238 lines
6.5 KiB
C
238 lines
6.5 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds
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*/
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#include <linux/types.h>
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#include <linux/kernel.h>
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#include <linux/termios.h>
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#include <linux/tty.h>
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#include <linux/export.h>
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/*
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* Routine which returns the baud rate of the tty
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*
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* Note that the baud_table needs to be kept in sync with the
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* include/asm/termbits.h file.
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*/
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static const speed_t baud_table[] = {
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0, 50, 75, 110, 134, 150, 200, 300, 600, 1200, 1800, 2400,
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4800, 9600, 19200, 38400, 57600, 115200, 230400, 460800,
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#ifdef __sparc__
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76800, 153600, 307200, 614400, 921600, 500000, 576000,
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1000000, 1152000, 1500000, 2000000
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#else
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500000, 576000, 921600, 1000000, 1152000, 1500000, 2000000,
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2500000, 3000000, 3500000, 4000000
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#endif
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};
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static const tcflag_t baud_bits[] = {
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B0, B50, B75, B110, B134, B150, B200, B300, B600, B1200, B1800, B2400,
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B4800, B9600, B19200, B38400, B57600, B115200, B230400, B460800,
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#ifdef __sparc__
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B76800, B153600, B307200, B614400, B921600, B500000, B576000,
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B1000000, B1152000, B1500000, B2000000
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#else
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B500000, B576000, B921600, B1000000, B1152000, B1500000, B2000000,
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B2500000, B3000000, B3500000, B4000000
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#endif
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};
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static int n_baud_table = ARRAY_SIZE(baud_table);
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/**
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* tty_termios_baud_rate
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* @termios: termios structure
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*
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* Convert termios baud rate data into a speed. This should be called
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* with the termios lock held if this termios is a terminal termios
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* structure. May change the termios data. Device drivers can call this
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* function but should use ->c_[io]speed directly as they are updated.
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*
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* Locking: none
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*/
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speed_t tty_termios_baud_rate(struct ktermios *termios)
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{
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unsigned int cbaud;
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cbaud = termios->c_cflag & CBAUD;
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#ifdef BOTHER
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/* Magic token for arbitrary speed via c_ispeed/c_ospeed */
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if (cbaud == BOTHER)
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return termios->c_ospeed;
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#endif
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if (cbaud & CBAUDEX) {
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cbaud &= ~CBAUDEX;
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if (cbaud < 1 || cbaud + 15 > n_baud_table)
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termios->c_cflag &= ~CBAUDEX;
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else
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cbaud += 15;
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}
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return cbaud >= n_baud_table ? 0 : baud_table[cbaud];
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}
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EXPORT_SYMBOL(tty_termios_baud_rate);
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/**
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* tty_termios_input_baud_rate
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* @termios: termios structure
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*
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* Convert termios baud rate data into a speed. This should be called
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* with the termios lock held if this termios is a terminal termios
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* structure. May change the termios data. Device drivers can call this
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* function but should use ->c_[io]speed directly as they are updated.
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*
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* Locking: none
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*/
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speed_t tty_termios_input_baud_rate(struct ktermios *termios)
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{
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#ifdef IBSHIFT
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unsigned int cbaud = (termios->c_cflag >> IBSHIFT) & CBAUD;
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if (cbaud == B0)
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return tty_termios_baud_rate(termios);
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#ifdef BOTHER
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/* Magic token for arbitrary speed via c_ispeed*/
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if (cbaud == BOTHER)
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return termios->c_ispeed;
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#endif
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if (cbaud & CBAUDEX) {
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cbaud &= ~CBAUDEX;
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if (cbaud < 1 || cbaud + 15 > n_baud_table)
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termios->c_cflag &= ~(CBAUDEX << IBSHIFT);
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else
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cbaud += 15;
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}
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return cbaud >= n_baud_table ? 0 : baud_table[cbaud];
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#else /* IBSHIFT */
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return tty_termios_baud_rate(termios);
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#endif /* IBSHIFT */
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}
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EXPORT_SYMBOL(tty_termios_input_baud_rate);
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/**
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* tty_termios_encode_baud_rate
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* @termios: ktermios structure holding user requested state
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* @ispeed: input speed
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* @ospeed: output speed
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*
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* Encode the speeds set into the passed termios structure. This is
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* used as a library helper for drivers so that they can report back
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* the actual speed selected when it differs from the speed requested
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*
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* For maximal back compatibility with legacy SYS5/POSIX *nix behaviour
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* we need to carefully set the bits when the user does not get the
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* desired speed. We allow small margins and preserve as much of possible
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* of the input intent to keep compatibility.
