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14249 pseudo-terminal nomenclature should reflect POSIX
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--- old/usr/src/man/man7d/pts.7d
+++ new/usr/src/man/man7d/pts.7d
1 1 '\" te
2 -.\" Copyright 2020 OmniOS Community Edition (OmniOSce) Association.
3 -.\" Copyright 1992 Sun Microsystems
2 +.\" Copyright (c) 1997, Sun Microsystems, Inc.
3 +.\" All Rights Reserved
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7 -.TH PTS 7D "Feb 29, 2020"
8 -.SH NAME
9 -pts \- STREAMS pseudo-tty slave driver
10 -.SH DESCRIPTION
11 -The pseudo-tty subsystem simulates a terminal connection, where the master side
12 -represents the terminal and the slave represents the user process's special
13 -device end point. In order to use the pseudo-tty subsystem, a node for the
14 -master side driver \fB/dev/ptmx\fR and N nodes for the slave driver (N is
15 -determined at installation time) must be installed. The names of the slave
16 -devices are \fB/dev/pts/M\fR where \fBM\fR has the values 0 through N-1. When
17 -the master device is opened, the corresponding slave device is automatically
18 -locked out. No user may open that slave device until its permissions are
19 -adjusted and the device unlocked by calling functions \fBgrantpt\fR(3C) and
20 -\fBunlockpt\fR(3C). The user can then invoke the open system call with the name
21 -that is returned by the \fBptsname\fR(3C) function. See the example below.
22 -.sp
23 -.LP
24 -Only one open is allowed on a master device. Multiple opens are allowed on the
25 -slave device. After both the master and slave have been opened, the user has
26 -two file descriptors which are end points of a full duplex connection composed
27 -of two streams automatically connected at the master and slave drivers. The
28 -user may then push modules onto either side of the stream pair. Unless compiled
29 -in XPG4v2 mode (see below), the consumer needs to push the \fBptem\fR(7M) and
30 -\fBldterm\fR(7M) modules onto the slave side of the pseudo-terminal subsystem
31 -to get terminal semantics.
32 -.sp
33 -.LP
34 -The master and slave drivers pass all messages to their adjacent queues. Only
35 -the \fBM_FLUSH\fR needs some processing. Because the read queue of one side is
36 -connected to the write queue of the other, the \fBFLUSHR\fR flag is changed to
37 -the \fBFLUSHW\fR flag and vice versa. When the master device is closed an
38 -\fBM_HANGUP\fR message is sent to the slave device which will render the device
39 -unusable. The process on the slave side gets the errno \fBEIO\fR when
40 -attempting to write on that stream but it will be able to read any data
41 -remaining on the stream head read queue. When all the data has been read, read
42 -returns 0 indicating that the stream can no longer be used. On the last close
43 -of the slave device, a 0-length message is sent to the master device. When the
44 -application on the master side issues a \fBread()\fR or \fBgetmsg()\fR and 0 is
45 -returned, the user of the master device decides whether to issue a
46 -\fBclose()\fR that dismantles the pseudo-terminal subsystem. If the master
47 -device is not closed, the pseudo-tty subsystem will be available to another
48 -user to open the slave device. Since 0-length messages are used to indicate
49 -that the process on the slave side has closed and should be interpreted that
50 -way by the process on the master side, applications on the slave side should
51 -not write 0-length messages. Unless the application is compiled in XPG4v2 mode
52 -(see below) then any 0-length messages written on the slave side will be
53 -discarded by the \fBptem\fR module.
54 -.sp
55 -.LP
56 -The standard STREAMS system calls can access the pseudo-tty devices. The slave
57 -devices support the \fBO_NDELAY\fR and \fBO_NONBLOCK\fR flags.
58 -.SH XPG4v2 MODE
59 -XPG4v2 requires that open of a slave pseudo terminal device provides the
60 -process with an interface that is identical to the terminal interface (without
61 -having to explicitly push any modules to achieve this). It also requires that
62 -0-length messages written on the slave side will be propagated to the master.
63 -.sp
64 -Experience has shown, however, that most software does not expect slave pty
65 -devices to operate in this manner and therefore this XPG4v2-compliant
66 -behaviour is only enabled in XPG4v2/SUS (see \fBstandards\fR(5)) mode.
