tools: add "libinput measure touchpad-tap"

This is the first tool of many more to come to enable users to gather
information aobut their devices and/or usage of these devices. Previously,
these required the users to record events, submit them to a bugzilla, have me
run various scripts over it and then decree that the scripts have spoken.
Push some of this into the hands of the users so they can query the numbers
locally and start investigating (or at least get an idea of what's happening).

This tool measures the time deltas between touch up and touch down and prints
a basic summary, together with the ability to print a dat file with the data
for visualization by e.g. gnuplot. Eventually, more of the current analysis
scripts will be moved into this or other helpers.

Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>

9 files changed, 870 insertions, 50 deletions

diff --git a/tools/Makefile.am b/tools/Makefile.am
index cc1ce19..8ef2a3b 100644
--- a/tools/Makefile.am
+++ b/tools/Makefile.am
@@ -14,7 +14,8 @@ AM_CXXFLAGS = $(GCC_CXXFLAGS)
 libshared_la_SOURCES = \
 		       shared.c \
 		       shared.h
-libshared_la_CFLAGS = $(AM_CFLAGS) $(LIBEVDEV_CFLAGS)
+libshared_la_CFLAGS = $(AM_CFLAGS) $(LIBEVDEV_CFLAGS) \
+		      -DLIBINPUT_TOOL_PATH="\"@libexecdir@/libinput\""
 libshared_la_LIBADD = $(LIBEVDEV_LIBS)
 
 ptraccel_debug_SOURCES = ptraccel-debug.c
@@ -23,8 +24,7 @@ ptraccel_debug_LDFLAGS = -no-install
 
 libinput_SOURCES = libinput-tool.c
 libinput_LDADD = ../src/libinput.la libshared.la $(LIBUDEV_LIBS) $(LIBEVDEV_LIBS)
-libinput_CFLAGS = $(AM_CFLAGS) $(LIBUDEV_CFLAGS) $(LIBEVDEV_CFLAGS) \
-		  -DLIBINPUT_TOOL_PATH="\"@libexecdir@/libinput\""
+libinput_CFLAGS = $(AM_CFLAGS) $(LIBUDEV_CFLAGS) $(LIBEVDEV_CFLAGS)
 dist_man1_MANS = libinput.1
 
 tools_PROGRAMS += libinput-list-devices
@@ -39,6 +39,20 @@ libinput_debug_events_LDADD = ../src/libinput.la libshared.la $(LIBUDEV_LIBS) $(
 libinput_debug_events_CFLAGS = $(AM_CFLAGS) $(LIBUDEV_CFLAGS) $(LIBEVDEV_CFLAGS)
 dist_man1_MANS += libinput-debug-events.1
 
