1 // SPDX-License-Identifier: GPL-2.0-only
3 * gpio-event-mon - monitor GPIO line events from userspace
5 * Copyright (C) 2016 Linus Walleij
8 * gpio-event-mon -n <device-name> -o <offset>
23 #include <sys/ioctl.h>
24 #include <sys/types.h>
25 #include <linux/gpio.h>
27 int monitor_device(const char *device_name,
33 struct gpioevent_request req;
34 struct gpiohandle_data data;
40 ret = asprintf(&chrdev_name, "/dev/%s", device_name);
44 fd = open(chrdev_name, 0);
47 fprintf(stderr, "Failed to open %s\n", chrdev_name);
48 goto exit_close_error;
51 req.lineoffset = line;
52 req.handleflags = handleflags;
53 req.eventflags = eventflags;
54 strcpy(req.consumer_label, "gpio-event-mon");
56 ret = ioctl(fd, GPIO_GET_LINEEVENT_IOCTL, &req);
59 fprintf(stderr, "Failed to issue GET EVENT "
62 goto exit_close_error;
65 /* Read initial states */
66 ret = ioctl(req.fd, GPIOHANDLE_GET_LINE_VALUES_IOCTL, &data);
69 fprintf(stderr, "Failed to issue GPIOHANDLE GET LINE "
70 "VALUES IOCTL (%d)\n",
72 goto exit_close_error;
75 fprintf(stdout, "Monitoring line %d on %s\n", line, device_name);
76 fprintf(stdout, "Initial line value: %d\n", data.values[0]);
79 struct gpioevent_data event;
81 ret = read(req.fd, &event, sizeof(event));
83 if (errno == -EAGAIN) {
84 fprintf(stderr, "nothing available\n");
88 fprintf(stderr, "Failed to read event (%d)\n",
94 if (ret != sizeof(event)) {
95 fprintf(stderr, "Reading event failed\n");
99 fprintf(stdout, "GPIO EVENT %llu: ", event.timestamp);
101 case GPIOEVENT_EVENT_RISING_EDGE:
102 fprintf(stdout, "rising edge");
104 case GPIOEVENT_EVENT_FALLING_EDGE:
105 fprintf(stdout, "falling edge");
108 fprintf(stdout, "unknown event");
110 fprintf(stdout, "\n");
119 perror("Failed to close GPIO character device file");
124 void print_usage(void)
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"
138 "gpio-event-mon -n gpiochip0 -o 4 -r -f\n"
142 int main(int argc, char **argv)
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;
151 while ((c = getopt(argc, argv, "c:n:o:dsrf?")) != -1) {
154 loops = strtoul(optarg, NULL, 10);
157 device_name = optarg;
160 line = strtoul(optarg, NULL, 10);
163 handleflags |= GPIOHANDLE_REQUEST_OPEN_DRAIN;
166 handleflags |= GPIOHANDLE_REQUEST_OPEN_SOURCE;
169 eventflags |= GPIOEVENT_REQUEST_RISING_EDGE;
172 eventflags |= GPIOEVENT_REQUEST_FALLING_EDGE;
180 if (!device_name || line == -1) {
185 printf("No flags specified, listening on both rising and "
187 eventflags = GPIOEVENT_REQUEST_BOTH_EDGES;
189 return monitor_device(device_name, line, handleflags,