ref: cbe4b116989c0bfec49b9ae7a1d9a85ead6648ae
dir: /sys/src/9/xen/xen-public/io/libxenvchan.h/
/**
* @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 a user-specified
* path.
*
* 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 <stdint.h>
#include <sys/types.h>
struct ring_shared {
uint32_t cons, prod;
};
#define VCHAN_NOTIFY_WRITE 0x1
#define VCHAN_NOTIFY_READ 0x2
/**
* vchan_interface: primary shared data structure
*/
struct vchan_interface {
/**
* Standard consumer/producer interface, one pair per buffer
* left is client write, server read
* right is client read, server write
*/
struct ring_shared left, right;
/**
* size of the rings, which determines their location
* 10 - at offset 1024 in ring's page
* 11 - at offset 2048 in ring's page
* 12+ - uses 2^(N-12) grants to describe the multi-page ring
* These should remain constant once the page is shared.
* Only one of the two orders can be 10 (or 11).
*/
uint16_t left_order, right_order;
/**
* Shutdown detection:
* 0: client (or server) has exited
* 1: client (or server) is connected
* 2: client has not yet connected
*/
uint8_t cli_live, srv_live;
/**
* Notification bits:
* VCHAN_NOTIFY_WRITE: send notify when data is written
* VCHAN_NOTIFY_READ: send notify when data is read (consumed)
* cli_notify is used for the client to inform the server of its action
*/
uint8_t cli_notify, srv_notify;
/**
* Grant list: ordering is left, right. Must not extend into actual ring
* or grow beyond the end of the initial shared page.
* These should remain constant once the page is shared, to allow
* for possible remapping by a client that restarts.
*/
uint32_t grants[0];
};