tools/gpio: add the gpio-event-mon tool

The gpio-event-mon is used from userspace as an example of how
to monitor GPIO line events. It will latch on to a certain
GPIO line on a certain gpiochip and print timestamped events
as they arrive.

Example output:
$ gpio-event-mon -n gpiochip2 -o 0 -r -f
Monitoring line 0 on gpiochip2
Initial line value: 1
GPIO EVENT 946685798487609863: falling edge
GPIO EVENT 946685798732482910: rising edge
GPIO EVENT 946685799115997314: falling edge
GPIO EVENT 946685799381469726: rising edge

Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

2 files changed, 195 insertions, 2 deletions

diff --git a/tools/gpio/Makefile b/tools/gpio/Makefile
index aea23949054e..619314ff9bd6 100644
--- a/tools/gpio/Makefile
+++ b/tools/gpio/Makefile
@@ -1,13 +1,14 @@
 CC = $(CROSS_COMPILE)gcc
 CFLAGS += -O2 -Wall -g -D_GNU_SOURCE
 
-all: lsgpio gpio-hammer
+all: lsgpio gpio-hammer gpio-event-mon
 
 lsgpio: lsgpio.o gpio-utils.o
 gpio-hammer: gpio-hammer.o gpio-utils.o
+gpio-event-mon: gpio-event-mon.o gpio-utils.o
 
 %.o: %.c gpio-utils.h
 
 .PHONY: clean
 clean:
-        rm -f *.o lsgpio gpio-hammer
+        rm -f *.o lsgpio gpio-hammer gpio-event-mon
diff --git a/tools/gpio/gpio-event-mon.c b/tools/gpio/gpio-event-mon.c
new file mode 100644
index 000000000000..448ed96b3b4f
--- /dev/null
+++ b/tools/gpio/gpio-event-mon.c
@@ -0,0 +1,192 @@
+/*
+ * gpio-hammer - example swiss army knife to shake GPIO lines on a system
+ *
+ * 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 <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);
+}