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attribute_container.c

/*
 * attribute_container.c - implementation of a simple container for classes
 *
 * Copyright (c) 2005 - James Bottomley <James.Bottomley@steeleye.com>
 *
 * This file is licensed under GPLv2
 *
 * The basic idea here is to enable a device to be attached to an
 * aritrary numer of classes without having to allocate storage for them.
 * Instead, the contained classes select the devices they need to attach
 * to via a matching function.
 */

#include <linux/attribute_container.h>
#include <linux/init.h>
#include <linux/device.h>
#include <linux/kernel.h>
#include <linux/slab.h>
#include <linux/list.h>
#include <linux/module.h>
#include <linux/mutex.h>

#include "base.h"

/* This is a private structure used to tie the classdev and the
 * container .. it should never be visible outside this file */
struct internal_container {
      struct klist_node node;
      struct attribute_container *cont;
      struct class_device classdev;
};

static void internal_container_klist_get(struct klist_node *n)
{
      struct internal_container *ic =
            container_of(n, struct internal_container, node);
      class_device_get(&ic->classdev);
}

static void internal_container_klist_put(struct klist_node *n)
{
      struct internal_container *ic =
            container_of(n, struct internal_container, node);
      class_device_put(&ic->classdev);
}


/**
 * attribute_container_classdev_to_container - given a classdev, return the container
 *
 * @classdev: the class device created by attribute_container_add_device.
 *
 * Returns the container associated with this classdev.
 */
struct attribute_container *
attribute_container_classdev_to_container(struct class_device *classdev)
{
      struct internal_container *ic =
            container_of(classdev, struct internal_container, classdev);
      return ic->cont;
}
EXPORT_SYMBOL_GPL(attribute_container_classdev_to_container);

static struct list_head attribute_container_list;

static DEFINE_MUTEX(attribute_container_mutex);

/**
 * attribute_container_register - register an attribute container
 *
 * @cont: The container to register.  This must be allocated by the
 *        callee and should also be zeroed by it.
 */
int
attribute_container_register(struct attribute_container *cont)
{
      INIT_LIST_HEAD(&cont->node);
      klist_init(&cont->containers,internal_container_klist_get,
               internal_container_klist_put);
            
      mutex_lock(&attribute_container_mutex);
      list_add_tail(&cont->node, &attribute_container_list);
      mutex_unlock(&attribute_container_mutex);

      return 0;
}
EXPORT_SYMBOL_GPL(attribute_container_register);

/**
 * attribute_container_unregister - remove a container registration
 *
 * @cont: previously registered container to remove
 */
int
attribute_container_unregister(struct attribute_container *cont)
{
      int retval = -EBUSY;
      mutex_lock(&attribute_container_mutex);
      spin_lock(&cont->containers.k_lock);
      if (!list_empty(&cont->containers.k_list))
            goto out;
      retval = 0;
      list_del(&cont->node);
 out:
      spin_unlock(&cont->containers.k_lock);
      mutex_unlock(&attribute_container_mutex);
      return retval;
            
}
EXPORT_SYMBOL_GPL(attribute_container_unregister);

/* private function used as class release */
static void attribute_container_release(struct class_device *classdev)
{
      struct internal_container *ic 
            = container_of(classdev, struct internal_container, classdev);
      struct device *dev = classdev->dev;

      kfree(ic);
      put_device(dev);
}

/**
 * attribute_container_add_device - see if any container is interested in dev
 *
 * @dev: device to add attributes to
 * @fn:      function to trigger addition of class device.
 *
 * This function allocates storage for the class device(s) to be
 * attached to dev (one for each matching attribute_container).  If no
 * fn is provided, the code will simply register the class device via
 * class_device_add.  If a function is provided, it is expected to add
 * the class device at the appropriate time.  One of the things that
 * might be necessary is to allocate and initialise the classdev and
 * then add it a later time.  To do this, call this routine for
 * allocation and initialisation and then use
 * attribute_container_device_trigger() to call class_device_add() on
 * it.  Note: after this, the class device contains a reference to dev
 * which is not relinquished until the release of the classdev.
 */
void
attribute_container_add_device(struct device *dev,
                         int (*fn)(struct attribute_container *,
                               struct device *,
                               struct class_device *))
{
      struct attribute_container *cont;

