initial

Makefile

@@ -0,0 +1,12 @@
+CC=gcc
+CFLAGS=-std=gnu99 -Wall -pedantic -Wextra `pkg-config --cflags ${LIBS}`
+LIBS=alsa dbus-1
+LDFLAGS=`pkg-config --libs ${LIBS}`
+
+all: main
+
+main: main.o
+	${CC} ${LDFLAGS} main.o -o alsa-volume-monitor
+
+main.o:
+	${CC} ${CFLAGS} -c main.c

main.c

@@ -0,0 +1,150 @@
+/**
+ * Based on alsactl/monitor.c (by Takashi Iwai <tiwai@suse.de>) from alsa-utils
+ * http://git.alsa-project.org/?p=alsa-utils.git;a=blob_plain;f=alsactl/monitor.c;hb=HEAD
+ *
+ * Inspired by kbdd
+ */
+
+#include <stdio.h>
+#include <alsa/asoundlib.h>
+#include <dbus/dbus.h>
+
+int notify(DBusConnection *conn)
+{
+    DBusMessage *msg;
+    dbus_uint32_t serial = 0;
+
+    msg = dbus_message_new_signal("/com/ch1p/Object", "com.ch1p.avm", "valueChanged");
+    if (NULL == msg) {
+        fprintf(stderr, "DBus: Message Null\n");
+        return 1;
+    }
+
+    if (!dbus_connection_send(conn, msg, &serial)) {
+        fprintf(stderr, "DBus send: Out Of Memory!\n");
+        return 1;
+    }
+    dbus_connection_flush(conn);
+
+    dbus_message_unref(msg);
+    return 0;
+}
+
+int open_ctl(const char *name, snd_ctl_t **ctlp)
+{
+	snd_ctl_t *ctl;
+	int err;
+
+	err = snd_ctl_open(&ctl, name, SND_CTL_READONLY);
+	if (err < 0) {
+		fprintf(stderr, "Cannot open ctl %s\n", name);
+		return err;
+	}
+	err = snd_ctl_subscribe_events(ctl, 1);
+	if (err < 0) {
+		fprintf(stderr, "Cannot open subscribe events to ctl %s\n", name);
+		snd_ctl_close(ctl);
+		return err;
+	}
+	*ctlp = ctl;
+	return 0;
+}
+
+int check_event(snd_ctl_t *ctl, DBusConnection *conn)
+{
+	snd_ctl_event_t *event;
+	unsigned int mask;
+	int err;
+
+	snd_ctl_event_alloca(&event);
+	err = snd_ctl_read(ctl, event);
+	if (err < 0)
+		return err;
+
+	if (snd_ctl_event_get_type(event) != SND_CTL_EVENT_ELEM)
+		return 0;
+	
+    mask = snd_ctl_event_elem_get_mask(event);
+    if (!(mask & SND_CTL_EVENT_MASK_VALUE))
+        return 0;
+
+    notify(conn);
+
+	return 0;
+}
+
+#define MAX_CARDS	256
+
+int monitor(const char *name, DBusConnection *conn) {
+    snd_ctl_t *ctl;
+	int err = 0;
+
+    err = open_ctl(name, &ctl);
+    if (err < 0)
+        goto error;
+
+    while (1) {
+		struct pollfd fd;
+
+		snd_ctl_poll_descriptors(ctl, &fd, 1);
+
+		err = poll(&fd, 1, -1);
+		if (err <= 0) {
+			err = 0;
+			break;
+		}
+
+        unsigned short revents;
+        snd_ctl_poll_descriptors_revents(ctl, &fd, 1,
+                         &revents);
+        if (revents & POLLIN)
+            check_event(ctl, conn);
+	}
+
+error:
+	snd_ctl_close(ctl);
+	return err;
+}
+
+void usage()
+{
+    fprintf(stderr,
+        "Usage:\n"
+        "   alsa-volume-monitor <card name>\n\n"
+        "Example:\n"
+        "   alsa-volume-monitor hw:0\n");
+    exit(1);
+}
+
+int main(int argc, char *argv[])
+{
+    if (argc < 2)
+        usage();
+
+    DBusConnection *connection;
+    DBusError err;
+    int ret;
+
+    dbus_error_init(&err);
+    connection = dbus_bus_get(DBUS_BUS_SESSION, &err);
+
+    if (dbus_error_is_set(&err)) {
+        fprintf(stderr, "DBus Connection Error (%s)\n", err.message);
+        dbus_error_free(&err);
+    }
+
+    if (!connection) {
+        return 1;
+    }
+
+    ret = dbus_bus_request_name(connection, "com.ch1p.avm",
+        DBUS_NAME_FLAG_REPLACE_EXISTING , &err);
+    if (dbus_error_is_set(&err)) {
+        fprintf(stderr, "DBus Name Error (%s)\n", err.message);
+        dbus_error_free(&err);
+    }
+
+    monitor(argv[1], connection);
+
+    return 0;
+}