ldterm - standard STREAMS terminal line discipline module
#include <sys/stream.h>
#include <sys/termios.h>
int ioctl(fd,I_PUSH,"ldterm");
The ldterm STREAMS module provides most of the
termio(4I) terminal interface. The vis module does not perform
the low-level device control 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 functions
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 specified 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.
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-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), 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.
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
message is the size of
struct iocblk,
ldterm will perform
functional negotiation to determine where the
termio(4I) 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 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
MC_DO_CANON, all input processing 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.
The ldterm module processes the following
TRANSPARENT ioctls. All others 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 eucioc data 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 discipline. If the current codeset of the line discipline is
not an EUC one, the result is meaningless.