67 -.SH EXAMPLES
68 -.in +2
69 -.nf
70 -int fdm fds;
71 -char *slavename;
72 -extern char *ptsname();
73 -
74 -fdm = open("/dev/ptmx", O_RDWR); /* open master */
75 -grantpt(fdm); /* change permission of slave */
76 -unlockpt(fdm); /* unlock slave */
77 -slavename = ptsname(fdm); /* get name of slave */
78 -fds = open(slavename, O_RDWR); /* open slave */
79 -ioctl(fds, I_PUSH, "ptem"); /* push ptem */
80 -ioctl(fds, I_PUSH, "ldterm"); /* push ldterm*/
81 -.fi
82 -.in -2
83 -
84 -.SH FILES
85 -.ne 2
86 -.na
87 -\fB\fB/dev/ptmx\fR\fR
88 -.ad
89 -.RS 14n
90 -master clone device
91 -.RE
92 -
93 -.sp
94 -.ne 2
95 -.na
96 -\fB\fB/dev/pts/M\fR\fR
97 -.ad
98 -.RS 14n
99 -slave devices (M = 0 -> N-1)
100 -.RE
101 -
102 -.SH SEE ALSO
103 -\fBgrantpt\fR(3C), \fBptsname\fR(3C), \fBunlockpt\fR(3C), \fBldterm\fR(7M),
104 -\fBptm\fR(7D), \fBptem\fR(7M), \fBstandards\fR(5)
105 -.sp
106 -.LP
107 -\fISTREAMS Programming Guide\fR
7 +.\" Copyright 2022 Oxide Computer Company
8 +.Dd February 5, 2022
9 +.Dt PTM 7D
10 +.Os
11 +.Sh NAME
12 +.Nm ptm ,
13 +.Nm pts
14 +.Nd STREAMS pseudo-terminal manager and subsidiary drivers
15 +.Sh SYNOPSIS
16 +.Pa /dev/ptmx
17 +.Pp
18 +.Pa /dev/pts/*
19 +.Sh DESCRIPTION
20 +The pseudo-terminal subsystem simulates a terminal connection, where the
21 +manager side represents the terminal and the subsidiary represents the user
22 +process's special device end point.
23 +The manager device is set up as a cloned device where its major device number
24 +is the major for the clone device and its minor device number is the major for
25 +the
26 +.Nm ptm
27 +driver; see
28 +.Dv CLONE_DEV
29 +in
30 +.Xr ddi_create_minor_node 9F .
31 +.Pp
32 +There are no nodes in the file system for manager devices.
33 +The manager pseudo driver is opened using the
34 +.Xr open 2
35 +system call with
36 +.Pa /dev/ptmx
37 +as the device parameter.
38 +The clone open finds the next available minor device for the
39 +.Nm ptm
40 +major device.
41 +.Pp
42 +A manager device is only available if it and its corresponding subsidiary
43 +device are not already open.
44 +Only one open is allowed on a manager device.
45 +Multiple opens are allowed on the subsidiary device.
46 +.Pp
47 +When the manager device is opened, the corresponding subsidiary device is
48 +automatically locked out.
49 +No user may open the subsidiary device until its permissions are adjusted and
50 +the device is unlocked by calling the functions
51 +.Xr grantpt 3C
52 +and
53 +.Xr unlockpt 3C .
54 +The user can then invoke the
55 +.Xr open 2
56 +system call with the device name returned by the
57 +.Xr ptsname 3C
58 +function.
59 +.Pp
60 +After both the manager and subsidiary have been opened, the user has two file
61 +descriptors which are the end points of a full duplex connection composed of
62 +two streams which are automatically connected at the manager and subsidiary
63 +drivers.
64 +The user may then push modules onto either side of the stream pair.
65 +Unless compiled in XPG4v2 mode
66 +.Po
67 +see
68 +.Sx "XPG4v2 MODE"
69 +.Pc ,
70 +the consumer needs to push the
71 +.Xr ptem 7M
72 +and
73 +.Xr ldterm 7M
74 +modules onto the subsidiary device to get terminal semantics.
75 +.Pp
76 +The manager and subsidiary drivers pass all messages to their adjacent queues.
77 +Only the
78 +.Dv M_FLUSH
79 +needs some processing.
80 +Because the read queue of one side is connected to the write queue of the
81 +other, the
82 +.Dv FLUSHR
83 +flag is changed to the
84 +.Dv FLUSHW
85 +flag and vice versa.
86 +.Pp
87 +When the manager device is closed, an
88 +.Dv M_HANGUP
89 +message is sent to the subsidiary device which will render the device unusable.
90 +The process on the subsidiary side gets an
91 +.Er EIO
92 +error when attempting to write on that stream, but it will be able to read
93 +any data remaining on the stream head read queue.
94 +When all the data has been read,
95 +.Xr read 2
96 +returns
97 +.Sy 0
98 +indicating that the stream can no longer be used.
99 +.Pp
100 +On the last close of the subsidiary device, a 0-length message is sent to the
101 +manager device.
102 +When the application on the manager side issues a
103 +.Xr read 2
104 +or
105 +.Xr getmsg 2
106 +and
107 +.Sy 0
108 +is returned, the user of the manager device decides whether to issue a
109 +.Xr close 2
110 +that dismantles the entire pseudo-terminal.
111 +If the manager device is not closed, the pseudo-terminal will be available to
112 +another user to open the subsidiary device.
113 +.Pp
114 +Since 0-length messages are used to indicate that the process on the
115 +subsidiary side has closed, and should be interpreted that way by the process
116 +on the manager side, applications on the subsidiary side should not write
117 +0-length messages.
