/*  Xenbus code for blkif tap

    A Warfield.

    Hastily modified from the oroginal backend code:

    Copyright (C) 2005 Rusty Russell <rusty@rustcorp.com.au>

    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.

    You should have received a copy of the GNU General Public License
    along with this program; if not, write to the Free Software
    Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
*/

#include <stdarg.h>
#include <linux/module.h>
#include <xen/xenbus.h>
#include "common.h"

struct backend_info
{
	struct xenbus_device *dev;

	/* our communications channel */
	blkif_t *blkif;

	long int frontend_id;

	/* watch back end for changes */
	struct xenbus_watch backend_watch;

	/* watch front end for changes */
	struct xenbus_watch watch;
	char *frontpath;
};

static int blkback_remove(struct xenbus_device *dev)
{
	struct backend_info *be = dev->data;

	if (be->watch.node)
		unregister_xenbus_watch(&be->watch);
	unregister_xenbus_watch(&be->backend_watch);
	if (be->blkif)
		blkif_put(be->blkif);
	kfree(be->frontpath);
	kfree(be);
	return 0;
}

/* Front end tells us frame. */
static void frontend_changed(struct xenbus_watch *watch,
			     const char **vec, unsigned int len)
{
	unsigned long ring_ref;
	unsigned int evtchn;
	int err;
	struct backend_info *be
		= container_of(watch, struct backend_info, watch);

	/* If other end is gone, delete ourself. */
	if (vec && !xenbus_exists(be->frontpath, "")) {
		xenbus_rm(be->dev->nodename, "");
		device_unregister(&be->dev->dev);
		return;
	}
	if (be->blkif == NULL || be->blkif->status == CONNECTED)
		return;

	err = xenbus_gather(be->frontpath, "ring-ref", "%lu", &ring_ref,
			    "event-channel", "%u", &evtchn, NULL);
	if (err) {
		xenbus_dev_error(be->dev, err,
				 "reading %s/ring-ref and event-channel",
				 be->frontpath);
		return;
	}

	/* Map the shared frame, irq etc. */
	err = blkif_map(be->blkif, ring_ref, evtchn);
	if (err) {
		xenbus_dev_error(be->dev, err, "mapping ring-ref %lu port %u",
				 ring_ref, evtchn);
		goto abort;
	}

	xenbus_dev_ok(be->dev);

	return;

abort:
	xenbus_transaction_end(1);
}

/* 
   Setup supplies physical device.  
   We provide event channel and device details to front end.
   Frontend supplies shared frame and event channel.
 */
static void backend_changed(struct xenbus_watch *watch,
			    const char **vec, unsigned int len)
{
	int err;