    and add it to the system. The two steps can be called
 *    separately, but this is the easiest and most common.
 *    I.e. you should only call the two helpers separately if
 *    have a clearly defined need to use and refcount the device
 *    before it is added to the hierarchy.
 */

int device_register(struct device *dev)
{
      device_initialize(dev);
      return device_add(dev);
}


/**
 *    get_device - increment reference count for device.
 *    @dev: device.
 *
 *    This simply forwards the call to kobject_get(), though
 *    we do take care to provide for the case that we get a NULL
 *    pointer passed in.
 */

struct device * get_device(struct device * dev)
{
      return dev ? to_dev(kobject_get(&dev->kobj)) : NULL;
}


/**
 *    put_device - decrement reference count.
 *    @dev: device in question.
 */
void put_device(struct device * dev)
{
      if (dev)
            kobject_put(&dev->kobj);
}


/**
 *    device_del - delete device from system.
 *    @dev: device.
 *
 *    This is the first part of the device unregistration
 *    sequence. This removes the device from the lists we control
 *    from here, has it removed from the other driver model
 *    subsystems it was added to in device_add(), and removes it
 *    from the kobject hierarchy.
 *
 *    NOTE: this should be called manually _iff_ device_add() was
 *    also called manually.
 */

void device_del(struct device * dev)
{
      struct device * parent = dev->parent;
      struct class_interface *class_intf;

      if (parent)
            klist_del(&dev->knode_parent);
      if (MAJOR(dev->devt))
            device_remove_file(dev, &devt_attr);
      if (dev->class) {
            sysfs_remove_link(&dev->kobj, "subsystem");
            /* If this is not a "fake" compatible device, remove the
             * symlink from the class to the device. */
            if (dev->kobj.parent != &dev->class->subsys.kobj)
                  sysfs_remove_link(&dev->class->subsys.kobj,
                                dev->bus_id);
            if (parent) {
#ifdef CONFIG_SYSFS_DEPRECATED
                  char *class_name = make_class_name(dev->class->name,
                                             &dev->kobj);
                  if (class_name)
                        sysfs_remove_link(&dev->parent->kobj,
                                      class_name);
                  kfree(class_name);
#endif
                  sysfs_remove_link(&dev->kobj, "device");
            }

            down(&dev->class->sem);
            /* notify any interfaces that the device is now gone */
            list_for_each_entry(class_intf, &dev->class->interfaces, node)
                  if (class_intf->remove_dev)
                        class_intf->remove_dev(dev, class_intf);
            /* remove the device from the class list */
            list_del_init(&dev->node);
            up(&dev->class->sem);

            /* If we live in a parent class-directory, unreference it */
            if (dev->kobj.parent->kset == &dev->class->class_dirs) {
                  struct device *d;
                  int other = 0;

                  /*
                   * if we are the last child of our class, delete
                   * our class-directory at this parent
                   */
                  down(&dev->class->sem);
                  list_for_each_entry(d, &dev->class->devices, node) {
                        if (d == dev)
                              continue;
                        if (d->kobj.parent == dev->kobj.parent) {
                              other = 1;
                              break;
                        }
                  }
                  if (!other)
                        kobject_del(dev->kobj.parent);

                  kobject_put(dev->kobj.parent);
                  up(&dev->class->sem);
            }
      }
      device_remove_file(dev, &uevent_attr);
      device_remove_attrs(dev);
      bus_remove_device(dev);

      /*
       * Some platform devices are driven without driver attached
       * and managed resources may have been acquired.  Make sure
       * all resources are released.
       */
      devres_release_all(dev);

      /* Notify the platform of the removal, in case they
       * need to do anything...
       */
      if (platform_notify_remove)
            platform_notify_remove(dev);
      if (dev->bus)
            blocking_notifier_call_chain(&dev->bus->bus_notifier,
                                   BUS_NOTIFY_DEL_DEVICE, dev);
      device_pm_remove(dev);
      kobject_uevent(&dev->kobj, KOBJ_REMOVE);
      kobject_del(&dev->kobj);
      if (parent)
            put_device(parent);
}

/**
 *    device_unregister - unregister device from system.
 *    @dev: device going away.
 *
 *    We do this in two parts, like we do device_register(). First,
 *    we remove it from all the subsystems with device_del(), then
 *    we decrement the reference count via put_device(). If that
 *    is the final reference count, the device will be cleaned up
 *    via device_release() above. Otherwise, the structure will
 *    stick around until the final reference to the device is dropped.
 */
void device_unregister(struct device * dev)
{
      pr_debug("DEV: Unregistering device. ID = '%s'\n", dev->bus_id);
      device_del(dev);
      put_device(dev);
}


static struct device * next_device(struct klist_iter * i)
{
      struct klist_node * n = klist_next(i);
      return n ? container_of(n, struct device, knode_parent) : NULL;
}

