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}