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Linux/tools/gpio/gpio-event-mon.c

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  1 // SPDX-License-Identifier: GPL-2.0-only
  2 /*
  3  * gpio-event-mon - monitor GPIO line events from userspace
  4  *
  5  * Copyright (C) 2016 Linus Walleij
  6  *
  7  * Usage:
  8  *      gpio-event-mon -n <device-name> -o <offset>
  9  */
 10 
 11 #include <unistd.h>
 12 #include <stdlib.h>
 13 #include <stdbool.h>
 14 #include <stdint.h>
 15 #include <stdio.h>
 16 #include <dirent.h>
 17 #include <errno.h>
 18 #include <string.h>
 19 #include <poll.h>
 20 #include <fcntl.h>
 21 #include <getopt.h>
 22 #include <inttypes.h>
 23 #include <sys/ioctl.h>
 24 #include <sys/types.h>
 25 #include <linux/gpio.h>
 26 
 27 int monitor_device(const char *device_name,
 28                    unsigned int line,
 29                    uint32_t handleflags,
 30                    uint32_t eventflags,
 31                    unsigned int loops)
 32 {
 33         struct gpioevent_request req;
 34         struct gpiohandle_data data;
 35         char *chrdev_name;
 36         int fd;
 37         int ret;
 38         int i = 0;
 39 
 40         ret = asprintf(&chrdev_name, "/dev/%s", device_name);
 41         if (ret < 0)
 42                 return -ENOMEM;
 43 
 44         fd = open(chrdev_name, 0);
 45         if (fd == -1) {
 46                 ret = -errno;
 47                 fprintf(stderr, "Failed to open %s\n", chrdev_name);
 48                 goto exit_close_error;
 49         }
 50 
 51         req.lineoffset = line;
 52         req.handleflags = handleflags;
 53         req.eventflags = eventflags;
 54         strcpy(req.consumer_label, "gpio-event-mon");
 55 
 56         ret = ioctl(fd, GPIO_GET_LINEEVENT_IOCTL, &req);
 57         if (ret == -1) {
 58                 ret = -errno;
 59                 fprintf(stderr, "Failed to issue GET EVENT "
 60                         "IOCTL (%d)\n",
 61                         ret);
 62                 goto exit_close_error;
 63         }
 64 
 65         /* Read initial states */
 66         ret = ioctl(req.fd, GPIOHANDLE_GET_LINE_VALUES_IOCTL, &data);
 67         if (ret == -1) {
 68                 ret = -errno;
 69                 fprintf(stderr, "Failed to issue GPIOHANDLE GET LINE "
 70                         "VALUES IOCTL (%d)\n",
 71                         ret);
 72                 goto exit_close_error;
 73         }
 74 
 75         fprintf(stdout, "Monitoring line %d on %s\n", line, device_name);
 76         fprintf(stdout, "Initial line value: %d\n", data.values[0]);
 77 
 78         while (1) {
 79                 struct gpioevent_data event;
 80 
 81                 ret = read(req.fd, &event, sizeof(event));
 82                 if (ret == -1) {
 83                         if (errno == -EAGAIN) {
 84                                 fprintf(stderr, "nothing available\n");
 85                                 continue;
 86                         } else {
 87                                 ret = -errno;
 88                                 fprintf(stderr, "Failed to read event (%d)\n",
 89                                         ret);
 90                                 break;
 91                         }
 92                 }
 93 
 94                 if (ret != sizeof(event)) {
 95                         fprintf(stderr, "Reading event failed\n");
 96                         ret = -EIO;
 97                         break;
 98                 }
 99                 fprintf(stdout, "GPIO EVENT %llu: ", event.timestamp);
100                 switch (event.id) {
101                 case GPIOEVENT_EVENT_RISING_EDGE:
102                         fprintf(stdout, "rising edge");
103                         break;
104                 case GPIOEVENT_EVENT_FALLING_EDGE:
105                         fprintf(stdout, "falling edge");
106                         break;
107                 default:
108                         fprintf(stdout, "unknown event");
109                 }
110                 fprintf(stdout, "\n");
111 
112                 i++;
113                 if (i == loops)
114                         break;
115         }
116 
117 exit_close_error:
118         if (close(fd) == -1)
119                 perror("Failed to close GPIO character device file");
120         free(chrdev_name);
121         return ret;
122 }
123 
124 void print_usage(void)
125 {
126         fprintf(stderr, "Usage: gpio-event-mon [options]...\n"
127                 "Listen to events on GPIO lines, 0->1 1->0\n"
128                 "  -n <name>  Listen on GPIOs on a named device (must be stated)\n"
129                 "  -o <n>     Offset to monitor\n"
130                 "  -d         Set line as open drain\n"
131                 "  -s         Set line as open source\n"
132                 "  -r         Listen for rising edges\n"
133                 "  -f         Listen for falling edges\n"
134                 " [-c <n>]    Do <n> loops (optional, infinite loop if not stated)\n"
135                 "  -?         This helptext\n"
136                 "\n"
137                 "Example:\n"
138                 "gpio-event-mon -n gpiochip0 -o 4 -r -f\n"
139         );
140 }
141 
142 int main(int argc, char **argv)
143 {
144         const char *device_name = NULL;
145         unsigned int line = -1;
146         unsigned int loops = 0;
147         uint32_t handleflags = GPIOHANDLE_REQUEST_INPUT;
148         uint32_t eventflags = 0;
149         int c;
150 
151         while ((c = getopt(argc, argv, "c:n:o:dsrf?")) != -1) {
152                 switch (c) {
153                 case 'c':
154                         loops = strtoul(optarg, NULL, 10);
155                         break;
156                 case 'n':
157                         device_name = optarg;
158                         break;
159                 case 'o':
160                         line = strtoul(optarg, NULL, 10);
161                         break;
162                 case 'd':
163                         handleflags |= GPIOHANDLE_REQUEST_OPEN_DRAIN;
164                         break;
165                 case 's':
166                         handleflags |= GPIOHANDLE_REQUEST_OPEN_SOURCE;
167                         break;
168                 case 'r':
169                         eventflags |= GPIOEVENT_REQUEST_RISING_EDGE;
170                         break;
171                 case 'f':
172                         eventflags |= GPIOEVENT_REQUEST_FALLING_EDGE;
173                         break;
174                 case '?':
175                         print_usage();
176                         return -1;
177                 }
178         }
179 
180         if (!device_name || line == -1) {
181                 print_usage();
182                 return -1;
183         }
184         if (!eventflags) {
185                 printf("No flags specified, listening on both rising and "
186                        "falling edges\n");
187                 eventflags = GPIOEVENT_REQUEST_BOTH_EDGES;
188         }
189         return monitor_device(device_name, line, handleflags,
190                               eventflags, loops);
191 }
192 

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