/**
 *    device_for_each_child - device child iterator.
 *    @parent: parent struct device.
 *    @data:      data for the callback.
 *    @fn:  function to be called for each device.
 *
 *    Iterate over @parent's child devices, and call @fn for each,
 *    passing it @data.
 *
 *    We check the return of @fn each time. If it returns anything
 *    other than 0, we break out and return that value.
 */
int device_for_each_child(struct device * parent, void * data,
                 int (*fn)(struct device *, void *))
{
      struct klist_iter i;
      struct device * child;
      int error = 0;

      klist_iter_init(&parent->klist_children, &i);
      while ((child = next_device(&i)) && !error)
            error = fn(child, data);
      klist_iter_exit(&i);
      return error;
}

/**
 * device_find_child - device iterator for locating a particular device.
 * @parent: parent struct device
 * @data: Data to pass to match function
 * @match: Callback function to check device
 *
 * This is similar to the device_for_each_child() 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 and a reference to the
 * current device can be obtained, this function will return to the caller
 * and not iterate over any more devices.
 */
struct device * device_find_child(struct device *parent, void *data,
                          int (*match)(struct device *, void *))
{
      struct klist_iter i;
      struct device *child;

      if (!parent)
            return NULL;

      klist_iter_init(&parent->klist_children, &i);
      while ((child = next_device(&i)))
            if (match(child, data) && get_device(child))
                  break;
      klist_iter_exit(&i);
      return child;
}

int __init devices_init(void)
{
      return subsystem_register(&devices_subsys);
}

EXPORT_SYMBOL_GPL(device_for_each_child);
EXPORT_SYMBOL_GPL(device_find_child);

EXPORT_SYMBOL_GPL(device_initialize);
EXPORT_SYMBOL_GPL(device_add);
EXPORT_SYMBOL_GPL(device_register);

EXPORT_SYMBOL_GPL(device_del);
EXPORT_SYMBOL_GPL(device_unregister);
EXPORT_SYMBOL_GPL(get_device);
EXPORT_SYMBOL_GPL(put_device);

EXPORT_SYMBOL_GPL(device_create_file);
EXPORT_SYMBOL_GPL(device_remove_file);


static void device_create_release(struct device *dev)
{
      pr_debug("%s called for %s\n", __FUNCTION__, dev->bus_id);
      kfree(dev);
}

/**
 * device_create - creates a device and registers it with sysfs
 * @class: pointer to the struct class that this device should be registered to
 * @parent: pointer to the parent struct device of this new device, if any
 * @devt: the dev_t for the char device to be added
 * @fmt: string for the device's name
 *
 * This function can be used by char device classes.  A struct device
 * will be created in sysfs, registered to the specified class.
 *
 * A "dev" file will be created, showing the dev_t for the device, if
 * the dev_t is not 0,0.
 * If a pointer to a parent struct device is passed in, the newly created
 * struct device will be a child of that device in sysfs.
 * The pointer to the struct device will be returned from the call.
 * Any further sysfs files that might be required can be created using this
 * pointer.
 *
 * Note: the struct class passed to this function must have previously
 * been created with a call to class_create().
 */
struct device *device_create(struct class *class, struct device *parent,
                       dev_t devt, const char *fmt, ...)
{
      va_list args;
      struct device *dev = NULL;
      int retval = -ENODEV;

      if (class == NULL || IS_ERR(class))
            goto error;

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

      dev->devt = devt;
      dev->class = class;
      dev->parent = parent;
      dev->release = device_create_release;

      va_start(args, fmt);
      vsnprintf(dev->bus_id, BUS_ID_SIZE, fmt, args);
      va_end(args);
      retval = device_register(dev);
      if (retval)
            goto error;

      return dev;

error:
      kfree(dev);
      return ERR_PTR(retval);
}
EXPORT_SYMBOL_GPL(device_create);

/**
 * device_destroy - removes a device that was created with device_create()
 * @class: pointer to the struct class that this device was registered with
 * @devt: the dev_t of the device that was previously registered
 *
 * This call unregisters and cleans up a device that was created with a
 * call to device_create().
 */
void device_destroy(struct class *class, dev_t devt)
{
      struct device *dev = NULL;
      struct device *dev_tmp;

      down(&class->sem);
      list_for_each_entry(dev_tmp, &class->devices, node) {
            if (dev_tmp->devt == devt) {
                  dev = dev_tmp;
                  break;
            }
      }
      up(&class->sem);

      if (dev)
            device_unregister(dev);
}
EXPORT_SYMBOL_GPL(device_destroy);

/**
 * device_rename - renames a device
 * @dev: the pointer to the struct device to be renamed
 * @new_name: the new name of the device
 */
int device_rename(struct device *dev, char *new_name)
{
      char *old_class_name = NULL;
      char *new_class_name = NULL;
      char *old_device_name = NULL;
      int error;

      dev = get_device(dev);
      if (!dev)
            return -EINVAL;

      pr_debug("DEVICE: renaming '%s' to '%s'\n", dev->bus_id, new_name);

