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glibc/termios/termios.h
H. Peter Anvin (Intel) 5f138519eb termios: add new baud_t interface, defined to be explicitly numeric 
Add an explicitly numeric interface for baudrate setting. For glibc,
this only announces what is a fair accompli, but this is a plausible
way forward for standardization, and may be possible to infill on
non-compliant systems. The POSIX committee has stated:

[https://www.austingroupbugs.net/view.php?id=1916#c7135]

	A future version of this standard is expected to add at least
	the following symbolic constants for use as values of objects
	of type speed_t: B57600, B115200, B230400, B460800, and
	B921600.

	Implementations are encouraged to propose additional
	interfaces which will make it possible to set and query a
	wider range of speeds than just those enumerated by the
	constants beginning with B. If a set of common interfaces
	emerges between several implementations, a future version of
	this standard will likely add those interfaces.

This is exactly that interface.

The use of the term "baud" is due to the need to have a term
contrasting "speed", and it is already well established as a legacy
term -- including in the names of the legacy Bxxx
constants. Futhermore, it *is* valid from the point of view that the
termios interface fundamentally emulates an RS-232 serial port as far
as the application software is concerned.

The documentation states that for the current version of glibc,
speed_t == baud_t, but explicitly declares that this may not be the
case in the future.

Signed-off-by: H. Peter Anvin (Intel) <hpa@zytor.com>
Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>
2025-06-17 09:11:38 -03:00

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/* Copyright (C) 1991-2025 Free Software Foundation, Inc.
This file is part of the GNU C Library.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library; if not, see
<https://www.gnu.org/licenses/>. */
/*
* POSIX Standard: 7.1-2 General Terminal Interface <termios.h>
*/
#ifndef _TERMIOS_H
#define _TERMIOS_H 1
#include <features.h>
#if defined __USE_XOPEN_EXTENDED || defined __USE_XOPEN2K8
/* We need `pid_t'. */
# include <bits/types.h>
# ifndef __pid_t_defined
typedef __pid_t pid_t;
# define __pid_t_defined
# endif
#endif
__BEGIN_DECLS
/* Get the system-dependent definitions of `struct termios', `tcflag_t',
`cc_t', `speed_t', and all the macros specifying the flag bits. */
#include <bits/termios.h>
#ifdef __USE_MISC
/* Compare a character C to a value VAL from the `c_cc' array in a
`struct termios'. If VAL is _POSIX_VDISABLE, no character can match it. */
# define CCEQ(val, c) ((c) == (val) && (val) != _POSIX_VDISABLE)
#endif
/* Return the output baud rate stored in *TERMIOS_P. */
extern speed_t cfgetospeed (const struct termios *__termios_p) __THROW;
/* Return the input baud rate stored in *TERMIOS_P. */
extern speed_t cfgetispeed (const struct termios *__termios_p) __THROW;
/* Set the output baud rate stored in *TERMIOS_P to SPEED. */
extern int cfsetospeed (struct termios *__termios_p, speed_t __speed) __THROW;
/* Set the input baud rate stored in *TERMIOS_P to SPEED. */
extern int cfsetispeed (struct termios *__termios_p, speed_t __speed) __THROW;
#ifdef __USE_MISC
/* Set both the input and output baud rates in *TERMIOS_OP to SPEED. */
extern int cfsetspeed (struct termios *__termios_p, speed_t __speed) __THROW;
/* Interfaces that are explicitly numeric representations of baud rates */
typedef speed_t baud_t;
/* Return the output baud rate stored in *TERMIOS_P. */
extern baud_t cfgetobaud (const struct termios *__termios_p) __THROW;
/* Return the input baud rate stored in *TERMIOS_P. */
extern baud_t cfgetibaud (const struct termios *__termios_p) __THROW;
/* Set the output baud rate stored in *TERMIOS_P to BAUD. */
extern int cfsetobaud (struct termios *__termios_p, baud_t __baud) __THROW;
/* Set the input baud rate stored in *TERMIOS_P to BAUD. */
extern int cfsetibaud (struct termios *__termios_p, baud_t __baud) __THROW;
/* Set both the input and output baud rates in *TERMIOS_OP to BAUD. */
extern int cfsetbaud (struct termios *__termios_p, baud_t __baud) __THROW;
#endif
/* Put the state of FD into *TERMIOS_P. */
extern int tcgetattr (int __fd, struct termios *__termios_p) __THROW;
/* Set the state of FD to *TERMIOS_P.
Values for OPTIONAL_ACTIONS (TCSA*) are in <bits/termios.h>. */
extern int tcsetattr (int __fd, int __optional_actions,
const struct termios *__termios_p) __THROW;
#ifdef __USE_MISC
/* Set *TERMIOS_P to indicate raw mode. */
extern void cfmakeraw (struct termios *__termios_p) __THROW;
#endif
/* Send zero bits on FD. */
extern int tcsendbreak (int __fd, int __duration) __THROW;
/* Wait for pending output to be written on FD.
This function is a cancellation point and therefore not marked with
__THROW. */
extern int tcdrain (int __fd);
/* Flush pending data on FD.
Values for QUEUE_SELECTOR (TC{I,O,IO}FLUSH) are in <bits/termios.h>. */
extern int tcflush (int __fd, int __queue_selector) __THROW;
/* Suspend or restart transmission on FD.
Values for ACTION (TC[IO]{OFF,ON}) are in <bits/termios.h>. */
extern int tcflow (int __fd, int __action) __THROW;
#if defined __USE_XOPEN_EXTENDED || defined __USE_XOPEN2K8
/* Get process group ID for session leader for controlling terminal FD. */
extern __pid_t tcgetsid (int __fd) __THROW;
#endif
#ifdef __USE_MISC
# include <sys/ttydefaults.h>
#endif
__END_DECLS
#endif /* termios.h */
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