+tools_PROGRAMS += libinput-measure
+libinput_measure_SOURCES = libinput-measure.c $(shared_sources)
+libinput_measure_LDADD = ../src/libinput.la libshared.la $(LIBUDEV_LIBS) $(LIBEVDEV_LIBS)
+libinput_measure_CFLAGS = $(AM_CFLAGS) $(LIBUDEV_CFLAGS) $(LIBEVDEV_CFLAGS) \
+		  -DLIBINPUT_TOOL_PATH="\"@libexecdir@/libinput\""
+dist_man1_MANS += libinput-measure.1
+
+tools_PROGRAMS += libinput-measure-touchpad-tap
+libinput_measure_touchpad_tap_SOURCES = \
+		     libinput-measure-touchpad-tap.c
+libinput_measure_touchpad_tap_LDADD = ../src/libinput.la libshared.la $(LIBUDEV_LIBS) $(LIBEVDEV_LIBS)
+libinput_measure_touchpad_tap_CFLAGS = $(AM_CFLAGS) $(LIBUDEV_CFLAGS) $(LIBEVDEV_CFLAGS)
+dist_man1_MANS += libinput-measure-touchpad-tap.1
+
 if BUILD_DEBUG_GUI
 tools_PROGRAMS += libinput-debug-gui
 libinput_debug_gui_SOURCES = libinput-debug-gui.c
diff --git a/tools/libinput-measure-touchpad-tap.1 b/tools/libinput-measure-touchpad-tap.1
new file mode 100644
index 0000000..3cea584
--- /dev/null
+++ b/tools/libinput-measure-touchpad-tap.1
@@ -0,0 +1,73 @@
+.TH LIBINPUT-MEASURE-TOUCHPAD-TAP "1"
+.SH NAME
+libinput-measure-touchpad-tap \- measure tap-to-click properities of devices
+.SH SYNOPSIS
+.B libinput measure touchpad-tap [--help] [--format=<format>] [/dev/input/event0]
+.SH DESCRIPTION
+.PP
+The
+.B "libinput measure touchpad-tap"
+tool measures properties of the tap-to-click behavior of the user. This is
+an interactive tool. When executed, the tool will prompt the user to
+interact with the touchpad. On termination, the tool prints a summary of the
+tap interactions seen. This data should be attached to any tap-related bug
+report.
+.PP
+For a full description on how libinput's tap-to-click behavior works, see
+the online documentation here:
+.I https://wayland.freedesktop.org/libinput/doc/latest/tapping.html
+.PP
+This is a debugging tool only, its output may change at any time. Do not
+rely on the output.
+.PP
+This tool usually needs to be run as root to have access to the
+/dev/input/eventX nodes.
+.SH OPTIONS
+.TP 8
+.B --help
+Print help
+.TP 8
+.B --format=summary|dat
+Specify the data format to be printed. The default (or if
+.B --format
+is omitted) is "summary". See section
+.B DATA FORMATS
+
+.SH DATA FORMATS
+This section describes the data formats printed with the
+.B --format
+commandline argument. Note that any of the output may change at any time.
+.RE
+.PP
+summary
+.RS 4
+The
+.I summary
+format prints a summary of the data collected. This format is useful to
+get a quick overview of a user's tapping behavior and why some taps may or
+may not be detected.
+.RE
+.PP
+dat
+.RS 4
+The
+.I dat
+format prints the touch sequence data (raw and processed) in column-style
+format, suitable for processing by other tools such as
+.B gnuplot(1).
+The data is aligned in one row per touch with each column containing a
+separate data entry.
+.B libinput-measure-touchpad-tap
+prints comments at the top of the file to describe each column.
+.PP
+.B WARNING:
+The data contained in the output is grouped by different sort orders. For
+example, the first few columns may list tap information in the 'natural'
+sort order (i.e. as they occured), the data in the next few columns may list
+tap information sorted by the delta time between touch down and touch up.
+Comparing columns across these group boundaries will compare data of two
+different touch points and result in invalid analysis.
+.SH LIBINPUT
+Part of the
+.B libinput(1)
+suite
diff --git a/tools/libinput-measure-touchpad-tap.c b/tools/libinput-measure-touchpad-tap.c
new file mode 100644
index 0000000..123630c
--- /dev/null
+++ b/tools/libinput-measure-touchpad-tap.c
