Merge tag 'io_uring-5.11-2021-01-16' of git://git.kernel.dk/linux-block

[linux/fpc-iii.git] / drivers / base / attribute_container.c

// SPDX-License-Identifier: GPL-2.0
/*
 * attribute_container.c - implementation of a simple container for classes
 *
 * Copyright (c) 2005 - James Bottomley <James.Bottomley@steeleye.com>
 *
 * 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/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 */
static void attribute_container_release(struct device *classdev)
{
        struct internal_container *ic
                = container_of(classdev, struct internal_container, classdev);
        struct device *dev = classdev->parent;

        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
 * 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 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 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_err(dev, "failed to allocate class container\n");
                        continue;
                }

                ic->cont = cont;
                device_initialize(&ic->classdev);
                ic->classdev.parent = get_device(dev);
                ic->classdev.class = cont->class;
                cont->class->dev_release = attribute_container_release;
                dev_set_name(&ic->classdev, "%s", dev_name(dev));
                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 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
 * 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 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.parent)
                                continue;
                        klist_del(&ic->node);
                        if (fn)
                                fn(cont, dev, &ic->classdev);
                        else {
                                attribute_container_remove_attrs(&ic->classdev);
                                device_unregister(&ic->classdev);
                        }
                }
        }
        mutex_unlock(&attribute_container_mutex);
}

static int
do_attribute_container_device_trigger_safe(struct device *dev,
                                           struct attribute_container *cont,
                                           int (*fn)(struct attribute_container *,
                                                     struct device *, struct device *),
                                           int (*undo)(struct attribute_container *,
                                                       struct device *, struct device *))
{
        int ret;
        struct internal_container *ic, *failed;
        struct klist_iter iter;

        if (attribute_container_no_classdevs(cont))
                return fn(cont, dev, NULL);

        klist_for_each_entry(ic, &cont->containers, node, &iter) {
                if (dev == ic->classdev.parent) {
                        ret = fn(cont, dev, &ic->classdev);
                        if (ret) {
                                failed = ic;
                                klist_iter_exit(&iter);
                                goto fail;
                        }
                }
        }
        return 0;

fail:
        if (!undo)
                return ret;

        /* Attempt to undo the work partially done. */
        klist_for_each_entry(ic, &cont->containers, node, &iter) {
                if (ic == failed) {
                        klist_iter_exit(&iter);
                        break;
                }
                if (dev == ic->classdev.parent)
                        undo(cont, dev, &ic->classdev);
        }
        return ret;
}

/**
 * attribute_container_device_trigger_safe - execute a trigger for each
 * matching classdev or fail all of them.
 *
 * @dev:  The generic device to run the trigger for
 * @fn    the function to execute for each classdev.
 * @undo  A function to undo the work previously done in case of error
 *
 * This function is a safe version of
 * attribute_container_device_trigger. It stops on the first error and
 * undo the partial work that has been done, on previous classdev.  It
 * is guaranteed that either they all succeeded, or none of them
 * succeeded.
 */
int
attribute_container_device_trigger_safe(struct device *dev,
                                        int (*fn)(struct attribute_container *,
                                                  struct device *,
                                                  struct device *),
                                        int (*undo)(struct attribute_container *,
                                                    struct device *,
                                                    struct device *))
{
        struct attribute_container *cont, *failed = NULL;
        int ret = 0;

        mutex_lock(&attribute_container_mutex);

        list_for_each_entry(cont, &attribute_container_list, node) {

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

                ret = do_attribute_container_device_trigger_safe(dev, cont,
                                                                 fn, undo);
                if (ret) {
                        failed = cont;
                        break;
                }
        }

        if (ret && !WARN_ON(!undo)) {
                list_for_each_entry(cont, &attribute_container_list, node) {

                        if (failed == cont)
                                break;

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

                        do_attribute_container_device_trigger_safe(dev, cont,
                                                                   undo, NULL);
                }
        }

        mutex_unlock(&attribute_container_mutex);
        return ret;

}

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

        BUG_ON(attrs && cont->grp);

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

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

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

        return 0;
}

/**
 * attribute_container_add_class_device - same function as device_add
 *
 * @classdev:   the class device to add
 *
 * This performs essentially the same function as 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 device *classdev)
{
        int error = 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 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 device *classdev)
{
        struct attribute_container *cont =
                attribute_container_classdev_to_container(classdev);
        struct device_attribute **attrs = cont->attrs;
        int i;

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

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

        for (i = 0; attrs[i]; i++)
                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
 * device_del.
 */
void
attribute_container_class_device_del(struct device *classdev)
{
        attribute_container_remove_attrs(classdev);
        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 device *
attribute_container_find_class_device(struct attribute_container *cont,
                                      struct device *dev)
{
        struct device *cdev = NULL;
        struct internal_container *ic;
        struct klist_iter iter;

        klist_for_each_entry(ic, &cont->containers, node, &iter) {
                if (ic->classdev.parent == 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);