xemu/include/hw/xen/xen-bus-helper.h
Paul Durrant 82a29e3048 xen: add xenstore watcher infrastructure
A Xen PV frontend communicates its state to the PV backend by writing to
the 'state' key in the frontend area in xenstore. It is therefore
necessary for a XenDevice implementation to be notified whenever the
value of this key changes.

This patch adds code to do this as follows:

- an 'fd handler' is registered on the libxenstore handle which will be
  triggered whenever a 'watch' event occurs
- primitives are added to xen-bus-helper to add or remove watch events
- a list of Notifier objects is added to XenBus to provide a mechanism
  to call the appropriate 'watch handler' when its associated event
  occurs

The xen-block implementation is extended with a 'frontend_changed' method,
which calls as-yet stub 'connect' and 'disconnect' functions when the
relevant frontend state transitions occur. A subsequent patch will supply
a full implementation for these functions.

Signed-off-by: Paul Durrant <paul.durrant@citrix.com>
Reviewed-by: Anthony Perard <anthony.perard@citrix.com>
Signed-off-by: Anthony PERARD <anthony.perard@citrix.com>
2019-01-14 13:45:40 +00:00

46 lines
1.9 KiB
C

/*
* Copyright (c) 2018 Citrix Systems Inc.
*
* This work is licensed under the terms of the GNU GPL, version 2 or later.
* See the COPYING file in the top-level directory.
*/
#ifndef HW_XEN_BUS_HELPER_H
#define HW_XEN_BUS_HELPER_H
#include "hw/xen/xen_common.h"
const char *xs_strstate(enum xenbus_state state);
void xs_node_create(struct xs_handle *xsh, xs_transaction_t tid,
const char *node, struct xs_permissions perms[],
unsigned int nr_perms, Error **errp);
void xs_node_destroy(struct xs_handle *xsh, xs_transaction_t tid,
const char *node, Error **errp);
/* Write to node/key unless node is empty, in which case write to key */
void xs_node_vprintf(struct xs_handle *xsh, xs_transaction_t tid,
const char *node, const char *key, Error **errp,
const char *fmt, va_list ap)
GCC_FMT_ATTR(6, 0);
void xs_node_printf(struct xs_handle *xsh, xs_transaction_t tid,
const char *node, const char *key, Error **errp,
const char *fmt, ...)
GCC_FMT_ATTR(6, 7);
/* Read from node/key unless node is empty, in which case read from key */
int xs_node_vscanf(struct xs_handle *xsh, xs_transaction_t tid,
const char *node, const char *key, Error **errp,
const char *fmt, va_list ap);
int xs_node_scanf(struct xs_handle *xsh, xs_transaction_t tid,
const char *node, const char *key, Error **errp,
const char *fmt, ...);
/* Watch node/key unless node is empty, in which case watch key */
void xs_node_watch(struct xs_handle *xsh, const char *node, const char *key,
char *token, Error **errp);
void xs_node_unwatch(struct xs_handle *xsh, const char *node, const char *key,
const char *token, Error **errp);
#endif /* HW_XEN_BUS_HELPER_H */