/*
 * 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_set(EventNotifier *e)
{
    uint64_t value = 1;
    int r = write(e->fd, &value, sizeof(value));
    return r == sizeof(value);
}

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);
}