      mutex_lock(&attribute_container_mutex);
      list_for_each_entry(cont, &attribute_container_list, node) {
            struct internal_container *ic;

            if (attribute_container_no_classdevs(cont))
                  continue;

            if (!cont->match(cont, dev))
                  continue;

            ic = kzalloc(sizeof(*ic), GFP_KERNEL);
            if (!ic) {
                  dev_printk(KERN_ERR, dev, "failed to allocate class container\n");
                  continue;
            }

            ic->cont = cont;
            class_device_initialize(&ic->classdev);
            ic->classdev.dev = get_device(dev);
            ic->classdev.class = cont->class;
            cont->class->release = attribute_container_release;
            strcpy(ic->classdev.class_id, dev->bus_id);
            if (fn)
                  fn(cont, dev, &ic->classdev);
            else
                  attribute_container_add_class_device(&ic->classdev);
            klist_add_tail(&ic->node, &cont->containers);
      }
      mutex_unlock(&attribute_container_mutex);
}

/* FIXME: can't break out of this unless klist_iter_exit is also
 * called before doing the break
 */
#define klist_for_each_entry(pos, head, member, iter) \
      for (klist_iter_init(head, iter); (pos = ({ \
            struct klist_node *n = klist_next(iter); \
            n ? container_of(n, typeof(*pos), member) : \
                  ({ klist_iter_exit(iter) ; NULL; }); \
      }) ) != NULL; )
                  

/**
 * attribute_container_remove_device - make device eligible for removal.
 *
 * @dev:  The generic device
 * @fn:       A function to call to remove the device
 *
 * This routine triggers device removal.  If fn is NULL, then it is
 * simply done via class_device_unregister (note that if something
 * still has a reference to the classdev, then the memory occupied
 * will not be freed until the classdev is released).  If you want a
 * two phase release: remove from visibility and then delete the
 * device, then you should use this routine with a fn that calls
 * class_device_del() and then use
 * attribute_container_device_trigger() to do the final put on the
 * classdev.
 */
void
attribute_container_remove_device(struct device *dev,
                          void (*fn)(struct attribute_container *,
                                   struct device *,
                                   struct class_device *))
{
      struct attribute_container *cont;

      mutex_lock(&attribute_container_mutex);
      list_for_each_entry(cont, &attribute_container_list, node) {
            struct internal_container *ic;
            struct klist_iter iter;

            if (attribute_container_no_classdevs(cont))
                  continue;

            if (!cont->match(cont, dev))
                  continue;

            klist_for_each_entry(ic, &cont->containers, node, &iter) {
                  if (dev != ic->classdev.dev)
                        continue;
                  klist_del(&ic->node);
                  if (fn)
                        fn(cont, dev, &ic->classdev);
                  else {
                        attribute_container_remove_attrs(&ic->classdev);
                        class_device_unregister(&ic->classdev);
                  }
            }
      }
      mutex_unlock(&attribute_container_mutex);
}

/**
 * attribute_container_device_trigger - execute a trigger for each matching classdev
 *
 * @dev:  The generic device to run the trigger for
 * @fn        the function to execute for each classdev.
 *
 * This funcion is for executing a trigger when you need to know both
 * the container and the classdev.  If you only care about the
 * container, then use attribute_container_trigger() instead.
 */
void
attribute_container_device_trigger(struct device *dev, 
                           int (*fn)(struct attribute_container *,
                                   struct device *,
                                   struct class_device *))
{
      struct attribute_container *cont;

      mutex_lock(&attribute_container_mutex);
      list_for_each_entry(cont, &attribute_container_list, node) {
            struct internal_container *ic;
            struct klist_iter iter;

            if (!cont->match(cont, dev))
                  continue;

            if (attribute_container_no_classdevs(cont)) {
                  fn(cont, dev, NULL);
                  continue;
            }

            klist_for_each_entry(ic, &cont->containers, node, &iter) {
                  if (dev == ic->classdev.dev)
                        fn(cont, dev, &ic->classdev);
            }
      }
      mutex_unlock(&attribute_container_mutex);
}

