NAME

xt - STREAMS-based multiplexed tty driver for AT&T windowing terminals

DESCRIPTION

The xt driver provides virtual tty(7) circuits multiplexed onto STREAMS-based device drivers. STREAMS-based xt is a streams upper multiplexor pseudo-device driver that sits between the stream head and a STREAMS hardware device driver.

Virtual tty(7) circuits are named by character-special files of the form /dev/xt/???. Filenames end in three digits, where the first two represent the channel group and the last represents the virtual tty(7) number (0-7) of the channel group. Allocation of a new channel group is done dynamically by attempting to open a name ending in 0 with the O_EXCL flag set. After a successful open, the tty(7) file onto which the channels are to be multiplexed should be passed to xt via the I_LINK streamio(7) request. Afterwards, all the channels in the group will behave as normal tty(7) files, with data passed in packets via the real tty(7) line.

The xt driver implements the protocol described in xtproto(5) and in layers(5). Packets are formatted as described in xtproto(5), while the contents of packets conform to the description in layers(5).

There are four groups of ioctl(2) requests recognized by xt. The first group contains the normal tty ioctl(2) request described in termio(7), with the addition of the following:

TIOCGWINSZ Requires the address of a winsize structure as an argument. The window sizes of the layer associated with the file descriptor argument to ioctl(2) are copied to the structure.

The second group of ioctl(2) requests concerns control of the windowing terminal. Request from this second group which involve communication with the terminal are described in more detail in layers(5). These requests are defined in the header file <sys/jioctl.h>. The requests are as follows:

JTYPE, JMPX Both return the value JMPX. These are used to identify a terminal device as an xt channel.

JBOOT, JTERM Both generate an appropriate command packet to the windowing terminal affecting the layer associated with the file descriptor argument to ioctl(2). They may return the error code EAGAIN on STREAMS buffer allocation failure.

JTIMOM Specifies the timeouts in milliseconds. Invalid except on channel 0. This may return the error code EAGAIN on STREAMS buffer allocation failure.

JWINSIZE Requires the address of a jwinsize structure as an argument. The window sizes of the layer associated with the file descriptor argument to ioctl(2) are copied to the structure.

JTRUN Requires the address of a string of the form channel, UNIX system command as an argument. Run the UNIX system command in the specified channel (layer). It may return the error code EAGAIN on STREAMS buffer allocation failure.

JZOMBOOT Generate a command packet to the windowing terminal to enter download mode on the channel associated with the file descriptor argument to ioctl(2), like JBOOT; but when the download is finished, make the layer a zombie (ready for debugging). It may return the error code EAGAIN on STREAMS buffer allocation failure.

JAGENT Send the supplied data as a command packet to invoke a windowing terminal agent routine, and return the terminal's response to the calling process. Invalid except on the file descriptor for channel 0. See jagent(5). It may return the error code EAGAIN on STREAMS buffer allocation failure.

JXTPROTO Set xt protocol type [see xtproto(5)]. It may return the error code EAGAIN on STREAMS buffer allocation failure.

The third group of ioctl(2) requests concerns the configuration of xt, and is described in the header file <sys/nxt.h>. The requests are as follows:

XTIOCTYPE Returns the value XTIOCTYPE. Identical in purpose to JMPX.

XTIOCHEX Specifies that ENCODING MODE should be turned on.

XTIOCTRACE Requires the address of a Tbuf structure as an argument. The structure is filled with the contents of the driver trace buffer. Tracing is enabled. See xtt(1).

XTIOCNOTRACE Tracing is disabled.

XTIOCSTATS Requires an argument that is the address of an array of size S_NSTATS, of type Stats_t. The array is filled with the contents of the driver statistics array. See xts(1).

The fourth group of ioctl(2) requests concerns configuring streamio(7) multiplexor. The requests are as follows:

I_LINK Links the hardware driver underneath xt. The arguments to the ioctl are documented in streamio(7).

I_UNLINK Unlinks the hardware driver underneath xt. The arguments to the ioctl are documented in streamio(7).

FILES

/dev/xt/??[0-7]                       multiplexed special files
/usr/include/sys/jioctl.h      packet command types
/usr/include/sys/nxtproto.h   channel multiplexing protocol definitions
/usr/include/sys/nxt.h           STREAMS-based driver specific definitions

SEE ALSO

layers(1), xts(1M), xtt(1M)
ioctl(2), open(2)
jagent(5), layers(5), xtproto(5)
streamio(7), termio(7), tty(7).
Programmer's Guide: STREAMS