audio: add "dbus" audio backend

Add a new -audio backend that accepts D-Bus clients/listeners to handle
playback & recording, to be exported via the -display dbus.

Example usage:
-audiodev dbus,in.mixing-engine=off,out.mixing-engine=off,id=dbus
-display dbus,audiodev=dbus

Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Acked-by: Gerd Hoffmann <kraxel@redhat.com>

audio/audio.c

@@ -2000,6 +2000,7 @@ void audio_create_pdos(Audiodev *dev)
         CASE(NONE, none, );
         CASE(ALSA, alsa, Alsa);
         CASE(COREAUDIO, coreaudio, Coreaudio);
+        CASE(DBUS, dbus, );
         CASE(DSOUND, dsound, );
         CASE(JACK, jack, Jack);
         CASE(OSS, oss, Oss);

audio/audio_int.h

@@ -31,6 +31,10 @@
 #endif
 #include "mixeng.h"
 
+#ifdef CONFIG_GIO
+#include <gio/gio.h>
+#endif
+
 struct audio_pcm_ops;
 
 struct audio_callback {
@@ -140,6 +144,9 @@ struct audio_driver {
     const char *descr;
     void *(*init) (Audiodev *);
     void (*fini) (void *);
+#ifdef CONFIG_GIO
+    void (*set_dbus_server) (AudioState *s, GDBusObjectManagerServer *manager);
+#endif
     struct audio_pcm_ops *pcm_ops;
     int can_be_default;
     int max_voices_out;

audio/audio_template.h

@@ -327,6 +327,8 @@ AudiodevPerDirectionOptions *glue(audio_get_pdo_, TYPE)(Audiodev *dev)
     case AUDIODEV_DRIVER_COREAUDIO:
         return qapi_AudiodevCoreaudioPerDirectionOptions_base(
             dev->u.coreaudio.TYPE);
+    case AUDIODEV_DRIVER_DBUS:
+        return dev->u.dbus.TYPE;
     case AUDIODEV_DRIVER_DSOUND:
         return dev->u.dsound.TYPE;
     case AUDIODEV_DRIVER_JACK:

audio/meson.build

@@ -26,4 +26,10 @@ foreach m : [
   endif
 endforeach
 
+if dbus_display
+    module_ss = ss.source_set()
+    module_ss.add(when: gio, if_true: files('dbusaudio.c'))
+    audio_modules += {'dbus': module_ss}
+endif
+
 modules += {'audio': audio_modules}

audio/trace-events

@@ -13,6 +13,11 @@ alsa_resume_out(void) "Resuming suspended output stream"
 # ossaudio.c
 oss_version(int version) "OSS version = 0x%x"
 
+# dbusaudio.c
+dbus_audio_register(const char *s, const char *dir) "sender = %s, dir = %s"
+dbus_audio_put_buffer_out(size_t len) "len = %zu"
+dbus_audio_read(size_t len) "len = %zu"
+
 # audio.c
 audio_timer_start(int interval) "interval %d ms"
 audio_timer_stop(void) ""

qapi/audio.json

@@ -386,7 +386,7 @@
 # Since: 4.0
 ##
 { 'enum': 'AudiodevDriver',
-  'data': [ 'none', 'alsa', 'coreaudio', 'dsound', 'jack', 'oss', 'pa',
+  'data': [ 'none', 'alsa', 'coreaudio', 'dbus', 'dsound', 'jack', 'oss', 'pa',
             'sdl', 'spice', 'wav' ] }
 
