// 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);