Line data Source code
1 : // SPDX-License-Identifier: GPL-2.0
2 : /*
3 : * Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds
4 : */
5 :
6 : #include <linux/types.h>
7 : #include <linux/kernel.h>
8 : #include <linux/termios.h>
9 : #include <linux/tty.h>
10 : #include <linux/export.h>
11 : #include "tty.h"
12 :
13 :
14 : /*
15 : * Routine which returns the baud rate of the tty
16 : *
17 : * Note that the baud_table needs to be kept in sync with the
18 : * include/asm/termbits.h file.
19 : */
20 : static const speed_t baud_table[] = {
21 : 0, 50, 75, 110, 134, 150, 200, 300, 600, 1200, 1800, 2400,
22 : 4800, 9600, 19200, 38400, 57600, 115200, 230400, 460800,
23 : #ifdef __sparc__
24 : 76800, 153600, 307200, 614400, 921600, 500000, 576000,
25 : 1000000, 1152000, 1500000, 2000000
26 : #else
27 : 500000, 576000, 921600, 1000000, 1152000, 1500000, 2000000,
28 : 2500000, 3000000, 3500000, 4000000
29 : #endif
30 : };
31 :
32 : static const tcflag_t baud_bits[] = {
33 : B0, B50, B75, B110, B134, B150, B200, B300, B600, B1200, B1800, B2400,
34 : B4800, B9600, B19200, B38400, B57600, B115200, B230400, B460800,
35 : #ifdef __sparc__
36 : B76800, B153600, B307200, B614400, B921600, B500000, B576000,
37 : B1000000, B1152000, B1500000, B2000000
38 : #else
39 : B500000, B576000, B921600, B1000000, B1152000, B1500000, B2000000,
40 : B2500000, B3000000, B3500000, B4000000
41 : #endif
42 : };
43 :
44 : static int n_baud_table = ARRAY_SIZE(baud_table);
45 :
46 : /**
47 : * tty_termios_baud_rate
48 : * @termios: termios structure
49 : *
50 : * Convert termios baud rate data into a speed. This should be called
51 : * with the termios lock held if this termios is a terminal termios
52 : * structure. Device drivers can call this function but should use
53 : * ->c_[io]speed directly as they are updated.
54 : *
55 : * Locking: none
56 : */
57 :
58 12 : speed_t tty_termios_baud_rate(const struct ktermios *termios)
59 : {
60 12 : unsigned int cbaud;
61 :
62 12 : cbaud = termios->c_cflag & CBAUD;
63 :
64 : /* Magic token for arbitrary speed via c_ispeed/c_ospeed */
65 12 : if (cbaud == BOTHER)
66 0 : return termios->c_ospeed;
67 :
68 12 : if (cbaud & CBAUDEX) {
69 0 : cbaud &= ~CBAUDEX;
70 0 : cbaud += 15;
71 0 : }
72 12 : return cbaud >= n_baud_table ? 0 : baud_table[cbaud];
73 12 : }
74 : EXPORT_SYMBOL(tty_termios_baud_rate);
75 :
76 : /**
77 : * tty_termios_input_baud_rate
78 : * @termios: termios structure
79 : *
80 : * Convert termios baud rate data into a speed. This should be called
81 : * with the termios lock held if this termios is a terminal termios
82 : * structure. Device drivers can call this function but should use
83 : * ->c_[io]speed directly as they are updated.
84 : *
85 : * Locking: none
86 : */
87 :
88 6 : speed_t tty_termios_input_baud_rate(const struct ktermios *termios)
89 : {
90 6 : unsigned int cbaud = (termios->c_cflag >> IBSHIFT) & CBAUD;
91 :
92 6 : if (cbaud == B0)
93 6 : return tty_termios_baud_rate(termios);
94 :
95 : /* Magic token for arbitrary speed via c_ispeed */
96 0 : if (cbaud == BOTHER)
97 0 : return termios->c_ispeed;
98 :
99 0 : if (cbaud & CBAUDEX) {
100 0 : cbaud &= ~CBAUDEX;
101 0 : cbaud += 15;
102 0 : }
103 0 : return cbaud >= n_baud_table ? 0 : baud_table[cbaud];
104 6 : }
105 : EXPORT_SYMBOL(tty_termios_input_baud_rate);
106 :
107 : /**
108 : * tty_termios_encode_baud_rate
109 : * @termios: ktermios structure holding user requested state
110 : * @ibaud: input speed
111 : * @obaud: output speed
112 : *
113 : * Encode the speeds set into the passed termios structure. This is
114 : * used as a library helper for drivers so that they can report back
115 : * the actual speed selected when it differs from the speed requested
116 : *
117 : * For maximal back compatibility with legacy SYS5/POSIX *nix behaviour
118 : * we need to carefully set the bits when the user does not get the
119 : * desired speed. We allow small margins and preserve as much of possible
120 : * of the input intent to keep compatibility.
