keyack: Add program to wait for key press and release

Useful for testing buttons bound to a gpio-key, e.g. a factory reset
button.

package/Config.in

@@ -6,6 +6,7 @@ source "$BR2_EXTERNAL_INFIX_PATH/package/faux/Config.in"
 source "$BR2_EXTERNAL_INFIX_PATH/package/finit/Config.in"
 source "$BR2_EXTERNAL_INFIX_PATH/package/ifupdown-ng/Config.in"
 source "$BR2_EXTERNAL_INFIX_PATH/package/iito/Config.in"
+source "$BR2_EXTERNAL_INFIX_PATH/package/keyack/Config.in"
 source "$BR2_EXTERNAL_INFIX_PATH/package/klish-plugin-infix/Config.in"
 source "$BR2_EXTERNAL_INFIX_PATH/package/klish/Config.in"
 source "$BR2_EXTERNAL_INFIX_PATH/package/klish-plugin-sysrepo/Config.in"

package/keyack/Config.in

@@ -0,0 +1,6 @@
+config BR2_PACKAGE_KEYACK
+	bool "keyack"
+	help
+	  Blocks until a specific key is pressed and released. Useful
+	  when you want a user to confirm some action by physically
+	  pressing a button.

package/keyack/keyack.mk

@@ -0,0 +1,24 @@
+################################################################################
+#
+# keyack
+#
+################################################################################
+
+KEYACK_VERSION = 1.0
+KEYACK_LICENSE = MIT
+KEYACK_LICENSE_FILES = LICENSE
+KEYACK_SITE_METHOD = local
+KEYACK_SITE = $(BR2_EXTERNAL_INFIX_PATH)/src/keyack
+KEYACK_REDISTRIBUTE = NO
+
+define KEYACK_BUILD_CMDS
+	$(TARGET_MAKE_ENV) $(TARGET_CONFIGURE_OPTS) $(MAKE) -C $(@D) \
+		LDLIBS="$(TARGET_LDFLAGS)"
+endef
+
+define KEYACK_INSTALL_TARGET_CMDS
+	$(TARGET_MAKE_ENV) $(TARGET_CONFIGURE_OPTS) $(MAKE) -C $(@D) \
+		DESTDIR="$(TARGET_DIR)" install
+endef
+
+$(eval $(generic-package))

src/keyack/Makefile

@@ -0,0 +1,12 @@
+CFLAGS += -Wall -Wextra -Werror
+
+all: keyack
+
+clean:
+	-rm -f keyack
+
+distclean: clean
+	-rm *~
+
+install:
+	install -D keyack $(DESTDIR)/sbin/

src/keyack/keyack.c

@@ -0,0 +1,84 @@
+#include <getopt.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <linux/input.h>
+
+static void usage()
+{
+	fputs("keyack - Wait for key press and release\n"
+	      "\n"
+	      "Usage:\n"
+	      "  keyack [options]\n"
+	      "\n"
+	      "Options:\n"
+	      "  -d DEVICE      Operate on DEVICE, instead of /dev/input/event0.\n"
+	      "  -k KEYCODE     Wait for KEYCODE, instead of KEY_RESTART.\n"
+	      "  -h             Print usage message and exit.\n",
+	      stderr);
+}
+
+static const char *sopts = "d:hk:";
+static struct option lopts[] = {
+	{ "device", required_argument, 0, 'd' },
+	{ "help",   no_argument,       0, 'h' },
+	{ "key",    required_argument, 0, 'k' },
+
+	{ NULL }
+};
+
+bool wait_key_state(FILE *fp, int code, int val)
+{
+	struct input_event ev;
+
+	while (fread(&ev, sizeof(ev), 1, fp)) {
+		if (ev.type == EV_KEY && ev.code == code && ev.value == val)
+			return true;
+        }
+
+	return false;
+}
+
+int main(int argc, char **argv)
+{
+	char *dev = "/dev/input/event0";
+	int opt, code = KEY_RESTART;
+	bool success;
+	FILE *fp;
+
+	while ((opt = getopt_long(argc, argv, sopts, lopts, NULL)) > 0) {
+		switch (opt) {
+		case 'd':
+			dev = optarg;
+			break;
+		case 'h':
+			usage(); exit(0);
+			break;
+		case 'k':
+			code = strtol(optarg, NULL, 0);
+			break;
+
+		default:
+			fprintf(stderr, "unknown option '%c'\n", opt);
+			usage(); exit(1);
+			break;
+		}
+	}
+
+	fp = fopen(dev, "r");
+	if (!fp) {
+		fprintf(stderr, "Unable to open \"%s\": %m\n", dev);
+		exit(1);
+	}
+
+	success = wait_key_state(fp, code, 1) && wait_key_state(fp, code, 0);
+
+	fclose(fp);
+
+	if (!success) {
+		fprintf(stderr, "Failed to read events");
+		exit(1);
+	}
+
+	return 0;
+}