make alsa/ardour dbus-device request tool generally useful.

libs/ardouralsautil/request_device.c

@@ -1,4 +1,5 @@
-/*
+/* alsa/ardour dbus device request tool
+ *
  * Copyright (C) 2014 Robin Gareus <robin@gareus.org>
  *
  * This program is free software; you can redistribute it and/or modify
@@ -16,9 +17,13 @@
  * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  */
 
+// NB generate man-page with
+// help2man -N -n "alsa/ardour dbus device request tool" -o ardour-request-device.1 ./build/libs/ardouralsautil/ardour-request-device
+
 #include <stdio.h>
 #include <stdlib.h>
 #include <unistd.h>
+#include <getopt.h>
 #include <signal.h>
 #include <string.h>
 #include <fcntl.h>
@@ -27,6 +32,8 @@
 #include "ardouralsautil/reserve.h"
 
 static int run = 1;
+static int release_wait_for_signal = 0;
+static pid_t parent_pid = 0;
 
 static void wearedone(int sig) {
 	(void) sig; // skip 'unused variable' compiler warning;
@@ -40,21 +47,45 @@ static int stdin_available(void) {
 	return errno != EBADF;
 }
 
+static void print_version(int status) {
+	printf ("ardour-request-device 0.2\n\n");
+	printf (
+		"Copyright (C) 2014 Robin Gareus <robin@gareus.org>\n"
+		"This is free software; see the source for copying conditions.  There is NO\n"
+		"warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.\n\n"
+		);
+	exit (status);
+}
+
 static void usage(int status) {
 	printf ("ardour-request-device - DBus Audio Reservation Utility.\n");
 	printf ("Usage: ardour-request-device [ OPTIONS ] <Audio-Device-ID>\n");
 	printf ("Options:\n\
       -h, --help                 display this help and exit\n\
+      -p, --priority <int>       reservation priority (default: int32_max)\n\
+      -P, --pid <int>            process-id to watch (default 0: none)\n\
+      -n, --name <string>        application name to use for registration\n\
       -V, --version              print version information and exit\n\
+      -w, --releasewait          wait for signal on yield-release\n\
 ");
 
 	printf ("\n\
 This tool issues a dbus request to reserve an ALSA Audio-device.\n\
 If successful other users of the device (e.g. pulseaudio) will\n\
-release the device so that ardour can access it.\n\
+release the device.\n\
 \n\
-ardour-request-device announces itself as \"Ardour ALSA Backend\" and uses the\n\
+ardour-request-device by default announces itself as \"Ardour ALSA Backend\"\n\
-maximum possible priority for requesting the device.\n\
+and uses the maximum possible priority for requesting the device.\n\
+These settings can be overriden using the -n and -p options respectively.\n\
+\n\
+If a PID is given the tool will watch the process and if that is not running\n\
+release the device and exit.  Otherwise ardour-request-device runs until\n\
+either stdin is closed, a SIGINT or SIGTERM is received or some other\n\
+application requests the device with a higher priority.\n\
+\n\
+Without the -w option, ardour-request-device yields the device after 500ms to\n\
+any higher-priority request. With the -w option this tool waits until it\n\
+for SIGINT or SIGTERM - but at most 4 sec to acknowledge before releasing.\n\
 \n\
 The audio-device-id is a string e.g. 'Audio1'\n\
 \n\
@@ -66,39 +97,107 @@ ardour-request-device Audio0\n\
 	exit (status);
 }
 
-static void print_version(void) {
+static struct option const long_options[] =
-	printf ("ardour-request-device 0.1\n\n");
+{
-	printf (
+	{"help", no_argument, 0, 'h'},
-			"Copyright (C) 2014 Robin Gareus <robin@gareus.org>\n"
+	{"name", required_argument, 0, 'n'},
-			"This is free software; see the source for copying conditions.  There is NO\n"
+	{"pid", required_argument, 0, 'P'},
-			"warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.\n\n"
+	{"priority", required_argument, 0, 'p'},
-			);
+	{"version", no_argument, 0, 'V'},
-	exit (0);
+	{"releasewait", no_argument, 0, 'w'},
+	{NULL, 0, NULL, 0}
+};
+
+static int request_cb(rd_device *d, int forced) {
+	(void) d; // skip 'unused variable' compiler warning;
+	(void) forced; // skip 'unused variable' compiler warning;
+	fprintf(stdout, "Received higher priority request - releasing device.\n");
+	fflush(stdout);
+	if(!release_wait_for_signal) {
+		usleep (500000);
+		run = 0;
+	} else if (run) {
+		int timeout = 4000;
+		fprintf(stdout, "Waiting for acknowledge signal to release.\n");
+		while (release_wait_for_signal && run && --timeout) {
+			if (!stdin_available()) {
+				break;
+			}
+			if (parent_pid > 0 && kill (parent_pid, 0)) {
+				break;
+			}
+			usleep (1000);
+		}
+		run = 0;
+	}
+	return 1; // OK
 }
 
