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
 27int 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_free_name;
 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
117exit_close_error:
118	if (close(fd) == -1)
119		perror("Failed to close GPIO character device file");
120exit_free_name:
121	free(chrdev_name);
122	return ret;
123}
124
125void 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
143int main(int argc, char **argv)
144{
145	const char *device_name = NULL;
146	unsigned int line = -1;
147	unsigned int loops = 0;
148	uint32_t handleflags = GPIOHANDLE_REQUEST_INPUT;
149	uint32_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}