su(7D) Devices su(7D)NAMEsu - asynchronous serial port driver
SYNOPSIS
#include <fcntl.h>
#include <sys/termios.h>
open("/dev/tty[a-z]", _mode);
open("/dev/term[a-z]", _mode);
open("/dev/cua[a-z]", _mode);
DESCRIPTION
The su module is a loadable STREAMS driver that provides basic support
for standard UARTS that use Intel-8250, National Semiconduc‐
tor-16450/16550 hardware and Southbridge 1535D (16550 compatable) Super
I/O hardware. The module also provides keyboard and mouse I/O support
for Sun machines using those same Intel, National Semiconductor and
Southbridge chipsets. The su driver provides basic asynchronous commu‐
nication support for serial ports. Both the serial devices and key‐
board/mouse devices will have streams built with appropriate modules
pushed atop the su driver by means of either the autopush(1M) or
dacf.conf(4) facilities, depending on the OS revision and architecture
in use.
The su module supports those termio(7I) device control functions speci‐
fied by flags in the c_cflag word of the termios structure, and by the
IGNBRK, IGNPAR, PARMRK, or INPCK flags in the c_iflag word of the
termios structure. All other termio(7I) functions must be performed by
STREAMS modules pushed atop the driver. When a device is opened, the
ldterm(7M) and ttcompat(7M) STREAMS modules are automatically pushed on
top of the stream, providing the standard termio(7I) interface.
The character-special devices /dev/ttya and /dev/ttyb are used to
access the two standard serial ports. The su module supports up to ten
serial ports, including the standard ports. The tty[a-z] devices have
minor device numbers in the range 00-03, and may be assigned names of
the form /dev/ttyd_n_, where _n_ denotes the line to be accessed.
These device names are typically used to provide a logical access point
for a _dial-in_ line that is used with a modem.
To allow a single tty line to be connected to a modem and used for
incoming and outgoing calls, a special feature is available that is
controlled by the minor device number. By accessing character-special
devices with names of the form /dev/cua_n, it is possible to open a
port without the Carrier Detect signal being asserted, either through
hardware or an equivalent software mechanism. These devices are com‐
monly known as _dial-out_ lines.
APPLICATION PROGRAMMING INTERFACE
Once a /dev/cua_n_ line is opened, the corresponding tty, or ttyd line
cannot be opened until the /dev/cua_n_ line is closed. A blocking open
will wait until the /dev/cua_n_ line is closed (which will drop Data
Terminal Ready, after which Carrier Detect will usually drop as well)
and carrier is detected again. A non-blocking open will return an
error. If the /dev/ttyd_n_ line has been opened successfully (usually
only when carrier is recognized on the modem), the corresponding
/dev/cua_n_ line cannot be opened. This allows a modem to be attached
to a device, (for example, /dev/ttyd0, which is renamed from
/dev/tty00) and used for dial-in (by enabling the line for login in
/etc/inittab) or dial-out (by tip(1) or uucp(1C)) as /dev/cua0 when no
one is logged in on the line.
IOCTLS
The standard set of termio ioctl() calls are supported by su.
Breaks can be generated by the TCSBRK, TIOCSBRK, and TIOCCBRK ioctl()
calls.
The input and output line speeds may be set to any of the following
baud rates: 0, 50, 75, 110, 134, 150, 200, 300, 600, 1200, 1800,
2400, 4800, 9600, 19200, 38400, 57600 or 115200. The speeds cannot be
set independently; for example, when the output speed is set, the input
speed is automatically set to the same speed.
When the su module is used to service the serial console port, it sup‐
ports a BREAK condition that allows the system to enter the debugger or
the monitor. The BREAK condition is generated by hardware and it is
usually enabled by default.
A BREAK condition originating from erroneous electrical signals cannot
be distinguished from one deliberately sent by remote DCE. The Alter‐
nate Break sequence can be used as a remedy against this. Due to a risk
of incorrect sequence interpretation, SLIP and certain other binary
protocols should not be run over the serial console port when Alternate
Break sequence is in effect. Although PPP is a binary protocol, it is
able to avoid these sequences using the ACCM feature in RFC 1662. For
Solaris PPP 4.0, you do this by adding the following line to the
/etc/ppp/options file (or other configuration files used for the con‐
nection; see pppd(1M) for details):
asyncmap 0x00002000
By default, the Alternate Break sequence is a three character sequence:
carriage return, tilde and control-B (CR ~ CTRL-B), but may be changed
by the driver. For more information on breaking (entering the debugger
or monitor), see kbd(1) and kb(7M).
ERRORS
An open() will fail under the following conditions:
ENXIO The unit being opened does not exist.
EBUSY The dial-out device is being opened while the dial-in
device is already open, or the dial-in device is being
opened with a no-delay open and the dial-out device is
already open.
EBUSY The unit has been marked as exclusive-use by another
process with a TIOCEXCL ioctl() call.
FILES
/dev/cua/[a-z] dial-out tty lines
/dev/term/[a-z] dial-in tty lines
/dev/tty[a-z] binary compatibility package device names
ATTRIBUTES
See attributes(5) for descriptions of the following attributes:
┌─────────────────────────────┬─────────────────────────────┐
│ ATTRIBUTE TYPE │ ATTRIBUTE VALUE │
├─────────────────────────────┼─────────────────────────────┤
│Architecture │ SPARC │
└─────────────────────────────┴─────────────────────────────┘
SEE ALSOstrconf(1), kbd(1), tip(1),uucp(1C), autopush(1M), kstat(1M), pppd(1M),
ioctl(2), open(2), termios(3C), dacf.conf(4), attributes(5), kb(7M),
ldterm(7M), ttcompat(7M), termio(7I)DIAGNOSTICS
The su driver keeps track of various warning and error conditions using
kstat counters. The output of the kstat su command provides kstat coun‐
ters. The counters and their meaning follow:
silo overflow The internal chip FIFO received more data than
it could handle. This indicates that the
Solaris operating environment was not servicing
data interrupts fast enough possibly due to a
system with too many interrupts or a data line
with a data rate that is too high.
ring buffer overflow The su module was unable to store data it
removed from the chips internal FIFO into a
software buffer. The user process is not read‐
ing data fast enough, possibly due to an over‐
loaded system. If possible, the application
should enable flow control (either CTSRTS or
XONXOFF) to allow the driver to backpressure
the remote system when the local buffers fill
up.
SunOS 5.10 18 June 2004 su(7D)
