// 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>
  
  
  /*
   * 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. May change the termios data. 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(struct ktermios *termios)
  {
  	unsigned int cbaud;
  
  	cbaud = termios->c_cflag & CBAUD;
  
  #ifdef BOTHER
  	/* Magic token for arbitrary speed via c_ispeed/c_ospeed */
  	if (cbaud == BOTHER)
  		return termios->c_ospeed;
  #endif
  	if (cbaud & CBAUDEX) {
  		cbaud &= ~CBAUDEX;
  
  		if (cbaud < 1 || cbaud + 15 > n_baud_table)
  			termios->c_cflag &= ~CBAUDEX;
  		else
  			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. May change the termios data. 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(struct ktermios *termios)
  {
  #ifdef IBSHIFT
  	unsigned int cbaud = (termios->c_cflag >> IBSHIFT) & CBAUD;
  
  	if (cbaud == B0)
  		return tty_termios_baud_rate(termios);

  #ifdef BOTHER

  	/* Magic token for arbitrary speed via c_ispeed*/
  	if (cbaud == BOTHER)
  		return termios->c_ispeed;

  #endif

  	if (cbaud & CBAUDEX) {
  		cbaud &= ~CBAUDEX;
  
  		if (cbaud < 1 || cbaud + 15 > n_baud_table)
  			termios->c_cflag &= ~(CBAUDEX << IBSHIFT);
  		else
  			cbaud += 15;
  	}

  	return cbaud >= n_baud_table ? 0 : baud_table[cbaud];

  #else	/* IBSHIFT */

  	return tty_termios_baud_rate(termios);

  #endif	/* IBSHIFT */

  }
  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;

  #ifdef IBSHIFT

  	if ((termios->c_cflag >> IBSHIFT) & CBAUD)
  		ibinput = 1;	/* An input speed was specified */

  #endif
  #ifdef BOTHER

  	/* 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;

  #endif
  	termios->c_cflag &= ~CBAUD;

  #ifdef IBSHIFT
  	termios->c_cflag &= ~(CBAUD << IBSHIFT);
  #endif

  
  	/*
  	 *	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;
  #ifdef IBSHIFT
  			else {
  				ifound = i;
  				termios->c_cflag |= (baud_bits[i] << IBSHIFT);
  			}
  #endif
  		}
  	} while (++i < n_baud_table);
  
  	/*
  	 *	If we found no match then use BOTHER if provided or warn
  	 *	the user their platform maintainer needs to wake up if not.
  	 */
  #ifdef 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);
  #else
  	if (ifound == -1 || ofound == -1)
  		pr_warn_once("tty: Unable to return correct speed data as your architecture needs updating.
  ");
  #endif
  }
  EXPORT_SYMBOL_GPL(tty_termios_encode_baud_rate);
  
  /**
   *	tty_encode_baud_rate		-	set baud rate of the tty
   *	@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);