1// SPDX-License-Identifier: GPL-2.0-only
 2/*
 3 * gpio-watch - monitor unrequested lines for property changes using the
 4 *              character device
 5 *
 6 * Copyright (C) 2019 BayLibre SAS
 7 * Author: Bartosz Golaszewski <bgolaszewski@baylibre.com>
 8 */
 9
10#include <ctype.h>
11#include <errno.h>
12#include <fcntl.h>
13#include <linux/gpio.h>
14#include <poll.h>
15#include <stdbool.h>
16#include <stdio.h>
17#include <stdlib.h>
18#include <string.h>
19#include <sys/ioctl.h>
20#include <unistd.h>
21
22int main(int argc, char **argv)
23{
24	struct gpioline_info_changed chg;
25	struct gpioline_info req;
26	struct pollfd pfd;
27	int fd, i, j, ret;
28	char *event, *end;
29	ssize_t rd;
30
31	if (argc < 3)
32		goto err_usage;
33
34	fd = open(argv[1], O_RDWR | O_CLOEXEC);
35	if (fd < 0) {
36		perror("unable to open gpiochip");
37		return EXIT_FAILURE;
38	}
39
40	for (i = 0, j = 2; i < argc - 2; i++, j++) {
41		memset(&req, 0, sizeof(req));
42
43		req.line_offset = strtoul(argv[j], &end, 0);
44		if (*end != '\0')
45			goto err_usage;
46
47		ret = ioctl(fd, GPIO_GET_LINEINFO_WATCH_IOCTL, &req);
48		if (ret) {
49			perror("unable to set up line watch");
50			return EXIT_FAILURE;
51		}
52	}
53
54	pfd.fd = fd;
55	pfd.events = POLLIN | POLLPRI;
56
57	for (;;) {
58		ret = poll(&pfd, 1, 5000);
59		if (ret < 0) {
60			perror("error polling the linechanged fd");
61			return EXIT_FAILURE;
62		} else if (ret > 0) {
63			memset(&chg, 0, sizeof(chg));
64			rd = read(pfd.fd, &chg, sizeof(chg));
65			if (rd < 0 || rd != sizeof(chg)) {
66				if (rd != sizeof(chg))
67					errno = EIO;
68
69				perror("error reading line change event");
70				return EXIT_FAILURE;
71			}
72
73			switch (chg.event_type) {
74			case GPIOLINE_CHANGED_REQUESTED:
75				event = "requested";
76				break;
77			case GPIOLINE_CHANGED_RELEASED:
78				event = "released";
79				break;
80			case GPIOLINE_CHANGED_CONFIG:
81				event = "config changed";
82				break;
83			default:
84				fprintf(stderr,
85					"invalid event type received from the kernel\n");
86				return EXIT_FAILURE;
87			}
88
89			printf("line %u: %s at %llu\n",
90			       chg.info.line_offset, event, chg.timestamp);
91		}
92	}
93
94	return 0;
95
96err_usage:
97	printf("%s: <gpiochip> <line0> <line1> ...\n", argv[0]);
98	return EXIT_FAILURE;
99}