commands/diskctl/diskctl.c
/* diskctl - control disk device driver parameters - by D.C. van Moolenbroek */
#include <stdlib.h>
#include <stdio.h>
#include <sys/ioctl.h>
#include <unistd.h>
#include <fcntl.h>

static char *name, *dev;

static void usage(void)
{
	fprintf(stderr, "usage: %s <device> <command> [args]\n"
			"\n"
			"supported commands:\n"
			"  getwcache           return write cache status\n"
			"  setwcache [on|off]  set write cache status\n"
			"  flush               flush write cache\n",
			name);

	exit(EXIT_FAILURE);
}

static int open_dev(int flags)
{
	int fd;

	fd = open(dev, flags);

	if (fd < 0) {
		perror("open");

		exit(EXIT_FAILURE);
	}

	return fd;
}

int main(int argc, char **argv)
{
	int fd, val;

	name = argv[0];

	if (argc < 3) usage();

	dev = argv[1];

	if (!strcasecmp(argv[2], "getwcache")) {
		if (argc != 3) usage();

		fd = open_dev(O_RDONLY);

		if (ioctl(fd, DIOCGETWC, &val) != 0) {
			perror("ioctl");

			return EXIT_FAILURE;
		}

		close(fd);

		printf("write cache is %s\n", val ? "on" : "off");
	}
	else if (!strcasecmp(argv[2], "setwcache")) {
		if (argc != 4) usage();

		fd = open_dev(O_WRONLY);

		if (!strcasecmp(argv[3], "on")) val = 1;
		else if (!strcasecmp(argv[3], "off")) val = 0;
		else usage();

		if (ioctl(fd, DIOCSETWC, &val) != 0) {
			perror("ioctl");

			return EXIT_FAILURE;
		}

		close(fd);

		printf("write cache %sabled\n", val ? "en" : "dis");
	}
	else if (!strcasecmp(argv[2], "flush")) {
		if (argc != 3) usage();

		fd = open_dev(O_WRONLY);

		if (ioctl(fd, DIOCFLUSH, NULL) != 0) {
			perror("ioctl");

			return EXIT_FAILURE;
		}

		close(fd);

		printf("write cache flushed\n");
	}
	else usage();

	return EXIT_SUCCESS;
}
