/*
 * Mediated device Core Driver
 *
 * Copyright (c) 2016, NVIDIA CORPORATION. All rights reserved.
 *     Author: Neo Jia <cjia@nvidia.com>
 *             Kirti Wankhede <kwankhede@nvidia.com>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 */

#include <linux/module.h>
#include <linux/device.h>
#include <linux/slab.h>
#include <linux/uuid.h>
#include <linux/sysfs.h>
#include <linux/mdev.h>

#include "mdev_private.h"

#define DRIVER_VERSION          "0.1"
#define DRIVER_AUTHOR           "NVIDIA Corporation"
#define DRIVER_DESC             "Mediated device Core Driver"

static LIST_HEAD(parent_list);
static DEFINE_MUTEX(parent_list_lock);
static struct class_compat *mdev_bus_compat_class;

static LIST_HEAD(mdev_list);
static DEFINE_MUTEX(mdev_list_lock);

struct device *mdev_parent_dev(struct mdev_device *mdev)
{
        return mdev->parent->dev;
}
EXPORT_SYMBOL(mdev_parent_dev);

void *mdev_get_drvdata(struct mdev_device *mdev)
{
        return mdev->driver_data;
}
EXPORT_SYMBOL(mdev_get_drvdata);

void mdev_set_drvdata(struct mdev_device *mdev, void *data)
{
        mdev->driver_data = data;
}
EXPORT_SYMBOL(mdev_set_drvdata);

struct device *mdev_dev(struct mdev_device *mdev)
{
        return &mdev->dev;
}
EXPORT_SYMBOL(mdev_dev);

struct mdev_device *mdev_from_dev(struct device *dev)
{
        return dev_is_mdev(dev) ? to_mdev_device(dev) : NULL;
}
EXPORT_SYMBOL(mdev_from_dev);

uuid_le mdev_uuid(struct mdev_device *mdev)
{
        return mdev->uuid;
}
EXPORT_SYMBOL(mdev_uuid);

static int _find_mdev_device(struct device *dev, void *data)
{
        struct mdev_device *mdev;

        if (!dev_is_mdev(dev))
                return 0;

        mdev = to_mdev_device(dev);

        if (uuid_le_cmp(mdev->uuid, *(uuid_le *)data) == 0)
                return 1;

        return 0;
}

static bool mdev_device_exist(struct mdev_parent *parent, uuid_le uuid)
{
        struct device *dev;

        dev = device_find_child(parent->dev, &uuid, _find_mdev_device);
        if (dev) {
                put_device(dev);
                return true;
        }

        return false;
}

/* Should be called holding parent_list_lock */
static struct mdev_parent *__find_parent_device(struct device *dev)
{
        struct mdev_parent *parent;

        list_for_each_entry(parent, &parent_list, next) {
                if (parent->dev == dev)
                        return parent;
        }
        return NULL;
}

static void mdev_release_parent(struct kref *kref)
{
        struct mdev_parent *parent = container_of(kref, struct mdev_parent,
                                                  ref);
        struct device *dev = parent->dev;

        kfree(parent);
        put_device(dev);
}

static
inline struct mdev_parent *mdev_get_parent(struct mdev_parent *parent)
{
        if (parent)
                kref_get(&parent->ref);

        return parent;
}

static inline void mdev_put_parent(struct mdev_parent *parent)
{
        if (parent)
                kref_put(&parent->ref, mdev_release_parent);
}

static int mdev_device_create_ops(struct kobject *kobj,
                                  struct mdev_device *mdev)
{
        struct mdev_parent *parent = mdev->parent;
        int ret;

        ret = parent->ops->create(kobj, mdev);
        if (ret)
                return ret;

        ret = sysfs_create_groups(&mdev->dev.kobj,
                                  parent->ops->mdev_attr_groups);
        if (ret)
                parent->ops->remove(mdev);

        return ret;
}

/*
 * mdev_device_remove_ops gets called from sysfs's 'remove' and when parent
 * device is being unregistered from mdev device framework.
 * - 'force_remove' is set to 'false' when called from sysfs's 'remove' which
 *   indicates that if the mdev device is active, used by VMM or userspace
 *   application, vendor driver could return error then don't remove the device.
 * - 'force_remove' is set to 'true' when called from mdev_unregister_device()
 *   which indicate that parent device is being removed from mdev device
 *   framework so remove mdev device forcefully.
 */
static int mdev_device_remove_ops(struct mdev_device *mdev, bool force_remove)
{
        struct mdev_parent *parent = mdev->parent;
        int ret;

