| .\" Copyright (C) 2022 Jens Axboe <axboe@kernel.dk> |
| .\" |
| .\" SPDX-License-Identifier: LGPL-2.0-or-later |
| .\" |
| .TH io_uring_prep_poll_add 3 "March 12, 2022" "liburing-2.2" "liburing Manual" |
| .SH NAME |
| io_uring_prep_poll_add \- prepare a poll request |
| .SH SYNOPSIS |
| .nf |
| .B #include <poll.h> |
| .B #include <liburing.h> |
| .PP |
| .BI "void io_uring_prep_poll_add(struct io_uring_sqe *" sqe "," |
| .BI " int " fd "," |
| .BI " unsigned " poll_mask ");" |
| .PP |
| .BI "void io_uring_prep_poll_multishot(struct io_uring_sqe *" sqe "," |
| .BI " int " fd "," |
| .BI " unsigned " poll_mask ");" |
| .fi |
| .SH DESCRIPTION |
| .PP |
| The |
| .BR io_uring_prep_poll_add (3) |
| function prepares a poll request. The submission queue entry |
| .I sqe |
| is setup to use the file descriptor |
| .I fd |
| that should get polled, with the events desired specified in the |
| .I poll_mask |
| argument. |
| |
| The default behavior is a single-shot poll request. When the specified event |
| has triggered, a completion CQE is posted and no more events will be generated |
| by the poll request. |
| .BR io_uring_prep_poll_multishot (3) |
| behaves identically in terms of events, but it persists across notifications |
| and will repeatedly post notifications for the same registration. A CQE |
| posted from a multishot poll request will have |
| .B IORING_CQE_F_MORE |
| set in the CQE |
| .I flags |
| member, indicating that the application should expect more completions from |
| this request. If the multishot poll request gets terminated or experiences |
| an error, this flag will not be set in the CQE. If this happens, the application |
| should not expect further CQEs from the original request and must reissue a |
| new one if it still wishes to get notifications on this file descriptor. |
| |
| .SH RETURN VALUE |
| None |
| .SH ERRORS |
| The CQE |
| .I res |
| field will contain the result of the operation, which is a bitmask of the |
| events notified. See the |
| .BR poll (2) |
| man page for details. Note that where synchronous system calls will return |
| .B -1 |
| on failure and set |
| .I errno |
| to the actual error value, io_uring never uses |
| .IR errno . |
| Instead it returns the negated |
| .I errno |
| directly in the CQE |
| .I res |
| field. |
| .SH SEE ALSO |
| .BR io_uring_get_sqe (3), |
| .BR io_uring_submit (3), |
| .BR poll (2), |
| .BR epoll_ctl (3) |
