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
12
13 /*
14 * Routine which returns the baud rate of the tty
15 *
16 * Note that the baud_table needs to be kept in sync with the
17 * include/asm/termbits.h file.
18 */
19 static const speed_t baud_table[] = {
20 0, 50, 75, 110, 134, 150, 200, 300, 600, 1200, 1800, 2400, 4800,
21 9600, 19200, 38400, 57600, 115200, 230400, 460800,
22 #ifdef __sparc__
23 76800, 153600, 307200, 614400, 921600
24 #else
25 500000, 576000, 921600, 1000000, 1152000, 1500000, 2000000,
26 2500000, 3000000, 3500000, 4000000
27 #endif
28 };
29
30 #ifndef __sparc__
31 static const tcflag_t baud_bits[] = {
32 B0, B50, B75, B110, B134, B150, B200, B300, B600,
33 B1200, B1800, B2400, B4800, B9600, B19200, B38400,
34 B57600, B115200, B230400, B460800, B500000, B576000,
35 B921600, B1000000, B1152000, B1500000, B2000000, B2500000,
36 B3000000, B3500000, B4000000
37 };
38 #else
39 static const tcflag_t baud_bits[] = {
40 B0, B50, B75, B110, B134, B150, B200, B300, B600,
41 B1200, B1800, B2400, B4800, B9600, B19200, B38400,
42 B57600, B115200, B230400, B460800, B76800, B153600,
43 B307200, B614400, B921600
44 };
45 #endif
46
47 static int n_baud_table = ARRAY_SIZE(baud_table);
48
49 /**
50 * tty_termios_baud_rate
51 * @termios: termios structure
52 *
53 * Convert termios baud rate data into a speed. This should be called
54 * with the termios lock held if this termios is a terminal termios
55 * structure. May change the termios data. Device drivers can call this
56 * function but should use ->c_[io]speed directly as they are updated.
57 *
58 * Locking: none
59 */
60
61 speed_t tty_termios_baud_rate(struct ktermios *termios)
62 {
63 unsigned int cbaud;
64
65 cbaud = termios->c_cflag & CBAUD;
66
67 #ifdef BOTHER
68 /* Magic token for arbitrary speed via c_ispeed/c_ospeed */
69 if (cbaud == BOTHER)
70 return termios->c_ospeed;
71 #endif
72 if (cbaud & CBAUDEX) {
73 cbaud &= ~CBAUDEX;
74
75 if (cbaud < 1 || cbaud + 15 > n_baud_table)
76 termios->c_cflag &= ~CBAUDEX;
77 else
78 cbaud += 15;
79 }
80 return cbaud >= n_baud_table ? 0 : baud_table[cbaud];
81 }
82 EXPORT_SYMBOL(tty_termios_baud_rate);
83
84 /**
85 * tty_termios_input_baud_rate
86 * @termios: termios structure
87 *
88 * Convert termios baud rate data into a speed. This should be called
89 * with the termios lock held if this termios is a terminal termios
90 * structure. May change the termios data. Device drivers can call this
91 * function but should use ->c_[io]speed directly as they are updated.
92 *
93 * Locking: none
94 */
95
96 speed_t tty_termios_input_baud_rate(struct ktermios *termios)
97 {
98 #ifdef IBSHIFT
99 unsigned int cbaud = (termios->c_cflag >> IBSHIFT) & CBAUD;
100
101 if (cbaud == B0)
102 return tty_termios_baud_rate(termios);
103 #ifdef BOTHER
104 /* Magic token for arbitrary speed via c_ispeed*/
105 if (cbaud == BOTHER)
106 return termios->c_ispeed;
107 #endif
108 if (cbaud & CBAUDEX) {
109 cbaud &= ~CBAUDEX;
110
111 if (cbaud < 1 || cbaud + 15 > n_baud_table)
112 termios->c_cflag &= ~(CBAUDEX << IBSHIFT);
113 else
114 cbaud += 15;
115 }
116 return cbaud >= n_baud_table ? 0 : baud_table[cbaud];
117 #else /* IBSHIFT */
118 return tty_termios_baud_rate(termios);
119 #endif /* IBSHIFT */
120 }
121 EXPORT_SYMBOL(tty_termios_input_baud_rate);
122
123 /**
124 * tty_termios_encode_baud_rate
125 * @termios: ktermios structure holding user requested state
126 * @ispeed: input speed
127 * @ospeed: output speed
128 *
129 * Encode the speeds set into the passed termios structure. This is
130 * used as a library helper for drivers so that they can report back
131 * the actual speed selected when it differs from the speed requested
132 *
133 * For maximal back compatibility with legacy SYS5/POSIX *nix behaviour
134 * we need to carefully set the bits when the user does not get the
135 * desired speed. We allow small margins and preserve as much of possible
136 * of the input intent to keep compatibility.
