diff options
Diffstat (limited to 'drivers/tty/tty_baudrate.c')
| -rw-r--r-- | drivers/tty/tty_baudrate.c | 215 |
1 files changed, 215 insertions, 0 deletions
diff --git a/drivers/tty/tty_baudrate.c b/drivers/tty/tty_baudrate.c new file mode 100644 index 0000000000..f9b49939c2 --- /dev/null +++ b/drivers/tty/tty_baudrate.c @@ -0,0 +1,215 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds + */ + +#include <linux/types.h> +#include <linux/kernel.h> +#include <linux/termios.h> +#include <linux/tty.h> +#include <linux/export.h> +#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); |