From 2292b33986de9e2ac10b2674f85722bdfbc977d5 Mon Sep 17 00:00:00 2001 From: "Michael S. Tsirkin" Date: Wed, 17 Mar 2010 13:07:58 +0200 Subject: 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 Signed-off-by: Anthony Liguori --- hw/event_notifier.c | 62 +++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 62 insertions(+) create mode 100644 hw/event_notifier.c (limited to 'hw/event_notifier.c') diff --git a/hw/event_notifier.c b/hw/event_notifier.c new file mode 100644 index 0000000000..13f3656460 --- /dev/null +++ b/hw/event_notifier.c @@ -0,0 +1,62 @@ +/* + * event notifier support + * + * Copyright Red Hat, Inc. 2010 + * + * Authors: + * Michael S. Tsirkin + * + * 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 +#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); +} -- cgit v1.2.3