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 12 13 /* 14 * Routine which returns the baud rate of the tty 15 * 16 * Note that the baud_table needs to be kept in sync with the 17 * include/asm/termbits.h file. 18 */ 19 static const speed_t baud_table[] = { 20 0, 50, 75, 110, 134, 150, 200, 300, 600, 1200, 1800, 2400, 4800, 21 9600, 19200, 38400, 57600, 115200, 230400, 460800, 22 #ifdef __sparc__ 23 76800, 153600, 307200, 614400, 921600 24 #else 25 500000, 576000, 921600, 1000000, 1152000, 1500000, 2000000, 26 2500000, 3000000, 3500000, 4000000 27 #endif 28 }; 29 30 #ifndef __sparc__ 31 static const tcflag_t baud_bits[] = { 32 B0, B50, B75, B110, B134, B150, B200, B300, B600, 33 B1200, B1800, B2400, B4800, B9600, B19200, B38400, 34 B57600, B115200, B230400, B460800, B500000, B576000, 35 B921600, B1000000, B1152000, B1500000, B2000000, B2500000, 36 B3000000, B3500000, B4000000 37 }; 38 #else 39 static const tcflag_t baud_bits[] = { 40 B0, B50, B75, B110, B134, B150, B200, B300, B600, 41 B1200, B1800, B2400, B4800, B9600, B19200, B38400, 42 B57600, B115200, B230400, B460800, B76800, B153600, 43 B307200, B614400, B921600 44 }; 45 #endif 46 47 static int n_baud_table = ARRAY_SIZE(baud_table); 48 49 /** 50 * tty_termios_baud_rate 51 * @termios: termios structure 52 * 53 * Convert termios baud rate data into a speed. This should be called 54 * with the termios lock held if this termios is a terminal termios 55 * structure. May change the termios data. Device drivers can call this 56 * function but should use ->c_[io]speed directly as they are updated. 57 * 58 * Locking: none 59 */ 60 61 speed_t tty_termios_baud_rate(struct ktermios *termios) 62 { 63 unsigned int cbaud; 64 65 cbaud = termios->c_cflag & CBAUD; 66 67 #ifdef BOTHER 68 /* Magic token for arbitrary speed via c_ispeed/c_ospeed */ 69 if (cbaud == BOTHER) 70 return termios->c_ospeed; 71 #endif 72 if (cbaud & CBAUDEX) { 73 cbaud &= ~CBAUDEX; 74 75 if (cbaud < 1 || cbaud + 15 > n_baud_table) 76 termios->c_cflag &= ~CBAUDEX; 77 else 78 cbaud += 15; 79 } 80 return cbaud >= n_baud_table ? 0 : baud_table[cbaud]; 81 } 82 EXPORT_SYMBOL(tty_termios_baud_rate); 83 84 /** 85 * tty_termios_input_baud_rate 86 * @termios: termios structure 87 * 88 * Convert termios baud rate data into a speed. This should be called 89 * with the termios lock held if this termios is a terminal termios 90 * structure. May change the termios data. Device drivers can call this 91 * function but should use ->c_[io]speed directly as they are updated. 92 * 93 * Locking: none 94 */ 95 96 speed_t tty_termios_input_baud_rate(struct ktermios *termios) 97 { 98 #ifdef IBSHIFT 99 unsigned int cbaud = (termios->c_cflag >> IBSHIFT) & CBAUD; 100 101 if (cbaud == B0) 102 return tty_termios_baud_rate(termios); 103 #ifdef BOTHER 104 /* Magic token for arbitrary speed via c_ispeed*/ 105 if (cbaud == BOTHER) 106 return termios->c_ispeed; 107 #endif 108 if (cbaud & CBAUDEX) { 109 cbaud &= ~CBAUDEX; 110 111 if (cbaud < 1 || cbaud + 15 > n_baud_table) 112 termios->c_cflag &= ~(CBAUDEX << IBSHIFT); 113 else 114 cbaud += 15; 115 } 116 return cbaud >= n_baud_table ? 