gpio-chip-info.c

 1// SPDX-License-Identifier: GPL-2.0-or-later
 2/*
 3 * GPIO character device helper for reading chip information.
 4 *
 5 * Copyright (C) 2021 Bartosz Golaszewski <brgl@bgdev.pl>
 6 */
 7
 8#include <fcntl.h>
 9#include <linux/gpio.h>
10#include <stdio.h>
11#include <stdlib.h>
12#include <string.h>
13#include <sys/ioctl.h>
14#include <sys/types.h>
15
16static void print_usage(void)
17{
18	printf("usage:\n");
19	printf("  gpio-chip-info <chip path> [name|label|num-lines]\n");
20}
21
22int main(int argc, char **argv)
23{
24	struct gpiochip_info info;
25	int fd, ret;
26
27	if (argc != 3) {
28		print_usage();
29		return EXIT_FAILURE;
30	}
31
32	fd = open(argv[1], O_RDWR);
33	if (fd < 0) {
34		perror("unable to open the GPIO chip");
35		return EXIT_FAILURE;
36	}
37
38	memset(&info, 0, sizeof(info));
39	ret = ioctl(fd, GPIO_GET_CHIPINFO_IOCTL, &info);
40	if (ret) {
41		perror("chip info ioctl failed");
42		return EXIT_FAILURE;
43	}
44
45	if (strcmp(argv[2], "name") == 0) {
46		printf("%s\n", info.name);
47	} else if (strcmp(argv[2], "label") == 0) {
48		printf("%s\n", info.label);
49	} else if (strcmp(argv[2], "num-lines") == 0) {
50		printf("%u\n", info.lines);
51	} else {
52		fprintf(stderr, "unknown command: %s\n", argv[2]);
53		return EXIT_FAILURE;
54	}
55
56	return EXIT_SUCCESS;
57}