/* mkmisc - make misc device nodes with dynamic minor number
 * 
 * Copyright (C) 2011  Antonio Ospite <ospite@studenti.unina.it>
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

/* A misc device is a character device node which can have a dynamic minor
 * number, see:
 * http://www.linux.it/~rubini/docs/misc/misc.html
 */

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <libgen.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include <ctype.h>

static int verbose = 0;
static int force = 0;
static unsigned int mode = 0664;

static int misc_get_major(void)
{
	FILE *fp;
	char line[256];
	int major;
	char name[64];

	fp = fopen("/proc/devices", "r");
	if (fp == NULL) {
		perror("/proc/devices");
		return -1;
	}

	while (fgets(line, sizeof(line) - 1, fp)) {
		if(sscanf(line, "%d %64s", &major, name) == 2)
			if (strcmp(name, "misc") == 0) {
				fclose(fp);
				return major;
			}
	}
	fclose(fp);

	return -1;
}

static int misc_get_minor(char *device)
{
	FILE *fp;
	int minor;
	char name[64];
	char *path;
	char *node;

	fp = fopen("/proc/misc", "r");
	if (fp == NULL) {
		perror("/proc/misc");
		return -1;
	}

	path = strdup(device);
	node = basename(path);

	while (fscanf(fp, "%d %64s", &minor, name) == 2) {
		if (strcmp(name, node) == 0) {
			free(path);
			fclose(fp);
			return minor;
		}
	}
	free(path);
	fclose(fp);

	return -1;
}

static int mkmisc(char *device)
{
	int major;
	int minor;
	dev_t dev;
	int ret;

	major = misc_get_major();
	if (major < 0) {
		fprintf(stderr, "Cannot get misc major number\n");
		return major;
	}

	minor = misc_get_minor(device);
	if (minor < 0) {
		fprintf(stderr, "Cannot get misc minor for %s\n", device);
		return minor;
	}

	if (verbose)
		printf("Creating device: %s, major: %d, minor: %d\n",
		       device, major, minor);

	if (force) {
		ret = unlink(device);
		if (ret < 0) {
			perror("unlink");
			/*
			return ret;
			*/
		}
	}

	dev = makedev(major, minor);
	mode |= S_IFCHR;
	ret = mknod(device, mode, dev);
	if (ret < 0) {
		perror("mknod");
		return ret;
	}

	return 0;
}

static void usage(void)
{
	printf("Usage: mkmisc [OPTION]... NAME\n");
	printf("Create the special file NAME as a misc device with a dynamic minor number.\n");
	printf("\n");
	printf("OPTION can be any of:\n");
	printf("  -f       force creation even if the file already exists\n");
	printf("  -m MODE  set file permission bits to MODE, not a=rw - umask\n");
	printf("  -v       verbose output\n");
	printf("  -h       display this help and exit\n");
}

static void parse_options(int argc, char *argv[])
{
	int c;
	int ret;

	while ((c = getopt (argc, argv, "fm:vh")) != -1)
		switch (c) {
		case 'f':
			force = 1;
			break;
		case 'm':
			ret = sscanf(optarg, "0%o", &mode);
			if (ret != 1) {
				fprintf(stderr, "mode must be octal (e.g 0664)\n");
				exit(EXIT_FAILURE);
			}
			break;
		case 'v':
			verbose = 1;
			break;
		case 'h':
			usage();
			exit(0);
		case '?':
			/* skip known options with missing arguments */
			if (optopt != 'm') {
				if(isprint(optopt))
					fprintf (stderr,
					         "Unknown option `-%c'.\n",
					         optopt);
				else
					fprintf (stderr,
					         "Unknown option character `\\x%x'.\n",
					         optopt);
			}
		default:
			usage();
			exit(EXIT_FAILURE);
		}
}

int main(int argc, char *argv[])
{
	int ret;
	char *device = NULL;

	parse_options(argc, argv);

	if (optind >= argc) {
		fprintf(stderr, "Missing argument NAME\n\n");
		usage();
		exit(EXIT_FAILURE);
	} else if ((argc - optind) > 1) {
		fprintf(stderr, "Too many arguments\n\n");
		usage();
		exit(EXIT_FAILURE);
	}

	device = strdup(argv[optind]);

	ret = mkmisc(device);
	if (ret < 0)
		fprintf(stderr, "Cannot create %s\n", device);

	free(device);

	return ret;
}