bc093719ca
The last half year I've been working on a replacement TTY layer for the FreeBSD kernel. The new TTY layer was designed to improve the following: - Improved driver model: The old TTY layer has a driver model that is not abstract enough to make it friendly to use. A good example is the output path, where the device drivers directly access the output buffers. This means that an in-kernel PPP implementation must always convert network buffers into TTY buffers. If a PPP implementation would be built on top of the new TTY layer (still needs a hooks layer, though), it would allow the PPP implementation to directly hand the data to the TTY driver. - Improved hotplugging: With the old TTY layer, it isn't entirely safe to destroy TTY's from the system. This implementation has a two-step destructing design, where the driver first abandons the TTY. After all threads have left the TTY, the TTY layer calls a routine in the driver, which can be used to free resources (unit numbers, etc). The pts(4) driver also implements this feature, which means posix_openpt() will now return PTY's that are created on the fly. - Improved performance: One of the major improvements is the per-TTY mutex, which is expected to improve scalability when compared to the old Giant locking. Another change is the unbuffered copying to userspace, which is both used on TTY device nodes and PTY masters. Upgrading should be quite straightforward. Unlike previous versions, existing kernel configuration files do not need to be changed, except when they reference device drivers that are listed in UPDATING. Obtained from: //depot/projects/mpsafetty/... Approved by: philip (ex-mentor) Discussed: on the lists, at BSDCan, at the DevSummit Sponsored by: Snow B.V., the Netherlands dcons(4) fixed by: kan
136 lines
4.2 KiB
Groff
136 lines
4.2 KiB
Groff
.\" Copyright (c) 2008 Ed Schouten <ed@FreeBSD.org>
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.\" All rights reserved.
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.\"
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.\" Portions of this software were developed under sponsorship from Snow
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.\" B.V., the Netherlands.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" Portions of this text are reprinted and reproduced in electronic form
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.\" from IEEE Std 1003.1, 2004 Edition, Standard for Information Technology --
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.\" Portable Operating System Interface (POSIX), The Open Group Base
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.\" Specifications Issue 6, Copyright (C) 2001-2004 by the Institute of
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.\" Electrical and Electronics Engineers, Inc and The Open Group. In the
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.\" event of any discrepancy between this version and the original IEEE and
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.\" The Open Group Standard, the original IEEE and The Open Group Standard is
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.\" the referee document. The original Standard can be obtained online at
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.\" http://www.opengroup.org/unix/online.html.
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.\"
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.\" $FreeBSD$
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.\"
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.Dd August 20, 2008
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.Dt POSIX_OPENPT 2
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.Os
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.Sh NAME
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.Nm posix_openpt
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.Nd "open a pseudo-terminal device"
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.Sh LIBRARY
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.Lb libc
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.Sh SYNOPSIS
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.In stdlib.h
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.In fcntl.h
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.Ft int
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.Fn posix_openpt "int oflag"
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.Sh DESCRIPTION
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The
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.Fn posix_openpt
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function allocates a new pseudo-terminal and establishes a connection
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with its master device.
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A slave device shall be created in
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.Pa /dev/pts .
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After the pseudo-terminal has been allocated, the slave device should
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have the proper permissions before it can be used (see
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.Xr grantpt 3 ) .
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The name of the slave device can be determined by calling
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.Xr ptsname 3 .
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.Pp
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The file status flags and file access modes of the open file description
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shall be set according to the value of
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.Fa oflag .
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Values for
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.Fa oflag
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are constructed by a bitwise-inclusive OR of flags from the following
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list, defined in
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.In fcntl.h :
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.Bl -tag -width ".Dv O_NOCTTY"
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.It Dv O_RDWR
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Open for reading and writing.
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.It Dv O_NOCTTY
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If set
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.Fn posix_openpt
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shall not cause the terminal device to become the controlling terminal
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for the process.
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.El
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.Pp
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The
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.Fn posix_openpt
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function shall fail when
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.Fa oflag
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contains other values.
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.Sh RETURN VALUES
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Upon successful completion, the
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.Fn posix_openpt
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function shall allocate a new pseudo-terminal device and return a
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non-negative integer representing a file descriptor, which is connected
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to its master device.
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Otherwise, -1 shall be returned and errno set to indicate the error.
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.Sh ERRORS
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The
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.Fn posix_openpt
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function shall fail if:
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.Bl -tag -width Er
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.It Bq Er ENFILE
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The system file table is full.
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.It Bq Er EINVAL
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The value of
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.Fa oflag
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is not valid.
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.It Bq Er EAGAIN
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Out of pseudo-terminal resources.
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.El
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.Sh SEE ALSO
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.Xr pts 4 ,
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.Xr ptsname 3 ,
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.Xr tty 4
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.Sh STANDARDS
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The
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.Fn posix_openpt
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function conforms to
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.St -p1003.1-2001 .
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.Sh HISTORY
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The
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.Fn posix_openpt
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function appeared in
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.Fx 5.0 .
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In
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.Fx 8.0 ,
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this function was changed to a system call.
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.Sh NOTES
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The flag
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.Dv O_NOCTTY
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is included for compatibility; in
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.Fx ,
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opening a terminal does not cause it to become a process's controlling
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terminal.
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.Sh AUTHORS
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.An Ed Schouten Aq ed@FreeBSD.org
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