Date: Mon, 19 Mar 2001 21:30:55 +0100 From: Volker Jahns <Volker.Jahns@thalreit.de> To: hackers@freebsd.org Cc: Volker.Jahns@dpma.de Subject: Serial port open Message-ID: <20010319213055.A881@ikarus.thalreit>
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I do have a small problem w/ serial IO. I have attached code to
1. open a serial line,
2. set terminal attributes,
3. close the serial port,
4. iterate thru 1.-3. a second time.
<snip>
/* serial test */
/*
FreeBSD 3 second
*/
#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <fcntl.h>
#include <errno.h>
#include <termios.h>
#include <sys/ioctl.h>
#define BENCHMARK 2
int
main (int argc, char **argv)
{
int err, rfd, tset, i, j;
struct termios tp, op;
/* test loop to check how long it takes to open/close the port */
for ( j = 0; j < BENCHMARK; j++) {
rfd = open("/dev/ttyd0", O_RDWR | O_NOCTTY | O_NONBLOCK | O_NDELAY);
printf("open\t\t: errno %d\n", errno);
if (rfd == -1)
{
perror("open: couldn't open /dev/ttyd0");
}
else {
fcntl(rfd, F_SETFL, 0);
}
/* get terminal attributes */
tcgetattr(rfd, &op);
tcgetattr(rfd, &tp);
/* set terminal attr */
cfsetispeed(&tp, 9600);
cfsetospeed(&tp, 9600);
tp.c_iflag = 0;
tp.c_oflag = 0;
tp.c_cflag = 0;
tp.c_lflag = 0;
for ( i = 0; i < NCCS; i++) {
tp.c_cc[i] = 0;
}
tp.c_iflag &= (IXON | IXOFF | IXANY);
tp.c_cflag |= PARENB;
tp.c_cflag &= ~PARODD;
tp.c_cflag |= CLOCAL;
tp.c_cflag |= CREAD;
tp.c_cflag |= CS8;
tp.c_cflag |= CSTOPB;
tp.c_cflag |= CSIZE;
tp.c_lflag &= ~(ICANON | ECHO | ECHOE | ISIG);
tp.c_cc[VMIN]=0;
tp.c_cc[VTIME]=1;
/* set terminal attributes */
tcsetattr(rfd, TCSANOW, &tp);
/* reset terminal attributes */
tcsetattr(rfd, TCSANOW, &op);
close(rfd);
/* 2nd service */
}
}
<snap>
between the 1st call to close and the 2nd call to open the system spends
some 3 (three !) seconds.
<snip>
volker@nemo testing > time ./io_fbsd-2
open : errno 0
open : errno 0
real 0m2.998s
user 0m0.000s
sys 0m0.004s
<snap>
I am running
<snip>
FreeBSD nemo.zvr.dpma.de 4.2-RELEASE FreeBSD 4.2-RELEASE #0: Thu Mar 15
12:58:51 CET 2001
<snap>
but happens also w/ 4.1.
What is actually wrong about the code? What is it I am missing?
If this is the incorrect list to consider the problem, could you please
redirect?
for case anybody wants to know, here is the relevant output of kdump
<snip>
21753 io_fbsd-2 985009390.419433 RET close 0
21753 io_fbsd-2 985009390.419451 CALL
open(0x80488a0,0x8006,0xbfbff6a0)
21753 io_fbsd-2 985009390.419467 NAMI "/dev/ttyd0"
21753 io_fbsd-2 985009393.411359 RET open 3
21753 io_fbsd-2 985009393.411426 CALL write(0x1,0x804b000,0x10)
<snap>
It shows, that it takes approx 3 seconds between the call to open and
the return of the call.
This is actually is striped down version of code to read out data of a
serially connected weatherstation.
--
Volker Jahns, Thalreit/DE, +49 80 35 69 25, mailto:Volker.Jahns@thalreit.de
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