NAME

       io_uring_register_eventfd - register an eventfd with a ring

SYNOPSIS

       #include <liburing.h>

       int io_uring_register_eventfd(struct io_uring *ring,
                                     int fd);

       int io_uring_register_eventfd_async(struct io_uring *ring,
                                           int fd);

       int io_uring_unregister_eventfd(struct io_uring *ring);

DESCRIPTION

       io_uring_register_eventfd(3)  registers  the  eventfd  file  descriptor  fd  with the ring
       identified by ring.

       Whenever completions are posted to the CQ ring, an eventfd notification is generated  with
       the  registered  eventfd  descriptor.  If io_uring_register_eventfd_async(3) is used, only
       events that completed out-of-line will trigger a notification.

       It notifications are no longer desired, io_uring_unregister_eventfd(3) may  be  called  to
       remove  the eventfd registration. No eventfd argument is needed, as a ring can only have a
       single eventfd registered.

NOTES

       While io_uring generally takes care to avoid spurious events, they can occur.   Similarly,
       batched  completions  of  CQEs  may  only  trigger  a  single eventfd notification even if
       multiple CQEs are posted. The application should make no assumptions on number  of  events
       being  available  having  a direct correlation to eventfd notifications posted. An eventfd
       notification must thus only be treated as a hint to check the CQ ring for completions.

RETURN VALUE

       Returns 0 on success, or or -errno on error.

SEE ALSO

       eventfd(2)