// 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);