noise.c

/*
 * Copyright (c) 2013 Luc Verhaegen <libv@skynet.be>
 *
 * 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 2 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, write to the Free Software Foundation, Inc.,
 * 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
 */

/*
 * Really trivial program to make constant noise on many available serial
 * busses, so that UART pins may be found. Copyright is ascertained to at
 * least attempt to mitigate some of the stupidity of android forums, and
 * to perhaps see some changes get back to linux-sunxi.org from time to time.
 *
 * For usage information, please refer to http://linux-sunxi.org/UART
 */
#include <stdio.h>
#include <errno.h>
#include <string.h>
#include <unistd.h>
#include <sys/stat.h>

#define SERIAL_COUNT 32
#define FILENAME_SIZE 32

struct files {
	FILE *file;
	char name[FILENAME_SIZE];
};

int
console_open(struct files *file, char *format, int index)
{
	struct stat stat_buf;
	int ret;

	ret = snprintf(file->name, FILENAME_SIZE, format, index);
	if (ret <= 0) {
		printf("error writing filename!\n");
		return -1;
	}

	ret = stat(file->name, &stat_buf);
	if (ret == -1) {
		if (errno != ENOENT)
			printf("Error: failed to stat %s: %s\n",
			       file->name, strerror(errno));
		return -1;
	}

	file->file = fopen(file->name, "w");
	if (!(file->file)) {
		printf("Error: failed to open %s: %s\n", file->name,
		       strerror(errno));
		return -1;
	}

	return 0;
}

int
main(int argc, char *argv[])
{
	struct files files[SERIAL_COUNT] = {{NULL,}, };
	int i = 0, j, ret, found;

	if (argc != 1) {
		printf("\n");
		printf("Copyright (c) 2013 Luc Verhaegen <libv@skynet.be>\n");
		printf("\n");
		printf("This program is free software; you can redistribute it "
		       "and/or modify it\n");
		printf("under the terms of the GNU General Public License as "
		       "published by the\n");
		printf("Free Software Foundation; either version 2 of the "
		       "License, or (at your\n");
		printf("option) any later version.\n");
		printf("\n");
		printf("This program is distributed in the hope that it will be"
		       " useful, but\n");
		printf("WITHOUT ANY WARRANTY; without even the implied warranty"
		       " of\n");
		printf("MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. "
		       "See the GNU\n");
		printf("General Public License for more details.\n");
		printf("\n");
		printf("You should have received a copy of the GNU General "
		       "Public License along\n");
		printf("with this program; if not, write to the Free Software "
		       "Foundation, Inc.,\n");
		printf("59 Temple Place, Suite 330, Boston, MA 02111-1307 "
		       "USA\n");
		printf("\n");
		printf("For more information, refer to "
		       "http://linux-sunxi.org/UART\n");
		printf("\n");
		return 0;
	}

	for (j = 0; j < 8; j++) {
		ret = console_open(&files[i], "/dev/ttyS%d", j);
		if (ret)
			continue;
		i++;
	}

	/* special device nodes for telechips */
	for (j = 0; j < 8; j++) {
		ret = console_open(&files[i], "/dev/tcc-uart%d", j);
		if (ret)
			continue;
		i++;
	}

	printf("Flooding serial consoles with text...\n");

	while (1) {
		for (i = 0, found = 0; i < SERIAL_COUNT; i++) {
			if (!files[i].file)
				continue;

			found = 1;

			ret = fprintf(files[i].file, "%s\n", files[i].name);
			if (ret > 0)
				continue;

			printf("Error: failed to write to %s: %s\n",
			       files[i].name, strerror(errno));
			fclose(files[i].file);
			files[i].file = NULL;
		}

		if (!found) {
 			printf("Error: No serial consoles found. Exiting.\n");
			return -1;
		}

		usleep(20000);
	}

	return 0;
}