tjh.dev
Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
1/*
2 * Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds
3 */
4
5#include <linux/types.h>
6#include <linux/kernel.h>
7#include <linux/termios.h>
8#include <linux/tty.h>
9#include <linux/export.h>
10
11
12/*
13 * Routine which returns the baud rate of the tty
14 *
15 * Note that the baud_table needs to be kept in sync with the
16 * include/asm/termbits.h file.
17 */
18static const speed_t baud_table[] = {
19 0, 50, 75, 110, 134, 150, 200, 300, 600, 1200, 1800, 2400, 4800,
20 9600, 19200, 38400, 57600, 115200, 230400, 460800,
21#ifdef __sparc__
22 76800, 153600, 307200, 614400, 921600
23#else
24 500000, 576000, 921600, 1000000, 1152000, 1500000, 2000000,
25 2500000, 3000000, 3500000, 4000000
26#endif
27};
28
29#ifndef __sparc__
30static const tcflag_t baud_bits[] = {
31 B0, B50, B75, B110, B134, B150, B200, B300, B600,
32 B1200, B1800, B2400, B4800, B9600, B19200, B38400,
33 B57600, B115200, B230400, B460800, B500000, B576000,
34 B921600, B1000000, B1152000, B1500000, B2000000, B2500000,
35 B3000000, B3500000, B4000000
36};
37#else
38static const tcflag_t baud_bits[] = {
39 B0, B50, B75, B110, B134, B150, B200, B300, B600,
40 B1200, B1800, B2400, B4800, B9600, B19200, B38400,
41 B57600, B115200, B230400, B460800, B76800, B153600,
42 B307200, B614400, B921600
43};
44#endif
45
46static int n_baud_table = ARRAY_SIZE(baud_table);
47
48/**
49 * tty_termios_baud_rate
50 * @termios: termios structure
51 *
52 * Convert termios baud rate data into a speed. This should be called
53 * with the termios lock held if this termios is a terminal termios
54 * structure. May change the termios data. Device drivers can call this
55 * function but should use ->c_[io]speed directly as they are updated.
56 *
57 * Locking: none
58 */
59
60speed_t tty_termios_baud_rate(struct ktermios *termios)
61{
62 unsigned int cbaud;
63
64 cbaud = termios->c_cflag & CBAUD;
65
66#ifdef BOTHER
67 /* Magic token for arbitrary speed via c_ispeed/c_ospeed */
68 if (cbaud == BOTHER)
69 return termios->c_ospeed;
70#endif
71 if (cbaud & CBAUDEX) {
72 cbaud &= ~CBAUDEX;
73
74 if (cbaud < 1 || cbaud + 15 > n_baud_table)
75 termios->c_cflag &= ~CBAUDEX;
76 else
77 cbaud += 15;
78 }
79 return baud_table[cbaud];
80}
81EXPORT_SYMBOL(tty_termios_baud_rate);
82
83/**
84 * tty_termios_input_baud_rate
85 * @termios: termios structure
86 *
87 * Convert termios baud rate data into a speed. This should be called
88 * with the termios lock held if this termios is a terminal termios
89 * structure. May change the termios data. Device drivers can call this
90 * function but should use ->c_[io]speed directly as they are updated.
91 *
92 * Locking: none
93 */
94
95speed_t tty_termios_input_baud_rate(struct ktermios *termios)
96{
97#ifdef IBSHIFT
98 unsigned int cbaud = (termios->c_cflag >> IBSHIFT) & CBAUD;
99
100 if (cbaud == B0)
101 return tty_termios_baud_rate(termios);
102
103 /* Magic token for arbitrary speed via c_ispeed*/
104 if (cbaud == BOTHER)
105 return termios->c_ispeed;
106
107 if (cbaud & CBAUDEX) {
108 cbaud &= ~CBAUDEX;
109
110 if (cbaud < 1 || cbaud + 15 > n_baud_table)
111 termios->c_cflag &= ~(CBAUDEX << IBSHIFT);
112 else
113 cbaud += 15;
114 }
115 return baud_table[cbaud];
116#else
117 return tty_termios_baud_rate(termios);
118#endif
119}
120EXPORT_SYMBOL(tty_termios_input_baud_rate);
121
122/**
123 * tty_termios_encode_baud_rate
124 * @termios: ktermios structure holding user requested state
125 * @ispeed: input speed
126 * @ospeed: output speed
127 *
128 * Encode the speeds set into the passed termios structure. This is
129 * used as a library helper for drivers so that they can report back
130 * the actual speed selected when it differs from the speed requested
131 *
132 * For maximal back compatibility with legacy SYS5/POSIX *nix behaviour
133 * we need to carefully set the bits when the user does not get the
134 * desired speed. We allow small margins and preserve as much of possible
135 * of the input intent to keep compatibility.
