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 :
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,
21 : 4800, 9600, 19200, 38400, 57600, 115200, 230400, 460800,
22 : #ifdef __sparc__
23 : 76800, 153600, 307200, 614400, 921600, 500000, 576000,
24 : 1000000, 1152000, 1500000, 2000000
25 : #else
26 : 500000, 576000, 921600, 1000000, 1152000, 1500000, 2000000,
27 : 2500000, 3000000, 3500000, 4000000
28 : #endif
29 : };
30 :
31 : static const tcflag_t baud_bits[] = {
32 : B0, B50, B75, B110, B134, B150, B200, B300, B600, B1200, B1800, B2400,
33 : B4800, B9600, B19200, B38400, B57600, B115200, B230400, B460800,
34 : #ifdef __sparc__
35 : B76800, B153600, B307200, B614400, B921600, B500000, B576000,
36 : B1000000, B1152000, B1500000, B2000000
37 : #else
38 : B500000, B576000, B921600, B1000000, B1152000, B1500000, B2000000,
39 : B2500000, B3000000, B3500000, B4000000
40 : #endif
41 : };
42 :
43 : static int n_baud_table = ARRAY_SIZE(baud_table);
44 :
45 : /**
46 : * tty_termios_baud_rate
47 : * @termios: termios structure
48 : *
49 : * Convert termios baud rate data into a speed. This should be called
50 : * with the termios lock held if this termios is a terminal termios
51 : * structure. May change the termios data. Device drivers can call this
52 : * function but should use ->c_[io]speed directly as they are updated.
53 : *
54 : * Locking: none
55 : */
56 :
57 338 : speed_t tty_termios_baud_rate(struct ktermios *termios)
58 : {
59 338 : unsigned int cbaud;
60 :
61 338 : cbaud = termios->c_cflag & CBAUD;
62 :
63 : #ifdef BOTHER
64 : /* Magic token for arbitrary speed via c_ispeed/c_ospeed */
65 338 : if (cbaud == BOTHER)
66 0 : return termios->c_ospeed;
67 : #endif
68 338 : if (cbaud & CBAUDEX) {
69 0 : cbaud &= ~CBAUDEX;
70 :
71 0 : if (cbaud < 1 || cbaud + 15 > n_baud_table)
72 0 : termios->c_cflag &= ~CBAUDEX;
73 : else
74 : cbaud += 15;
75 : }
76 338 : return cbaud >= n_baud_table ? 0 : baud_table[cbaud];
77 : }
78 : EXPORT_SYMBOL(tty_termios_baud_rate);
79 :
80 : /**
81 : * tty_termios_input_baud_rate
82 : * @termios: termios structure
83 : *
84 : * Convert termios baud rate data into a speed. This should be called
85 : * with the termios lock held if this termios is a terminal termios
86 : * structure. May change the termios data. Device drivers can call this
87 : * function but should use ->c_[io]speed directly as they are updated.
88 : *
89 : * Locking: none
90 : */
91 :
92 167 : speed_t tty_termios_input_baud_rate(struct ktermios *termios)
93 : {
94 : #ifdef IBSHIFT
95 167 : unsigned int cbaud = (termios->c_cflag >> IBSHIFT) & CBAUD;
96 :
97 167 : if (cbaud == B0)
98 167 : return tty_termios_baud_rate(termios);
99 : #ifdef BOTHER
100 : /* Magic token for arbitrary speed via c_ispeed*/
101 0 : if (cbaud == BOTHER)
102 0 : return termios->c_ispeed;
103 : #endif
104 0 : if (cbaud & CBAUDEX) {
105 0 : cbaud &= ~CBAUDEX;
106 :
107 0 : if (cbaud < 1 || cbaud + 15 > n_baud_table)
108 0 : termios->c_cflag &= ~(CBAUDEX << IBSHIFT);
109 : else
110 : cbaud += 15;
111 : }
112 0 : return cbaud >= n_baud_table ? 0 : baud_table[cbaud];
113 : #else /* IBSHIFT */
114 : return tty_termios_baud_rate(termios);
115 : #endif /* IBSHIFT */
116 : }
117 : EXPORT_SYMBOL(tty_termios_input_baud_rate);
118 :
119 : /**
120 : * tty_termios_encode_baud_rate
121 : * @termios: ktermios structure holding user requested state
122 : * @ibaud: input speed
123 : * @obaud: output speed
124 : *
125 : * Encode the speeds set into the passed termios structure. This is
126 : * used as a library helper for drivers so that they can report back
127 : * the actual speed selected when it differs from the speed requested
128 : *
129 : * For maximal back compatibility with legacy SYS5/POSIX *nix behaviour
130 : * we need to carefully set the bits when the user does not get the
131 : * desired speed. We allow small margins and preserve as much of possible
132 : * of the input intent to keep compatibility.
