// SPDX-License-Identifier: GPL-2.0-only
/*
 * gpio-watch - monitor unrequested lines for property changes using the
 *              character device
 *
 * Copyright (C) 2019 BayLibre SAS
 * Author: Bartosz Golaszewski <bgolaszewski@baylibre.com>
 */

#include <ctype.h>
#include <errno.h>
#include <fcntl.h>
#include <inttypes.h>
#include <linux/gpio.h>
#include <poll.h>
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/ioctl.h>
#include <unistd.h>

int main(int argc, char **argv)
{
        struct gpio_v2_line_info_changed chg;
        struct gpio_v2_line_info req;
        struct pollfd pfd;
        int fd, i, j, ret;
        char *event, *end;
        ssize_t rd;

        if (argc < 3)
                goto err_usage;

        fd = open(argv[1], O_RDWR | O_CLOEXEC);
        if (fd < 0) {
                perror("unable to open gpiochip");
                return EXIT_FAILURE;
        }

        for (i = 0, j = 2; i < argc - 2; i++, j++) {
                memset(&req, 0, sizeof(req));

                req.offset = strtoul(argv[j], &end, 0);
                if (*end != '\0')
                        goto err_usage;

                ret = ioctl(fd, GPIO_V2_GET_LINEINFO_WATCH_IOCTL, &req);
                if (ret) {
                        perror("unable to set up line watch");
                        return EXIT_FAILURE;
                }
        }

        pfd.fd = fd;
        pfd.events = POLLIN | POLLPRI;

        for (;;) {
                ret = poll(&pfd, 1, 5000);
                if (ret < 0) {
                        perror("error polling the linechanged fd");
                        return EXIT_FAILURE;
                } else if (ret > 0) {
                        memset(&chg, 0, sizeof(chg));
                        rd = read(pfd.fd, &chg, sizeof(chg));
                        if (rd < 0 || rd != sizeof(chg)) {
                                if (rd != sizeof(chg))
                                        errno = EIO;

                                perror("error reading line change event");
                                return EXIT_FAILURE;
                        }

                        switch (chg.event_type) {
                        case GPIO_V2_LINE_CHANGED_REQUESTED:
                                event = "requested";
                                break;
                        case GPIO_V2_LINE_CHANGED_RELEASED:
                                event = "released";
                                break;
                        case GPIO_V2_LINE_CHANGED_CONFIG:
                                event = "config changed";
                                break;
                        default:
                                fprintf(stderr,
                                        "invalid event type received from the kernel\n");
                                return EXIT_FAILURE;
                        }

                        printf("line %u: %s at %" PRIu64 "\n",
                               chg.info.offset, event, (uint64_t)chg.timestamp_ns);
                }
        }

        return 0;

err_usage:
        printf("%s: <gpiochip> <line0> <line1> ...\n", argv[0]);
        return EXIT_FAILURE;
}