glibc/sysdeps/unix/sysv/linux/tcsetattr.c

/* Copyright (C) 1993-2025 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/>.  */

#include <termios_internals.h>

#define static_assert_equal(x,y) _Static_assert ((x) == (y), #x " != " #y)

/* Set the state of FD to *TERMIOS_P.  */
int
__tcsetattr (int fd, int optional_actions, const struct termios *termios_p)
{
  struct termios2 k_termios;
  unsigned long cmd;

  memset (&k_termios, 0, sizeof k_termios);

  k_termios.c_iflag = termios_p->c_iflag;
  k_termios.c_oflag = termios_p->c_oflag;
  k_termios.c_cflag = termios_p->c_cflag;
  k_termios.c_lflag = termios_p->c_lflag;
  k_termios.c_line  = termios_p->c_line;

  k_termios.c_ospeed = termios_p->c_ospeed;
  k_termios.c_ispeed = termios_p->c_ispeed;

  ___termios2_canonicalize_speeds (&k_termios);

  copy_c_cc (k_termios.c_cc, _TERMIOS2_NCCS, termios_p->c_cc, NCCS);

  /*
   * Choose the proper ioctl number to invoke.
   *
   * Alpha got TCSETS2 late (Linux 4.20), but has the same structure
   * format, and it only needs TCSETS2 if either it needs to use
   * __BOTHER or split speed.  All other architectures have TCSETS2 as
   * far back as the current glibc supports.  Calling TCSETS with
   * __BOTHER causes unpredictable results on old Alpha kernels and
   * could even crash them.
   */
  static_assert_equal(TCSADRAIN, TCSANOW + 1);
  static_assert_equal(TCSAFLUSH, TCSANOW + 2);
  static_assert_equal(TCSETSW2,  TCSETS2 + 1);
  static_assert_equal(TCSETSF2,  TCSETS2 + 2);
  static_assert_equal(TCSETSW,   TCSETS  + 1);
  static_assert_equal(TCSETSF,   TCSETS  + 2);

  cmd = (long)optional_actions - TCSANOW;
  if (cmd > 2)
    return INLINE_SYSCALL_ERROR_RETURN_VALUE (EINVAL);

  if (__ASSUME_TERMIOS2 ||
      k_termios.c_ospeed != k_termios.c_ispeed ||
      cbaud (k_termios.c_cflag) == __BOTHER)
    {
      cmd += TCSETS2;
    }
  else
    {
      cmd += TCSETS;
      k_termios.c_cflag &= ~CIBAUD;
    }

  return INLINE_SYSCALL_CALL (ioctl, fd, cmd, &k_termios);
}
libc_hidden_def (__tcsetattr)

#if _HAVE_STRUCT_OLD_TERMIOS && _TERMIOS_OLD_COMPAT

versioned_symbol (libc, __tcsetattr, tcsetattr, GLIBC_2_42);

/* Legacy version for shorter struct termios without speed fields */
int
attribute_compat_text_section
__old_tcsetattr (int fd, int optional_actions, const old_termios_t *termios_p)
{
  struct termios new_termios;

  memset (&new_termios, 0, sizeof (new_termios));
  new_termios.c_iflag  = termios_p->c_iflag;
  new_termios.c_oflag  = termios_p->c_oflag;
  new_termios.c_cflag  = termios_p->c_cflag;
  new_termios.c_lflag  = termios_p->c_lflag;
  new_termios.c_line   = termios_p->c_line;
  copy_c_cc(new_termios.c_cc, NCCS, termios_p->c_cc, OLD_NCCS);

  return __tcsetattr (fd, optional_actions, &new_termios);
}
compat_symbol (libc, __old_tcsetattr, tcsetattr, GLIBC_2_0);

#else

weak_alias (__tcsetattr, tcsetattr)

#endif