xen/9pfs: introduce Xen 9pfs transport driver

/*

 * linux/fs/9p/trans_xen

 *

 * Xen transport layer.

 *

 * Copyright (C) 2017 by 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 version 2

 * as published by the Free Software Foundation; or, when distributed

 * separately from the Linux kernel or incorporated into other

 * software packages, subject to the following license:

 *

 * Permission is hereby granted, free of charge, to any person obtaining a copy

 * of this source file (the "Software"), to deal in the Software without

 * restriction, including without limitation the rights to use, copy, modify,

 * merge, publish, distribute, sublicense, and/or sell copies of the Software,

 * and to permit persons to whom the Software is furnished to do so, subject to

 * the following conditions:

 *

 * The above copyright notice and this permission notice shall be included in

 * all copies or substantial portions of the Software.

 *

 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR

 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,

 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE

 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER

 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING

 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS

 * IN THE SOFTWARE.

 */

#include <xen/events.h>

#include <xen/grant_table.h>

#include <xen/xen.h>

#include <xen/xenbus.h>

#include <xen/interface/io/9pfs.h>

#include <linux/module.h>

#include <net/9p/9p.h>

#include <net/9p/client.h>

#include <net/9p/transport.h>

static int p9_xen_cancel(struct p9_client *client, struct p9_req_t *req)

{

	return 0;

}

static int p9_xen_create(struct p9_client *client, const char *addr, char *args)

{

	return 0;

}

static void p9_xen_close(struct p9_client *client)

{

}

static int p9_xen_request(struct p9_client *client, struct p9_req_t *p9_req)

{

	return 0;

}

static struct p9_trans_module p9_xen_trans = {

	.name = "xen",

	.maxsize = 1 << (XEN_9PFS_RING_ORDER + XEN_PAGE_SHIFT),

	.def = 1,

	.create = p9_xen_create,

	.close = p9_xen_close,

	.request = p9_xen_request,

	.cancel = p9_xen_cancel,

	.owner = THIS_MODULE,

};

static const struct xenbus_device_id xen_9pfs_front_ids[] = {

	{ "9pfs" },

	{ "" }

};

static int xen_9pfs_front_remove(struct xenbus_device *dev)

{

	return 0;

}

static int xen_9pfs_front_probe(struct xenbus_device *dev,

				const struct xenbus_device_id *id)

{

	return 0;

}

static int xen_9pfs_front_resume(struct xenbus_device *dev)

{

	return 0;

}

static void xen_9pfs_front_changed(struct xenbus_device *dev,

				   enum xenbus_state backend_state)

{

}

static struct xenbus_driver xen_9pfs_front_driver = {

	.ids = xen_9pfs_front_ids,

	.probe = xen_9pfs_front_probe,

	.remove = xen_9pfs_front_remove,

	.resume = xen_9pfs_front_resume,

	.otherend_changed = xen_9pfs_front_changed,

};

int p9_trans_xen_init(void)

{

	if (!xen_domain())

		return -ENODEV;

	pr_info("Initialising Xen transport for 9pfs\n");

	v9fs_register_trans(&p9_xen_trans);

	return xenbus_register_frontend(&xen_9pfs_front_driver);

}

module_init(p9_trans_xen_init);

void p9_trans_xen_exit(void)

{

	v9fs_unregister_trans(&p9_xen_trans);

	return xenbus_unregister_driver(&xen_9pfs_front_driver);

}

module_exit(p9_trans_xen_exit);