// SPDX-License-Identifier: GPL-2.0 /* * Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds */ #include #include #include #include #include #include "tty.h" /* * Routine which returns the baud rate of the tty * * Note that the baud_table needs to be kept in sync with the * include/asm/termbits.h file. */ static const speed_t baud_table[] = { 0, 50, 75, 110, 134, 150, 200, 300, 600, 1200, 1800, 2400, 4800, 9600, 19200, 38400, 57600, 115200, 230400, 460800, #ifdef __sparc__ 76800, 153600, 307200, 614400, 921600, 500000, 576000, 1000000, 1152000, 1500000, 2000000 #else 500000, 576000, 921600, 1000000, 1152000, 1500000, 2000000, 2500000, 3000000, 3500000, 4000000 #endif }; static const tcflag_t baud_bits[] = { B0, B50, B75, B110, B134, B150, B200, B300, B600, B1200, B1800, B2400, B4800, B9600, B19200, B38400, B57600, B115200, B230400, B460800, #ifdef __sparc__ B76800, B153600, B307200, B614400, B921600, B500000, B576000, B1000000, B1152000, B1500000, B2000000 #else B500000, B576000, B921600, B1000000, B1152000, B1500000, B2000000, B2500000, B3000000, B3500000, B4000000 #endif }; static int n_baud_table = ARRAY_SIZE(baud_table); /** * tty_termios_baud_rate * @termios: termios structure * * Convert termios baud rate data into a speed. This should be called * with the termios lock held if this termios is a terminal termios * structure. Device drivers can call this function but should use * ->c_[io]speed directly as they are updated. * * Locking: none */ speed_t tty_termios_baud_rate(const struct ktermios *termios) { unsigned int cbaud; cbaud = termios->c_cflag & CBAUD; /* Magic token for arbitrary speed via c_ispeed/c_ospeed */ if (cbaud == BOTHER) return termios->c_ospeed; if (cbaud & CBAUDEX) { cbaud &= ~CBAUDEX; cbaud += 15; } return cbaud >= n_baud_table ? 0 : baud_table[cbaud]; } EXPORT_SYMBOL(tty_termios_baud_rate); /** * tty_termios_input_baud_rate * @termios: termios structure * * Convert termios baud rate data into a speed. This should be called * with the termios lock held if this termios is a terminal termios * structure. Device drivers can call this function but should use * ->c_[io]speed directly as they are updated. * * Locking: none */ speed_t tty_termios_input_baud_rate(const struct ktermios *termios) { unsigned int cbaud = (termios->c_cflag >> IBSHIFT) & CBAUD; if (cbaud == B0) return tty_termios_baud_rate(termios); /* Magic token for arbitrary speed via c_ispeed */ if (cbaud == BOTHER) return termios->c_ispeed; if (cbaud & CBAUDEX) { cbaud &= ~CBAUDEX; cbaud += 15; } return cbaud >= n_baud_table ? 0 : baud_table[cbaud]; } EXPORT_SYMBOL(tty_termios_input_baud_rate); /** * tty_termios_encode_baud_rate * @termios: ktermios structure holding user requested state * @ibaud: input speed * @obaud: output speed * * Encode the speeds set into the passed termios structure. This is * used as a library helper for drivers so that they can report back * the actual speed selected when it differs from the speed requested * * For maximal back compatibility with legacy SYS5/POSIX *nix behaviour * we need to carefully set the bits when the user does not get the * desired speed. We allow small margins and preserve as much of possible * of the input intent to keep compatibility. * * Locking: Caller should hold termios lock. This is already held * when calling this function from the driver termios handler. * * The ifdefs deal with platforms whose owners have yet to update them * and will all go away once this is done. */ void tty_termios_encode_baud_rate(struct ktermios *termios, speed_t ibaud, speed_t obaud) { int i = 0; int ifound = -1, ofound = -1; int iclose = ibaud/50, oclose = obaud/50; int ibinput = 0; if (obaud == 0) /* CD dropped */ ibaud = 0; /* Clear ibaud to be sure */ termios->c_ispeed = ibaud; termios->c_ospeed = obaud; if (((termios->c_cflag >> IBSHIFT) & CBAUD) != B0) ibinput = 1; /* An input speed was specified */ /* If the user asked for a precise weird speed give a precise weird * answer. If they asked for a Bfoo speed they may have problems * digesting non-exact replies so fuzz a bit. */ if ((termios->c_cflag & CBAUD) == BOTHER) { oclose = 0; if (!ibinput) iclose = 0; } if (((termios->c_cflag >> IBSHIFT) & CBAUD) == BOTHER) iclose = 0; termios->c_cflag &= ~CBAUD; termios->c_cflag &= ~(CBAUD << IBSHIFT); /* * Our goal is to find a close match to the standard baud rate * returned. Walk the baud rate table and if we get a very close * match then report back the speed as a POSIX Bxxxx value by * preference */ do { if (obaud - oclose <= baud_table[i] && obaud + oclose >= baud_table[i]) { termios->c_cflag |= baud_bits[i]; ofound = i; } if (ibaud - iclose <= baud_table[i] && ibaud + iclose >= baud_table[i]) { /* For the case input == output don't set IBAUD bits * if the user didn't do so. */ if (ofound == i && !ibinput) { ifound = i; } else { ifound = i; termios->c_cflag |= (baud_bits[i] << IBSHIFT); } } } while (++i < n_baud_table); /* If we found no match then use BOTHER. */ if (ofound == -1) termios->c_cflag |= BOTHER; /* Set exact input bits only if the input and output differ or the * user already did. */ if (ifound == -1 && (ibaud != obaud || ibinput)) termios->c_cflag |= (BOTHER << IBSHIFT); } EXPORT_SYMBOL_GPL(tty_termios_encode_baud_rate); /** * tty_encode_baud_rate - set baud rate of the tty * @tty: terminal device * @ibaud: input baud rate * @obaud: output baud rate * * Update the current termios data for the tty with the new speed * settings. The caller must hold the termios_rwsem for the tty in * question. */ void tty_encode_baud_rate(struct tty_struct *tty, speed_t ibaud, speed_t obaud) { tty_termios_encode_baud_rate(&tty->termios, ibaud, obaud); } EXPORT_SYMBOL_GPL(tty_encode_baud_rate);