usbsacm - USB communication device class ACM driver


#include <sys/termio.h>



The usbsacm driver is a loadable STREAMS and USBA (Solaris USB
architecture)-compliant client driver that provides basic asynchronous
communication support for USB modems and ISDN terminal adapters that
conform to the Universal Serial Bus Communication Device Class Abstract
Control Model (USB CDC ACM) specification. You can download the USB CDC
specification from the USB website at Supported
devices include mobile phones and PCMCIA cards which provide modem
function by the usb cable. Serial device streams are built with
appropriate modules that are pushed atop the usbsacm driver by the
autopush(8) facility.

The usbsacm module supports the termio(4I) device control functions
specified by flags in the c_cflag word of termios structure, and by the
IGNBRK, IGNPAR, PARMRK and INPCK flags in the c_iflag word of the termios
structure. All other termio(4I) functions must be performed by STREAMS
modules pushed atop the driver. When a device is opened, the ldterm(4M)
and ttcompat(4M) STREAMS modules are automatically pushed on top of the
stream, providing the standard termio(4I) interface.

You use device logical names /dev/term/[0-9]* to access the serial ports.
These names are typically used to provide a logical access point for a
dial-in line that is used with a modem. You can use pppd(8) to transmit
datagrams over these serial ports.

A special feature (controlled by the minor device number) is available
that enables a single tty line to be connected to a modem and used for
incoming and outgoing calls. By accessing through device logical name
/dev/cua/[0-9]*, you can open a port without the carrier detect signal
being asserted, either through hardware or an equivalent software
mechanism. These devices are commonly known as 'dial-out' lines.

Unlike onboard serial ports, the usbsacm ports cannot serve as a local
serial console.


A dial-in line can be opened only if the corresponding dial-out
line is closed. A blocking /dev/term open waits until the /dev/cua line
is closed (which drops Data Terminal Ready, after which Carrier Detect
usually drops as well) and carrier is detected again. A non-blocking
/dev/term open returns an error if the /dev/cua is open.

If the /dev/term line is opened successfully (usually only when
carrier is recognized on the modem), the corresponding /dev/cua line
cannot be opened. This allows a modem and port to be 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.

Device hot-removal is functionally equivalent to a modem disconnect
event, as defined in termio(4I).


The usbsacm driver supports the standard set of termio(4I) ioctl calls.

The input and output line speeds may be set to any of the following baud
rates: 75, 150, 300, 600, 1200, 1800, 2400, 4800, 9600, 19200, 38400,
57600, 115200, 230400, 460800, 921600, 1000000, 1152000, 1500000,
2000000, 2500000, 3000000, 3500000, or 4000000. The speeds cannot be set
independently. For example, when the output speed is set, the input speed
is automatically set to the same speed.


An open() fails under the following conditions:

The unit being opened does not exist.

The /dev/cua (dial-out) device is being opened while the
/dev/term (dial-in device) is open, or the dial-in device is
being opened with a no-delay open while the dial-out device is

The unit has been marked as exclusive-use by another process
with a TIOCEXCL ioctl() call.

USB device I/O error.



32-bit ELF kernel module. (x86)


64-bit ELF kernel module. (x86)


64-bit ELF kernel module. (SPARC)


dial-out tty lines


dial-in tty lines


See attributes(7) for descriptions of the following attributes:

|Architecture | SPARC, x86 PCI-based systems |


strconf(1), tip(1), uucp(1C), ioctl(2), open(2), termios(3C), usba(4D),
termio(4I), ldterm(4M), ttcompat(4M), attributes(7), autopush(8), pppd(8)


In addition to being logged, the following messages may appear on the
system console. All messages are formatted in the following manner:

Warning: <device path> (usbsacm<instance num>):Error Message...

Device was disconnected while open. Data may have been lost.

The device has been hot-removed or powered off while it was open and
a possible data transfer was in progress. The job may be aborted.

Device is not identical to the previous one on this port. Please
disconnect and reconnect.

The device was hot-removed while open. A new device was hot-inserted
which is not identical to the original device. Please disconnect the
device and reconnect the original device to the same port.

Device has been reconnected, but data may have been lost.

The device that was hot-removed from its USB port has been re-
inserted again to the same port. It is available for access but data
from a previous transfer may be lost.

Cannot access <device>. Please reconnect.

This device has been disconnected because a device other than the
original one has been inserted. The driver informs you of this fact
by displaying the name of the original device.

The following messages may be logged into the system log. They are
formatted in the following manner:

<device path><usbsacm<instance number>): message...

Input overrun.
Data was lost.

August 13, 2021 USBSACM(4D)