 ##
@@ -412,6 +412,7 @@
     'none':      'AudiodevGenericOptions',
     'alsa':      'AudiodevAlsaOptions',
     'coreaudio': 'AudiodevCoreaudioOptions',
+    'dbus':      'AudiodevGenericOptions',
     'dsound':    'AudiodevDsoundOptions',
     'jack':      'AudiodevJackOptions',
     'oss':       'AudiodevOssOptions',

qapi/ui.json

@@ -1134,13 +1134,16 @@
 # @p2p: Whether to use peer-to-peer connections (accepted through
 #       ``add_client``).
 #
+# @audiodev: Use the specified DBus audiodev to export audio.
+#
 # Since: 7.0
 #
 ##
 { 'struct'  : 'DisplayDBus',
   'data'    : { '*rendernode' : 'str',
                 '*addr': 'str',
-                '*p2p': 'bool' } }
+                '*p2p': 'bool',
+                '*audiodev': 'str' } }
 
  ##
  # @DisplayGLMode:

qemu-options.hx

@@ -659,6 +659,9 @@ DEF("audiodev", HAS_ARG, QEMU_OPTION_audiodev,
 #endif
 #ifdef CONFIG_SPICE
     "-audiodev spice,id=id[,prop[=value][,...]]\n"
+#endif
+#ifdef CONFIG_DBUS_DISPLAY
+    "-audiodev dbus,id=id[,prop[=value][,...]]\n"
 #endif
     "-audiodev wav,id=id[,prop[=value][,...]]\n"
     "                path= path of wav file to record\n",

