/**
 * @file
 * @section AUTHORS
 *
 * Copyright (C) 2010  Rafal Wojtczuk  <rafal@invisiblethingslab.com>
 *
 *  Authors:
 *       Rafal Wojtczuk  <rafal@invisiblethingslab.com>
 *       Daniel De Graaf <dgdegra@tycho.nsa.gov>
 *
 * @section LICENSE
 *
 *  This library is free software; you can redistribute it and/or
 *  modify it under the terms of the GNU Lesser General Public
 *  License as published by the Free Software Foundation; either
 *  version 2.1 of the License, or (at your option) any later version.
 *
 *  This library 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
 *  Lesser General Public License for more details.
 *
 *  You should have received a copy of the GNU Lesser General Public
 *  License along with this library; if not, write to the Free Software
 *  Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301 USA
 *
 * @section DESCRIPTION
 *
 *  Originally borrowed from the Qubes OS Project, http://www.qubes-os.org,
 *  this code has been substantially rewritten to use the gntdev and gntalloc
 *  devices instead of raw MFNs and map_foreign_range.
 *
 *  This is a library for inter-domain communication.  A standard Xen ring
 *  buffer is used, with a datagram-based interface built on top.  The grant
 *  reference and event channels are shared in XenStore under the path
 *  /local/domain/<srv-id>/data/vchan/<cli-id>/<port>/{ring-ref,event-channel}
 *
 *  The ring.h macros define an asymmetric interface to a shared data structure
 *  that assumes all rings reside in a single contiguous memory space. This is
 *  not suitable for vchan because the interface to the ring is symmetric except
 *  for the setup. Unlike the producer-consumer rings defined in ring.h, the
 *  size of the rings used in vchan are determined at execution time instead of
 *  compile time, so the macros in ring.h cannot be used to access the rings.
 */

#include <xen/io/libxenvchan.h>
#include <xen/sys/evtchn.h>
#include <xenctrl.h>

struct libxenvchan_ring {
	/* Pointer into the shared page. Offsets into buffer. */
	struct ring_shared* shr;
	/* ring data; may be its own shared page(s) depending on order */
	void* buffer;
	/**
	 * The size of the ring is (1 << order); offsets wrap around when they
	 * exceed this. This copy is required because we can't trust the order
	 * in the shared page to remain constant.
	 */
	int order;
};

/**
 * struct libxenvchan: control structure passed to all library calls
 */
struct libxenvchan {
	/* Mapping handle for shared ring page */
	union {
		xc_gntshr *gntshr; /* for server */
		xc_gnttab *gnttab; /* for client */
	};
	/* Pointer to shared ring page */
	struct vchan_interface *ring;
	/* event channel interface */
	xc_evtchn *event;
	uint32_t event_port;
	/* informative flags: are we acting as server? */
	int