@@ -0,0 +1,512 @@
+/*
+ * Copyright © 2017 Red Hat, Inc.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice (including the next
+ * paragraph) shall be included in all copies or substantial portions of the
+ * Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+ * DEALINGS IN THE SOFTWARE.
+ */
+
+#include "config.h"
+
+#include <errno.h>
+#include <fcntl.h>
+#include <getopt.h>
+#include <poll.h>
+#include <signal.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include <string.h>
+#include <unistd.h>
+#include <sys/signalfd.h>
+
+#include <libudev.h>
+#include <libevdev/libevdev.h>
+
+#include <libinput-util.h>
+#include <libinput-version.h>
+
+#include "shared.h"
+
+static bool print_dat_file;
+/* interactive goes to stdout unless we're redirected, then it goes to
+ * stderr */
+static FILE *pdest;
+
+#define error(...) fprintf(stderr, __VA_ARGS__)
+#define msg(...) fprintf(pdest, __VA_ARGS__)
+
+struct touch {
+	uint32_t tdown, tup; /* in ms */
+};
+
+struct tap_data {
+	struct touch *touches;
+	size_t touches_sz;
+	unsigned int count;
+
+	uint32_t toffset; /* in ms */
+};
+
+static inline uint32_t
+touch_tdelta_ms(const struct touch *t)
+{
+	return t->tup - t->tdown;
+}
+
+static inline struct tap_data *
+tap_data_new(void)
+{
+	struct tap_data *tap_data = zalloc(sizeof(struct tap_data));
+	assert(tap_data);
+
+	return tap_data;
+}
+
+static inline unsigned int
+tap_data_ntouches(struct tap_data *tap_data)
+{
+	return tap_data->count;
+}
+
+static inline void
+tap_data_free(struct tap_data **tap_data)
+{
+	free((*tap_data)->touches);
+	free((*tap_data));
+	*tap_data = NULL;
+}
+
+static inline struct touch *
+tap_data_get_current_touch(struct tap_data *tap_data)
+{
+	assert(tap_data->count > 0);
+
+	return &tap_data->touches[tap_data->count - 1];
+}
+
+static inline struct touch *
+tap_data_get_touch(struct tap_data *tap_data, unsigned int idx)
+{
+	assert(idx < tap_data->count);
+
+	return &tap_data->touches[idx];
+}
+
+#define tap_data_for_each(tapdata_, t_) \
+	for (unsigned i_ = 0; i_ < (tapdata_)->count && (t_ = &(tapdata_)->touches[i_]); i_++)
+
+static inline struct tap_data *
+tap_data_duplicate_sorted(const struct tap_data *src,
+			  int (*cmp)(const void *a, const void *b))
+{
+	struct tap_data *dest= tap_data_new();
+
+	assert(src->count > 0);
+
+	dest->count = src->count;
+	dest->touches_sz = dest->count;
+	dest->touches = zalloc(dest->count * sizeof(*dest->touches));
+	memcpy(dest->touches,
+	       src->touches,
+	       dest->count * sizeof(*dest->touches));
+
+	if (cmp)
+		qsort(dest->touches,
+		      dest->count,
+		      sizeof(*dest->touches),
+		      cmp);
+
+	return dest;
+}
+
+static inline struct touch*
+tap_data_new_touch(struct tap_data *tap_data)
+{
+	tap_data->count++;
+	if (tap_data->touches_sz < tap_data->count) {
+		tap_data->touches_sz += 50;
+		tap_data->touches = realloc(tap_data->touches,
+			     tap_data->touches_sz * sizeof(*tap_data->touches));
+		if (tap_data->touches == NULL) {
+			error("Allocation error. Oops\n");
+			abort();
+		}
+		memset(&tap_data->touches[tap_data->count - 1],
+		       0,
+		       sizeof(*tap_data->touches));
+	}
+
+	return &tap_data->touches[tap_data->count - 1];
+}
+
+static int
+sort_by_time_delta(const void *ap, const void *bp)
+{
+	const struct touch *a = ap;
+	const struct touch *b = bp;
+	uint32_t da, db;
+
+	da = touch_tdelta_ms(a);
+	db = touch_tdelta_ms(b);
+
+	return da == db ? 0 : da > db ? 1 : -1;
+}
+
+static inline void
+print_statistics(struct tap_data *tap_data)
+{
+	uint64_t delta_sum = 0;
+	uint32_t average;
+	uint32_t max = 0,
+		 min = UINT_MAX;
+	struct tap_data *data_sorted_tdelta;
