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 /* 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 71 if (cbaud < 1 || cbaud + 15 > n_baud_table) 72 termios->c_cflag &= ~CBAUDEX; 73 else 74 cbaud += 15; 75 } 76 return cbaud >= n_baud_table ? 0 : baud_table[cbaud]; 77 } 78 EXPORT_SYMBOL(tty_termios_baud_rate); 79 80 /** 81 * tty_termios_input_baud_rate 82 * @termios: termios structure 83 * 84 * Convert termios baud rate data into a speed. This should be called 85 * with the termios lock held if this termios is a terminal termios 86 * structure. May change the termios data. Device drivers can call this 87 * function but should use ->c_[io]speed directly as they are updated. 88 * 89 * Locking: none 90 */ 91 92 speed_t tty_termios_input_baud_rate(struct ktermios *termios) 93 { 94 unsigned int cbaud = (termios->c_cflag >> IBSHIFT) & CBAUD; 95 96 if (cbaud == B0) 97 return tty_termios_baud_rate(termios); 98 99 /* Magic token for arbitrary speed via c_ispeed*/ 100 if (cbaud == BOTHER) 101 return termios->c_ispeed; 102 103 if (cbaud & CBAUDEX) { 104 cbaud &= ~CBAUDEX; 105 106 if (cbaud < 1 || cbaud + 15 > n_baud_table) 107 termios->c_cflag &= ~(CBAUDEX << IBSHIFT); 108 else 109 cbaud += 15; 110 } 111 return cbaud >= n_baud_table ? 0 : baud_table[cbaud]; 112 } 113 EXPORT_SYMBOL(tty_termios_input_baud_rate); 114 115 /** 116 * tty_termios_encode_baud_rate 117 * @termios: ktermios structure holding user requested state 118 * @ibaud: input speed 119 * @obaud: output speed 120 * 121 * Encode the speeds set into the passed termios structure. This is 122 * used as a library helper for drivers so that they can report back 123 * the actual speed selected when it differs from the speed requested 124 * 125 * For maximal back compatibility with legacy SYS5/POSIX *nix behaviour 126 * we need to carefully set the bits when the user does not get the 127 * desired speed. We allow small margins and preserve as much of possible 128 * of the input intent to keep compatibility. 129 * 130 * Locking: Caller should hold termios lock. This is already held 131 * when calling this function from the driver termios handler. 132 * 133 * The ifdefs deal with platforms whose owners have yet to update them 134 * and will all go away once this is done. 135 */ 136 137 void tty_termios_encode_baud_rate(struct ktermios *termios, 138 speed_t ibaud, speed_t obaud) 139 { 140 int i = 0; 141 int ifound = -1, ofound = -1; 142 int iclose = ibaud/50, oclose = obaud/50; 143 int ibinput = 0; 144 145 if (obaud == 0) /* CD dropped */ 146 ibaud = 0; /* Clear ibaud to be sure */ 147 148 termios->c_ispeed = ibaud; 149 termios->c_ospeed = obaud; 150 151 if (((termios->c_cflag >> IBSHIFT) & CBAUD) != B0) 152 ibinput = 1; /* An input speed was specified */ 153 154 /* If the user asked for a precise weird speed give a precise weird 155 * answer. If they asked for a Bfoo speed they may have problems 156 * digesting non-exact replies so fuzz a bit. 157 */ 158 159 if ((termios->c_cflag & CBAUD) == BOTHER) { 160 oclose = 0; 161 if (!ibinput) 162 iclose = 0; 163 } 164 if (((termios->c_cflag >> IBSHIFT) & CBAUD) == BOTHER) 165 iclose = 0; 166 167 termios->c_cflag &= ~CBAUD; 168 termios->c_cflag &= ~(CBAUD << IBSHIFT); 169 170 /* 171 * Our goal is to find a close match to the standard baud rate 172 * returned. Walk the baud rate table and if we get a very close 173 * match then report back the speed as a POSIX Bxxxx value by 174 * preference 175 */ 176 177 do { 178 if (obaud - oclose <= baud_table[i] && 179 obaud + oclose >= baud_table[i]) { 180 termios->c_cflag |= baud_bits[i]; 181 ofound = i; 182 } 183 if (ibaud - iclose <= baud_table[i] && 184 ibaud + iclose >= baud_table[i]) { 185 /* For the case input == output don't set IBAUD bits 186 * if the user didn't do so. 187 */ 188 if (ofound == i && !ibinput) { 189 ifound = i; 190 } else { 191 ifound = i; 192 termios->c_cflag |= (baud_bits[i] << IBSHIFT); 193 } 194 } 195 } while (++i < n_baud_table); 196 197 /* If we found no match then use BOTHER. */ 198 if (ofound == -1) 199 termios->c_cflag |= BOTHER; 200 /* Set exact input bits only if the input and output differ or the 201 * user already did. 202 */ 203 if (ifound == -1 && (ibaud != obaud || ibinput)) 204 termios->c_cflag |= (BOTHER << IBSHIFT); 205 } 206 EXPORT_SYMBOL_GPL(tty_termios_encode_baud_rate); 207 208 /** 209 * tty_encode_baud_rate - set baud rate of the tty 210 * @tty: terminal device 211 * @ibaud: input baud rate 212 * @obaud: output baud rate 213 * 214 * Update the current termios data for the tty with the new speed 215 * settings. The caller must hold the termios_rwsem for the tty in 216 * question. 217 */ 218 219 void tty_encode_baud_rate(struct tty_struct *tty, speed_t ibaud, speed_t obaud) 220 { 221 tty_termios_encode_baud_rate(&tty->termios, ibaud, obaud); 222 } 223 EXPORT_SYMBOL_GPL(tty_encode_baud_rate); 224