        /*
         * Vendor driver can return error if VMM or userspace application is
         * using this mdev device.
         */
        ret = parent->ops->remove(mdev);
        if (ret && !force_remove)
                return -EBUSY;

        sysfs_remove_groups(&mdev->dev.kobj, parent->ops->mdev_attr_groups);
        return 0;
}

static int mdev_device_remove_cb(struct device *dev, void *data)
{
        if (!dev_is_mdev(dev))
                return 0;

        return mdev_device_remove(dev, data ? *(bool *)data : true);
}

/*
 * mdev_register_device : Register a device
 * @dev: device structure representing parent device.
 * @ops: Parent device operation structure to be registered.
 *
 * Add device to list of registered parent devices.
 * Returns a negative value on error, otherwise 0.
 */
int mdev_register_device(struct device *dev, const struct mdev_parent_ops *ops)
{
        int ret;
        struct mdev_parent *parent;

        /* check for mandatory ops */
        if (!ops || !ops->create || !ops->remove || !ops->supported_type_groups)
                return -EINVAL;

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

        mutex_lock(&parent_list_lock);

        /* Check for duplicate */
        parent = __find_parent_device(dev);
        if (parent) {
                ret = -EEXIST;
                goto add_dev_err;
        }

        parent = kzalloc(sizeof(*parent), GFP_KERNEL);
        if (!parent) {
                ret = -ENOMEM;
                goto add_dev_err;
        }

        kref_init(&parent->ref);
        mutex_init(&parent->lock);

        parent->dev = dev;
        parent->ops = ops;

        if (!mdev_bus_compat_class) {
                mdev_bus_compat_class = class_compat_register("mdev_bus");
                if (!mdev_bus_compat_class) {
                        ret = -ENOMEM;
                        goto add_dev_err;
                }
        }

        ret = parent_create_sysfs_files(parent);
        if (ret)
                goto add_dev_err;

        ret = class_compat_create_link(mdev_bus_compat_class, dev, NULL);
        if (ret)
                dev_warn(dev, "Failed to create compatibility class link\n");

        list_add(&parent->next, &parent_list);
        mutex_unlock(&parent_list_lock);

        dev_info(dev, "MDEV: Registered\n");
        return 0;

add_dev_err:
        mutex_unlock(&parent_list_lock);
        if (parent)
                mdev_put_parent(parent);
        else
                put_device(dev);
        return ret;
}
EXPORT_SYMBOL(mdev_register_device);

/*
 * mdev_unregister_device : Unregister a parent device
 * @dev: device structure representing parent device.
 *
 * Remove device from list of registered parent devices. Give a chance to free
 * existing mediated devices for given device.
 */

void mdev_unregister_device(struct device *dev)
{
        struct mdev_parent *parent;
        bool force_remove = true;

        mutex_lock(&parent_list_lock);
        parent = __find_parent_device(dev);

        if (!parent) {
                mutex_unlock(&parent_list_lock);
                return;
        }
        dev_info(dev, "MDEV: Unregistering\n");

        list_del(&parent->next);
        class_compat_remove_link(mdev_bus_compat_class, dev, NULL);

        device_for_each_child(dev, (void *)&force_remove,
                              mdev_device_remove_cb);

        parent_remove_sysfs_files(parent);

        mutex_unlock(&parent_list_lock);
        mdev_put_parent(parent);
}
EXPORT_SYMBOL(mdev_unregister_device);

