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// 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);
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