0 : baud_table[cbaud]; 117 #else /* IBSHIFT */ 118 return tty_termios_baud_rate(termios); 119 #endif /* IBSHIFT */ 120 } 121 EXPORT_SYMBOL(tty_termios_input_baud_rate); 122 123 /** 124 * tty_termios_encode_baud_rate 125 * @termios: ktermios structure holding user requested state 126 * @ispeed: input speed 127 * @ospeed: output speed 128 * 129 * Encode the speeds set into the passed termios structure. This is 130 * used as a library helper for drivers so that they can report back 131 * the actual speed selected when it differs from the speed requested 132 * 133 * For maximal back compatibility with legacy SYS5/POSIX *nix behaviour 134 * we need to carefully set the bits when the user does not get the 135 * desired speed. We allow small margins and preserve as much of possible 136 * of the input intent to keep compatibility. 137 * 138 * Locking: Caller should hold termios lock. This is already held 139 * when calling this function from the driver termios handler. 140 * 141 * The ifdefs deal with platforms whose owners have yet to update them 142 * and will all go away once this is done. 143 */ 144 145 void tty_termios_encode_baud_rate(struct ktermios *termios, 146 speed_t ibaud, speed_t obaud) 147 { 148 int i = 0; 149 int ifound = -1, ofound = -1; 150 int iclose = ibaud/50, oclose = obaud/50; 151 int ibinput = 0; 152 153 if (obaud == 0) /* CD dropped */ 154 ibaud = 0; /* Clear ibaud to be sure */ 155 156 termios->c_ispeed = ibaud; 157 termios->c_ospeed = obaud; 158 159 #ifdef IBSHIFT 160 if ((termios->c_cflag >> IBSHIFT) & CBAUD) 161 ibinput = 1; /* An input speed was specified */ 162 #endif 163 #ifdef BOTHER 164 /* If the user asked for a precise weird speed give a precise weird 165 answer. If they asked for a Bfoo speed they may have problems 166 digesting non-exact replies so fuzz a bit */ 167 168 if ((termios->c_cflag & CBAUD) == BOTHER) { 169 oclose = 0; 170 if (!ibinput) 171 iclose = 0; 172 } 173 if (((termios->c_cflag >> IBSHIFT) & CBAUD) == BOTHER) 174 iclose = 0; 175 #endif 176 termios->c_cflag &= ~CBAUD; 177 #ifdef IBSHIFT 178 termios->c_cflag &= ~(CBAUD << IBSHIFT); 179 #endif 180 181 /* 182 * Our goal is to find a close match to the standard baud rate 183 * returned. Walk the baud rate table and if we get a very close 184 * match then report back the speed as a POSIX Bxxxx value by 185 * preference 186 */ 187 188 do { 189 if (obaud - oclose <= baud_table[i] && 190 obaud + oclose >= baud_table[i]) { 191 termios->c_cflag |= baud_bits[i]; 192 ofound = i; 193 } 194 if (ibaud - iclose <= baud_table[i] && 195 ibaud + iclose >= baud_table[i]) { 196 /* For the case input == output don't set IBAUD bits 197 if the user didn't do so */ 198 if (ofound == i && !ibinput) 199 ifound = i; 200 #ifdef IBSHIFT 201 else { 202 ifound = i; 203 termios->c_cflag |= (baud_bits[i] << IBSHIFT); 204 } 205 #endif 206 } 207 } while (++i < n_baud_table); 208 209 /* 210 * If we found no match then use BOTHER if provided or warn 211 * the user their platform maintainer needs to wake up if not. 212 */ 213 #ifdef BOTHER 214 if (ofound == -1) 215 termios->c_cflag |= BOTHER; 216 /* Set exact input bits only if the input and output differ or the 217 user already did */ 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 * @ibaud: input baud rate 230 * @obad: output baud rate 231 * 232 * Update the current termios data for the tty with the new speed 233 * settings. The caller must hold the termios_rwsem for the tty in 234 * question. 235 */ 236 237 void tty_encode_baud_rate(struct tty_struct *tty, speed_t ibaud, speed_t obaud) 238 { 239 tty_termios_encode_baud_rate(&tty->termios, ibaud, obaud); 240 } 241 EXPORT_SYMBOL_GPL(tty_encode_baud_rate); 242