static void mdev_device_release(struct device *dev)
{
        struct mdev_device *mdev = to_mdev_device(dev);

        dev_dbg(&mdev->dev, "MDEV: destroying\n");
        kfree(mdev);
}

int mdev_device_create(struct kobject *kobj, struct device *dev, uuid_le uuid)
{
        int ret;
        struct mdev_device *mdev;
        struct mdev_parent *parent;
        struct mdev_type *type = to_mdev_type(kobj);

        parent = mdev_get_parent(type->parent);
        if (!parent)
                return -EINVAL;

        mutex_lock(&parent->lock);

        /* Check for duplicate */
        if (mdev_device_exist(parent, uuid)) {
                ret = -EEXIST;
                goto create_err;
        }

        mdev = kzalloc(sizeof(*mdev), GFP_KERNEL);
        if (!mdev) {
                ret = -ENOMEM;
                goto create_err;
        }

        memcpy(&mdev->uuid, &uuid, sizeof(uuid_le));
        mdev->parent = parent;
        kref_init(&mdev->ref);

        mdev->dev.parent  = dev;
        mdev->dev.bus     = &mdev_bus_type;
        mdev->dev.release = mdev_device_release;
        dev_set_name(&mdev->dev, "%pUl", uuid.b);

        ret = device_register(&mdev->dev);
        if (ret) {
                put_device(&mdev->dev);
                goto create_err;
        }

        ret = mdev_device_create_ops(kobj, mdev);
        if (ret)
                goto create_failed;

        ret = mdev_create_sysfs_files(&mdev->dev, type);
        if (ret) {
                mdev_device_remove_ops(mdev, true);
                goto create_failed;
        }

        mdev->type_kobj = kobj;
        dev_dbg(&mdev->dev, "MDEV: created\n");

        mutex_unlock(&parent->lock);

        mutex_lock(&mdev_list_lock);
        list_add(&mdev->next, &mdev_list);
        mutex_unlock(&mdev_list_lock);

        return ret;

create_failed:
        device_unregister(&mdev->dev);

create_err:
        mutex_unlock(&parent->lock);
        mdev_put_parent(parent);
        return ret;
}

int mdev_device_remove(struct device *dev, bool force_remove)
{
        struct mdev_device *mdev, *tmp;
        struct mdev_parent *parent;
        struct mdev_type *type;
        int ret;
        bool found = false;

        mdev = to_mdev_device(dev);

        mutex_lock(&mdev_list_lock);
        list_for_each_entry(tmp, &mdev_list, next) {
                if (tmp == mdev) {
                        found = true;
                        break;
                }
        }

        if (found)
                list_del(&mdev->next);

        mutex_unlock(&mdev_list_lock);

        if (!found)
                return -ENODEV;

        type = to_mdev_type(mdev->type_kobj);
        parent = mdev->parent;
        mutex_lock(&parent->lock);

        ret = mdev_device_remove_ops(mdev, force_remove);
        if (ret) {
                mutex_unlock(&parent->lock);

                mutex_lock(&mdev_list_lock);
                list_add(&mdev->next, &mdev_list);
                mutex_unlock(&mdev_list_lock);

                return ret;
        }

        mdev_remove_sysfs_files(dev, type);
        device_unregister(dev);
        mutex_unlock(&parent->lock);
        mdev_put_parent(parent);

        return 0;
}

static int __init mdev_init(void)
{
        return mdev_bus_register();
}

static void __exit mdev_exit(void)
{
        if (mdev_bus_compat_class)
                class_compat_unregister(mdev_bus_compat_class);

        mdev_bus_unregister();
}

module_init(mdev_init)
module_exit(mdev_exit)

MODULE_VERSION(DRIVER_VERSION);
MODULE_LICENSE("GPL v2");
MODULE_AUTHOR(DRIVER_AUTHOR);
MODULE_DESCRIPTION(DRIVER_DESC);
MODULE_SOFTDEP("post: vfio_mdev");