litmus-rt.git - The LITMUS^RT kernel.

/*
 * 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 device classdev;
};

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

static void internal_container_klist_put(struct klist_node *n)
{
	struct internal_container *ic =
		container_of(n, struct internal_container, node);
	put_device(&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 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 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 */


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