Re: [RFC 03/24] audio/dbus: make "dbus" the default backend when using -display dbus

[Akihiko Odaki]

On 2025/12/01 20:22, marcandre.lur...@redhat.com wrote:

From: Marc-André Lureau <marcandre.lur...@redhat.com>

Set "using_dbus_display" during early_dbus_init(), so that we can try to
create the "dbus" audio backend by default from audio_prio_list.

This makes dbus audio work by default when using an audio device,
without having to setup and wire up the -audiodev manually.

The added FIXME is addressed in the following commits.

Signed-off-by: Marc-André Lureau <marcandre.lur...@redhat.com>
---
  audio/audio.c     |  3 +++
  audio/dbusaudio.c |  8 +++++++-
  ui/dbus.c         | 17 +++++++++++++----
  3 files changed, 23 insertions(+), 5 deletions(-)

diff --git a/audio/audio.c b/audio/audio.c
index 86e674410a..0f992a775c 100644
--- a/audio/audio.c
+++ b/audio/audio.c
@@ -57,6 +57,9 @@
      that we generate the list.
  */
  const char *audio_prio_list[] = {
+#ifdef CONFIG_GIO
+    "dbus",
+#endif
      "spice",
      CONFIG_AUDIO_DRIVERS
      "none",
diff --git a/audio/dbusaudio.c b/audio/dbusaudio.c
index d729a810aa..1fe7c4ed64 100644
--- a/audio/dbusaudio.c
+++ b/audio/dbusaudio.c
@@ -32,6 +32,7 @@
  #endif

#include "ui/dbus.h"

+#include "ui/dbus-display.h"
  #include "ui/dbus-display1.h"

#define AUDIO_CAP "dbus"

@@ -408,8 +409,13 @@ dbus_enable_in(HWVoiceIn *hw, bool enable)
  static void *
  dbus_audio_init(Audiodev *dev, Error **errp)
  {
-    DBusAudio *da = g_new0(DBusAudio, 1);
+    DBusAudio *da;

+ if (!qemu_using_dbus_display(errp)) {

+        return NULL;
+    }
+
+    da = g_new0(DBusAudio, 1);
      da->dev = dev;
      da->out_listeners = g_hash_table_new_full(g_str_hash, g_str_equal,
                                                  g_free, g_object_unref);
diff --git a/ui/dbus.c b/ui/dbus.c
index d2dff33258..45fb3c1aa3 100644
--- a/ui/dbus.c
+++ b/ui/dbus.c
@@ -35,6 +35,7 @@
  #include "ui/egl-context.h"
  #endif
  #include "qemu/audio.h"
+#include "audio/audio_int.h" /* FIXME: use QOM dynamic cast instead of 
drv->name */
  #include "qapi/error.h"
  #include "trace.h"

@@ -218,12 +219,20 @@ dbus_display_complete(UserCreatable *uc, Error **errp)

          return;
      }

+ AudioBackend *audio_be = audio_get_default_audio_be(NULL);

Here is a mixed declaration disallowed by docs/devel/style.rst

Regards,
Akihiko Odaki

+    if (audio_be && !g_str_equal(audio_be->drv->name, "dbus")) {
+        audio_be = NULL;
+    }
      if (dd->audiodev && *dd->audiodev) {
-        AudioBackend *audio_be = audio_be_by_name(dd->audiodev, errp);
-        if (!audio_be || !audio_be_set_dbus_server(audio_be, dd->server, 
dd->p2p, errp)) {
+        audio_be = audio_be_by_name(dd->audiodev, errp);
+        if (!audio_be) {
              return;
          }
      }
+    if (audio_be && !audio_be_set_dbus_server(audio_be, dd->server, dd->p2p, 
errp)) {
+        return;
+    }
+

consoles = g_array_new(FALSE, FALSE, sizeof(guint32));

      for (idx = 0;; idx++) {
@@ -475,6 +484,8 @@ early_dbus_init(DisplayOptions *opts)
  #endif
      }

+ using_dbus_display = 1;

+
      type_register_static(&dbus_vc_type_info);
  }

@@ -488,8 +499,6 @@ dbus_init(DisplayState *ds, DisplayOptions *opts)

          exit(1);
      }

- using_dbus_display = 1;

-
      object_new_with_props(TYPE_DBUS_DISPLAY,
                            object_get_objects_root(),
                            "dbus-display", &error_fatal,