Mmap io_uring ring after setup
# DESCRIPTION
The [io_uring_queue_mmap] function maps the io_uring ring file
descriptor *fd* into memory using the parameters in *p*. The resulting
ring is stored in *ring*.
This function is a helper for applications that need to customize the
ring setup process. Most applications should use
[io_uring_queue_init] or [io_uring_queue_init_params] instead,
which call [io_uring_setup] and this function automatically.
The *fd* argument should be a file descriptor returned by
[io_uring_setup], and *p* should contain the parameters returned by
the setup call.
# RETURN VALUE
Returns 0 on success, or a negative errno value on error.
# SEE ALSO
[io_uring_setup], [io_uring_queue_init],
[io_uring_queue_init_params], [io_uring_queue_exit]