https://bugs.freedesktop.org/show_bug.cgi?id=88572

From 6074a20cd8be0db82eb9425538c507075ff6fb61 Mon Sep 17 00:00:00 2001
From: Joseph Hwang <josephsih@chromium.org>
Date: Fri, 23 Jan 2015 16:22:16 +0800
Subject: [PATCH] add grab flag

If the --grab flag is given in capture mode, evtest keeps an EVIOCGRAB
on the device. While this grab is active, other processes will not
receive events from the kernel devices. The grab is released again
when evtest quits.

TEST=Check that the cursor is frozen when --grab option is specified.
$ evtest --grab
---
 evtest.c   | 45 +++++++++++++++++++++++++++++++++++++--------
 evtest.txt |  6 +++++-
 2 files changed, 42 insertions(+), 9 deletions(-)

diff --git a/evtest.c b/evtest.c
index 74230ea..7263bdb 100644
--- a/evtest.c
+++ b/evtest.c
@@ -55,6 +55,10 @@
 #include <errno.h>
 #include <getopt.h>
 #include <ctype.h>
+#include <signal.h>
+#include <sys/time.h>
+#include <sys/types.h>
+#include <unistd.h>
 
 #define BITS_PER_LONG (sizeof(long) * 8)
 #define NBITS(x) ((((x)-1)/BITS_PER_LONG)+1)
@@ -93,6 +97,14 @@ static const struct query_mode {
 	{ "EV_SW",  EV_SW, SW_MAX, EVIOCGSW(SW_MAX) },
 };
 
+static int grab_flag = 0;
+static volatile sig_atomic_t stop = 0;
+
+static void interrupt_handler(int sig)
+{
+	stop = 1;
+}
+
 /**
  * Look up an entry in the query_modes table by its textual name.
  *
@@ -675,8 +687,9 @@ static int version(void)
 static int usage(void)
 {
 	printf("USAGE:\n");
-	printf(" Grab mode:\n");
-	printf("   %s /dev/input/eventX\n", program_invocation_short_name);
+	printf(" Capture mode:\n");
+	printf("   %s [--grab] /dev/input/eventX\n", program_invocation_short_name);
+	printf("     --grab  grab the device for exclusive access\n");
 	printf("\n");
 	printf(" Query mode: (check exit code)\n");
 	printf("   %s --query /dev/input/eventX <type> <value>\n",
@@ -768,8 +781,15 @@ static int print_events(int fd)
 {
 	struct input_event ev[64];
 	int i, rd;
+	fd_set rdfs;
 
-	while (1) {
+	FD_ZERO(&rdfs);
+	FD_SET(fd, &rdfs);
+
+	while (!stop) {
+		select(fd + 1, &rdfs, NULL, NULL, NULL);
+		if (stop)
+			break;
 		rd = read(fd, ev, sizeof(struct input_event) * 64);
 
 		if (rd < (int) sizeof(struct input_event)) {
@@ -800,6 +820,9 @@ static int print_events(int fd)
 		}
 
 	}
+
+	ioctl(fd, EVIOCGRAB, (void*)0);
+	return EXIT_SUCCESS;
 }
 
 /**
@@ -808,13 +831,13 @@ static int print_events(int fd)
  * @param fd The file descriptor to the device.
  * @return 0 if the grab was successful, or 1 otherwise.
  */
-static int test_grab(int fd)
+static int test_grab(int fd, int grab_flag)
 {
 	int rc;
 
 	rc = ioctl(fd, EVIOCGRAB, (void*)1);
 
-	if (!rc)
+	if (rc == 0 && !grab_flag)
 		ioctl(fd, EVIOCGRAB, (void*)0);
 
 	return rc;
@@ -827,7 +850,7 @@ static int test_grab(int fd)
  * @param device The device to monitor, or NULL if the user should be prompted.
  * @return 0 on success, non-zero on error.
  */
-static int do_capture(const char *device)
+static int do_capture(const char *device, int grab_flag)
 {
 	int fd;
 	char *filename;
@@ -867,7 +890,7 @@ static int do_capture(const char *device)
 
 	printf("Testing ... (interrupt to exit)\n");
 
-	if (test_grab(fd))
+	if (test_grab(fd, grab_flag))
 	{
 		printf("***********************************************\n");
 		printf("  This device is grabbed by another process.\n");
@@ -878,6 +901,9 @@ static int do_capture(const char *device)
 		printf("***********************************************\n");
 	}
 
+	signal(SIGINT, interrupt_handler);
+	signal(SIGTERM, interrupt_handler);
+
 	return print_events(fd);
 }
 
@@ -954,6 +980,7 @@ static int do_query(const char *device, const char *event_type, const char *keyn
 }
 
 static const struct option long_options[] = {
+	{ "grab", no_argument, &grab_flag, 1 },
 	{ "query", no_argument, NULL, MODE_QUERY },
 	{ "version", no_argument, NULL, MODE_VERSION },
 	{ 0, },
@@ -972,6 +999,8 @@ int main (int argc, char **argv)
 		if (c == -1)
 			break;
 		switch (c) {
+		case 0:
+			break;
 		case MODE_QUERY:
 			mode = c;
 			break;
@@ -986,7 +1015,7 @@ int main (int argc, char **argv)
 		device = argv[optind++];
 
 	if (mode == MODE_CAPTURE)
-		return do_capture(device);
+		return do_capture(device, grab_flag);
 
 	if ((argc - optind) < 2) {
 		fprintf(stderr, "Query mode requires device, type and key parameters\n");
diff --git a/evtest.txt b/evtest.txt
index b614482..f64b44b 100644
--- a/evtest.txt
+++ b/evtest.txt
@@ -8,7 +8,7 @@ NAME
 
 SYNOPSIS
 --------
-     evtest /dev/input/eventX
+     evtest [--grab] /dev/input/eventX
 
      evtest --query /dev/input/eventX <type> <value>
 
@@ -19,6 +19,10 @@ display information about the specified input device, including all the events
 supported by the device. It then monitors the device and displays all the
 events layer events generated.
 
+If the --grab flag is given in capture mode, evtest keeps an EVIOCGRAB on the
+device. While this grab is active, other processes will not receive events
+from the kernel devices. The grab is released again when evtest quits.
+
 In the second invocation type ("query mode"), evtest performs a one-shot query
 of the state of a specific key *value* of an event *type*.
 
-- 
2.2.0.rc0.207.ga3a616c