133 : *
134 : * Locking: Caller should hold termios lock. This is already held
135 : * when calling this function from the driver termios handler.
136 : *
137 : * The ifdefs deal with platforms whose owners have yet to update them
138 : * and will all go away once this is done.
139 : */
140 :
141 3 : void tty_termios_encode_baud_rate(struct ktermios *termios,
142 : speed_t ibaud, speed_t obaud)
143 : {
144 3 : int i = 0;
145 3 : int ifound = -1, ofound = -1;
146 3 : int iclose = ibaud/50, oclose = obaud/50;
147 3 : int ibinput = 0;
148 :
149 3 : if (obaud == 0) /* CD dropped */
150 0 : ibaud = 0; /* Clear ibaud to be sure */
151 :
152 3 : termios->c_ispeed = ibaud;
153 3 : termios->c_ospeed = obaud;
154 :
155 : #ifdef IBSHIFT
156 3 : if ((termios->c_cflag >> IBSHIFT) & CBAUD)
157 0 : ibinput = 1; /* An input speed was specified */
158 : #endif
159 : #ifdef BOTHER
160 : /* If the user asked for a precise weird speed give a precise weird
161 : answer. If they asked for a Bfoo speed they may have problems
162 : digesting non-exact replies so fuzz a bit */
163 :
164 3 : if ((termios->c_cflag & CBAUD) == BOTHER) {
165 0 : oclose = 0;
166 0 : if (!ibinput)
167 0 : iclose = 0;
168 : }
169 3 : if (((termios->c_cflag >> IBSHIFT) & CBAUD) == BOTHER)
170 0 : iclose = 0;
171 : #endif
172 3 : termios->c_cflag &= ~CBAUD;
173 : #ifdef IBSHIFT
174 3 : termios->c_cflag &= ~(CBAUD << IBSHIFT);
175 : #endif
176 :
177 : /*
178 : * Our goal is to find a close match to the standard baud rate
179 : * returned. Walk the baud rate table and if we get a very close
180 : * match then report back the speed as a POSIX Bxxxx value by
181 : * preference
182 : */
183 :
184 93 : do {
185 93 : if (obaud - oclose <= baud_table[i] &&
186 54 : obaud + oclose >= baud_table[i]) {
187 3 : termios->c_cflag |= baud_bits[i];
188 3 : ofound = i;
189 : }
190 93 : if (ibaud - iclose <= baud_table[i] &&
191 54 : ibaud + iclose >= baud_table[i]) {
192 : /* For the case input == output don't set IBAUD bits
193 : if the user didn't do so */
194 3 : if (ofound == i && !ibinput)
195 : ifound = i;
196 : #ifdef IBSHIFT
197 : else {
198 0 : ifound = i;
199 0 : termios->c_cflag |= (baud_bits[i] << IBSHIFT);
200 : }
201 : #endif
202 : }
203 93 : } while (++i < n_baud_table);
204 :
205 : /*
206 : * If we found no match then use BOTHER if provided or warn
207 : * the user their platform maintainer needs to wake up if not.
208 : */
209 : #ifdef BOTHER
210 3 : if (ofound == -1)
211 0 : termios->c_cflag |= BOTHER;
212 : /* Set exact input bits only if the input and output differ or the
213 : user already did */
214 3 : if (ifound == -1 && (ibaud != obaud || ibinput))
215 0 : termios->c_cflag |= (BOTHER << IBSHIFT);
216 : #else
217 : if (ifound == -1 || ofound == -1)
218 : pr_warn_once("tty: Unable to return correct speed data as your architecture needs updating.\n");
219 : #endif
220 3 : }
221 : EXPORT_SYMBOL_GPL(tty_termios_encode_baud_rate);
222 :
223 : /**
224 : * tty_encode_baud_rate - set baud rate of the tty
225 : * @tty: terminal device
226 : * @ibaud: input baud rate
227 : * @obaud: output baud rate
228 : *
229 : * Update the current termios data for the tty with the new speed
230 : * settings. The caller must hold the termios_rwsem for the tty in
231 : * question.
232 : */
233 :
234 0 : void tty_encode_baud_rate(struct tty_struct *tty, speed_t ibaud, speed_t obaud)
235 : {
236 0 : tty_termios_encode_baud_rate(&tty->termios, ibaud, obaud);
237 0 : }
238 : EXPORT_SYMBOL_GPL(tty_encode_baud_rate);
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