ui/dbus-display1.xml

@@ -375,4 +375,215 @@
       </arg>
     </method>
   </interface>
+
+  <!--
+      org.qemu.Display1.Audio:
+
+      Audio backend may be available on ``/org/qemu/Display1/Audio``.
+  -->
+  <interface name="org.qemu.Display1.Audio">
+    <!--
+        RegisterOutListener:
+        @listener: a Unix socket FD, for peer-to-peer D-Bus communication.
+
+        Register an audio backend playback handler.
+
+        Multiple listeners may be registered simultaneously.
+
+        The listener is expected to implement the
+        :dbus:iface:`org.qemu.Display1.AudioOutListener` interface.
+    -->
+    <method name="RegisterOutListener">
+      <arg type="h" name="listener" direction="in"/>
+    </method>
+
+    <!--
+        RegisterInListener:
+        @listener: a Unix socket FD, for peer-to-peer D-Bus communication.
+
+        Register an audio backend record handler.
+
+        Multiple listeners may be registered simultaneously.
+
+        The listener is expected to implement the
+        :dbus:iface:`org.qemu.Display1.AudioInListener` interface.
+    -->
+    <method name="RegisterInListener">
+      <arg type="h" name="listener" direction="in"/>
+    </method>
+  </interface>
+
+  <!--
+      org.qemu.Display1.AudioOutListener:
+
+      This client-side interface must be available on
+      ``/org/qemu/Display1/AudioOutListener`` when registering the peer-to-peer
+      connection with :dbus:meth:`~org.qemu.Display1.Audio.RegisterOutListener`.
+  -->
+  <interface name="org.qemu.Display1.AudioOutListener">
+    <!--
+        Init:
+        @id: the stream ID.
+        @bits: PCM bits per sample.
+        @is_signed: whether the PCM data is signed.
+        @is_float: PCM floating point format.
+        @freq: the PCM frequency in Hz.
+        @nchannels: the number of channels.
+        @bytes_per_frame: the bytes per frame.
+        @bytes_per_second: the bytes per second.
+        @be: whether using big-endian format.
+
+        Initializes a PCM playback stream.
+    -->
+    <method name="Init">
+      <arg name="id" type="t" direction="in"/>
+      <arg name="bits" type="y" direction="in"/>
+      <arg name="is_signed" type="b" direction="in"/>
+      <arg name="is_float" type="b" direction="in"/>
+      <arg name="freq" type="u" direction="in"/>
+      <arg name="nchannels" type="y" direction="in"/>
+      <arg name="bytes_per_frame" type="u" direction="in"/>
+      <arg name="bytes_per_second" type="u" direction="in"/>
+      <arg name="be" type="b" direction="in"/>
+    </method>
+
+    <!--
+        Fini:
+        @id: the stream ID.
+
+        Finish & close a playback stream.
+    -->
+    <method name="Fini">
+      <arg name="id" type="t" direction="in"/>
+    </method>
+
+    <!--
+        SetEnabled:
+        @id: the stream ID.
+
+        Resume or suspend the playback stream.
+    -->
+    <method name="SetEnabled">
+      <arg name="id" type="t" direction="in"/>
+      <arg name="enabled" type="b" direction="in"/>
+    </method>
+
+    <!--
+        SetVolume:
+        @id: the stream ID.
+        @mute: whether the stream is muted.
+        @volume: the volume per-channel.
+
+        Set the stream volume and mute state (volume without unit, 0-255).
+    -->
+    <method name="SetVolume">
+      <arg name="id" type="t" direction="in"/>
+      <arg name="mute" type="b" direction="in"/>
+      <arg name="volume" type="ay" direction="in">
+        <annotation name="org.gtk.GDBus.C.ForceGVariant" value="true"/>
+      </arg>
+    </method>
+
+    <!--
+        Write:
+        @id: the stream ID.
+        @data: the PCM data.
+
+        PCM stream to play.
+    -->
+    <method name="Write">
+      <arg name="id" type="t" direction="in"/>
+      <arg type="ay" name="data" direction="in">
+        <annotation name="org.gtk.GDBus.C.ForceGVariant" value="true"/>
+      </arg>
+    </method>
+  </interface>
+
+  <!--
+      org.qemu.Display1.AudioInListener:
+
+      This client-side interface must be available on
+      ``/org/qemu/Display1/AudioInListener`` when registering the peer-to-peer
+      connection with :dbus:meth:`~org.qemu.Display1.Audio.RegisterInListener`.
+  -->
+  <interface name="org.qemu.Display1.AudioInListener">
+    <!--
+        Init:
+        @id: the stream ID.
+        @bits: PCM bits per sample.
+        @is_signed: whether the PCM data is signed.
+        @is_float: PCM floating point format.
+        @freq: the PCM frequency in Hz.
+        @nchannels: the number of channels.
+        @bytes_per_frame: the bytes per frame.
+        @bytes_per_second: the bytes per second.
+        @be: whether using big-endian format.
+
+        Initializes a PCM record stream.
+    -->
+    <method name="Init">
+      <arg name="id" type="t" direction="in"/>
+      <arg name="bits" type="y" direction="in"/>
+      <arg name="is_signed" type="b" direction="in"/>
+      <arg name="is_float" type="b" direction="in"/>
+      <arg name="freq" type="u" direction="in"/>
+      <arg name="nchannels" type="y" direction="in"/>
+      <arg name="bytes_per_frame" type="u" direction="in"/>
+      <arg name="bytes_per_second" type="u" direction="in"/>
+      <arg name="be" type="b" direction="in"/>
+    </method>
+
+    <!--
+        Fini:
+        @id: the stream ID.
+
+        Finish & close a record stream.
+    -->
+    <method name="Fini">
+      <arg name="id" type="t" direction="in"/>
+    </method>
+
+    <!--
+        SetEnabled:
+        @id: the stream ID.
+
+        Resume or suspend the record stream.
+    -->
+    <method name="SetEnabled">
+      <arg name="id" type="t" direction="in"/>
+      <arg name="enabled" type="b" direction="in"/>
+    </method>
+
+    <!--
+        SetVolume:
+        @id: the stream ID.
+        @mute: whether the stream is muted.
+        @volume: the volume per-channel.
+
+        Set the stream volume and mute state (volume without unit, 0-255).
+    -->
+    <method name="SetVolume">
+      <arg name="id" type="t" direction="in"/>
+      <arg name="mute" type="b" direction="in"/>
+      <arg name="volume" type="ay" direction="in">
+        <annotation name="org.gtk.GDBus.C.ForceGVariant" value="true"/>
+      </arg>
+    </method>
+
+    <!--
+        Read:
+        @id: the stream ID.
+        @size: the amount to read, in bytes.
+        @data: the recorded data (which may be less than requested).
+
+        Read "size" bytes from the record stream.
+    -->
+    <method name="Read">
+      <arg name="id" type="t" direction="in"/>
+      <arg name="size" type="t" direction="in"/>
+      <arg type="ay" name="data" direction="out">
+        <annotation name="org.gtk.GDBus.C.ForceGVariant" value="true"/>
+      </arg>
+    </method>
+  </interface>
 </node>

