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
 28int 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
118exit_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
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	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}