/*
 * This program cycles DTR.
 * Do not use stdin because we must open with O_NONBLOCK.
 */
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <fcntl.h>
#include <sys/types.h>
#include <sys/ioctl.h>	/* Provides TIOCMBIC/TIOCMBIS */
#include <errno.h>
#include <unistd.h>

/* This comes from <asm/termbits.h>, which cannot be included */
#define TIOCM_DTR  0x002
#define TIOCM_RTS  0x004

#define NAME "cycle"

void Usage(void);

int main(int argc, char *argv[])
{
	char *name;
	int fd;
	unsigned int b;

	if (argc != 2) Usage();
	name = argv[1];

	/*
	 * Standard nonblocking open for Linux.
	 */
	if ((fd = open(name, O_RDWR|O_NONBLOCK)) < 0) {
		fprintf(stderr, NAME ": Cannot open %s: %s\n", name,
		    strerror(errno));
		exit(1);
	}
	/* (void) ioctl(fd, TCFLSH, TCIOFLUSH); */
	/* make the serial port blocking again */
	(void) fcntl(fd, F_SETFL, fcntl(fd, F_GETFL, 0) & ~O_NONBLOCK);

	/*
	 * Cycle DTR
	 */
	printf("Dropping DTR...\n");
	b = TIOCM_DTR;
	if (ioctl(fd, TIOCMBIC, &b) != 0) {
		fprintf(stderr, NAME ": TIOCMBIC %s: %s\n", name,
		    strerror(errno));
		exit(1);
	}
	
	printf("Sleeping...\n");
	sleep(5);

	printf("Raising DTR...\n");
	b = TIOCM_DTR;
	if (ioctl(fd, TIOCMBIS, &b) != 0) {
		fprintf(stderr, NAME ": TIOCMBIS %s: %s\n", name,
		    strerror(errno));
		exit(1);
	}

	printf("Sleeping...\n");
	sleep(5);

	exit(0);
}

void Usage()
{
	fprintf(stderr, "Usage: cycle device\n");
	exit(1);
}