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