136 *
137 * Locking: Caller should hold termios lock. This is already held
138 * when calling this function from the driver termios handler.
139 *
140 * The ifdefs deal with platforms whose owners have yet to update them
141 * and will all go away once this is done.
142 */
143
144void tty_termios_encode_baud_rate(struct ktermios *termios,
145 speed_t ibaud, speed_t obaud)
146{
147 int i = 0;
148 int ifound = -1, ofound = -1;
149 int iclose = ibaud/50, oclose = obaud/50;
150 int ibinput = 0;
151
152 if (obaud == 0) /* CD dropped */
153 ibaud = 0; /* Clear ibaud to be sure */
154
155 termios->c_ispeed = ibaud;
156 termios->c_ospeed = obaud;
157
158#ifdef BOTHER
159 /* If the user asked for a precise weird speed give a precise weird
160 answer. If they asked for a Bfoo speed they may have problems
161 digesting non-exact replies so fuzz a bit */
162
163 if ((termios->c_cflag & CBAUD) == BOTHER)
164 oclose = 0;
165 if (((termios->c_cflag >> IBSHIFT) & CBAUD) == BOTHER)
166 iclose = 0;
167 if ((termios->c_cflag >> IBSHIFT) & CBAUD)
168 ibinput = 1; /* An input speed was specified */
169#endif
170 termios->c_cflag &= ~CBAUD;
171
172 /*
173 * Our goal is to find a close match to the standard baud rate
174 * returned. Walk the baud rate table and if we get a very close
175 * match then report back the speed as a POSIX Bxxxx value by
176 * preference
177 */
178
179 do {
180 if (obaud - oclose <= baud_table[i] &&
181 obaud + oclose >= baud_table[i]) {
182 termios->c_cflag |= baud_bits[i];
183 ofound = i;
184 }
185 if (ibaud - iclose <= baud_table[i] &&
186 ibaud + iclose >= baud_table[i]) {
187 /* For the case input == output don't set IBAUD bits
188 if the user didn't do so */
189 if (ofound == i && !ibinput)
190 ifound = i;
191#ifdef IBSHIFT
192 else {
193 ifound = i;
194 termios->c_cflag |= (baud_bits[i] << IBSHIFT);
195 }
196#endif
197 }
198 } while (++i < n_baud_table);
199
200 /*
201 * If we found no match then use BOTHER if provided or warn
202 * the user their platform maintainer needs to wake up if not.
203 */
204#ifdef BOTHER
205 if (ofound == -1)
206 termios->c_cflag |= BOTHER;
207 /* Set exact input bits only if the input and output differ or the
208 user already did */
209 if (ifound == -1 && (ibaud != obaud || ibinput))
210 termios->c_cflag |= (BOTHER << IBSHIFT);
211#else
212 if (ifound == -1 || ofound == -1)
213 pr_warn_once("tty: Unable to return correct speed data as your architecture needs updating.\n");
214#endif
215}
216EXPORT_SYMBOL_GPL(tty_termios_encode_baud_rate);
217
218/**
219 * tty_encode_baud_rate - set baud rate of the tty
220 * @ibaud: input baud rate
221 * @obad: output baud rate
222 *
223 * Update the current termios data for the tty with the new speed
224 * settings. The caller must hold the termios_rwsem for the tty in
225 * question.
226 */
227
228void tty_encode_baud_rate(struct tty_struct *tty, speed_t ibaud, speed_t obaud)
229{
230 tty_termios_encode_baud_rate(&tty->termios, ibaud, obaud);
231}
232EXPORT_SYMBOL_GPL(tty_encode_baud_rate);