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