216 lines · c
1// SPDX-License-Identifier: GPL-2.02/*3 * Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds4 */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 tty16 *17 * Note that the baud_table needs to be kept in sync with the18 * include/asm/termbits.h file.19 */20static 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, 200000026#else27 500000, 576000, 921600, 1000000, 1152000, 1500000, 2000000,28 2500000, 3000000, 3500000, 400000029#endif30};31 32static 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, B200000038#else39 B500000, B576000, B921600, B1000000, B1152000, B1500000, B2000000,40 B2500000, B3000000, B3500000, B400000041#endif42};43 44static int n_baud_table = ARRAY_SIZE(baud_table);45 46/**47 * tty_termios_baud_rate48 * @termios: termios structure49 *50 * Convert termios baud rate data into a speed. This should be called51 * with the termios lock held if this termios is a terminal termios52 * structure. Device drivers can call this function but should use53 * ->c_[io]speed directly as they are updated.54 *55 * Locking: none56 */57 58speed_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}74EXPORT_SYMBOL(tty_termios_baud_rate);75 76/**77 * tty_termios_input_baud_rate78 * @termios: termios structure79 *80 * Convert termios baud rate data into a speed. This should be called81 * with the termios lock held if this termios is a terminal termios82 * structure. Device drivers can call this function but should use83 * ->c_[io]speed directly as they are updated.84 *85 * Locking: none86 */87 88speed_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}105EXPORT_SYMBOL(tty_termios_input_baud_rate);106 107/**108 * tty_termios_encode_baud_rate109 * @termios: ktermios structure holding user requested state110 * @ibaud: input speed111 * @obaud: output speed112 *113 * Encode the speeds set into the passed termios structure. This is114 * used as a library helper for drivers so that they can report back115 * the actual speed selected when it differs from the speed requested116 *117 * For maximal back compatibility with legacy SYS5/POSIX *nix behaviour118 * we need to carefully set the bits when the user does not get the119 * desired speed. We allow small margins and preserve as much of possible120 * of the input intent to keep compatibility.121 *122 * Locking: Caller should hold termios lock. This is already held123 * when calling this function from the driver termios handler.124 *125 * The ifdefs deal with platforms whose owners have yet to update them126 * and will all go away once this is done.127 */128 129void 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 weird147 * answer. If they asked for a Bfoo speed they may have problems148 * 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 rate164 * returned. Walk the baud rate table and if we get a very close165 * match then report back the speed as a POSIX Bxxxx value by166 * preference167 */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 bits178 * 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 the193 * user already did.194 */195 if (ifound == -1 && (ibaud != obaud || ibinput))196 termios->c_cflag |= (BOTHER << IBSHIFT);197}198EXPORT_SYMBOL_GPL(tty_termios_encode_baud_rate);199 200/**201 * tty_encode_baud_rate - set baud rate of the tty202 * @tty: terminal device203 * @ibaud: input baud rate204 * @obaud: output baud rate205 *206 * Update the current termios data for the tty with the new speed207 * settings. The caller must hold the termios_rwsem for the tty in208 * question.209 */210 211void 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}215EXPORT_SYMBOL_GPL(tty_encode_baud_rate);216