Content-type: text/html Man page of usbsacm


Section: Devices (7D)
Updated: 1 Nov 2006
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usbsacm - USB communication device class ACM driver  


#include <sys/termio.h>

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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(1M) facility.

The usbsacm module supports the termio(7I) 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(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.

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(1M) 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(7I).  


The usbsacm driver supports the standard set of termio(7I) 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 or 460800. 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 open.


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(5) for descriptions of the following attributes:


Architecture SPARC, x86 PCI-based systems




strconf(1), tip(1),uucp(1C), autopush(1M), pppd(1M), ioctl(2), open(2), termios(3C), attributes(5), usba(7D), termio(7I), ldterm(7M), ttcompat(7M)  


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.




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Time: 02:40:00 GMT, October 02, 2010