/**
 * attribute_container_trigger - trigger a function for each matching container
 *
 * @dev:  The generic device to activate the trigger for
 * @fn:       the function to trigger
 *
 * This routine triggers a function that only needs to know the
 * matching containers (not the classdev) associated with a device.
 * It is more lightweight than attribute_container_device_trigger, so
 * should be used in preference unless the triggering function
 * actually needs to know the classdev.
 */
void
attribute_container_trigger(struct device *dev,
                      int (*fn)(struct attribute_container *,
                              struct device *))
{
      struct attribute_container *cont;

      mutex_lock(&attribute_container_mutex);
      list_for_each_entry(cont, &attribute_container_list, node) {
            if (cont->match(cont, dev))
                  fn(cont, dev);
      }
      mutex_unlock(&attribute_container_mutex);
}

/**
 * attribute_container_add_attrs - add attributes
 *
 * @classdev: The class device
 *
 * This simply creates all the class device sysfs files from the
 * attributes listed in the container
 */
int
attribute_container_add_attrs(struct class_device *classdev)
{
      struct attribute_container *cont =
            attribute_container_classdev_to_container(classdev);
      struct class_device_attribute **attrs =   cont->attrs;
      int i, error;

      if (!attrs)
            return 0;

      for (i = 0; attrs[i]; i++) {
            error = class_device_create_file(classdev, attrs[i]);
            if (error)
                  return error;
      }

      return 0;
}

/**
 * attribute_container_add_class_device - same function as class_device_add
 *
 * @classdev:     the class device to add
 *
 * This performs essentially the same function as class_device_add except for
 * attribute containers, namely add the classdev to the system and then
 * create the attribute files
 */
int
attribute_container_add_class_device(struct class_device *classdev)
{
      int error = class_device_add(classdev);
      if (error)
            return error;
      return attribute_container_add_attrs(classdev);
}

/**
 * attribute_container_add_class_device_adapter - simple adapter for triggers
 *
 * This function is identical to attribute_container_add_class_device except
 * that it is designed to be called from the triggers
 */
int
attribute_container_add_class_device_adapter(struct attribute_container *cont,
                                   struct device *dev,
                                   struct class_device *classdev)
{
      return attribute_container_add_class_device(classdev);
}

/**
 * attribute_container_remove_attrs - remove any attribute files
 *
 * @classdev: The class device to remove the files from
 *
 */
void
attribute_container_remove_attrs(struct class_device *classdev)
{
      struct attribute_container *cont =
            attribute_container_classdev_to_container(classdev);
      struct class_device_attribute **attrs =   cont->attrs;
      int i;

      if (!attrs)
            return;

      for (i = 0; attrs[i]; i++)
            class_device_remove_file(classdev, attrs[i]);
}

/**
 * attribute_container_class_device_del - equivalent of class_device_del
 *
 * @classdev: the class device
 *
 * This function simply removes all the attribute files and then calls
 * class_device_del.
 */
void
attribute_container_class_device_del(struct class_device *classdev)
{
      attribute_container_remove_attrs(classdev);
      class_device_del(classdev);
}

/**
 * attribute_container_find_class_device - find the corresponding class_device
 *
 * @cont:   the container
 * @dev:    the generic device
 *
 * Looks up the device in the container's list of class devices and returns
 * the corresponding class_device.
 */
struct class_device *
attribute_container_find_class_device(struct attribute_container *cont,
                              struct device *dev)
{
      struct class_device *cdev = NULL;
      struct internal_container *ic;
      struct klist_iter iter;

      klist_for_each_entry(ic, &cont->containers, node, &iter) {
            if (ic->classdev.dev == dev) {
                  cdev = &ic->classdev;
                  /* FIXME: must exit iterator then break */
                  klist_iter_exit(&iter);
                  break;
            }
      }

      return cdev;
}
EXPORT_SYMBOL_GPL(attribute_container_find_class_device);

int __init
attribute_container_init(void)
{
      INIT_LIST_HEAD(&attribute_container_list);
      return 0;
}

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