 int main(int argc, char **argv) {
 	DBusConnection* dbus_connection = NULL;
 	rd_device * reserved_device = NULL;
 	DBusError error;
-	int ret;
+	int ret, c;
 
-	if (argc < 2 || argc > 2) {
+	int32_t priority = INT32_MAX;
+	char *name = strdup("Ardour ALSA Backend");
+
+	while ((c = getopt_long (argc, argv,
+					"h"  /* help */
+					"n:" /* name */
+					"P:" /* pid */
+					"p:" /* priority */
+					"V"  /* version */
+					"w", /* release wait for signal */
+					long_options, (int *) 0)) != EOF)
+	{
+		switch (c) {
+			case 'h':
+				free(name);
+				usage(EXIT_SUCCESS);
+				break;
+			case 'n':
+				free(name);
+				name = strdup(optarg);
+				break;
+			case 'p':
+				priority = atoi (optarg);
+				if (priority < 0) priority = 0;
+				break;
+			case 'P':
+				parent_pid = atoi (optarg);
+				break;
+			case 'V':
+				free(name);
+				print_version(EXIT_SUCCESS);
+				break;
+			case 'w':
+				release_wait_for_signal = 1;
+				break;
+			default:
+				free(name);
+				usage(EXIT_FAILURE);
+				break;
+		}
+	}
+
+	if (optind + 1 != argc) {
+		free(name);
 		usage(EXIT_FAILURE);
 	}
-	if (!strcmp(argv[1], "-V") || !strcmp(argv[1], "--version")) {
+	const char *device_name = argv[optind];
-		print_version();
-	}
-	if (!strcmp(argv[1], "-h") || !strcmp(argv[1], "--help")) {
-		usage(EXIT_SUCCESS);
-	}
 
-	const char *device_name = argv[1];
+	if (parent_pid > 0 && kill (parent_pid, 0)) {
+		fprintf(stderr, "Given PID to watch is not running.\n");
+		return EXIT_FAILURE;
+	}
 
 	dbus_error_init(&error);
 
 	if (!(dbus_connection = dbus_bus_get (DBUS_BUS_SESSION, &error))) {
 		fprintf(stderr, "Failed to connect to session bus for device reservation: %s\n", error.message ? error.message : "unknown error.");
 		dbus_error_free(&error);
+		free(name);
 		return EXIT_FAILURE;
 	}
 
@@ -106,14 +205,15 @@ int main(int argc, char **argv) {
 					&reserved_device,
 					dbus_connection,
 					device_name,
-					"Ardour ALSA Backend",
+					name,
-					INT32_MAX,
+					priority,
-					NULL,
+					request_cb,
 					&error)) < 0)
 	{
 		fprintf(stderr, "Failed to acquire device: '%s'\n%s\n", device_name, (error.message ? error.message : strerror(-ret)));
 		dbus_error_free(&error);
 		dbus_connection_unref(dbus_connection);
+		free(name);
 		return EXIT_FAILURE;
 	}
 
@@ -126,14 +226,20 @@ int main(int argc, char **argv) {
 
 	while (run && dbus_connection_read_write_dispatch (dbus_connection, 200)) {
 		if (!stdin_available()) {
-			fprintf(stderr, "stdin closed - shutting down.\n");
+			fprintf(stderr, "stdin closed - releasing device.\n");
+			break;
+		}
+		if (parent_pid > 0 && kill (parent_pid, 0)) {
+			fprintf(stderr, "watched PID no longer exists - releasing device.\n");
 			break;
 		}
 	}
 
 	rd_release (reserved_device);
 	fprintf(stdout, "Released audio-card '%s'\n", device_name);
-	dbus_error_free(&error);
+
 	dbus_connection_unref(dbus_connection);
+	dbus_error_free(&error);
+	free(name);
 	return EXIT_SUCCESS;
 }