PPC: E500: Implement msgclr
[qemu.git] / event_notifier.c
1 /*
2 * event notifier support
3 *
4 * Copyright Red Hat, Inc. 2010
5 *
6 * Authors:
7 * Michael S. Tsirkin <mst@redhat.com>
8 *
9 * This work is licensed under the terms of the GNU GPL, version 2 or later.
10 * See the COPYING file in the top-level directory.
11 */
12
13 #include "event_notifier.h"
14 #ifdef CONFIG_EVENTFD
15 #include <sys/eventfd.h>
16 #endif
17
18 int event_notifier_init(EventNotifier *e, int active)
19 {
20 #ifdef CONFIG_EVENTFD
21 int fd = eventfd(!!active, EFD_NONBLOCK | EFD_CLOEXEC);
22 if (fd < 0)
23 return -errno;
24 e->fd = fd;
25 return 0;
26 #else
27 return -ENOSYS;
28 #endif
29 }
30
31 void event_notifier_cleanup(EventNotifier *e)
32 {
33 close(e->fd);
34 }
35
36 int event_notifier_get_fd(EventNotifier *e)
37 {
38 return e->fd;
39 }
40
41 int event_notifier_test_and_clear(EventNotifier *e)
42 {
43 uint64_t value;
44 int r = read(e->fd, &value, sizeof(value));
45 return r == sizeof(value);
46 }
47
48 int event_notifier_test(EventNotifier *e)
49 {
50 uint64_t value;
51 int r = read(e->fd, &value, sizeof(value));
52 if (r == sizeof(value)) {
53 /* restore previous value. */
54 int s = write(e->fd, &value, sizeof(value));
55 /* never blocks because we use EFD_SEMAPHORE.
56 * If we didn't we'd get EAGAIN on overflow
57 * and we'd have to write code to ignore it. */
58 assert(s == sizeof(value));
59 }
60 return r == sizeof(value);
61 }