1994-05-27 05:00:24 +00:00
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.\" Copyright (c) 1991, 1993
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.\" The Regents of the University of California. All rights reserved.
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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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2017-02-28 23:42:47 +00:00
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.\" 3. Neither the name of the University nor the names of its contributors
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1994-05-27 05:00:24 +00:00
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.\" may be used to endorse or promote products derived from this software
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.\" without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS 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 REGENTS 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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.\" @(#)tcsendbreak.3 8.1 (Berkeley) 6/4/93
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1999-08-28 00:22:10 +00:00
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.\" $FreeBSD$
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1994-05-27 05:00:24 +00:00
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.\"
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Rework tty_drain() to poll the hardware for completion, and restore
drain timeout handling to historical freebsd behavior.
The primary reason for these changes is the need to have tty_drain() call
ttydevsw_busy() at some reasonable sub-second rate, to poll hardware that
doesn't signal an interrupt when the transmit shift register becomes empty
(which includes virtually all USB serial hardware). Such hardware hangs
in a ttyout wait, because it never gets an opportunity to trigger a wakeup
from the sleep in tty_drain() by calling ttydisc_getc() again, after
handing the last of the buffered data to the hardware.
While researching the history of changes to tty_drain() I stumbled across
some email describing the historical BSD behavior of tcdrain() and close()
on serial ports, and the ability of comcontrol(1) to control timeout
behavior. Using that and some advice from Bruce Evans as a guide, I've
put together these changes to implement the hardware polling and restore
the historical timeout behaviors...
- tty_drain() now calls ttydevsw_busy() in a loop at 10 Hz to accomodate
hardware that requires polling for busy state.
- The "new historical" behavior for draining during close(2) is retained:
the drain timeout is "1 second without making any progress". When the
1-second timeout expires, if the count of bytes remaining in the tty
layer buffer is smaller than last time, the timeout is extended for
another second. Unfortunately, the same logic cannot be extended all
the way down to the hardware, because the interface to that layer is a
simple busy/not-busy indication.
- Due to the previous point, an application that needs a guarantee that
all data has been transmitted must use TIOCDRAIN/tcdrain(3) before
calling close(2).
- The historical behavior of honoring the drainwait setting for TIOCDRAIN
(used by tcdrain(3)) is restored.
- The historical kern.drainwait sysctl to control the global default
drainwait time is restored, but is now named kern.tty_drainwait.
- The historical default drainwait timeout of 300 seconds is restored.
- Handling of TIOCGDRAINWAIT and TIOCSDRAINWAIT ioctls is restored
(this also makes the comcontrol(1) drainwait verb work again).
- Manpages are updated to document these behaviors.
Reviewed by: bde (prior version)
2017-01-12 00:48:06 +00:00
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.Dd January 11, 2017
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1994-05-27 05:00:24 +00:00
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.Dt TCSENDBREAK 3
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.Os
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.Sh NAME
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.Nm tcsendbreak ,
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.Nm tcdrain ,
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.Nm tcflush ,
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.Nm tcflow
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.Nd line control functions
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2000-04-21 09:42:15 +00:00
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.Sh LIBRARY
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.Lb libc
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1994-05-27 05:00:24 +00:00
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.Sh SYNOPSIS
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2001-10-01 16:09:29 +00:00
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.In termios.h
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1994-05-27 05:00:24 +00:00
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.Ft int
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.Fn tcdrain "int fd"
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.Ft int
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.Fn tcflow "int fd" "int action"
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.Ft int
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.Fn tcflush "int fd" "int action"
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.Ft int
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.Fn tcsendbreak "int fd" "int len"
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.Sh DESCRIPTION
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The
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1996-08-22 22:05:59 +00:00
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.Fn tcdrain
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1994-05-27 05:00:24 +00:00
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function waits until all output written to the terminal referenced by
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.Fa fd
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has been transmitted to the terminal.
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.Pp
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The
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1996-08-22 22:05:59 +00:00
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.Fn tcflow
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1994-05-27 05:00:24 +00:00
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function suspends transmission of data to or the reception of data from
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the terminal referenced by
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.Fa fd
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depending on the value of
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.Fa action .
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The value of
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.Fa action
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must be one of the following:
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.Bl -tag -width "TCIOFF"
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.It Fa TCOOFF
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Suspend output.
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.It Fa TCOON
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Restart suspended output.
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.It Fa TCIOFF
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Transmit a STOP character, which is intended to cause the terminal to stop
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transmitting data to the system.
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(See the description of IXOFF in the
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.Ql Input Modes
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section of
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2001-01-16 09:08:22 +00:00
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.Xr termios 4 ) .
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1994-05-27 05:00:24 +00:00
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.It Fa TCION
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Transmit a START character, which is intended to cause the terminal to start
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transmitting data to the system.
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(See the description of IXOFF in the
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.Ql Input Modes
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section of
|
2001-01-16 09:08:22 +00:00
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.Xr termios 4 ) .
|
1994-05-27 05:00:24 +00:00
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.El
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.Pp
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The
|
1996-08-22 22:05:59 +00:00
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.Fn tcflush
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1994-05-27 05:00:24 +00:00
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function discards any data written to the terminal referenced by
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.Fa fd
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which has not been transmitted to the terminal, or any data received
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from the terminal but not yet read, depending on the value of
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.Fa action .
