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termios(3)-like functions that allow custom baud rates.
Uses the "termios2" linux-kernel interface (ioctls TCGETS2, TCSETS2, TCSETSF2, etc) to provide termios(3)-like functions that allow setting custom baud rates. Only works for Linux.
This commit is contained in:
Nick Patavalis
236
termios2.c
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236
termios2.c
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/*
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* termios2.c
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*
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* Use termios2 interface to set custom baud rates to serial ports.
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*
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* by Nick Patavalis (npat@efault.net)
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*
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* ATTENTION: Very linux-specific kludge!
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License as
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* published by the Free Software Foundation; either version 2 of the
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* License, or (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful, but
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* WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307
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* USA
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*/
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#ifndef __linux__
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#error "Linux specific code!"
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#endif /* of __linux__ */
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#include <stdio.h>
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#include <string.h>
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#include <errno.h>
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#include <termios.h>
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#include <sys/ioctl.h>
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/* These definitions must correspond to the kernel structures as
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defined in:
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<linux-kernel>/arch/<arch>/include/uapi/asm/termbits.h
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or <linux-kernel>/include/uapi/asm-generic/termbits.h
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which is the same as:
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/usr/include/<arch>/asm/termbits.h
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or /usr/include/asm-generic/termbits.h
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Unfortunatelly, we cannot just include <asm/termbits.h> or
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<asm/termios.h> or <linux/termios.h> (all would do the trick)
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because then "struct termios" would be re-defined to the kernel
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version, which is not the same as the libc version. In effect, you
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cannot both include <termios.h> and <linux/termios.h> because both
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define a "struct termios" which may or maynot be the same. We want
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our "struct termios" here to be the libc version (as defined in
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<termios.h>), because that's what our callers use. As a result we
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cannot get the definion of "struct termios2" from the above header
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files since this would also bring-in the clashing definition of the
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kernel version of "struct termios". If you have an idea for a better
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way out of this mess, I would REALLY like to hear it.
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*/
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/* These (especially NCCS) *may* need to be ifdef'ed according to
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architecture. */
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#define K_NCCS 19
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struct termios2 {
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tcflag_t c_iflag; /* input mode flags */
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tcflag_t c_oflag; /* output mode flags */
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tcflag_t c_cflag; /* control mode flags */
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tcflag_t c_lflag; /* local mode flags */
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cc_t c_line; /* line discipline */
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cc_t c_cc[K_NCCS]; /* control characters */
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speed_t c_ispeed; /* input speed */
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speed_t c_ospeed; /* output speed */
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};
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#define BOTHER 0010000
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#define IBSHIFT 16
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/* GLIBC termios use an (otherwise unused) bit in c_iflags to
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internally record the fact that ispeed was set to zero (which is
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special behavior and means "same as ospeed". We want to clear this
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bit before passing c_iflags back to the kernel. See:
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<glibc-source>/sysdeps/unix/sysv/linux/speed.c
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*/
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#define IBAUD0 020000000000
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int
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tc2setattr(int fd, int optional_actions, const struct termios *tios)
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{
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struct termios2 t2;
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int cmd;
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switch (optional_actions) {
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case TCSANOW:
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cmd = TCSETS2;
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break;
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case TCSADRAIN:
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cmd = TCSETSW2;
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break;
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case TCSAFLUSH:
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cmd = TCSETSF2;
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break;
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default:
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errno = EINVAL;
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return -1;
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}
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t2.c_iflag = tios->c_iflag & ~IBAUD0;
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t2.c_oflag = tios->c_oflag;
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t2.c_cflag = tios->c_cflag;
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t2.c_lflag = tios->c_lflag;
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t2.c_line = tios->c_line;
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t2.c_ispeed = tios->c_ispeed;
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t2.c_ospeed = tios->c_ospeed;
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memcpy(&t2.c_cc[0], &tios->c_cc[0], K_NCCS * sizeof (cc_t));
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return ioctl(fd, cmd, &t2);
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}
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int
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tc2getattr(int fd, struct termios *tios)
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{
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struct termios2 t2;
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int r;
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r = ioctl(fd, TCGETS2, &t2);
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if (r < 0) return r;
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tios->c_iflag = t2.c_iflag & ~IBAUD0;
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tios->c_oflag = t2.c_oflag;
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tios->c_cflag = t2.c_cflag;
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tios->c_lflag = t2.c_lflag;
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tios->c_line = t2.c_line;
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tios->c_ispeed = t2.c_ispeed;
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tios->c_ospeed = t2.c_ospeed;
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memcpy(&tios->c_cc[0], &t2.c_cc[0], K_NCCS * sizeof (cc_t));
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return 0;
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}
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/* The termios2 interface supports separate input and output
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speeds. Old termios supported only one terminal speed. So the
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standard tcsetispeed(3), actually sets the output-speed field, not
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the input-speed field (or does nothing if speed == B0). Use
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tc2setispeed if you want to set a standard input speed (one of the
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Bxxxxx speeds) that may be different from the output speed. Also if
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someone, somehow, has set the input speed to something other than
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B0, then you *must* use c2setispeed() to change it. Using the
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standard cfsetispeed() obviously won't do (since it affects only
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the output-speed field).
