/*
 * 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>
#include <ctype.h>

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

#define NAME "cycle"

struct params {
	char *devname;
	int sleep;		/* Seconds */
};

void parse_args(struct params *p, int argc, char **argv);
void Usage(void);

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

	parse_args(&par, argc, argv);

	/*
	 * Standard nonblocking open for Linux.
	 */
	if ((fd = open(par.devname, O_RDWR|O_NONBLOCK)) < 0) {
		fprintf(stderr, NAME ": Cannot open %s: %s\n", par.devname,
		    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", par.devname,
		    strerror(errno));
		exit(1);
	}
	
	printf("Sleeping (%ds)...\n", par.sleep);
	sleep(par.sleep);

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

	printf("Sleeping (%ds)...\n", par.sleep);
	sleep(par.sleep);

	exit(0);
}

void parse_args(struct params *p, int argc, char **argv)
{
	char *arg;

	p->devname = NULL;
	p->sleep = 5;

	argv++;
	while ((arg = *argv++) != NULL) {
		if (arg[0] == '-') {
			switch (arg[1]) {
			case 's':
				if ((arg = *argv) == NULL)
					Usage();
				argv++;
				if (!isdigit(arg[0]))
					Usage();
				p->sleep = atoi(arg);
				if (p->sleep < 0) {
					fprintf(stderr, NAME
					    ": sleep value is bad (%s)\n", arg);
					exit(1);
				}
				break;
			default:
				Usage();
			}
		} else {
			p->devname = arg;
			if (*argv != NULL)
				Usage();
		}
	}
	if (p->devname == NULL)
		Usage();
}

void Usage()
{
	fprintf(stderr, "Usage: cycle [-s sleep] device\n");
	exit(1);
}