diff options
author | Michael S. Tsirkin <mst@redhat.com> | 2010-03-17 13:07:58 +0200 |
---|---|---|
committer | Anthony Liguori <aliguori@us.ibm.com> | 2010-04-01 13:56:43 -0500 |
commit | 2292b33986de9e2ac10b2674f85722bdfbc977d5 (patch) | |
tree | bdc0ccf007042957f24fa4275b68602dd6bfdb7d /hw | |
parent | ca82180603446831187203383de4b5ede4e2c346 (diff) | |
download | hqemu-2292b33986de9e2ac10b2674f85722bdfbc977d5.zip hqemu-2292b33986de9e2ac10b2674f85722bdfbc977d5.tar.gz |
notifier: event notifier implementation
event notifiers are slightly generalized eventfd descriptors. Current
implementation depends on eventfd because vhost is the only user, and
vhost depends on eventfd anyway, but a stub is provided for non-eventfd
case.
We'll be able to further generalize this when another user comes along
and we see how to best do this.
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
Diffstat (limited to 'hw')
-rw-r--r-- | hw/event_notifier.c | 62 | ||||
-rw-r--r-- | hw/event_notifier.h | 16 |
2 files changed, 78 insertions, 0 deletions
diff --git a/hw/event_notifier.c b/hw/event_notifier.c new file mode 100644 index 0000000..13f3656 --- /dev/null +++ b/hw/event_notifier.c @@ -0,0 +1,62 @@ +/* + * event notifier support + * + * Copyright Red Hat, Inc. 2010 + * + * Authors: + * Michael S. Tsirkin <mst@redhat.com> + * + * This work is licensed under the terms of the GNU GPL, version 2. See + * the COPYING file in the top-level directory. + */ + +#include "hw.h" +#include "event_notifier.h" +#ifdef CONFIG_EVENTFD +#include <sys/eventfd.h> +#endif + +int event_notifier_init(EventNotifier *e, int active) +{ +#ifdef CONFIG_EVENTFD + int fd = eventfd(!!active, EFD_NONBLOCK | EFD_CLOEXEC); + if (fd < 0) + return -errno; + e->fd = fd; + return 0; +#else + return -ENOSYS; +#endif +} + +void event_notifier_cleanup(EventNotifier *e) +{ + close(e->fd); +} + +int event_notifier_get_fd(EventNotifier *e) +{ + return e->fd; +} + +int event_notifier_test_and_clear(EventNotifier *e) +{ + uint64_t value; + int r = read(e->fd, &value, sizeof(value)); + return r == sizeof(value); +} + +int event_notifier_test(EventNotifier *e) +{ + uint64_t value; + int r = read(e->fd, &value, sizeof(value)); + if (r == sizeof(value)) { + /* restore previous value. */ + int s = write(e->fd, &value, sizeof(value)); + /* never blocks because we use EFD_SEMAPHORE. + * If we didn't we'd get EAGAIN on overflow + * and we'd have to write code to ignore it. */ + assert(s == sizeof(value)); + } + return r == sizeof(value); +} diff --git a/hw/event_notifier.h b/hw/event_notifier.h new file mode 100644 index 0000000..24117ea --- /dev/null +++ b/hw/event_notifier.h @@ -0,0 +1,16 @@ +#ifndef QEMU_EVENT_NOTIFIER_H +#define QEMU_EVENT_NOTIFIER_H + +#include "qemu-common.h" + +struct EventNotifier { + int fd; +}; + +int event_notifier_init(EventNotifier *, int active); +void event_notifier_cleanup(EventNotifier *); +int event_notifier_get_fd(EventNotifier *); +int event_notifier_test_and_clear(EventNotifier *); +int event_notifier_test(EventNotifier *); + +#endif |