media: videobuf2-core: update vb2_thread if wait_finish/prepare are NULL

The vb2_thread is used for DVB support. This will queue and dequeue buffers
automatically.

It calls wait_finish/prepare around vb2_core_dqbuf() and vb2_core_qbuf(),
but that assumes all drivers have these ops set. But that will change
due to commit 8878598 ("media: vb2: use lock if wait_prepare/finish
are NULL").

So instead just check if the callback is available, and if not, use
q->lock, just as __vb2_wait_for_done_vb() does.

Signed-off-by: Hans Verkuil <hverkuil@xs4all.nl>
Reviewed-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>

drivers/media/common/videobuf2/videobuf2-core.c

@@ -3218,10 +3218,17 @@ static int vb2_thread(void *data)
 				continue;
 			prequeue--;
 		} else {
-			call_void_qop(q, wait_finish, q);
-			if (!threadio->stop)
+			if (!threadio->stop) {
+				if (q->ops->wait_finish)
+					call_void_qop(q, wait_finish, q);
+				else if (q->lock)
+					mutex_lock(q->lock);
 				ret = vb2_core_dqbuf(q, &index, NULL, 0);
-			call_void_qop(q, wait_prepare, q);
+				if (q->ops->wait_prepare)
+					call_void_qop(q, wait_prepare, q);
+				else if (q->lock)
+					mutex_unlock(q->lock);
+			}
 			dprintk(q, 5, "file io: vb2_dqbuf result: %d\n", ret);
 			if (!ret)
 				vb = vb2_get_buffer(q, index);
@@ -3233,12 +3240,19 @@ static int vb2_thread(void *data)
 		if (vb->state != VB2_BUF_STATE_ERROR)
 			if (threadio->fnc(vb, threadio->priv))
 				break;
-		call_void_qop(q, wait_finish, q);
 		if (copy_timestamp)
 			vb->timestamp = ktime_get_ns();
-		if (!threadio->stop)
+		if (!threadio->stop) {
+			if (q->ops->wait_finish)
+				call_void_qop(q, wait_finish, q);
+			else if (q->lock)
+				mutex_lock(q->lock);
 			ret = vb2_core_qbuf(q, vb, NULL, NULL);
-		call_void_qop(q, wait_prepare, q);
+			if (q->ops->wait_prepare)
+				call_void_qop(q, wait_prepare, q);
+			else if (q->lock)
+				mutex_unlock(q->lock);
+		}
 		if (ret || threadio->stop)
 			break;
 	}