#ifdef CONFIG_SYSFS_DEPRECATED
      if ((dev->class) && (dev->parent))
            old_class_name = make_class_name(dev->class->name, &dev->kobj);
#endif

      old_device_name = kmalloc(BUS_ID_SIZE, GFP_KERNEL);
      if (!old_device_name) {
            error = -ENOMEM;
            goto out;
      }
      strlcpy(old_device_name, dev->bus_id, BUS_ID_SIZE);
      strlcpy(dev->bus_id, new_name, BUS_ID_SIZE);

      error = kobject_rename(&dev->kobj, new_name);
      if (error) {
            strlcpy(dev->bus_id, old_device_name, BUS_ID_SIZE);
            goto out;
      }

#ifdef CONFIG_SYSFS_DEPRECATED
      if (old_class_name) {
            new_class_name = make_class_name(dev->class->name, &dev->kobj);
            if (new_class_name) {
                  error = sysfs_create_link(&dev->parent->kobj,
                                      &dev->kobj, new_class_name);
                  if (error)
                        goto out;
                  sysfs_remove_link(&dev->parent->kobj, old_class_name);
            }
      }
#else
      if (dev->class) {
            sysfs_remove_link(&dev->class->subsys.kobj, old_device_name);
            error = sysfs_create_link(&dev->class->subsys.kobj, &dev->kobj,
                                dev->bus_id);
            if (error) {
                  dev_err(dev, "%s: sysfs_create_symlink failed (%d)\n",
                        __FUNCTION__, error);
            }
      }
#endif

out:
      put_device(dev);

      kfree(new_class_name);
      kfree(old_class_name);
      kfree(old_device_name);

      return error;
}
EXPORT_SYMBOL_GPL(device_rename);

static int device_move_class_links(struct device *dev,
                           struct device *old_parent,
                           struct device *new_parent)
{
      int error = 0;
#ifdef CONFIG_SYSFS_DEPRECATED
      char *class_name;

      class_name = make_class_name(dev->class->name, &dev->kobj);
      if (!class_name) {
            error = -ENOMEM;
            goto out;
      }
      if (old_parent) {
            sysfs_remove_link(&dev->kobj, "device");
            sysfs_remove_link(&old_parent->kobj, class_name);
      }
      if (new_parent) {
            error = sysfs_create_link(&dev->kobj, &new_parent->kobj,
                                "device");
            if (error)
                  goto out;
            error = sysfs_create_link(&new_parent->kobj, &dev->kobj,
                                class_name);
            if (error)
                  sysfs_remove_link(&dev->kobj, "device");
      }
      else
            error = 0;
out:
      kfree(class_name);
      return error;
#else
      if (old_parent)
            sysfs_remove_link(&dev->kobj, "device");
      if (new_parent)
            error = sysfs_create_link(&dev->kobj, &new_parent->kobj,
                                "device");
      return error;
#endif
}

/**
 * device_move - moves a device to a new parent
 * @dev: the pointer to the struct device to be moved
 * @new_parent: the new parent of the device (can by NULL)
 */
int device_move(struct device *dev, struct device *new_parent)
{
      int error;
      struct device *old_parent;
      struct kobject *new_parent_kobj;

      dev = get_device(dev);
      if (!dev)
            return -EINVAL;

      new_parent = get_device(new_parent);
      new_parent_kobj = get_device_parent (dev, new_parent);
      if (IS_ERR(new_parent_kobj)) {
            error = PTR_ERR(new_parent_kobj);
            put_device(new_parent);
            goto out;
      }
      pr_debug("DEVICE: moving '%s' to '%s'\n", dev->bus_id,
             new_parent ? new_parent->bus_id : "<NULL>");
      error = kobject_move(&dev->kobj, new_parent_kobj);
      if (error) {
            put_device(new_parent);
            goto out;
      }
      old_parent = dev->parent;
      dev->parent = new_parent;
      if (old_parent)
            klist_remove(&dev->knode_parent);
      if (new_parent)
            klist_add_tail(&dev->knode_parent, &new_parent->klist_children);
      if (!dev->class)
            goto out_put;
      error = device_move_class_links(dev, old_parent, new_parent);
      if (error) {
            /* We ignore errors on cleanup since we're hosed anyway... */
            device_move_class_links(dev, new_parent, old_parent);
            if (!kobject_move(&dev->kobj, &old_parent->kobj)) {
                  if (new_parent)
                        klist_remove(&dev->knode_parent);
                  if (old_parent)
                        klist_add_tail(&dev->knode_parent,
                                     &old_parent->klist_children);
            }
            put_device(new_parent);
            goto out;
      }
out_put:
      put_device(old_parent);
out:
      put_device(dev);
      return error;
}

EXPORT_SYMBOL_GPL(device_move);

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