include/posix/sys/eventfd.h

/*
 * Copyright (c) 2020 Tobias Svehagen
 *
 * SPDX-License-Identifier: Apache-2.0
 */

#ifndef ZEPHYR_INCLUDE_POSIX_SYS_EVENTFD_H_
#define ZEPHYR_INCLUDE_POSIX_SYS_EVENTFD_H_

#include <zephyr.h>
#include <sys/fdtable.h>
#include <sys/types.h>

#include <fcntl.h>

#ifdef __cplusplus
extern "C" {
#endif

#define EFD_IN_USE    0x1
#define EFD_SEMAPHORE 0x2
#define EFD_NONBLOCK  O_NONBLOCK
#define EFD_FLAGS_SET (EFD_SEMAPHORE | EFD_NONBLOCK)

typedef uint64_t eventfd_t;

/**
 * @brief Create a file descriptor for event notification
 *
 * The returned file descriptor can be used with POSIX read/write calls or
 * with the eventfd_read/eventfd_write functions.
 *
 * It also supports polling and by including an eventfd in a call to poll,
 * it is possible to signal and wake the polling thread by simply writing to
 * the eventfd.
 *
 * When using read() and write() on an eventfd, the size must always be at
 * least 8 bytes or the operation will fail with EINVAL.
 *
 * @return New eventfd file descriptor on success, -1 on error
 */
int eventfd(unsigned int initval, int flags);

/**
 * @brief Read from an eventfd
 *
 * If call is successful, the value parameter will have the value 1
 *
 * @param fd File descriptor
 * @param value Pointer for storing the read value
 *
 * @return 0 on success, -1 on error
 */
static inline int eventfd_read(int fd, eventfd_t *value)
{
	const struct fd_op_vtable *efd_vtable;
	struct k_mutex *lock;
	ssize_t ret;
	void *obj;

	obj = z_get_fd_obj_and_vtable(fd, &efd_vtable, &lock);

	(void)k_mutex_lock(lock, K_FOREVER);

	ret = efd_vtable->read(obj, value, sizeof(*value));

	k_mutex_unlock(lock);

	return ret == sizeof(eventfd_t) ? 0 : -1;
}

/**
 * @brief Write to an eventfd
 *
 * @param fd File descriptor
 * @param value Value to write
 *
 * @return 0 on success, -1 on error
 */
static inline int eventfd_write(int fd, eventfd_t value)
{
	const struct fd_op_vtable *efd_vtable;
	struct k_mutex *lock;
	ssize_t ret;
	void *obj;

	obj = z_get_fd_obj_and_vtable(fd, &efd_vtable, &lock);

	(void)k_mutex_lock(lock, K_FOREVER);

	ret = efd_vtable->write(obj, &value, sizeof(value));

	k_mutex_unlock(lock);

	return ret == sizeof(eventfd_t) ? 0 : -1;
}

#ifdef __cplusplus
}
#endif

#endif /* ZEPHYR_INCLUDE_POSIX_SYS_EVENTFD_H_ */