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 <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
  23 int 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
  97 err_usage:
  98         printf("%s: <gpiochip> <line0> <line1> ...\n", argv[0]);
  99         return EXIT_FAILURE;
 100 }