audio-be: add common pre-conditions

assert() on valid values, and handle acceptable NULL arguments
gracefully.

Note audio_driver_write() and audio_driver_read() used to return
size (with a "XXX: Consider options") when sw was NULL. Imho, it is more
correct to not pretend to have read/written anything by default in the
AudioBackend base abstract class.

Reviewed-by: Mark Cave-Ayland <mark.caveayland@nutanix.com>
Reviewed-by: Akihiko Odaki <odaki@rsg.ci.i.u-tokyo.ac.jp>
Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>

audio/audio-be.c

@@ -29,6 +29,10 @@ SWVoiceIn *audio_be_open_in(
 {
     AudioBackendClass *klass = AUDIO_BACKEND_GET_CLASS(be);
 
+    assert(name != NULL);
+    assert(callback_fn != NULL);
+    assert(as != NULL);
+
     return klass->open_in(be, sw, name, callback_opaque, callback_fn, as);
 }
 
@@ -42,6 +46,10 @@ SWVoiceOut *audio_be_open_out(
 {
     AudioBackendClass *klass = AUDIO_BACKEND_GET_CLASS(be);
 
+    assert(name != NULL);
+    assert(callback_fn != NULL);
+    assert(as != NULL);
+
     return klass->open_out(be, sw, name, callback_opaque, callback_fn, as);
 }
 
@@ -49,6 +57,10 @@ void audio_be_close_out(AudioBackend *be, SWVoiceOut *sw)
 {
     AudioBackendClass *klass = AUDIO_BACKEND_GET_CLASS(be);
 
+    if (!sw) {
+        return;
+    }
+
     return klass->close_out(be, sw);
 }
 
@@ -56,6 +68,10 @@ void audio_be_close_in(AudioBackend *be, SWVoiceIn *sw)
 {
     AudioBackendClass *klass = AUDIO_BACKEND_GET_CLASS(be);
 
+    if (!sw) {
+        return;
+    }
+
     return klass->close_in(be, sw);
 }
 
@@ -63,6 +79,10 @@ bool audio_be_is_active_out(AudioBackend *be, SWVoiceOut *sw)
 {
     AudioBackendClass *klass = AUDIO_BACKEND_GET_CLASS(be);
 
+    if (!sw) {
+        return false;
+    }
+
     return klass->is_active_out(be, sw);
 }
 
@@ -70,6 +90,10 @@ bool audio_be_is_active_in(AudioBackend *be, SWVoiceIn *sw)
 {
     AudioBackendClass *klass = AUDIO_BACKEND_GET_CLASS(be);
 
+    if (!sw) {
+        return false;
+    }
+
     return klass->is_active_in(be, sw);
 }
 
@@ -77,6 +101,10 @@ size_t audio_be_write(AudioBackend *be, SWVoiceOut *sw, void *buf, size_t size)
 {
     AudioBackendClass *klass = AUDIO_BACKEND_GET_CLASS(be);
 
+    if (!sw) {
+        return 0;
+    }
+
     return klass->write(be, sw, buf, size);
 }
 
@@ -84,6 +112,10 @@ size_t audio_be_read(AudioBackend *be, SWVoiceIn *sw, void *buf, size_t size)
 {
     AudioBackendClass *klass = AUDIO_BACKEND_GET_CLASS(be);
 
+    if (!sw) {
+        return 0;
+    }
+
     return klass->read(be, sw, buf, size);
 }
 
@@ -91,6 +123,10 @@ int audio_be_get_buffer_size_out(AudioBackend *be, SWVoiceOut *sw)
 {
     AudioBackendClass *klass = AUDIO_BACKEND_GET_CLASS(be);
 
+    if (!sw) {
+        return 0;
+    }
+
     return klass->get_buffer_size_out(be, sw);
 }
 
@@ -98,6 +134,10 @@ void audio_be_set_active_out(AudioBackend *be, SWVoiceOut *sw, bool on)
 {
     AudioBackendClass *klass = AUDIO_BACKEND_GET_CLASS(be);
 
+    if (!sw) {
+        return;
+    }
+
     return klass->set_active_out(be, sw, on);
 }
 
@@ -105,6 +145,10 @@ void audio_be_set_active_in(AudioBackend *be, SWVoiceIn *sw, bool on)
 {
     AudioBackendClass *klass = AUDIO_BACKEND_GET_CLASS(be);
 
+    if (!sw) {
+        return;
+    }
+
     return klass->set_active_in(be, sw, on);
 }
 
@@ -112,6 +156,10 @@ void audio_be_set_volume_out(AudioBackend *be, SWVoiceOut *sw, Volume *vol)
 {
     AudioBackendClass *klass = AUDIO_BACKEND_GET_CLASS(be);
 
+    if (!sw) {
+        return;
+    }
+
     klass->set_volume_out(be, sw, vol);
 }
 
@@ -119,6 +167,10 @@ void audio_be_set_volume_in(AudioBackend *be, SWVoiceIn *sw, Volume *vol)
 {
     AudioBackendClass *klass = AUDIO_BACKEND_GET_CLASS(be);
 
+    if (!sw) {
+        return;
+    }
+
     klass->set_volume_in(be, sw, vol);
 }
 
@@ -130,6 +182,9 @@ CaptureVoiceOut *audio_be_add_capture(
 {
     AudioBackendClass *klass = AUDIO_BACKEND_GET_CLASS(be);
 
+    assert(as != NULL);
+    assert(ops != NULL);
+
     return klass->add_capture(be, as, ops, cb_opaque);
 }
 
@@ -137,6 +192,10 @@ void audio_be_del_capture(AudioBackend *be, CaptureVoiceOut *cap, void *cb_opaqu
 {
     AudioBackendClass *klass = AUDIO_BACKEND_GET_CLASS(be);
 
+    if (!cap) {
+        return;
+    }
+
     klass->del_capture(be, cap, cb_opaque);
 }
 
@@ -155,6 +214,8 @@ bool audio_be_set_dbus_server(AudioBackend *be,
 {
     AudioBackendClass *klass = AUDIO_BACKEND_GET_CLASS(be);
 
+    assert(server != NULL);
+
     if (!audio_be_can_set_dbus_server(be)) {
         error_setg(errp, "Audiodev '%s' is not compatible with DBus",
                    audio_be_get_id(be));

tests/audio/test-audio.c

@@ -493,11 +493,9 @@ static void test_audio_null_handling(void)
     /* audio_be_get_buffer_size_out(NULL) should return 0 */
     g_assert_cmpint(audio_be_get_buffer_size_out(be, NULL), ==, 0);
 
-    /* audio_be_write/read(NULL, ...) should return size (no-op) */
-    g_assert_cmpuint(audio_be_write(be, NULL, buffer, sizeof(buffer)), ==,
-                     sizeof(buffer));
-    g_assert_cmpuint(audio_be_read(be, NULL, buffer, sizeof(buffer)), ==,
-                     sizeof(buffer));
+    /* audio_be_write/read(NULL, ...) should return 0 */
+    g_assert_cmpuint(audio_be_write(be, NULL, buffer, sizeof(buffer)), ==, 0);
+    g_assert_cmpuint(audio_be_read(be, NULL, buffer, sizeof(buffer)), ==, 0);
 
     /* These should not crash */
     audio_be_set_active_out(be, NULL, true);