121 : *
122 : * Locking: Caller should hold termios lock. This is already held
123 : * when calling this function from the driver termios handler.
124 : *
125 : * The ifdefs deal with platforms whose owners have yet to update them
126 : * and will all go away once this is done.
127 : */
128 :
129 0 : void tty_termios_encode_baud_rate(struct ktermios *termios,
130 : speed_t ibaud, speed_t obaud)
131 : {
132 0 : int i = 0;
133 0 : int ifound = -1, ofound = -1;
134 0 : int iclose = ibaud/50, oclose = obaud/50;
135 0 : int ibinput = 0;
136 :
137 0 : if (obaud == 0) /* CD dropped */
138 0 : ibaud = 0; /* Clear ibaud to be sure */
139 :
140 0 : termios->c_ispeed = ibaud;
141 0 : termios->c_ospeed = obaud;
142 :
143 0 : if (((termios->c_cflag >> IBSHIFT) & CBAUD) != B0)
144 0 : ibinput = 1; /* An input speed was specified */
145 :
146 : /* If the user asked for a precise weird speed give a precise weird
147 : * answer. If they asked for a Bfoo speed they may have problems
148 : * digesting non-exact replies so fuzz a bit.
149 : */
150 :
151 0 : if ((termios->c_cflag & CBAUD) == BOTHER) {
152 0 : oclose = 0;
153 0 : if (!ibinput)
154 0 : iclose = 0;
155 0 : }
156 0 : if (((termios->c_cflag >> IBSHIFT) & CBAUD) == BOTHER)
157 0 : iclose = 0;
158 :
159 0 : termios->c_cflag &= ~CBAUD;
160 0 : termios->c_cflag &= ~(CBAUD << IBSHIFT);
161 :
162 : /*
163 : * Our goal is to find a close match to the standard baud rate
164 : * returned. Walk the baud rate table and if we get a very close
165 : * match then report back the speed as a POSIX Bxxxx value by
166 : * preference
167 : */
168 :
169 0 : do {
170 0 : if (obaud - oclose <= baud_table[i] &&
171 0 : obaud + oclose >= baud_table[i]) {
172 0 : termios->c_cflag |= baud_bits[i];
173 0 : ofound = i;
174 0 : }
175 0 : if (ibaud - iclose <= baud_table[i] &&
176 0 : ibaud + iclose >= baud_table[i]) {
177 : /* For the case input == output don't set IBAUD bits
178 : * if the user didn't do so.
179 : */
180 0 : if (ofound == i && !ibinput) {
181 0 : ifound = i;
182 0 : } else {
183 0 : ifound = i;
184 0 : termios->c_cflag |= (baud_bits[i] << IBSHIFT);
185 : }
186 0 : }
187 0 : } while (++i < n_baud_table);
188 :
189 : /* If we found no match then use BOTHER. */
190 0 : if (ofound == -1)
191 0 : termios->c_cflag |= BOTHER;
192 : /* Set exact input bits only if the input and output differ or the
193 : * user already did.
194 : */
195 0 : if (ifound == -1 && (ibaud != obaud || ibinput))
196 0 : termios->c_cflag |= (BOTHER << IBSHIFT);
197 0 : }
198 : EXPORT_SYMBOL_GPL(tty_termios_encode_baud_rate);
199 :
200 : /**
201 : * tty_encode_baud_rate - set baud rate of the tty
202 : * @tty: terminal device
203 : * @ibaud: input baud rate
204 : * @obaud: output baud rate
205 : *
206 : * Update the current termios data for the tty with the new speed
207 : * settings. The caller must hold the termios_rwsem for the tty in
208 : * question.
209 : */
210 :
211 0 : void tty_encode_baud_rate(struct tty_struct *tty, speed_t ibaud, speed_t obaud)
212 : {
213 0 : tty_termios_encode_baud_rate(&tty->termios, ibaud, obaud);
214 0 : }
215 : EXPORT_SYMBOL_GPL(tty_encode_baud_rate);
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