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+.\" Copyright (C) 2003 Free Software Foundation, Inc.
+.\"
+.\" SPDX-License-Identifier: GPL-1.0-or-later
+.\"
+.TH io_setup 2 (date) "Linux man-pages (unreleased)"
+.SH NAME
+io_setup \- create an asynchronous I/O context
+.SH LIBRARY
+Standard C library
+.RI ( libc ", " \-lc )
+.P
+Alternatively, Asynchronous I/O library
+.RI ( libaio ", " \-laio );
+see VERSIONS.
+.SH SYNOPSIS
+.nf
+.BR "#include <linux/aio_abi.h>" "          /* Defines needed types */"
+.P
+.BI "long io_setup(unsigned int " nr_events ", aio_context_t *" ctx_idp );
+.fi
+.P
+.IR Note :
+There is no glibc wrapper for this system call; see VERSIONS.
+.SH DESCRIPTION
+.IR Note :
+this page describes the raw Linux system call interface.
+The wrapper function provided by
+.I libaio
+uses a different type for the
+.I ctx_idp
+argument.
+See VERSIONS.
+.P
+The
+.BR io_setup ()
+system call
+creates an asynchronous I/O context suitable for concurrently processing
+\fInr_events\fP operations.
+The
+.I ctx_idp
+argument must not point to an AIO context that already exists, and must
+be initialized to 0 prior to the call.
+On successful creation of the AIO context, \fI*ctx_idp\fP is filled in
+with the resulting handle.
+.SH RETURN VALUE
+On success,
+.BR io_setup ()
+returns 0.
+For the failure return, see VERSIONS.
+.SH ERRORS
+.TP
+.B EAGAIN
+The specified \fInr_events\fP exceeds the limit of available events,
+as defined in
+.I /proc/sys/fs/aio\-max\-nr
+(see
+.BR proc (5)).
+.TP
+.B EFAULT
+An invalid pointer is passed for \fIctx_idp\fP.
+.TP
+.B EINVAL
+\fIctx_idp\fP is not initialized, or the specified \fInr_events\fP
+exceeds internal limits.
+\fInr_events\fP should be greater than 0.
+.TP
+.B ENOMEM
+Insufficient kernel resources are available.
+.TP
+.B ENOSYS
+.BR io_setup ()
+is not implemented on this architecture.
+.SH VERSIONS
+glibc does not provide a wrapper for this system call.
+You could invoke it using
+.BR syscall (2).
+But instead, you probably want to use the
+.BR io_setup ()
+wrapper function provided by
+.\" http://git.fedorahosted.org/git/?p=libaio.git
+.IR libaio .
+.P
+Note that the
+.I libaio
+wrapper function uses a different type
+.RI ( "io_context_t\ *" )
+.\" But glibc is confused, since <libaio.h> uses 'io_context_t' to declare
+.\" the system call.
+for the
+.I ctx_idp
+argument.
+Note also that the
+.I libaio
+wrapper does not follow the usual C library conventions for indicating errors:
+on error it returns a negated error number
+(the negative of one of the values listed in ERRORS).
+If the system call is invoked via
+.BR syscall (2),
+then the return value follows the usual conventions for
+indicating an error: \-1, with
+.I errno
+set to a (positive) value that indicates the error.
+.SH STANDARDS
+Linux.
+.SH HISTORY
+Linux 2.5.
+.SH SEE ALSO
+.BR io_cancel (2),
+.BR io_destroy (2),
+.BR io_getevents (2),
+.BR io_submit (2),
+.BR aio (7)
+.\" .SH AUTHOR
+.\" Kent Yoder.