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
90 lines
2.9 KiB
Groff
90 lines
2.9 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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.\" $FreeBSD$
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.\"
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.Dd August 20, 2008
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.Dt PTY 4
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.Os
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.Sh NAME
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.Nm pty
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.Nd BSD-style compatibility pseudo-terminal driver
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.Sh SYNOPSIS
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.Cd "device pty"
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.Sh DESCRIPTION
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The
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.Nm
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driver provides support for the traditional BSD naming scheme that was
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used for accessing pseudo-terminals.
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When the device
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.Pa /dev/ptyXX
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is being opened, a new terminal shall be created with the
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.Xr pts 4
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driver.
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A device node for this terminal shall be created, which has the name
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.Pa /dev/ttyXX .
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.Pp
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New code should not try to allocate pseudo-terminals using this
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interface.
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It is only provided for compatibility with older C libraries
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that tried to open such devices when
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.Xr posix_openpt 2
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was being called.
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.Sh FILES
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The BSD-style compatibility pseudo-terminal driver uses the following
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device names:
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.Pp
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.Bl -tag -width ".Pa /dev/pty[l-sL-S][0-9a-v]"
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.It Pa /dev/pty[l-sL-S][0-9a-v]
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Pseudo-terminal master devices.
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.It Pa /dev/tty[l-sL-S][0-9a-v]
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Pseudo-terminal slave devices.
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.El
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.Sh DIAGNOSTICS
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None.
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.Sh SEE ALSO
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.Xr posix_openpt 2 ,
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.Xr pts 4 ,
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.Xr tty 4
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.Sh HISTORY
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A
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pseudo-terminal driver appeared in
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.Bx 4.2 .
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.Sh BUGS
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Unlike previous implementations, the master slave device nodes are
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destroyed when the PTY becomes unused.
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A call to
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.Xr stat 2
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on a nonexistent master device will already cause a new master device
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node to be created.
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The master device can only be destroyed by opening and closing it.
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.Pp
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The
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.Nm
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driver cannot be unloaded, because it cannot determine if it is being
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used.
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