gpio-event-mon.c
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/*
* gpio-event-mon - monitor GPIO line events from userspace
*
* Copyright (C) 2016 Linus Walleij
*
* This program is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 as published by
* the Free Software Foundation.
*
* Usage:
* gpio-event-mon -n <device-name> -o <offset>
*/
#include <unistd.h>
#include <stdlib.h>
#include <stdbool.h>
#include <stdio.h>
#include <dirent.h>
#include <errno.h>
#include <string.h>
#include <poll.h>
#include <fcntl.h>
#include <getopt.h>
#include <inttypes.h>
#include <sys/ioctl.h>
#include <sys/types.h>
#include <linux/gpio.h>
int monitor_device(const char *device_name,
unsigned int line,
u_int32_t handleflags,
u_int32_t eventflags,
unsigned int loops)
{
struct gpioevent_request req;
struct gpiohandle_data data;
char *chrdev_name;
int fd;
int ret;
int i = 0;
ret = asprintf(&chrdev_name, "/dev/%s", device_name);
if (ret < 0)
return -ENOMEM;
fd = open(chrdev_name, 0);
if (fd == -1) {
ret = -errno;
fprintf(stderr, "Failed to open %s\n", chrdev_name);
goto exit_close_error;
}
req.lineoffset = line;
req.handleflags = handleflags;
req.eventflags = eventflags;
strcpy(req.consumer_label, "gpio-event-mon");
ret = ioctl(fd, GPIO_GET_LINEEVENT_IOCTL, &req);
if (ret == -1) {
ret = -errno;
fprintf(stderr, "Failed to issue GET EVENT "
"IOCTL (%d)\n",
ret);
goto exit_close_error;
}
/* Read initial states */
ret = ioctl(req.fd, GPIOHANDLE_GET_LINE_VALUES_IOCTL, &data);
if (ret == -1) {
ret = -errno;
fprintf(stderr, "Failed to issue GPIOHANDLE GET LINE "
"VALUES IOCTL (%d)\n",
ret);
goto exit_close_error;
}
fprintf(stdout, "Monitoring line %d on %s\n", line, device_name);
fprintf(stdout, "Initial line value: %d\n", data.values[0]);
while (1) {
struct gpioevent_data event;
ret = read(req.fd, &event, sizeof(event));
if (ret == -1) {
if (errno == -EAGAIN) {
fprintf(stderr, "nothing available\n");
continue;
} else {
ret = -errno;
fprintf(stderr, "Failed to read event (%d)\n",
ret);
break;
}
}
if (ret != sizeof(event)) {
fprintf(stderr, "Reading event failed\n");
ret = -EIO;
break;
}
fprintf(stdout, "GPIO EVENT %" PRIu64 ": ", event.timestamp);
switch (event.id) {
case GPIOEVENT_EVENT_RISING_EDGE:
fprintf(stdout, "rising edge");
break;
case GPIOEVENT_EVENT_FALLING_EDGE:
fprintf(stdout, "falling edge");
break;
default:
fprintf(stdout, "unknown event");
}
fprintf(stdout, "\n");
i++;
if (i == loops)
break;
}
exit_close_error:
if (close(fd) == -1)
perror("Failed to close GPIO character device file");
free(chrdev_name);
return ret;
}
void print_usage(void)
{
fprintf(stderr, "Usage: gpio-event-mon [options]...\n"
"Listen to events on GPIO lines, 0->1 1->0\n"
" -n <name> Listen on GPIOs on a named device (must be stated)\n"
" -o <n> Offset to monitor\n"
" -d Set line as open drain\n"
" -s Set line as open source\n"
" -r Listen for rising edges\n"
" -f Listen for falling edges\n"
" [-c <n>] Do <n> loops (optional, infinite loop if not stated)\n"
" -? This helptext\n"
"\n"
"Example:\n"
"gpio-event-mon -n gpiochip0 -o 4 -r -f\n"
);
}
int main(int argc, char **argv)
{
const char *device_name = NULL;
unsigned int line = -1;
unsigned int loops = 0;
u_int32_t handleflags = GPIOHANDLE_REQUEST_INPUT;
u_int32_t eventflags = 0;
int c;
while ((c = getopt(argc, argv, "c:n:o:dsrf?")) != -1) {
switch (c) {
case 'c':
loops = strtoul(optarg, NULL, 10);
break;
case 'n':
device_name = optarg;
break;
case 'o':
line = strtoul(optarg, NULL, 10);
break;
case 'd':
handleflags |= GPIOHANDLE_REQUEST_OPEN_DRAIN;
break;
case 's':
handleflags |= GPIOHANDLE_REQUEST_OPEN_SOURCE;
break;
case 'r':
eventflags |= GPIOEVENT_REQUEST_RISING_EDGE;
break;
case 'f':
eventflags |= GPIOEVENT_REQUEST_FALLING_EDGE;
break;
case '?':
print_usage();
return -1;
}
}
if (!device_name || line == -1) {
print_usage();
return -1;
}
if (!eventflags) {
printf("No flags specified, listening on both rising and "
"falling edges\n");
eventflags = GPIOEVENT_REQUEST_BOTH_EDGES;
}
return monitor_device(device_name, line, handleflags,
eventflags, loops);
}