+	struct touch *t,
+		     *median,
+		     *pc90,
+		     *pc95;
+
+	if (tap_data->count == 0) {
+		error("No tap data available.\n");
+		return;
+	}
+
+	tap_data_for_each(tap_data, t) {
+		uint32_t delta = touch_tdelta_ms(t);
+
+		delta_sum += delta;
+		max = max(delta, max);
+		min = min(delta, min);
+	}
+
+	average = delta_sum/tap_data_ntouches(tap_data);
+
+	printf("Time:\n");
+	printf("  Max delta: %dms\n", max);
+	printf("  Min delta: %dms\n", min);
+	printf("  Average delta: %dms\n", average);
+
+	/* Median, 90th, 95th percentile, requires sorting by time delta */
+	data_sorted_tdelta = tap_data_duplicate_sorted(tap_data,
+						       sort_by_time_delta);
+	median = tap_data_get_touch(tap_data,
+				    tap_data_ntouches(tap_data)/2);
+	pc90= tap_data_get_touch(tap_data,
+				 tap_data_ntouches(tap_data) * 0.9);
+	pc95 = tap_data_get_touch(tap_data,
+				  tap_data_ntouches(tap_data) * 0.95);
+	printf("  Median delta: %dms\n", touch_tdelta_ms(median));
+	printf("  90th percentile: %dms\n", touch_tdelta_ms(pc90));
+	printf("  95th percentile: %dms\n", touch_tdelta_ms(pc95));
+
+	tap_data_free(&data_sorted_tdelta);
+}
+
+static inline void
+print_dat(struct tap_data *tap_data)
+{
+	unsigned int i;
+	struct touch *t;
+	struct tap_data *sorted;
+
+	printf("# libinput-measure-touchpad-tap (v%s)\n", LIBINPUT_VERSION);
+	printf("# File contents:\n"
+	       "#    This file contains multiple prints of the data in different\n"
+	       "#    sort order. Row number is index of touch point within each group.\n"
+	       "#    Comparing data across groups will result in invalid analysis.\n"
+	       "# Columns (1-indexed):\n");
+	printf("# Group 1, sorted by time of occurence\n"
+	       "#  1: touch down time in ms, offset by first event\n"
+	       "#  2: touch up time in ms, offset by first event\n"
+	       "#  3: time delta in ms\n");
+	printf("# Group 2, sorted by touch down-up delta time (ascending)\n"
+	       "#  4: touch down time in ms, offset by first event\n"
+	       "#  5: touch up time in ms, offset by first event\n"
+	       "#  6: time delta in ms\n");
+
+	sorted = tap_data_duplicate_sorted(tap_data, sort_by_time_delta);
+
+	for (i = 0; i < tap_data_ntouches(tap_data); i++) {
+		t = tap_data_get_touch(tap_data, i);
+		printf("%d %d %d ",
+		       t->tdown,
+		       t->tup,
+		       touch_tdelta_ms(t));
+
+		t = tap_data_get_touch(sorted, i);
+		printf("%d %d %d ",
+		       t->tdown,
+		       t->tup,
+		       touch_tdelta_ms(t));
+
+		printf("\n");
+	}
+
+	tap_data_free(&sorted);
+}
+
+static inline void
+handle_btn_touch(struct tap_data *tap_data,
+		 struct libevdev *evdev,
+		 const struct input_event *ev)
+{
+
+	if (ev->value) {
+		struct touch *new_touch = tap_data_new_touch(tap_data);
+
+		new_touch->tdown = us2ms(tv2us(&ev->time)) - tap_data->toffset;
+	} else {
+		struct touch *current = tap_data_get_current_touch(tap_data);
+
+		msg("\rTouch sequences detected: %d", tap_data->count);
+
+		current->tup = us2ms(tv2us(&ev->time)) - tap_data->toffset;
+	}
+}
+
+static inline bool
+handle_key(struct tap_data *tap_data,
+	   struct libevdev *evdev,
+	   const struct input_event *ev)
+{
+	switch (ev->code) {
+	case BTN_TOOL_DOUBLETAP:
+	case BTN_TOOL_TRIPLETAP:
+	case BTN_TOOL_QUADTAP:
+	case BTN_TOOL_QUINTTAP:
+		error("This tool only supports single-finger taps. Aborting.\n");
+		return false;
+	case BTN_TOUCH:
+		handle_btn_touch(tap_data, evdev, ev);
+		break;
+	default:
+		break;
+	}
+
+	return true;
+}
+
+static inline bool
+handle_abs(struct tap_data *tap_data,
+	   struct libevdev *evdev,
+	   const struct input_event *ev)
+{
+	return true;
+}
+
+static inline bool