137 *
138 * Locking: Caller should hold termios lock. This is already held
139 * when calling this function from the driver termios handler.
140 *
141 * The ifdefs deal with platforms whose owners have yet to update them
142 * and will all go away once this is done.
143 */
144
145 void tty_termios_encode_baud_rate(struct ktermios *termios,
146 speed_t ibaud, speed_t obaud)
147 {
148 int i = 0;
149 int ifound = -1, ofound = -1;
150 int iclose = ibaud/50, oclose = obaud/50;
151 int ibinput = 0;
152
153 if (obaud == 0) /* CD dropped */
154 ibaud = 0; /* Clear ibaud to be sure */
155
156 termios->c_ispeed = ibaud;
157 termios->c_ospeed = obaud;
158
159 #ifdef IBSHIFT
160 if ((termios->c_cflag >> IBSHIFT) & CBAUD)
161 ibinput = 1; /* An input speed was specified */
162 #endif
163 #ifdef BOTHER
164 /* If the user asked for a precise weird speed give a precise weird
165 answer. If they asked for a Bfoo speed they may have problems
166 digesting non-exact replies so fuzz a bit */
167
168 if ((termios->c_cflag & CBAUD) == BOTHER) {
169 oclose = 0;
170 if (!ibinput)
171 iclose = 0;
172 }
173 if (((termios->c_cflag >> IBSHIFT) & CBAUD) == BOTHER)
174 iclose = 0;
175 #endif
176 termios->c_cflag &= ~CBAUD;
177 #ifdef IBSHIFT
178 termios->c_cflag &= ~(CBAUD << IBSHIFT);
179 #endif
180
181 /*
182 * Our goal is to find a close match to the standard baud rate
183 * returned. Walk the baud rate table and if we get a very close
184 * match then report back the speed as a POSIX Bxxxx value by
185 * preference
186 */
187
188 do {
189 if (obaud - oclose <= baud_table[i] &&
190 obaud + oclose >= baud_table[i]) {
191 termios->c_cflag |= baud_bits[i];
192 ofound = i;
193 }
194 if (ibaud - iclose <= baud_table[i] &&
195 ibaud + iclose >= baud_table[i]) {
196 /* For the case input == output don't set IBAUD bits
197 if the user didn't do so */
198 if (ofound == i && !ibinput)
199 ifound = i;
200 #ifdef IBSHIFT
201 else {
202 ifound = i;
203 termios->c_cflag |= (baud_bits[i] << IBSHIFT);
204 }
205 #endif
206 }
207 } while (++i < n_baud_table);
208
209 /*
210 * If we found no match then use BOTHER if provided or warn
211 * the user their platform maintainer needs to wake up if not.
212 */
213 #ifdef BOTHER
214 if (ofound == -1)
215 termios->c_cflag |= BOTHER;
216 /* Set exact input bits only if the input and output differ or the
217 user already did */
218 if (ifound == -1 && (ibaud != obaud || ibinput))
219 termios->c_cflag |= (BOTHER << IBSHIFT);
220 #else
221 if (ifound == -1 || ofound == -1)
222 pr_warn_once("tty: Unable to return correct speed data as your architecture needs updating.\n");
223 #endif
224 }
225 EXPORT_SYMBOL_GPL(tty_termios_encode_baud_rate);
226
227 /**
228 * tty_encode_baud_rate - set baud rate of the tty
229 * @ibaud: input baud rate
230 * @obad: output baud rate
231 *
232 * Update the current termios data for the tty with the new speed
233 * settings. The caller must hold the termios_rwsem for the tty in
234 * question.
235 */
236
237 void tty_encode_baud_rate(struct tty_struct *tty, speed_t ibaud, speed_t obaud)
238 {
239 tty_termios_encode_baud_rate(&tty->termios, ibaud, obaud);
240 }
241 EXPORT_SYMBOL_GPL(tty_encode_baud_rate);