tools/gpio/gpio-event-mon.c

   1 /*
   2  * gpio-event-mon - monitor GPIO line events from userspace
   3  *
   4  * Copyright (C) 2016 Linus Walleij
   5  *
   6  * This program is free software; you can redistribute it and/or modify it
   7  * under the terms of the GNU General Public License version 2 as published by
   8  * the Free Software Foundation.
   9  *
  10  * Usage:
  11  *      gpio-event-mon -n <device-name> -o <offset>
  12  */
  13
  14 #include <unistd.h>
  15 #include <stdlib.h>
  16 #include <stdbool.h>
  17 #include <stdio.h>
  18 #include <dirent.h>
  19 #include <errno.h>
  20 #include <string.h>
  21 #include <poll.h>
  22 #include <fcntl.h>
  23 #include <getopt.h>
  24 #include <inttypes.h>
  25 #include <sys/ioctl.h>
  26 #include <sys/types.h>
  27 #include <linux/gpio.h>
  28
  29 int monitor_device(const char *device_name,
  30                    unsigned int line,
  31                    u_int32_t handleflags,
  32                    u_int32_t eventflags,
  33                    unsigned int loops)
  34 {
  35         struct gpioevent_request req;
  36         struct gpiohandle_data data;
  37         char *chrdev_name;
  38         int fd;
  39         int ret;
  40         int i = 0;
  41
  42         ret = asprintf(&chrdev_name, "/dev/%s", device_name);
  43         if (ret < 0)
  44                 return -ENOMEM;
  45
  46         fd = open(chrdev_name, 0);
  47         if (fd == -1) {
  48                 ret = -errno;
  49                 fprintf(stderr, "Failed to open %s\n", chrdev_name);
  50                 goto exit_close_error;
  51         }
  52
  53         req.lineoffset = line;
  54         req.handleflags = handleflags;
  55         req.eventflags = eventflags;
  56         strcpy(req.consumer_label, "gpio-event-mon");
  57
  58         ret = ioctl(fd, GPIO_GET_LINEEVENT_IOCTL, &req);
  59         if (ret == -1) {
  60                 ret = -errno;
  61                 fprintf(stderr, "Failed to issue GET EVENT "
  62                         "IOCTL (%d)\n",
  63                         ret);
  64                 goto exit_close_error;
  65         }
  66
  67         /* Read initial states */
  68         ret = ioctl(req.fd, GPIOHANDLE_GET_LINE_VALUES_IOCTL, &data);
  69         if (ret == -1) {
  70                 ret = -errno;
  71                 fprintf(stderr, "Failed to issue GPIOHANDLE GET LINE "
  72                         "VALUES IOCTL (%d)\n",
  73                         ret);
  74                 goto exit_close_error;
  75         }
  76
  77         fprintf(stdout, "Monitoring line %d on %s\n", line, device_name);
  78         fprintf(stdout, "Initial line value: %d\n", data.values[0]);
  79
  80         while (1) {
  81                 struct gpioevent_data event;
  82
  83                 ret = read(req.fd, &event, sizeof(event));
  84                 if (ret == -1) {
  85                         if (errno == -EAGAIN) {
  86                                 fprintf(stderr, "nothing available\n");
  87                                 continue;
  88                         } else {
  89                                 ret = -errno;
  90                                 fprintf(stderr, "Failed to read event (%d)\n",
  91                                         ret);
  92                                 break;
  93                         }
  94                 }
  95
  96                 if (ret != sizeof(event)) {
  97                         fprintf(stderr, "Reading event failed\n");
  98                         ret = -EIO;
  99                         break;
 100                 }
 101                 fprintf(stdout, "GPIO EVENT %" PRIu64 ": ", event.timestamp);
 102                 switch (event.id) {
 103                 case GPIOEVENT_EVENT_RISING_EDGE:
 104                         fprintf(stdout, "rising edge");
 105                         break;
 106                 case GPIOEVENT_EVENT_FALLING_EDGE:
 107                         fprintf(stdout, "falling edge");
 108                         break;
 109                 default:
 110                         fprintf(stdout, "unknown event");
 111                 }
 112                 fprintf(stdout, "\n");
 113
 114                 i++;
 115                 if (i == loops)
 116                         break;
 117         }
 118
 119 exit_close_error:
 120         if (close(fd) == -1)
 121                 perror("Failed to close GPIO character device file");
 122         free(chrdev_name);
 123         return ret;
 124 }
 125
 126 void print_usage(void)
 127 {
 128         fprintf(stderr, "Usage: gpio-event-mon [options]...\n"
 129                 "Listen to events on GPIO lines, 0->1 1->0\n"
 130                 "  -n <name>  Listen on GPIOs on a named device (must be stated)\n"
 131                 "  -o <n>     Offset to monitor\n"
 132                 "  -d         Set line as open drain\n"
 133                 "  -s         Set line as open source\n"
 134                 "  -r         Listen for rising edges\n"
 135                 "  -f         Listen for falling edges\n"
 136                 " [-c <n>]    Do <n> loops (optional, infinite loop if not stated)\n"
 137                 "  -?         This helptext\n"
 138                 "\n"
 139                 "Example:\n"
 140                 "gpio-event-mon -n gpiochip0 -o 4 -r -f\n"
 141         );
 142 }
 143
 144 int main(int argc, char **argv)
 145 {
 146         const char *device_name = NULL;
 147         unsigned int line = -1;
 148         unsigned int loops = 0;
 149         u_int32_t handleflags = GPIOHANDLE_REQUEST_INPUT;
 150         u_int32_t eventflags = 0;
 151         int c;
 152
 153         while ((c = getopt(argc, argv, "c:n:o:dsrf?")) != -1) {
 154                 switch (c) {
 155                 case 'c':
 156                         loops = strtoul(optarg, NULL, 10);
 157                         break;
 158                 case 'n':
 159                         device_name = optarg;
 160                         break;
 161                 case 'o':
 162                         line = strtoul(optarg, NULL, 10);
 163                         break;
 164                 case 'd':
 165                         handleflags |= GPIOHANDLE_REQUEST_OPEN_DRAIN;
 166                         break;
 167                 case 's':
 168                         handleflags |= GPIOHANDLE_REQUEST_OPEN_SOURCE;
 169                         break;
 170                 case 'r':
 171                         eventflags |= GPIOEVENT_REQUEST_RISING_EDGE;
 172                         break;
 173                 case 'f':
 174                         eventflags |= GPIOEVENT_REQUEST_FALLING_EDGE;
 175                         break;
 176                 case '?':
 177                         print_usage();
 178                         return -1;
 179                 }
 180         }
 181
 182         if (!device_name || line == -1) {
 183                 print_usage();
 184                 return -1;
 185         }
 186         if (!eventflags) {
 187                 printf("No flags specified, listening on both rising and "
 188                        "falling edges\n");
 189                 eventflags = GPIOEVENT_REQUEST_BOTH_EDGES;
 190         }
 191         return monitor_device(device_name, line, handleflags,
 192                               eventflags, loops);
 193 }