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 <inttypes.h>
14#include <linux/gpio.h>
15#include <poll.h>
16#include <stdbool.h>
17#include <stdio.h>
18#include <stdlib.h>
19#include <string.h>
20#include <sys/ioctl.h>
21#include <unistd.h>
22
23int main(int argc, char **argv)
24{
25	struct gpio_v2_line_info_changed chg;
26	struct gpio_v2_line_info req;
27	struct pollfd pfd;
28	int fd, i, j, ret;
29	char *event, *end;
30	ssize_t rd;
31
32	if (argc < 3)
33		goto err_usage;
34
35	fd = open(argv[1], O_RDWR | O_CLOEXEC);
36	if (fd < 0) {
37		perror("unable to open gpiochip");
38		return EXIT_FAILURE;
39	}
40
41	for (i = 0, j = 2; i < argc - 2; i++, j++) {
42		memset(&req, 0, sizeof(req));
43
44		req.offset = strtoul(argv[j], &end, 0);
45		if (*end != '\0')
46			goto err_usage;
47
48		ret = ioctl(fd, GPIO_V2_GET_LINEINFO_WATCH_IOCTL, &req);
49		if (ret) {
50			perror("unable to set up line watch");
51			return EXIT_FAILURE;
52		}
53	}
54
55	pfd.fd = fd;
56	pfd.events = POLLIN | POLLPRI;
57
58	for (;;) {
59		ret = poll(&pfd, 1, 5000);
60		if (ret < 0) {
61			perror("error polling the linechanged fd");
62			return EXIT_FAILURE;
63		} else if (ret > 0) {
64			memset(&chg, 0, sizeof(chg));
65			rd = read(pfd.fd, &chg, sizeof(chg));
66			if (rd < 0 || rd != sizeof(chg)) {
67				if (rd != sizeof(chg))
68					errno = EIO;
69
70				perror("error reading line change event");
71				return EXIT_FAILURE;
72			}
73
74			switch (chg.event_type) {
75			case GPIO_V2_LINE_CHANGED_REQUESTED:
76				event = "requested";
77				break;
78			case GPIO_V2_LINE_CHANGED_RELEASED:
79				event = "released";
80				break;
81			case GPIO_V2_LINE_CHANGED_CONFIG:
82				event = "config changed";
83				break;
84			default:
85				fprintf(stderr,
86					"invalid event type received from the kernel\n");
87				return EXIT_FAILURE;
88			}
89
90			printf("line %u: %s at %" PRIu64 "\n",
91			       chg.info.offset, event, (uint64_t)chg.timestamp_ns);
92		}
93	}
94
95	return 0;
96
97err_usage:
98	printf("%s: <gpiochip> <line0> <line1> ...\n", argv[0]);
99	return EXIT_FAILURE;
100}
101