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The value of
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.Fa action
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must be one of the following:
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.Bl -tag -width "TCIOFLUSH"
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.It Fa TCIFLUSH
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Flush data received but not read.
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.It Fa TCOFLUSH
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Flush data written but not transmitted.
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.It Fa TCIOFLUSH
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Flush both data received but not read and data written but not transmitted.
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.El
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.Pp
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The
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1996-08-22 22:05:59 +00:00
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.Fn tcsendbreak
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1994-05-27 05:00:24 +00:00
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function transmits a continuous stream of zero-valued bits for four-tenths
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of a second to the terminal referenced by
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.Fa fd .
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The
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.Fa len
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2002-12-19 09:40:28 +00:00
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argument is ignored in this implementation.
|
1994-05-27 05:00:24 +00:00
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.Sh RETURN VALUES
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Upon successful completion, all of these functions return a value of zero.
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.Sh ERRORS
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If any error occurs, a value of -1 is returned and the global variable
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.Va errno
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is set to indicate the error, as follows:
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.Bl -tag -width Er
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.It Bq Er EBADF
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The
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.Fa fd
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argument is not a valid file descriptor.
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.It Bq Er EINVAL
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The
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.Fa action
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argument is not a proper value.
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.It Bq Er ENOTTY
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The file associated with
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.Fa fd
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is not a terminal.
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.It Bq Er EINTR
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A signal interrupted the
|
1996-08-22 22:05:59 +00:00
|
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.Fn tcdrain
|
1994-05-27 05:00:24 +00:00
|
|
|
function.
|
Rework tty_drain() to poll the hardware for completion, and restore
drain timeout handling to historical freebsd behavior.
The primary reason for these changes is the need to have tty_drain() call
ttydevsw_busy() at some reasonable sub-second rate, to poll hardware that
doesn't signal an interrupt when the transmit shift register becomes empty
(which includes virtually all USB serial hardware). Such hardware hangs
in a ttyout wait, because it never gets an opportunity to trigger a wakeup
from the sleep in tty_drain() by calling ttydisc_getc() again, after
handing the last of the buffered data to the hardware.
While researching the history of changes to tty_drain() I stumbled across
some email describing the historical BSD behavior of tcdrain() and close()
on serial ports, and the ability of comcontrol(1) to control timeout
behavior. Using that and some advice from Bruce Evans as a guide, I've
put together these changes to implement the hardware polling and restore
the historical timeout behaviors...
- tty_drain() now calls ttydevsw_busy() in a loop at 10 Hz to accomodate
hardware that requires polling for busy state.
- The "new historical" behavior for draining during close(2) is retained:
the drain timeout is "1 second without making any progress". When the
1-second timeout expires, if the count of bytes remaining in the tty
layer buffer is smaller than last time, the timeout is extended for
another second. Unfortunately, the same logic cannot be extended all
the way down to the hardware, because the interface to that layer is a
simple busy/not-busy indication.
- Due to the previous point, an application that needs a guarantee that
all data has been transmitted must use TIOCDRAIN/tcdrain(3) before
calling close(2).
- The historical behavior of honoring the drainwait setting for TIOCDRAIN
(used by tcdrain(3)) is restored.
- The historical kern.drainwait sysctl to control the global default
drainwait time is restored, but is now named kern.tty_drainwait.
- The historical default drainwait timeout of 300 seconds is restored.
- Handling of TIOCGDRAINWAIT and TIOCSDRAINWAIT ioctls is restored
(this also makes the comcontrol(1) drainwait verb work again).
- Manpages are updated to document these behaviors.
Reviewed by: bde (prior version)
2017-01-12 00:48:06 +00:00
|
|
|
.It Bq Er EWOULDBLOCK
|
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|
The configured timeout expired before the
|
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|
.Fn tcdrain
|
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|
|
function could write all buffered output.
|
1994-05-27 05:00:24 +00:00
|
|
|
.El
|
|
|
|
|
.Sh SEE ALSO
|
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|
|
|
.Xr tcsetattr 3 ,
|
Rework tty_drain() to poll the hardware for completion, and restore
drain timeout handling to historical freebsd behavior.
The primary reason for these changes is the need to have tty_drain() call
ttydevsw_busy() at some reasonable sub-second rate, to poll hardware that
doesn't signal an interrupt when the transmit shift register becomes empty
(which includes virtually all USB serial hardware). Such hardware hangs
in a ttyout wait, because it never gets an opportunity to trigger a wakeup
from the sleep in tty_drain() by calling ttydisc_getc() again, after
handing the last of the buffered data to the hardware.
While researching the history of changes to tty_drain() I stumbled across
some email describing the historical BSD behavior of tcdrain() and close()
on serial ports, and the ability of comcontrol(1) to control timeout
behavior. Using that and some advice from Bruce Evans as a guide, I've
put together these changes to implement the hardware polling and restore
the historical timeout behaviors...
