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

/* Copyright (C) 1993, 1996, 1997, 1998 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 Library General Public License as
   published by the Free Software Foundation; either version 2 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
   Library General Public License for more details.

   You should have received a copy of the GNU Library General Public
   License along with the GNU C Library; see the file COPYING.LIB.  If not,
   write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
   Boston, MA 02111-1307, USA.  */

#include <errno.h>
#include <string.h>
#include <termios.h>
#include <sys/ioctl.h>
#include <sys/types.h>

/* The difference here is that the termios structure used in the
   kernel is not the same as we use in the libc.  Therefore we must
   translate it here.  */
#include <kernel_termios.h>


/* This is a gross hack around a kernel bug.  If the cfsetispeed functions
   is called with the SPEED argument set to zero this means use the same
   speed as for output.  But we don't have independent input and output
   speeds and therefore cannot record this.

   We use an unused bit in the `c_iflag' field to keep track of this
   use of `cfsetispeed'.  The value here must correspond to the one used
   in `speed.c'.  */
#if !defined _HAVE_C_ISPEED || !defined _HAVE_C_OSPEED
# define IBAUD0	020000000000
#else
/* If we have separate values for input and output speed don't bother
   with this.  Define the value as zero so the compiler sees we don't
   have to do the AND below.  */
# define IBAUD0	0
#endif


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

  switch (optional_actions)
    {
    case TCSANOW:
      cmd = TCSETS;
      break;
    case TCSADRAIN:
      cmd = TCSETSW;
      break;
    case TCSAFLUSH:
      cmd = TCSETSF;
      break;
    default:
      __set_errno (EINVAL);
      return -1;
    }

  k_termios.c_iflag = termios_p->c_iflag & ~IBAUD0;
  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;
#ifdef _HAVE_C_ISPEED
  k_termios.c_ispeed = termios_p->c_ispeed;
#endif
#ifdef _HAVE_C_OSPEED
  k_termios.c_ospeed = termios_p->c_ospeed;
#endif
  memcpy (&k_termios.c_cc[0], &termios_p->c_cc[0],
	  __KERNEL_NCCS * sizeof (cc_t));

  retval = __ioctl (fd, cmd, &k_termios);

  if (retval == 0 && cmd == TCSETS)
    {
      /* The Linux kernel has a bug which silently ignore the invalid
	 c_cflag on pty. We have to check it here. */
      int save = errno;
      retval = __ioctl (fd, TCGETS, &k_termios);
      if (retval)
	{
	  /* We cannot verify if the setting is ok. We don't return
	     an error (?). */
	  __set_errno (save);
	  retval = 0;
	}
      else if ((termios_p->c_cflag & (PARENB | CREAD))
	       != (k_termios.c_cflag & (PARENB | CREAD))
	       || ((termios_p->c_cflag & CSIZE)
		   && ((termios_p->c_cflag & CSIZE)
		       != (k_termios.c_cflag & CSIZE))))
	{
	  /* It looks like the Linux kernel silently changed the
	     PARENB/CREAD/CSIZE bits in c_cflag. Report it as an
	     error. */
	  __set_errno (EINVAL);
	  retval = -1;
	}
    }

  return retval;
}