staging: vc04_services: bcm2835-audio: Use vchi_msg_hold()

vchi_msg_dequeue() provides the same functionality as vchi_msg_hold()
except it copies the message data as opposed to the later which provides
the data in place.

The copying is done on a local variable, so there is no need to keep the
message out the function's bounds, so use vchi_msg_hold() instead.
Signed-off-by: Nicolas Saenz Julienne <nsaenzjulienne@suse.de>
Link: https://lore.kernel.org/r/20200629150945.10720-14-nsaenzjulienne@suse.deSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/vc04_services/bcm2835-audio/bcm2835-vchiq.c

@@ -94,31 +94,34 @@ static void audio_vchi_callback(void *param,
 				void *msg_handle)
 {
 	struct bcm2835_audio_instance *instance = param;
-	struct vc_audio_msg m;
-	int msg_len;
+	struct vchi_held_msg handle;
+	struct vc_audio_msg *m;
+	unsigned size;
 	int status;
 
 	if (reason != VCHI_CALLBACK_MSG_AVAILABLE)
 		return;
 
-	status = vchi_msg_dequeue(instance->service,
-				  &m, sizeof(m), &msg_len, VCHI_FLAGS_NONE);
+	status = vchi_msg_hold(instance->service, (void **)&m, &size,
+			       VCHI_FLAGS_NONE, &handle);
 	if (status)
 		return;
 
-	if (m.type == VC_AUDIO_MSG_TYPE_RESULT) {
-		instance->result = m.result.success;
+	if (m->type == VC_AUDIO_MSG_TYPE_RESULT) {
+		instance->result = m->result.success;
 		complete(&instance->msg_avail_comp);
-	} else if (m.type == VC_AUDIO_MSG_TYPE_COMPLETE) {
-		if (m.complete.cookie1 != VC_AUDIO_WRITE_COOKIE1 ||
-		    m.complete.cookie2 != VC_AUDIO_WRITE_COOKIE2)
+	} else if (m->type == VC_AUDIO_MSG_TYPE_COMPLETE) {
+		if (m->complete.cookie1 != VC_AUDIO_WRITE_COOKIE1 ||
+		    m->complete.cookie2 != VC_AUDIO_WRITE_COOKIE2)
 			dev_err(instance->dev, "invalid cookie\n");
 		else
 			bcm2835_playback_fifo(instance->alsa_stream,
-					      m.complete.count);
+					      m->complete.count);
 	} else {
-		dev_err(instance->dev, "unexpected callback type=%d\n", m.type);
+		dev_err(instance->dev, "unexpected callback type=%d\n", m->type);
 	}
+
+	vchi_held_msg_release(&handle);
 }
 
 static int