Serial Driver - How do I detect break, part II

tzeruch@ceddec.com
Thu, 10 Jul 1997 15:16:28 -0400

What am I doing wrong? /proc/tty/driver/serial shows the number of breaks
incrementing (I am using minicom on a second system with a light box so I
am generating breaks which are being detected in the statistics).

But in the program below, breaks is never incrementing, nor is anything
returned by the read (other than a zero) when a break condition happens,
and it detects characters properly. It also detects control-c causing
sigint on the console (which does increment breaks).

Or is there something wrong in the kernel not generating or masking
signals, or otherwise not propogating them up to the user program?

---


#include <unistd.h>
#include <stdio.h>
#include <fcntl.h>
#include <termios.h>
#include <sys/ioctl.h>
#include <signal.h>


int                 breaks;


__sighandler_t      sighandle(int signum, __sighandler_t h)
{
        breaks++;
        fprintf(stderr, "BREAK DETECTED\n");
        signal(SIGINT, (__sighandler_t) sighandle);
        return SIG_IGN;
}


int                 main(int argc, char *argv[])
{
        int                 i;
        unsigned char       skresp[2];


        int                 serfd;
        int                 spd = -1;
        struct termios      tty;


        breaks = 0;
        signal(SIGINT, (__sighandler_t) sighandle);


        serfd = open("/dev/modem", O_RDWR);


        tcgetattr(serfd, &tty);


        spd = B9600;
        cfsetospeed(&tty, (speed_t) spd);
        cfsetispeed(&tty, (speed_t) spd);


        tty.c_iflag = BRKINT;
        tty.c_lflag = ISIG;
        tty.c_cflag = CS8 | CREAD | CLOCAL;


        tcsetattr(serfd, TCSANOW, &tty);


        while (1) {
                i = read(serfd, skresp, 1);
                if (i)
                        fprintf(stderr, "%d %d %02x\n", breaks, i,
				skresp[0]);
        }
}