ui/dbus.c

@@ -30,6 +30,8 @@
 #include "ui/dbus-module.h"
 #include "ui/egl-helpers.h"
 #include "ui/egl-context.h"
+#include "audio/audio.h"
+#include "audio/audio_int.h"
 #include "qapi/error.h"
 #include "trace.h"
 
@@ -84,6 +86,7 @@ dbus_display_finalize(Object *o)
     g_clear_object(&dd->bus);
     g_clear_object(&dd->iface);
     g_free(dd->dbus_addr);
+    g_free(dd->audiodev);
     dbus_display = NULL;
 }
 
@@ -140,6 +143,19 @@ dbus_display_complete(UserCreatable *uc, Error **errp)
         return;
     }
 
+    if (dd->audiodev && *dd->audiodev) {
+        AudioState *audio_state = audio_state_by_name(dd->audiodev);
+        if (!audio_state) {
+            error_setg(errp, "Audiodev '%s' not found", dd->audiodev);
+            return;
+        }
+        if (!g_str_equal(audio_state->drv->name, "dbus")) {
+            error_setg(errp, "Audiodev '%s' is not compatible with DBus",
+                       dd->audiodev);
+            return;
+        }
+        audio_state->drv->set_dbus_server(audio_state, dd->server);
+    }
 
     consoles = g_array_new(FALSE, FALSE, sizeof(guint32));
     for (idx = 0;; idx++) {
@@ -261,6 +277,23 @@ set_dbus_addr(Object *o, const char *str, Error **errp)
     dd->dbus_addr = g_strdup(str);
 }
 
+static char *
+get_audiodev(Object *o, Error **errp)
+{
+    DBusDisplay *dd = DBUS_DISPLAY(o);
+
+    return g_strdup(dd->audiodev);
+}
+
+static void
+set_audiodev(Object *o, const char *str, Error **errp)
+{
+    DBusDisplay *dd = DBUS_DISPLAY(o);
+
+    g_free(dd->audiodev);
+    dd->audiodev = g_strdup(str);
+}
+
 static int
 get_gl_mode(Object *o, Error **errp)
 {
@@ -285,6 +318,7 @@ dbus_display_class_init(ObjectClass *oc, void *data)
     ucc->complete = dbus_display_complete;
     object_class_property_add_bool(oc, "p2p", get_dbus_p2p, set_dbus_p2p);
     object_class_property_add_str(oc, "addr", get_dbus_addr, set_dbus_addr);
+    object_class_property_add_str(oc, "audiodev", get_audiodev, set_audiodev);
     object_class_property_add_enum(oc, "gl-mode",
                                    "DisplayGLMode", &DisplayGLMode_lookup,
                                    get_gl_mode, set_gl_mode);
@@ -321,6 +355,7 @@ dbus_init(DisplayState *ds, DisplayOptions *opts)
                           object_get_objects_root(),
                           "dbus-display", &error_fatal,
                           "addr", opts->u.dbus.addr ?: "",
+                          "audiodev", opts->u.dbus.audiodev ?: "",
                           "gl-mode", DisplayGLMode_str(mode),
                           "p2p", yes_no(opts->u.dbus.p2p),
                           NULL);

ui/dbus.h

@@ -36,6 +36,7 @@ struct DBusDisplay {
     DisplayGLMode gl_mode;
     bool p2p;
     char *dbus_addr;
+    char *audiodev;
     DisplayGLCtx glctx;
 
     GDBusConnection *bus;