+handle_event(struct tap_data *tap_data,
+	     struct libevdev *evdev,
+	     const struct input_event *ev)
+{
+	bool rc = true;
+
+	if (tap_data->toffset == 0)
+		tap_data->toffset = us2ms(tv2us(&ev->time));
+
+	switch (ev->type) {
+	default:
+		error("Unexpected event %s %s (%d, %d). Aborting.\n",
+		      libevdev_event_type_get_name(ev->type),
+		      libevdev_event_code_get_name(ev->type, ev->code),
+		      ev->type,
+		      ev->code);
+		break;
+	case EV_KEY:
+		rc = handle_key(tap_data, evdev, ev);
+		break;
+	case EV_ABS:
+		rc = handle_abs(tap_data, evdev, ev);
+		break;
+	case EV_SYN:
+		rc = true;
+		break;
+	}
+
+	return rc;
+}
+
+static int
+loop(struct tap_data *data, const char *path)
+{
+	struct libevdev *evdev;
+	struct pollfd fds[2];
+	sigset_t mask;
+	int fd;
+	int rc;
+
+	fd = open(path, O_RDONLY|O_NONBLOCK);
+	if (fd < 0) {
+		error("Failed to open device: %s\n", strerror(errno));
+		return EXIT_FAILURE;
+	}
+
+	rc = libevdev_new_from_fd(fd, &evdev);
+	if (rc < 0) {
+		error("Failed to init device: %s\n", strerror(-rc));
+		close(fd);
+		return EXIT_FAILURE;
+	}
+	libevdev_set_clock_id(evdev, CLOCK_MONOTONIC);
+
+	fds[0].fd = fd;
+	fds[0].events = POLLIN;
+
+	sigemptyset(&mask);
+	sigaddset(&mask, SIGINT);
+	fds[1].fd = signalfd(-1, &mask, SFD_NONBLOCK);
+	fds[1].events = POLLIN;
+
+	sigprocmask(SIG_BLOCK, &mask, NULL);
+
+	rc = EXIT_FAILURE;
+
+	error("Ready for recording data.\n"
+	      "Tap the touchpad multiple times with a single finger only.\n"
+	      "For useful data we recommend at least 20 taps.\n"
+	      "Ctrl+C to exit\n");
+
+	while (poll(fds, 2, -1)) {
+		struct input_event ev;
+		int rc;
+
+		if (fds[1].revents)
+			break;
+
+		do {
+			rc = libevdev_next_event(evdev, LIBEVDEV_READ_FLAG_NORMAL, &ev);
+			if (rc == LIBEVDEV_READ_STATUS_SYNC) {
+				error("Error: cannot keep up\n");
+				goto out;
+			} else if (rc == LIBEVDEV_READ_STATUS_SUCCESS) {
+				if (!handle_event(data, evdev, &ev))
+					goto out;
+			} else if (rc != -EAGAIN && rc < 0) {
+				error("Error: %s\n", strerror(-rc));
+				goto out;
+			}
+		} while (rc != -EAGAIN);
+	}
+
+	rc = EXIT_SUCCESS;
+out:
+	close(fd);
+	if (evdev)
+		libevdev_free(evdev);
+
+	printf("\n");
+
+	return rc;
+}
+
+static inline void
+usage(void)
+{
+	printf("Usage: libinput measure touchpad-tap [--help] [/dev/input/event0]\n");
+	printf("\n"
+	       "Measure various properties related to tap-to-click.\n"
+	       "If a path to the device is provided, that device is used. Otherwise, this tool\n"
+	       "will pick the first suitable touchpad device.\n"
+	       "\n"
+	       "Options:\n"
+	       "--help ...... show this help\n"
+	       "\n"
+	       "This tool requires access to the /dev/input/eventX nodes.\n");
+}
+
+int
+main(int argc, char **argv)
+{
+	struct tap_data *tap_data;
+	char path[PATH_MAX];
+	int option_index = 0;
+	const char *format = "summary";
+	int rc;
+
+	while (1) {
+		enum opts {
+			OPT_HELP,
+			OPT_FORMAT,
+		};
+		static struct option opts[] = {
+			{ "help",	      no_argument, 0, OPT_HELP },
+			{ "format",	required_argument, 0, OPT_FORMAT},
+			{ 0, 0, 0, 0 },
+		};
+		int c;
+
+		c = getopt_long(argc, argv, "", opts, &option_index);
+		if (c == -1)
+			break;
+
+		switch(c) {
+		case OPT_HELP:
+			usage();
+			return EXIT_SUCCESS;;
+		case OPT_FORMAT:
+			format = optarg;
+			break;
+		default:
+			usage();
+			return EXIT_FAILURE;
+		}
+	}
+
+	if (streq(format, "summary")) {
+		print_dat_file = false;
+	} else if (streq(format, "dat")) {
+		print_dat_file = true;
+	} else {
+		error("Unknown print format '%s'\n", format);
+		return EXIT_FAILURE;
+	}
+
+	if (optind == argc) {
