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. May change the termios data. Device drivers can call this
53 : * function but should use ->c_[io]speed directly as they are updated.
54 : *
55 : * Locking: none
56 : */
57 :
58 0 : speed_t tty_termios_baud_rate(struct ktermios *termios)
59 : {
60 : unsigned int cbaud;
61 :
62 0 : cbaud = termios->c_cflag & CBAUD;
63 :
64 : #ifdef BOTHER
65 : /* Magic token for arbitrary speed via c_ispeed/c_ospeed */
66 0 : if (cbaud == BOTHER)
67 0 : return termios->c_ospeed;
68 : #endif
69 0 : if (cbaud & CBAUDEX) {
70 0 : cbaud &= ~CBAUDEX;
71 :
72 0 : if (cbaud < 1 || cbaud + 15 > n_baud_table)
73 0 : termios->c_cflag &= ~CBAUDEX;
74 : else
75 : cbaud += 15;
76 : }
77 0 : return cbaud >= n_baud_table ? 0 : baud_table[cbaud];
78 : }
79 : EXPORT_SYMBOL(tty_termios_baud_rate);
80 :
81 : /**
82 : * tty_termios_input_baud_rate
83 : * @termios: termios structure
84 : *
85 : * Convert termios baud rate data into a speed. This should be called
86 : * with the termios lock held if this termios is a terminal termios
87 : * structure. May change the termios data. Device drivers can call this
88 : * function but should use ->c_[io]speed directly as they are updated.
89 : *
90 : * Locking: none
91 : */
92 :
93 0 : speed_t tty_termios_input_baud_rate(struct ktermios *termios)
94 : {
95 : #ifdef IBSHIFT
96 0 : unsigned int cbaud = (termios->c_cflag >> IBSHIFT) & CBAUD;
97 :
98 0 : if (cbaud == B0)
99 0 : return tty_termios_baud_rate(termios);
100 : #ifdef BOTHER
101 : /* Magic token for arbitrary speed via c_ispeed*/
102 0 : if (cbaud == BOTHER)
103 0 : return termios->c_ispeed;
104 : #endif
105 0 : if (cbaud & CBAUDEX) {
106 0 : cbaud &= ~CBAUDEX;
107 :
108 0 : if (cbaud < 1 || cbaud + 15 > n_baud_table)
109 0 : termios->c_cflag &= ~(CBAUDEX << IBSHIFT);
110 : else
111 : cbaud += 15;
112 : }
113 0 : return cbaud >= n_baud_table ? 0 : baud_table[cbaud];
114 : #else /* IBSHIFT */
115 : return tty_termios_baud_rate(termios);
116 : #endif /* IBSHIFT */
117 : }
118 : EXPORT_SYMBOL(tty_termios_input_baud_rate);
119 :
120 : /**
121 : * tty_termios_encode_baud_rate
122 : * @termios: ktermios structure holding user requested state
123 : * @ibaud: input speed
124 : * @obaud: output speed
125 : *
126 : * Encode the speeds set into the passed termios structure. This is
127 : * used as a library helper for drivers so that they can report back
128 : * the actual speed selected when it differs from the speed requested
129 : *
130 : * For maximal back compatibility with legacy SYS5/POSIX *nix behaviour
131 : * we need to carefully set the bits when the user does not get the
132 : * desired speed. We allow small margins and preserve as much of possible
133 : * of the input intent to keep compatibility.
134 : *
135 : * Locking: Caller should hold termios lock. This is already held
136 : * when calling this function from the driver termios handler.
137 : *
138 : * The ifdefs deal with platforms whose owners have yet to update them
139 : * and will all go away once this is done.
140 : */
141 :
142 0 : void tty_termios_encode_baud_rate(struct ktermios *termios,
143 : speed_t ibaud, speed_t obaud)
144 : {
145 0 : int i = 0;
146 0 : int ifound = -1, ofound = -1;
147 0 : int iclose = ibaud/50, oclose = obaud/50;
148 0 : int ibinput = 0;
149 :
150 0 : if (obaud == 0) /* CD dropped */
151 0 : ibaud = 0; /* Clear ibaud to be sure */
152 :
153 0 : termios->c_ispeed = ibaud;
154 0 : termios->c_ospeed = obaud;
155 :
156 : #ifdef IBSHIFT
157 0 : if (((termios->c_cflag >> IBSHIFT) & CBAUD) != B0)
158 0 : ibinput = 1; /* An input speed was specified */
159 : #endif
160 : #ifdef BOTHER
161 : /* If the user asked for a precise weird speed give a precise weird
162 : * answer. If they asked for a Bfoo speed they may have problems
163 : * digesting non-exact replies so fuzz a bit.
164 : */
165 :
166 0 : if ((termios->c_cflag & CBAUD) == BOTHER) {
167 0 : oclose = 0;
168 0 : if (!ibinput)
169 0 : iclose = 0;
170 : }
171 0 : if (((termios->c_cflag >> IBSHIFT) & CBAUD) == BOTHER)
172 0 : iclose = 0;
173 : #endif
174 0 : termios->c_cflag &= ~CBAUD;
175 : #ifdef IBSHIFT
176 0 : termios->c_cflag &= ~(CBAUD << IBSHIFT);
177 : #endif
178 :
179 : /*
180 : * Our goal is to find a close match to the standard baud rate
181 : * returned. Walk the baud rate table and if we get a very close
182 : * match then report back the speed as a POSIX Bxxxx value by
183 : * preference
184 : */
185 :
186 : do {
187 0 : if (obaud - oclose <= baud_table[i] &&
188 0 : obaud + oclose >= baud_table[i]) {
189 0 : termios->c_cflag |= baud_bits[i];
190 0 : ofound = i;
191 : }
192 0 : if (ibaud - iclose <= baud_table[i] &&
193 0 : ibaud + iclose >= baud_table[i]) {
194 : /* For the case input == output don't set IBAUD bits
195 : * if the user didn't do so.
196 : */
197 0 : if (ofound == i && !ibinput)
198 : ifound = i;
199 : #ifdef IBSHIFT
200 : else {
201 0 : ifound = i;
202 0 : termios->c_cflag |= (baud_bits[i] << IBSHIFT);
203 : }
204 : #endif
205 : }
206 0 : } while (++i < n_baud_table);
207 :
208 : /*
209 : * If we found no match then use BOTHER if provided or warn
210 : * the user their platform maintainer needs to wake up if not.
211 : */
212 : #ifdef BOTHER
213 0 : if (ofound == -1)
214 0 : termios->c_cflag |= BOTHER;
215 : /* Set exact input bits only if the input and output differ or the
216 : * user already did.
217 : */
218 0 : if (ifound == -1 && (ibaud != obaud || ibinput))
219 0 : 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 0 : }
225 : EXPORT_SYMBOL_GPL(tty_termios_encode_baud_rate);
226 :
227 : /**
228 : * tty_encode_baud_rate - set baud rate of the tty
229 : * @tty: terminal device
230 : * @ibaud: input baud rate
231 : * @obaud: output baud rate
232 : *
233 : * Update the current termios data for the tty with the new speed
234 : * settings. The caller must hold the termios_rwsem for the tty in
235 : * question.
236 : */
237 :
238 0 : void tty_encode_baud_rate(struct tty_struct *tty, speed_t ibaud, speed_t obaud)
239 : {
240 0 : tty_termios_encode_baud_rate(&tty->termios, ibaud, obaud);
241 0 : }
242 : EXPORT_SYMBOL_GPL(tty_encode_baud_rate);
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