tools/gpio/gpio-watch.c

   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
  22 int 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
  96 err_usage:
  97         printf("%s: <gpiochip> <line0> <line1> ...\n", argv[0]);
  98         return EXIT_FAILURE;
  99 }