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*
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* Locking: Caller should hold termios lock. This is already held
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* when calling this function from the driver termios handler.
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*
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* The ifdefs deal with platforms whose owners have yet to update them
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* and will all go away once this is done.
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*/
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void tty_termios_encode_baud_rate(struct ktermios *termios,
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speed_t ibaud, speed_t obaud)
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{
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int i = 0;
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int ifound = -1, ofound = -1;
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int iclose = ibaud/50, oclose = obaud/50;
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int ibinput = 0;
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if (obaud == 0) /* CD dropped */
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ibaud = 0; /* Clear ibaud to be sure */
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termios->c_ispeed = ibaud;
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termios->c_ospeed = obaud;
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#ifdef IBSHIFT
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if ((termios->c_cflag >> IBSHIFT) & CBAUD)
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ibinput = 1; /* An input speed was specified */
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#endif
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#ifdef BOTHER
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/* If the user asked for a precise weird speed give a precise weird
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answer. If they asked for a Bfoo speed they may have problems
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digesting non-exact replies so fuzz a bit */
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if ((termios->c_cflag & CBAUD) == BOTHER) {
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oclose = 0;
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if (!ibinput)
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iclose = 0;
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}
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if (((termios->c_cflag >> IBSHIFT) & CBAUD) == BOTHER)
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iclose = 0;
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#endif
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termios->c_cflag &= ~CBAUD;
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#ifdef IBSHIFT
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termios->c_cflag &= ~(CBAUD << IBSHIFT);
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#endif
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/*
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* Our goal is to find a close match to the standard baud rate
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* returned. Walk the baud rate table and if we get a very close
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* match then report back the speed as a POSIX Bxxxx value by
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* preference
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*/
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do {
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if (obaud - oclose <= baud_table[i] &&
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obaud + oclose >= baud_table[i]) {
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termios->c_cflag |= baud_bits[i];
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ofound = i;
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}
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if (ibaud - iclose <= baud_table[i] &&
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ibaud + iclose >= baud_table[i]) {
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/* For the case input == output don't set IBAUD bits
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if the user didn't do so */
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if (ofound == i && !ibinput)
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ifound = i;
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#ifdef IBSHIFT
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else {
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ifound = i;
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termios->c_cflag |= (baud_bits[i] << IBSHIFT);
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}
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#endif
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}
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} while (++i < n_baud_table);
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/*
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* If we found no match then use BOTHER if provided or warn
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* the user their platform maintainer needs to wake up if not.
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*/
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#ifdef BOTHER
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if (ofound == -1)
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termios->c_cflag |= BOTHER;
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/* Set exact input bits only if the input and output differ or the
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user already did */
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if (ifound == -1 && (ibaud != obaud || ibinput))
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termios->c_cflag |= (BOTHER << IBSHIFT);
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#else
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if (ifound == -1 || ofound == -1)
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pr_warn_once("tty: Unable to return correct speed data as your architecture needs updating.\n");
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#endif
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}
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EXPORT_SYMBOL_GPL(tty_termios_encode_baud_rate);
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/**
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* tty_encode_baud_rate - set baud rate of the tty
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* @ibaud: input baud rate
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* @obad: output baud rate
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*
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* Update the current termios data for the tty with the new speed
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* settings. The caller must hold the termios_rwsem for the tty in
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* question.
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*/
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void tty_encode_baud_rate(struct tty_struct *tty, speed_t ibaud, speed_t obaud)
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{
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tty_termios_encode_baud_rate(&tty->termios, ibaud, obaud);
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}
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EXPORT_SYMBOL_GPL(tty_encode_baud_rate);
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