+		if (!find_touchpad_device(path, sizeof(path))) {
+			error("Failed to find a touchpad device.\n");
+			return EXIT_FAILURE;
+		}
+	} else {
+		snprintf(path, sizeof(path), "%s", argv[optind]);
+		if (!is_touchpad_device(path)) {
+			error("Device is not a touchpad.\n");
+			return EXIT_FAILURE;
+		}
+	}
+
+	if (!isatty(STDOUT_FILENO)) {
+		pdest = stderr;
+	} else {
+		pdest = stdout;
+		setbuf(stdout, NULL);
+	}
+
+	tap_data = tap_data_new();
+	rc = loop(tap_data, path);
+
+	if (rc != EXIT_SUCCESS)
+		goto out;
+
+	if (print_dat_file)
+		print_dat(tap_data);
+	else
+		print_statistics(tap_data);
+
+	tap_data_free(&tap_data);
+out:
+	return rc;
+}
diff --git a/tools/libinput-measure.1 b/tools/libinput-measure.1
new file mode 100644
index 0000000..26d798f
--- /dev/null
+++ b/tools/libinput-measure.1
@@ -0,0 +1,30 @@
+.TH LIBINPUT-MEASURE "1"
+.SH NAME
+libinput-measure \- measure properties of devices
+.SH SYNOPSIS
+.B libinput measure [--help] <feature> [<args>]
+.SH DESCRIPTION
+.PP
+The
+.B "libinput measure"
+tool measures properties of one (or more) devices. Depending on what is to
+be measured, this too may not create a libinput context.
+.PP
+This is a debugging tool only, its output may change at any time. Do not
+rely on the output.
+.PP
+This tool usually needs to be run as root to have access to the
+/dev/input/eventX nodes.
+.SH OPTIONS
+.TP 8
+.B --help
+Print help
+.SH FEATURES
+Features that can be measured include
+.TP 8
+.B libinput-measure-touchpad-tap-time(1)
+Measure tap-to-click time.
+.SH LIBINPUT
+Part of the
+.B libinput(1)
+suite
diff --git a/tools/libinput-measure.c b/tools/libinput-measure.c
new file mode 100644
index 0000000..af9c1cf
--- /dev/null
+++ b/tools/libinput-measure.c
@@ -0,0 +1,92 @@
+/*
+ * Copyright © 2017 Red Hat, Inc.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice (including the next
+ * paragraph) shall be included in all copies or substantial portions of the
+ * Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+ * DEALINGS IN THE SOFTWARE.
+ */
+
+#include "config.h"
+
+#include <errno.h>
+#include <getopt.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include <string.h>
+#include <unistd.h>
+#include <libudev.h>
+
+#include <libinput-util.h>
+
+#include "shared.h"
+
+static inline void
+usage(void)
+{
+	printf("Usage: libinput measure [--help] FEATURE [/dev/input/event0]\n");
+	printf("\n"
+	       "Collect measurements related to FEATURE on the given device.\n"
+	       "\n"
+	       "Options:\n"
+	       "--help ...... show this help\n"
+	       "\n"
+	       "Available features are:\n"
+	       "  touchpad-tap-time\n"
+	       "	Measures the time for tap-to-click interactions\n"
+	       "     "
+	       "For information about each feature, see the --help output for that feature.\n"
+	       "\n"
+	       "This tool requires access to the /dev/input/eventX nodes.\n");
+}
+
+int
+main(int argc, char **argv)
+{
+	int option_index = 0;
+
+	while (1) {
+		int c;
+		static struct option opts[] = {
+			{ "help",	no_argument,	0, 'h' },
+			{ 0, 0, 0, 0}
+		};
+
+		c = getopt_long(argc, argv, "h", opts, &option_index);
+		if (c == -1)
+			break;
+
+		switch(c) {
+		case 'h':
+			usage();
+			return EXIT_SUCCESS;
+		default:
+			usage();
+			return EXIT_FAILURE;
+		}
+	}
+
+	if (optind >= argc) {
+		usage();
+		return EXIT_FAILURE;
+	}
+
+	argc--;
+	argv++;
+
+	return tools_exec_command("libinput-measure", argc, argv);
+}
diff --git a/tools/libinput-tool.c b/tools/libinput-tool.c
index f37d961..aa07c42 100644
--- a/tools/libinput-tool.c
+++ b/tools/libinput-tool.c
@@ -35,6 +35,7 @@
 #include <libinput-util.h>
 #include <libinput-version.h>
 