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*/
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int
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cf2setispeed(struct termios *tios, speed_t speed)
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{
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if ( (speed & ~CBAUD) != 0
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&& (speed < B57600 || speed > __MAX_BAUD) ) {
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errno = EINVAL;
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return -1;
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}
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tios->c_ispeed = speed;
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tios->c_cflag &= ~((CBAUD | CBAUDEX) << IBSHIFT);
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tios->c_cflag |= (speed << IBSHIFT);
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return 0;
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}
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speed_t
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cf2getispeed(struct termios *tios)
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{
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return (tios->c_cflag >> IBSHIFT) & (CBAUD | CBAUDEX);
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}
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int
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cf2setospeed_custom(struct termios *tios, int speed)
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{
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if ( speed <= 0 ) {
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errno = EINVAL;
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return -1;
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}
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tios->c_cflag = (tios->c_cflag & ~CBAUD) | BOTHER;
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tios->c_ospeed = speed;
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return 0;
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}
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int
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cf2setispeed_custom(struct termios *tios, int speed)
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{
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if ( speed < 0 ) {
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errno = EINVAL;
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return -1;
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}
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if ( speed == 0 ) {
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/* Special case: ispeed == 0 means "same as ospeed". Kernel
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* does this if it sees B0 in the "CIBAUD" field (i.e. in
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* CBAUD << IBSHIFT) */
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tios->c_cflag =
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(tios->c_cflag & ~(CBAUD << IBSHIFT)) | (B0 << IBSHIFT);
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} else {
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tios->c_cflag =
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(tios->c_cflag & ~(CBAUD << IBSHIFT)) | (BOTHER << IBSHIFT);
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tios->c_ispeed = speed;
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}
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return 0;
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}
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/* Helpers for debugging */
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void
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cf2showspeed(struct termios *tios)
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{
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printf("CB: %08o, CIB: %08o, ospeed = %d, ispeed = %d\r\n",
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tios->c_cflag & (CBAUD | CBAUDEX),
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(tios->c_cflag >> IBSHIFT) & (CBAUD | CBAUDEX),
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tios->c_ospeed,
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tios->c_ispeed);
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}
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void
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tc2showspeed(int fd)
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{
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struct termios tios;
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int r;
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r = tc2getattr(fd, &tios);
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if (r < 0) {
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printf("%d: Failed to get attrs: %s", fd, strerror(errno));
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return;
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}
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printf("%d: ", fd);
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cf2showspeed(&tios);
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}
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65
termios2.h
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65
termios2.h
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@ -0,0 +1,65 @@
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/*
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* termios2.h
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*
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* Use termios2 interface to set custom baud rates to serial ports.
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*
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* by Nick Patavalis (npat@efault.net)
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License as
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* published by the Free Software Foundation; either version 2 of the
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* License, or (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful, but
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* WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307
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* USA
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*/
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#ifndef TERMIOS2_H
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#define TERMIOS2_H
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#include <termios.h>
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/* Replacements for the standard tcsetattr(3), tcgetattr(3)
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* functions. Same interface, but these use the new termios2 kernel
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* interface (new ioctl's) which allow custom baud-rate
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* definitions. */
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int tc2setattr(int fd, int optional_actions, const struct termios *tios);
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int tc2getattr(int fd, struct termios *tios);
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/* Replacements for the standard cfgetispeed(3), cfsetispeed(3)
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* functions. Use these to set / get standard *input* baudrates. You
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* can still use cfgetospeed(3), cfsetospeed(3) to set / get the
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* standard output baudrates. The new termios2 interface, unlike the
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* old one, supports different input and output speeds for a
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* device. The "speed" argument must be (and the return value will be)
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* one of the standard "Bxxxx" macros. If cf2getispeed() or
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* cfgetospeed(3) return CBAUDEX, then the respective baudrate is a
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* custom one. Read the "termios.c_ispeed" / "termios.c_ospeed" fields
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* to get the custom value (as a numeric speed). */
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int cf2setispeed(struct termios *tios, speed_t speed);
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speed_t cf2getispeed(struct termios *tios);
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/* Use these to set *custom* input and output baudrates for a
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* device. The "speed" argument must be a numeric baudrate value
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* (e.g. 1234 for 1234 bps). */
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int cf2setispeed_custom(struct termios *tios, int speed);
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int cf2setospeed_custom(struct termios *tios, int speed);
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/* Helpers for debugging */
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void cf2showspeed(struct termios *tios);
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void tc2showspeed(int fd) ;
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#endif /* of TERMIOS2_H */
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