ldterm(7M) STREAMS Modules ldterm(7M)NAMEldterm - standard STREAMS terminal line discipline module
SYNOPSIS
#include <sys/stream.h>
#include <sys/termios.h>
int ioctl(fd,I_PUSH,"ldterm");
DESCRIPTION
The ldterm STREAMS module provides most of the termio(7I) terminal
interface. The vis module does not perform the low-level device con‐
trol functions specified by flags in the c_cflag word of the
termio/termios structure, or by the IGNBRK, IGNPAR, PARMRK, or INPCK
flags in the c_iflag word of the termio/termios structure. Those func‐
tions must be performed by the driver or by modules pushed below the
ldterm module. The ldterm module performs all other termio/termios
functions, though some may 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 c_iflag word and the delays speci‐
fied in the c_oflag word.
The ldterm module also handles single and multi-byte characters from
various codesets including both Extended Unix Code (EUC) and non-EUC
codesets.
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:
M_BREAK Depending on the state of the BRKINT flag, either an
interrupt signal is generated or the message is treated
as if it were an M_DATA message containing a single
ASCII NUL character when this message is received.
M_DATA 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-terminat‐
ing character is received. If the ICANON flag is not
set, other input processing is performed and the pro‐
cessed 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), M_STOP and M_START 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,
M_STOPI and M_STARTI messages are sent downstream.
M_DATA messages are sent downstream, as necessary, to
perform echoing.
If a signal is to be generated, an M_FLUSH message with
a flag byte of FLUSHR is placed on the read queue. If
the signal is also to flush output, an M_FLUSH message
with a flag byte of FLUSHW is sent downstream.
All other messages are passed upstream unchanged.
Write-side Behavior
Various types of STREAMS messages are processed as follows:
M_FLUSH The write queue of the module is flushed of all its
data messages and the message is passed downstream.
M_IOCTL 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.
M_DATA 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
M_DELAY messages generated. Otherwise, the message is
passed downstream without change.
M_CTL If the size of the data buffer associated with the mes‐
sage is the size of struct iocblk, ldterm will perform
functional negotiation to determine where the
termio(7I) processing is to be done. If the command
field of the iocblk structure (ioc_cmd) is set to
MC_NO_CANON, the input canonical processing normally
performed on M_DATA messages is disabled and those mes‐
sages 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 process‐
ing). If the command is MC_DO_CANON, all input process‐
ing is enabled. If the command is MC_PART_CANON, then
an M_DATA message containing a termios structure is
expected to be attached to the original M_CTL message.
The ldterm module will examine the iflag, oflag, and
lflag fields of the termios structure and from that
point on, will process only those flags that 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.
M_FLUSH 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.
M_IOCACK 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 downstream unchanged.
IOCTLS
The ldterm module processes the following TRANSPARENT ioctls. All oth‐
ers are passed downstream.
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 M_SETOPTS 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. In any case, ldterm passes the
ioctl on downstream for possible additional processing.
TCFLSH
If the argument is 0, an M_FLUSH 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
M_FLUSH 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 M_FLUSH 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 M_STOP
message is sent downstream. If the argument is 1 and output is
stopped, an M_START message is sent downstream. If the argument is
2 and input is not already stopped, an M_STOPI message is sent
downstream. If the argument is 3 and input is stopped, an M_STARTI
message is sent downstream.
TCSBRK
The message is passed downstream, so the driver has a chance to
drain the data and then send an M_IOCACK message upstream.
EUC_WSET
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
using M_CTL messages. When this call is received and the eucioc‐
structure contains valid data, the line discipline changes into EUC
handling mode once the euciocdata is completely transferred to an
internal data structure.
EUC_WGET
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 disci‐
pline. If the current codeset of the line discipline is not an EUC
one, the result is meaningless.
SEE ALSOtermios(3C), console(7D), termio(7I)
STREAMS Programming Guide
SunOS 5.10 7 Jun1999 ldterm(7M)