- tty_drain() now calls ttydevsw_busy() in a loop at 10 Hz to accomodate
hardware that requires polling for busy state.
- The "new historical" behavior for draining during close(2) is retained:
the drain timeout is "1 second without making any progress". When the
1-second timeout expires, if the count of bytes remaining in the tty
layer buffer is smaller than last time, the timeout is extended for
another second. Unfortunately, the same logic cannot be extended all
the way down to the hardware, because the interface to that layer is a
simple busy/not-busy indication.
- Due to the previous point, an application that needs a guarantee that
all data has been transmitted must use TIOCDRAIN/tcdrain(3) before
calling close(2).
- The historical behavior of honoring the drainwait setting for TIOCDRAIN
(used by tcdrain(3)) is restored.
- The historical kern.drainwait sysctl to control the global default
drainwait time is restored, but is now named kern.tty_drainwait.
- The historical default drainwait timeout of 300 seconds is restored.
- Handling of TIOCGDRAINWAIT and TIOCSDRAINWAIT ioctls is restored
(this also makes the comcontrol(1) drainwait verb work again).
- Manpages are updated to document these behaviors.
Reviewed by: bde (prior version)
2017-01-12 00:48:06 +00:00
|
|
|
.Xr termios 4 ,
|
|
|
|
|
.Xr tty 4 ,
|
|
|
|
|
.Xr comcontrol 8
|
1994-05-27 05:00:24 +00:00
|
|
|
.Sh STANDARDS
|
|
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|
The
|
1996-08-22 22:05:59 +00:00
|
|
|
.Fn tcsendbreak ,
|
|
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|
.Fn tcflush
|
1994-05-27 05:00:24 +00:00
|
|
|
and
|
1996-08-22 22:05:59 +00:00
|
|
|
.Fn tcflow
|
1994-05-27 05:00:24 +00:00
|
|
|
functions are expected to be compliant with the
|
|
|
|
|
.St -p1003.1-88
|
|
|
|
|
specification.
|
Rework tty_drain() to poll the hardware for completion, and restore
drain timeout handling to historical freebsd behavior.
The primary reason for these changes is the need to have tty_drain() call
ttydevsw_busy() at some reasonable sub-second rate, to poll hardware that
doesn't signal an interrupt when the transmit shift register becomes empty
(which includes virtually all USB serial hardware). Such hardware hangs
in a ttyout wait, because it never gets an opportunity to trigger a wakeup
from the sleep in tty_drain() by calling ttydisc_getc() again, after
handing the last of the buffered data to the hardware.
While researching the history of changes to tty_drain() I stumbled across
some email describing the historical BSD behavior of tcdrain() and close()
on serial ports, and the ability of comcontrol(1) to control timeout
behavior. Using that and some advice from Bruce Evans as a guide, I've
put together these changes to implement the hardware polling and restore
the historical timeout behaviors...
- tty_drain() now calls ttydevsw_busy() in a loop at 10 Hz to accomodate
hardware that requires polling for busy state.
- The "new historical" behavior for draining during close(2) is retained:
the drain timeout is "1 second without making any progress". When the
1-second timeout expires, if the count of bytes remaining in the tty
layer buffer is smaller than last time, the timeout is extended for
another second. Unfortunately, the same logic cannot be extended all
the way down to the hardware, because the interface to that layer is a
simple busy/not-busy indication.
- Due to the previous point, an application that needs a guarantee that
all data has been transmitted must use TIOCDRAIN/tcdrain(3) before
calling close(2).
- The historical behavior of honoring the drainwait setting for TIOCDRAIN
(used by tcdrain(3)) is restored.
- The historical kern.drainwait sysctl to control the global default
drainwait time is restored, but is now named kern.tty_drainwait.
- The historical default drainwait timeout of 300 seconds is restored.
- Handling of TIOCGDRAINWAIT and TIOCSDRAINWAIT ioctls is restored
(this also makes the comcontrol(1) drainwait verb work again).
- Manpages are updated to document these behaviors.
Reviewed by: bde (prior version)
2017-01-12 00:48:06 +00:00
|
|
|
.Pp
|
|
|
|
|
The
|
|
|
|
|
.Fn tcdrain
|
|
|
|
|
function is expected to be compliant with
|
|
|
|
|
.St -p1003.1-88
|
|
|
|
|
when the drain wait value is set to zero with
|
|
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|
|
.Xr comcontrol 8 ,
|
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|
|
|
or with
|
|
|
|
|
.Xr ioctl 2
|
|
|
|
|
.Va TIOCSDRAINWAIT ,
|
|
|
|
|
or with
|
|
|
|
|
.Xr sysctl 8
|
|
|
|
|
.Va kern.tty_drainwait .
|
|
|
|
|
A non-zero drain wait value can result in
|
|
|
|
|
.Fn tcdrain
|
|
|
|
|
returning
|
|
|
|
|
.Va EWOULDBLOCK
|
|
|
|
|
without writing all output.
|
|
|
|
|
The default value for
|
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|
|
|
.Va kern.tty_drainwait
|
|
|
|
|
is 300 seconds.
|