118 +Unless the application is compiled in XPG4v2 mode
119 +.Po
120 +see
121 +.Sx "XPG4v2 MODE"
122 +.Pc ,
123 +then any 0-length messages written to the subsidiary device will be discarded
124 +by the
125 +.Xr ptem 7M
126 +module.
127 +.Pp
128 +If
129 +.Dv O_NONBLOCK
130 +or
131 +.Dv O_NDELAY
132 +is set on the manager side:
133 +.Bl -bullet
134 +.It
135 +Read on the manager side returns
136 +.Sy -1
137 +with
138 +.Va errno
139 +set to
140 +.Er EAGAIN
141 +if no data is available
142 +.It
143 +Write returns
144 +.Sy -1
145 +with
146 +.Va errno
147 +set to
148 +.Er EAGAIN
149 +if there is internal flow control
150 +.El
151 +.Pp
152 +Standard STREAMS system calls can access pseudo-terminal devices.
153 +The subsidiary devices support the
154 +.Dv O_NDELAY
155 +and
156 +.Dv O_NONBLOCK
157 +flags.
158 +.Sh XPG4v2 MODE
159 +.Em XPG4v2
160 +requires that subsidiary pseudo-terminal devices provide the process with an
161 +interface that is identical to the terminal interface, without needing to
162 +explicitly push any modules to achieve this.
163 +It also requires that 0-length messages written on the subsidiary device will
164 +be propagated to the manager device.
165 +.Pp
166 +Experience has shown that most software does not expect subsidiary
167 +pseudo-terminal devices to operate in this manner.
168 +This XPG4v2-compliant behaviour is only enabled in XPG4v2/SUS
169 +.Po
170 +see
171 +.Xr standards 5
172 +.Pc
173 +mode.
174 +.Sh IOCTLS
175 +The manager driver provides several ioctls to support the
176 +.Xr grantpt 3C ,
177 +.Xr unlockpt 3C ,
178 +and
179 +.Xr ptsname 3C
180 +functions:
181 +.Bl -tag -width Ds
182 +.It Dv ISPTM
183 +Determines whether the file descriptor is that of an open manager device.
184 +On success, it returns the value
185 +.Sy 0 .
186 +.It Dv UNLKPT
187 +Unlocks the manager and subsidiary devices.
188 +It returns
189 +.Sy 0
190 +on success.
191 +On failure,
192 +.Vt errno
193 +is set to
194 +.Vt EINVAL
195 +indicating that the manager device is not open.
196 +.El
197 +.Sh FILES
198 +.Bl -tag -width Pa
199 +.It Pa /dev/ptmx
200 +Pseudo-terminal manager clone device.
201 +.It Pa /dev/pts/N
202 +Pseudo-terminal subsidiary devices, where
203 +.Sy N
204 +is a non-negative integer.
205 +Located via calls to
206 +.Xr ptsname 3C .
207 +.El
208 +.Sh EXAMPLES
209 +.Sy Example 1
210 +Opening the manager and subsidiary device for a pseudo-terminal.
211 +.Bd -literal -offset Ds
212 +#include <stdlib.h>
213 +#include <sys/types.h>
214 +#include <sys/stat.h>
215 +#include <unistd.h>
216 +#include <stropts.h>
217 +#include <fcntl.h>
218 +#include <err.h>
219 +\&...
220 +int fdm, fds;
221 +char *subsidiaryname;
222 +\&...
223 +/*
224 + * NOTE: Portable applications should use posix_openpt(3C) here:
225 + */
226 +if ((fdm = open("/dev/ptmx", O_RDWR | O_NOCTTY)) < 0) {
227 + err(1, "open manager");
228 +}
229 +if (grantpt(fdm) != 0 || unlockpt(fdm) != 0 ||
230 + (subsidiaryname = ptsname(fdm)) == NULL) {
231 + close(fdm);
232 + err(1, "locate subsidiary");
233 +}
234 +if ((fds = open(subsidiaryname, O_RDWR | O_NOCTTY)) < 0) {
235 + close(fdm);
236 + err(1, "open subsidiary");
237 +}
238 +if (ioctl(fds, I_PUSH, "ptem") != 0 ||
239 + ioctl(fds, I_PUSH, "ldterm") != 0) {
240 + close(fds);
241 + close(fdm);
242 + err(1, "push modules");
243 +}
244 +.Ed
245 +.Sh SEE ALSO
246 +.Xr close 2 ,
247 +.Xr getmsg 2 ,
248 +.Xr open 2 ,
249 +.Xr read 2 ,
250 +.Xr grantpt 3C ,
251 +.Xr posix_openpt 3C ,
252 +.Xr ptsname 3C ,
253 +.Xr unlockpt 3C ,
254 +.Xr standards 5 ,
255 +.Xr ldterm 7M ,
256 +.Xr pckt 7M ,
257 +.Xr ptem 7M ,
258 +.Xr ddi_create_minor_node 9F
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