xen/pvcalls: introduce the pvcalls xenbus backend

/*

 * (c) 2017 Stefano Stabellini <stefano@aporeto.com>

 *

 * This program is free software; you can redistribute it and/or modify

 * it under the terms of the GNU General Public License as published by

 * the Free Software Foundation; either version 2 of the License, or

 * (at your option) any later version.

 *

 * This program is distributed in the hope that it will be useful,

 * but WITHOUT ANY WARRANTY; without even the implied warranty of

 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

 * GNU General Public License for more details.

 */

#include <linux/kthread.h>

#include <linux/list.h>

#include <linux/radix-tree.h>

#include <linux/module.h>

#include <linux/semaphore.h>

#include <linux/wait.h>

#include <xen/events.h>

#include <xen/grant_table.h>

#include <xen/xen.h>

#include <xen/xenbus.h>

#include <xen/interface/io/pvcalls.h>

static int pvcalls_back_probe(struct xenbus_device *dev,

			      const struct xenbus_device_id *id)

{

	return 0;

}

static void pvcalls_back_changed(struct xenbus_device *dev,

				 enum xenbus_state frontend_state)

{

}

static int pvcalls_back_remove(struct xenbus_device *dev)

{

	return 0;

}

static int pvcalls_back_uevent(struct xenbus_device *xdev,

			       struct kobj_uevent_env *env)

{

	return 0;

}

static const struct xenbus_device_id pvcalls_back_ids[] = {

	{ "pvcalls" },

	{ "" }

};

static struct xenbus_driver pvcalls_back_driver = {

	.ids = pvcalls_back_ids,

	.probe = pvcalls_back_probe,

	.remove = pvcalls_back_remove,

	.uevent = pvcalls_back_uevent,

	.otherend_changed = pvcalls_back_changed,

};