attribute_container.c 12 KB
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/*
 * 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>
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#include <linux/mutex.h>
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#include "base.h"

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

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

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


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/**
 * 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 *
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attribute_container_classdev_to_container(struct device *classdev)
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{
	struct internal_container *ic =
		container_of(classdev, struct internal_container, classdev);
	return ic->cont;
}
EXPORT_SYMBOL_GPL(attribute_container_classdev_to_container);

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static LIST_HEAD(attribute_container_list);
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static DEFINE_MUTEX(attribute_container_mutex);
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/**
 * 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);
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	klist_init(&cont->containers,internal_container_klist_get,
		   internal_container_klist_put);
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	mutex_lock(&attribute_container_mutex);
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	list_add_tail(&cont->node, &attribute_container_list);
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	mutex_unlock(&attribute_container_mutex);
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	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;
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	mutex_lock(&attribute_container_mutex);
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	spin_lock(&cont->containers.k_lock);
	if (!list_empty(&cont->containers.k_list))
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		goto out;
	retval = 0;
	list_del(&cont->node);
 out:
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	spin_unlock(&cont->containers.k_lock);
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	mutex_unlock(&attribute_container_mutex);
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	return retval;
		
}
EXPORT_SYMBOL_GPL(attribute_container_unregister);

/* private function used as class release */
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static void attribute_container_release(struct device *classdev)
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{
	struct internal_container *ic 
		= container_of(classdev, struct internal_container, classdev);
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	struct device *dev = classdev->parent;
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	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
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 * device_add.  If a function is provided, it is expected to add
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 * 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
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 * attribute_container_device_trigger() to call device_add() on
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 * 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 *,
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					 struct device *))
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{
	struct attribute_container *cont;

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	mutex_lock(&attribute_container_mutex);
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	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;
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		ic = kzalloc(sizeof(*ic), GFP_KERNEL);
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		if (!ic) {
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			dev_err(dev, "failed to allocate class container\n");
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			continue;
		}
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		ic->cont = cont;
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		device_initialize(&ic->classdev);
		ic->classdev.parent = get_device(dev);
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		ic->classdev.class = cont->class;
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		cont->class->dev_release = attribute_container_release;
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		dev_set_name(&ic->classdev, "%s", dev_name(dev));
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		if (fn)
			fn(cont, dev, &ic->classdev);
		else
			attribute_container_add_class_device(&ic->classdev);
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		klist_add_tail(&ic->node, &cont->containers);
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	}
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	mutex_unlock(&attribute_container_mutex);
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}

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/* 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); \
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		n ? container_of(n, typeof(*pos), member) : \
			({ klist_iter_exit(iter) ; NULL; }); \
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	}) ) != NULL; )
			

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/**
 * 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
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 * simply done via device_unregister (note that if something
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 * 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
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 * device_del() and then use attribute_container_device_trigger()
 * to do the final put on the classdev.
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 */
void
attribute_container_remove_device(struct device *dev,
				  void (*fn)(struct attribute_container *,
					     struct device *,
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					     struct device *))
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{
	struct attribute_container *cont;

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

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

/**
 * 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 *,
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					     struct device *))
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{
	struct attribute_container *cont;

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	mutex_lock(&attribute_container_mutex);
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	list_for_each_entry(cont, &attribute_container_list, node) {
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		struct internal_container *ic;
		struct klist_iter iter;
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		if (!cont->match(cont, dev))
			continue;

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

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

/**
 * 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;

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

/**
 * 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
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attribute_container_add_attrs(struct device *classdev)
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{
	struct attribute_container *cont =
		attribute_container_classdev_to_container(classdev);
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	struct device_attribute **attrs = cont->attrs;
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	int i, error;

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	BUG_ON(attrs && cont->grp);

	if (!attrs && !cont->grp)
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		return 0;

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	if (cont->grp)
		return sysfs_create_group(&classdev->kobj, cont->grp);

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	for (i = 0; attrs[i]; i++) {
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		sysfs_attr_init(&attrs[i]->attr);
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		error = device_create_file(classdev, attrs[i]);
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		if (error)
			return error;
	}

	return 0;
}

/**
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 * attribute_container_add_class_device - same function as device_add
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 *
 * @classdev:	the class device to add
 *
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 * This performs essentially the same function as device_add except for
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 * attribute containers, namely add the classdev to the system and then
 * create the attribute files
 */
int
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attribute_container_add_class_device(struct device *classdev)
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{
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	int error = device_add(classdev);
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	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,
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					     struct device *classdev)
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{
	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
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attribute_container_remove_attrs(struct device *classdev)
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{
	struct attribute_container *cont =
		attribute_container_classdev_to_container(classdev);
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	struct device_attribute **attrs = cont->attrs;
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	int i;

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	if (!attrs && !cont->grp)
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		return;

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	if (cont->grp) {
		sysfs_remove_group(&classdev->kobj, cont->grp);
		return ;
	}

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

/**
 * 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
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 * device_del.
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 */
void
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attribute_container_class_device_del(struct device *classdev)
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{
	attribute_container_remove_attrs(classdev);
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	device_del(classdev);
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}

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/**
 * 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.
 */
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struct device *
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attribute_container_find_class_device(struct attribute_container *cont,
				      struct device *dev)
{
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	struct device *cdev = NULL;
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	struct internal_container *ic;
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	struct klist_iter iter;
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	klist_for_each_entry(ic, &cont->containers, node, &iter) {
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		if (ic->classdev.parent == dev) {
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			cdev = &ic->classdev;
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			/* FIXME: must exit iterator then break */
			klist_iter_exit(&iter);
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			break;
		}
	}

	return cdev;
}
EXPORT_SYMBOL_GPL(attribute_container_find_class_device);