+#include "shared.h"
 static void
 usage(void)
 {
@@ -61,6 +62,9 @@ usage(void)
 	       "\n"
 	       "  debug-gui\n"
 	       "	Display a simple GUI to visualize libinput's events.\n"
+	       "\n"
+	       "  measure\n"
+	       "	Measure various device properties. See the --help output for more info\n"
 	       "\n");
 }
 
@@ -69,52 +73,6 @@ enum global_opts {
 	GOPT_VERSION,
 };
 
-static inline void
-setup_path(void)
-{
-	const char *path = getenv("PATH");
-	char new_path[PATH_MAX];
-
-	snprintf(new_path,
-		 sizeof(new_path),
-		 "%s:%s",
-		 LIBINPUT_TOOL_PATH,
-		 path ? path : "");
-	setenv("PATH", new_path, 1);
-}
-
-static int
-exec_command(int real_argc, char **real_argv)
-{
-	char *argv[64] = {NULL};
-	char executable[128];
-	const char *command;
-	int rc;
-
-	assert((size_t)real_argc < ARRAY_LENGTH(argv));
-
-	command = real_argv[0];
-
-	rc = snprintf(executable, sizeof(executable), "libinput-%s", command);
-	if (rc >= (int)sizeof(executable)) {
-		usage();
-		return EXIT_FAILURE;
-	}
-
-	argv[0] = executable;
-	for (int i = 1; i < real_argc; i++)
-		argv[i] = real_argv[i];
-
-	setup_path();
-
-	rc = execvp(executable, argv);
-	fprintf(stderr,
-		"Failed to execute '%s' (%s)\n",
-		command,
-		strerror(errno));
-	return EXIT_FAILURE;
-}
-
 int
 main(int argc, char **argv)
 {
@@ -154,5 +112,5 @@ main(int argc, char **argv)
 	argv += optind;
 	argc -= optind;
 
