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 speed_t tty_termios_baud_rate(struct ktermios *termios) 59 { 60 unsigned int cbaud; 61 62 cbaud = termios->c_cflag & CBAUD; 63 64 #ifdef BOTHER 65 /* Magic token for arbitrary speed via c_ispeed/c_ospeed */ 66 if (cbaud == BOTHER) 67 return termios->c_ospeed; 68 #endif 69 if (cbaud & CBAUDEX) { 70 cbaud &= ~CBAUDEX; 71 72 if (cbaud < 1 || cbaud + 15 > n_baud_table) 73 termios->c_cflag &= ~CBAUDEX; 74 else 75 cbaud += 15; 76 } 77 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 speed_t tty_termios_input_baud_rate(struct ktermios *termios) 94 { 95 #ifdef IBSHIFT 96 unsigned int cbaud = (termios->c_cflag >> IBSHIFT) & CBAUD; 97 98 if (cbaud == B0) 99 return tty_termios_baud_rate(termios); 100 #ifdef BOTHER 101 /* Magic token for arbitrary speed via c_ispeed*/ 102 if (cbaud == BOTHER) 103 return termios->c_ispeed; 104 #endif 105 if (cbaud & CBAUDEX) { 106 cbaud &= ~CBAUDEX; 107 108 if (cbaud < 1 || cbaud + 15 > n_baud_table) 109 termios->c_cflag &= ~(CBAUDEX << IBSHIFT); 110 else 111 cbaud += 15; 112 } 113 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 void tty_termios_encode_baud_rate(struct ktermios *termios, 143 speed_t ibaud, speed_t obaud) 144 { 145 int i = 0; 146 int ifound = -1, ofound = -1; 147 int iclose = ibaud/50, oclose = obaud/50; 148 int ibinput = 0; 149 150 if (obaud == 0) /* CD dropped */ 151 ibaud = 0; /* Clear ibaud to be sure */ 152 153 termios->c_ispeed = ibaud; 154 termios->c_ospeed = obaud; 155 156 #ifdef IBSHIFT 157 if (((termios->c_cflag >> IBSHIFT) & CBAUD) != B0) 158 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 if ((termios->c_cflag & CBAUD) == BOTHER) { 167 oclose = 0; 168 if (!ibinput) 169 iclose = 0; 170 } 171 if (((termios->c_cflag >> IBSHIFT) & CBAUD) == BOTHER) 172 iclose = 0; 173 #endif 174 termios->c_cflag &= ~CBAUD; 175 #ifdef IBSHIFT 176 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 if (obaud - oclose <= baud_table[i] && 188 obaud + oclose >= baud_table[i]) { 189 termios->c_cflag |= baud_bits[i]; 190 ofound = i; 191 } 192 if (ibaud - iclose <= baud_table[i] && 193 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 if (ofound == i && !ibinput) 198 ifound = i; 199 #ifdef IBSHIFT 200 else { 201 ifound = i; 202 termios->c_cflag |= (baud_bits[i] << IBSHIFT); 203 } 204 #endif 205 } 206 } 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 if (ofound == -1) 214 termios->c_cflag |= BOTHER; 215 /* Set exact input bits only if the input and output differ or the 216 * user already did. 217 */ 218 if (ifound == -1 && (ibaud != obaud || ibinput)) 219 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 } 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 void tty_encode_baud_rate(struct tty_struct *tty, speed_t ibaud, speed_t obaud) 239 { 240 tty_termios_encode_baud_rate(&tty->termios, ibaud, obaud); 241 } 242 EXPORT_SYMBOL_GPL(tty_encode_baud_rate); 243