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 | speed_t tty_termios_baud_rate(const struct ktermios *termios) |
59 | { |
60 | unsigned int cbaud; |
61 | |
62 | cbaud = termios->c_cflag & CBAUD; |
63 | |
64 | /* Magic token for arbitrary speed via c_ispeed/c_ospeed */ |
65 | if (cbaud == BOTHER) |
66 | return termios->c_ospeed; |
67 | |
68 | if (cbaud & CBAUDEX) { |
69 | cbaud &= ~CBAUDEX; |
70 | cbaud += 15; |
71 | } |
72 | return cbaud >= n_baud_table ? 0 : baud_table[cbaud]; |
73 | } |
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 | speed_t tty_termios_input_baud_rate(const struct ktermios *termios) |
89 | { |
90 | unsigned int cbaud = (termios->c_cflag >> IBSHIFT) & CBAUD; |
91 | |
92 | if (cbaud == B0) |
93 | return tty_termios_baud_rate(termios); |
94 | |
95 | /* Magic token for arbitrary speed via c_ispeed */ |
96 | if (cbaud == BOTHER) |
97 | return termios->c_ispeed; |
98 | |
99 | if (cbaud & CBAUDEX) { |
100 | cbaud &= ~CBAUDEX; |
101 | cbaud += 15; |
102 | } |
103 | return cbaud >= n_baud_table ? 0 : baud_table[cbaud]; |
104 | } |
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 | void tty_termios_encode_baud_rate(struct ktermios *termios, |
130 | speed_t ibaud, speed_t obaud) |
131 | { |
132 | int i = 0; |
133 | int ifound = -1, ofound = -1; |
134 | int iclose = ibaud/50, oclose = obaud/50; |
135 | int ibinput = 0; |
136 | |
137 | if (obaud == 0) /* CD dropped */ |
138 | ibaud = 0; /* Clear ibaud to be sure */ |
139 | |
140 | termios->c_ispeed = ibaud; |
141 | termios->c_ospeed = obaud; |
142 | |
143 | if (((termios->c_cflag >> IBSHIFT) & CBAUD) != B0) |
144 | 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 | if ((termios->c_cflag & CBAUD) == BOTHER) { |
152 | oclose = 0; |
153 | if (!ibinput) |
154 | iclose = 0; |
155 | } |
156 | if (((termios->c_cflag >> IBSHIFT) & CBAUD) == BOTHER) |
157 | iclose = 0; |
158 | |
159 | termios->c_cflag &= ~CBAUD; |
160 | 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 | do { |
170 | if (obaud - oclose <= baud_table[i] && |
171 | obaud + oclose >= baud_table[i]) { |
172 | termios->c_cflag |= baud_bits[i]; |
173 | ofound = i; |
174 | } |
175 | if (ibaud - iclose <= baud_table[i] && |
176 | 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 | if (ofound == i && !ibinput) { |
181 | ifound = i; |
182 | } else { |
183 | ifound = i; |
184 | termios->c_cflag |= (baud_bits[i] << IBSHIFT); |
185 | } |
186 | } |
187 | } while (++i < n_baud_table); |
188 | |
189 | /* If we found no match then use BOTHER. */ |
190 | if (ofound == -1) |
191 | termios->c_cflag |= BOTHER; |
192 | /* Set exact input bits only if the input and output differ or the |
193 | * user already did. |
194 | */ |
195 | if (ifound == -1 && (ibaud != obaud || ibinput)) |
196 | termios->c_cflag |= (BOTHER << IBSHIFT); |
197 | } |
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 | void tty_encode_baud_rate(struct tty_struct *tty, speed_t ibaud, speed_t obaud) |
212 | { |
213 | tty_termios_encode_baud_rate(&tty->termios, ibaud, obaud); |
214 | } |
215 | EXPORT_SYMBOL_GPL(tty_encode_baud_rate); |
216 | |