-	return exec_command(argc, argv);
+	return tools_exec_command("libinput-", argc, argv);
 }
diff --git a/tools/libinput.1 b/tools/libinput.1
index bc19655..0734d3a 100644
--- a/tools/libinput.1
+++ b/tools/libinput.1
@@ -44,6 +44,12 @@ Show a GUI to visualize libinput's events.
 .TP 8
 .B libinput-list-devices(1)
 List all devices recognized by libinput.
+.TP 8
+.B libinput-measure(1)
+Measure various properties of devices.
+.TP 8
+.B libinput-measure-touchpad-tap(1)
+Measure tap-to-click time.
 .SH LIBINPUT
 Part of the
 .B libinput(1)
diff --git a/tools/shared.c b/tools/shared.c
index 51246ff..5eaca3f 100644
--- a/tools/shared.c
+++ b/tools/shared.c
@@ -29,6 +29,7 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
+#include <sys/stat.h>
 #include <libudev.h>
 
 #include <libevdev/libevdev.h>
@@ -546,3 +547,133 @@ tools_device_apply_config(struct libinput_device *device,
 								 options->profile);
 	}
 }
+
+static char*
+find_device(const char *udev_tag)
+{
+	struct udev *udev;
+	struct udev_enumerate *e;
+	struct udev_list_entry *entry;
+	struct udev_device *device;
+	const char *path, *sysname;
+	char *device_node = NULL;
+
+	udev = udev_new();
+	e = udev_enumerate_new(udev);
+	udev_enumerate_add_match_subsystem(e, "input");
+	udev_enumerate_scan_devices(e);
+
+	udev_list_entry_foreach(entry, udev_enumerate_get_list_entry(e)) {
+		path = udev_list_entry_get_name(entry);
+		device = udev_device_new_from_syspath(udev, path);
+		if (!device)
+			continue;
+
+		sysname = udev_device_get_sysname(device);
+		if (strncmp("event", sysname, 5) != 0) {
+			udev_device_unref(device);
+			continue;
+		}
+
+		if (udev_device_get_property_value(device, udev_tag))
+			device_node = strdup(udev_device_get_devnode(device));
+
+		udev_device_unref(device);
+
+		if (device_node)
+			break;
+	}
+	udev_enumerate_unref(e);
+	udev_unref(udev);
+
+	return device_node;
+}
+
+bool
+find_touchpad_device(char *path, size_t path_len)
+{
+	char *devnode = find_device("ID_INPUT_TOUCHPAD");
+
+	if (devnode) {
+		snprintf(path, path_len, "%s", devnode);
+		free(devnode);
+	}
+
+	return devnode != NULL;
+}
+
+bool
+is_touchpad_device(const char *devnode)
+{
+	struct udev *udev;
+	struct udev_device *dev = NULL;
+	struct stat st;
+	bool is_touchpad = false;
+
+	if (stat(devnode, &st) < 0)
+		return false;
+
+	udev = udev_new();
+	dev = udev_device_new_from_devnum(udev, 'c', st.st_rdev);
+	if (!dev)
+		goto out;
+
+	is_touchpad = udev_device_get_property_value(dev, "ID_INPUT_TOUCHPAD");
+out:
+	if (dev)
+		udev_device_unref(dev);
+	udev_unref(udev);
+
+	return is_touchpad;
+}
+
+static inline void
+setup_path(void)
+{
+	const char *path = getenv("PATH");
+	char new_path[PATH_MAX];
+
+	snprintf(new_path,
+		 sizeof(new_path),
+		 "%s:%s",
+		 LIBINPUT_TOOL_PATH,
+		 path ? path : "");
+	setenv("PATH", new_path, 1);
+}
+
+int
+tools_exec_command(const char *prefix, int real_argc, char **real_argv)
+{
+	char *argv[64] = {NULL};
+	char executable[128];
+	const char *command;
+	int rc;
+
+	assert((size_t)real_argc < ARRAY_LENGTH(argv));
+
+	command = real_argv[0];
+
+	rc = snprintf(executable,
+		      sizeof(executable),
+		      "%s-%s",
+		      prefix,
+		      command);
+	if (rc >= (int)sizeof(executable)) {
+		fprintf(stderr, "Failed to assemble command.\n");
+		return EXIT_FAILURE;
+	}
+
+	argv[0] = executable;
+	for (int i = 1; i < real_argc; i++)
+		argv[i] = real_argv[i];
+
+	setup_path();
+
+	rc = execvp(executable, argv);
+	fprintf(stderr,
+		"Failed to execute '%s' (%s)\n",
+		command,
+		strerror(errno));
+
+	return EXIT_FAILURE;
+}
diff --git a/tools/shared.h b/tools/shared.h
index 0fb8c28..0a39484 100644
--- a/tools/shared.h
+++ b/tools/shared.h
@@ -71,5 +71,9 @@ struct libinput* tools_open_backend(struct tools_context *context);
 void tools_device_apply_config(struct libinput_device *device,
 			       struct tools_options *options);
 void tools_usage(const char *command);
+int tools_exec_command(const char *prefix, int argc, char **argv);
+
+bool find_touchpad_device(char *path, size_t path_len);
+bool is_touchpad_device(const char *devnode);
 
 #endif