2 * gpio-event-mon - monitor GPIO line events from userspace
4 * Copyright (C) 2016 Linus Walleij
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.
11 * gpio-event-mon -n <device-name> -o <offset>
26 #include <sys/ioctl.h>
27 #include <sys/types.h>
28 #include <linux/gpio.h>
30 int monitor_device(const char *device_name,
36 struct gpioevent_request req;
37 struct gpiohandle_data data;
43 ret = asprintf(&chrdev_name, "/dev/%s", device_name);
47 fd = open(chrdev_name, 0);
50 fprintf(stderr, "Failed to open %s\n", chrdev_name);
51 goto exit_close_error;
54 req.lineoffset = line;
55 req.handleflags = handleflags;
56 req.eventflags = eventflags;
57 strcpy(req.consumer_label, "gpio-event-mon");
59 ret = ioctl(fd, GPIO_GET_LINEEVENT_IOCTL, &req);
62 fprintf(stderr, "Failed to issue GET EVENT "
65 goto exit_close_error;
68 /* Read initial states */
69 ret = ioctl(req.fd, GPIOHANDLE_GET_LINE_VALUES_IOCTL, &data);
72 fprintf(stderr, "Failed to issue GPIOHANDLE GET LINE "
73 "VALUES IOCTL (%d)\n",
75 goto exit_close_error;
78 fprintf(stdout, "Monitoring line %d on %s\n", line, device_name);
79 fprintf(stdout, "Initial line value: %d\n", data.values[0]);
82 struct gpioevent_data event;
84 ret = read(req.fd, &event, sizeof(event));
86 if (errno == -EAGAIN) {
87 fprintf(stderr, "nothing available\n");
91 fprintf(stderr, "Failed to read event (%d)\n",
97 if (ret != sizeof(event)) {
98 fprintf(stderr, "Reading event failed\n");
102 fprintf(stdout, "GPIO EVENT %llu: ", event.timestamp);
104 case GPIOEVENT_EVENT_RISING_EDGE:
105 fprintf(stdout, "rising edge");
107 case GPIOEVENT_EVENT_FALLING_EDGE:
108 fprintf(stdout, "falling edge");
111 fprintf(stdout, "unknown event");
113 fprintf(stdout, "\n");
122 perror("Failed to close GPIO character device file");
127 void print_usage(void)
129 fprintf(stderr, "Usage: gpio-event-mon [options]...\n"
130 "Listen to events on GPIO lines, 0->1 1->0\n"
131 " -n <name> Listen on GPIOs on a named device (must be stated)\n"
132 " -o <n> Offset to monitor\n"
133 " -d Set line as open drain\n"
134 " -s Set line as open source\n"
135 " -r Listen for rising edges\n"
136 " -f Listen for falling edges\n"
137 " [-c <n>] Do <n> loops (optional, infinite loop if not stated)\n"
138 " -? This helptext\n"
141 "gpio-event-mon -n gpiochip0 -o 4 -r -f\n"
145 int main(int argc, char **argv)
147 const char *device_name = NULL;
148 unsigned int line = -1;
149 unsigned int loops = 0;
150 uint32_t handleflags = GPIOHANDLE_REQUEST_INPUT;
151 uint32_t eventflags = 0;
154 while ((c = getopt(argc, argv, "c:n:o:dsrf?")) != -1) {
157 loops = strtoul(optarg, NULL, 10);
160 device_name = optarg;
163 line = strtoul(optarg, NULL, 10);
166 handleflags |= GPIOHANDLE_REQUEST_OPEN_DRAIN;
169 handleflags |= GPIOHANDLE_REQUEST_OPEN_SOURCE;
172 eventflags |= GPIOEVENT_REQUEST_RISING_EDGE;
175 eventflags |= GPIOEVENT_REQUEST_FALLING_EDGE;
183 if (!device_name || line == -1) {
188 printf("No flags specified, listening on both rising and "
190 eventflags = GPIOEVENT_REQUEST_BOTH_EDGES;
192 return monitor_device(device_name, line, handleflags,