ldterm(7) DG/UX R4.11MU05 ldterm(7)
NAME
ldterm - standard STREAMS terminal line discipline module
DESCRIPTION
ldterm is a STREAMS module that provides most of the termio(7)
terminal interface. This module does not perform the low-level
device control functions specified by flags in the ccflag word of
the termio/termios structure or by the IGNBRK, IGNPAR, PARMRK, or
INPCK flags in the ciflag word of the termio/termios structure;
those functions must be performed by the driver or by modules pushed
below the ldterm module. All other termio/termios functions are
performed by ldterm; some of them, however, require the cooperation
of the driver or modules pushed below ldterm and may not be performed
in some cases. These include the IXOFF flag in the ciflag word and
the delays specified in the coflag word.
ldterm also handles EUC and multi-byte characters.
The remainder of this section describes the processing of various
STREAMS messages on the read- and write-side.
Read-side Behavior
Various types of STREAMS messages are processed as follows:
MBREAK
When this message is received, either an interrupt signal is
generated or the message is treated as if it were an MDATA
message containing a single ASCII NUL character, depending on
the state of the BRKINT flag.
MDATA
This message is normally processed using the standard termio
input processing. If the ICANON flag is set, a single input
record (``line'') is accumulated in an internal buffer and sent
upstream when a line-terminating character is received. If the
ICANON flag is not set, other input processing is performed and
the processed data are passed upstream.
If output is to be stopped or started as a result of the arrival
of characters (usually CNTRL-Q and CNTRL-S), MSTOP and MSTART
messages are sent downstream. If the IXOFF flag is set and
input is to be stopped or started as a result of flow-control
considerations, MSTOPI and MSTARTI messages are sent
downstream.
MDATA messages are sent downstream, as necessary, to perform
echoing.
If a signal is to be generated, an MFLUSH message with a flag
byte of FLUSHR is placed on the read queue. If the signal is
also to flush output, an MFLUSH message with a flag byte of
FLUSHW is sent downstream.
MCTL
If the size of the data buffer associated with the message is
the size of struct iocblk, ldterm will perform functional
negotiation to determine where the termio(7) processing is to be
done. If the command field of the iocblk structure (ioccmd) is
set to MCNOCANON, the input canonical processing normally
performed on MDATA messages is disabled and those messages are
passed upstream unmodified; this is for the use of modules or
drivers that perform their own input processing, such as a
pseudo-terminal in TIOCREMOTE mode connected to a program that
performs this processing. If the command is MCDOCANON, all
input processing is enabled. If the command is MCPARTCANON,
then an MDATA message containing a termios structure is
expected to be attached to the original MCTL message. The
ldterm module will examine the iflag, oflag, and lflag fields of
the termios structure and from then on will process only those
flags which have not been turned ON. If none of the above
commands are found, the message is ignored; in any case, the
message is passed upstream.
MFLUSH
The read queue of the module is flushed of all its data messages
and all data in the record being accumulated are also flushed.
The message is passed upstream.
MIOCACK
The data contained within the message, which is to be returned
to the process, are augmented if necessary, and the message is
passed upstream.
All other messages are passed upstream unchanged.
Write-side Behavior
Various types of STREAMS messages are processed as follows:
MFLUSH
The write queue of the module is flushed of all its data
messages and the message is passed downstream.
MIOCTL
The function of this ioctl is performed and the message is
passed downstream in most cases. The TCFLSH and TCXONC ioctls
can be performed entirely in the ldterm module, so the reply is
sent upstream and the message is not passed downstream.
MDATA
If the OPOST flag is set, or both the XCASE and ICANON flags are
set, output processing is performed and the processed message is
passed downstream along with any MDELAY messages generated.
Otherwise, the message is passed downstream without change.
All other messages are passed downstream unchanged.
IOCTLS
The following ioctls are processed by the ldterm module. All others
are passed downstream. EUCWSET and EUCWGET are ISTR ioctl calls
whereas other ioctls listed here are TRANSPARENT ioctls.
TCGETS/TCGETA
The message is passed downstream; if an acknowledgment is seen,
the data provided by the driver and modules downstream are
augmented and the acknowledgement is passed upstream.
TCSETS/TCSETSW/TCSETSF/TCSETA/TCSETAW/TCSETAF
The parameters that control the behavior of the ldterm module
are changed. If a mode change requires options at the stream
head to be changed, an MSETOPTS message is sent upstream. If
the ICANON flag is turned on or off, the read mode at the stream
head is changed to message-nondiscard or byte-stream mode,
respectively. If the TOSTOP flag is turned on or off, the
tostop mode at the stream head is turned on or off,
respectively.
TCFLSH
If the argument is 0, an MFLUSH message with a flag byte of
FLUSHR is sent downstream and placed on the read queue. If the
argument is 1, the write queue is flushed of all its data
messages and an MFLUSH message with a flag byte of FLUSHW is
sent upstream and downstream. If the argument is 2, the write
queue is flushed of all its data messages and an MFLUSH message
with a flag byte of FLUSHRW is sent downstream and placed on the
read queue.
TCXONC
If the argument is 0 and output is not already stopped, an
MSTOP message is sent downstream. If the argument is 1 and
output is stopped, an MSTART message is sent downstream. If
the argument is 2 and input is not already stopped, an MSTOPI
message is sent downstream. If the argument is 3 and input is
stopped, an MSTARTI message is sent downstream.
TCSBRK
The message is passed downstream, so the driver has a chance to
drain the data and then send and an MIOCACK message upstream.
EUCWSET
This call takes a pointer to an eucioc structure, and uses it to
set the EUC line discipline's local definition for the code set
widths to be used for subsequent operations. Within the stream,
the line discipline may optionally notify other modules of this
setting via MCTL messages.
EUCWGET
This call takes a pointer to an eucioc structure, and returns in
it the EUC code set widths currently in use by the EUC line
discipline.
SEE ALSO
termios(2), console(7), ports(7), termio(7).
Programmer's Guide: STREAMS.
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