.\" Copyright (C) 2025 Jens Axboe <axboe@kernel.dk>
.\"
.\" SPDX-License-Identifier: LGPL-2.0-or-later
.\"
.TH io_uring_prep_readv_fixed 3 "January 18, 2025" "liburing-2.10" "liburing Manual"
.SH NAME
io_uring_prep_readv_fixed \- prepare a vectored read using fixed buffers
.SH SYNOPSIS
.nf
.B #include <liburing.h>
.PP
.BI "void io_uring_prep_readv_fixed(struct io_uring_sqe *" sqe ","
.BI "                               int " fd ","
.BI "                               const struct iovec *" iovecs ","
.BI "                               unsigned " nr_vecs ","
.BI "                               __u64 " offset ","
.BI "                               int " flags ","
.BI "                               int " buf_index ");"
.fi
.SH DESCRIPTION
.PP
The
.BR io_uring_prep_readv_fixed (3)
function prepares a vectored read request using fixed (registered) buffers.
The submission queue entry
.I sqe
is setup to use the file descriptor
.I fd
to start reading
.I nr_vecs
iovecs from the file position
.IR offset .

The
.I iovecs
argument points to an array of iovec structures describing the read
buffers. All buffers must be part of the registered buffer set at index
.IR buf_index ,
previously registered with
.BR io_uring_register_buffers (3).

The
.I flags
argument can contain any per-request flags, such as
.B RWF_NOWAIT
or other flags supported by
.BR preadv2 (2).

Using fixed buffers avoids the overhead of mapping buffers for each I/O
operation, improving performance for applications that reuse the same
buffers.

.SH RETURN VALUE
None
.SH ERRORS
The CQE
.I res
field will contain the result of the operation, the number of bytes read
on success. On error, a negative errno value is returned.
.SH SEE ALSO
.BR io_uring_get_sqe (3),
.BR io_uring_submit (3),
.BR io_uring_prep_readv (3),
.BR io_uring_prep_readv2 (3),
.BR io_uring_prep_read_fixed (3),
.BR io_uring_prep_writev_fixed (3),
.BR io_uring_register_buffers (3)