[media] soc-camera: make .clock_{start,stop} compulsory, .add / .remove optional

All existing soc-camera host drivers use .clock_start() and .clock_stop()
callbacks to activate and deactivate their camera interfaces, whereas
.add() and .remove() callbacks are usually dummy. Make the former two
compulsory and the latter two optional.
Signed-off-by: Guennadi Liakhovetski <g.liakhovetski@gmx.de>
Acked-by: Hans Verkuil <hans.verkuil@cisco.com>
Acked-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

drivers/media/platform/soc_camera/soc_camera.c

@@ -512,22 +512,21 @@ static int soc_camera_add_device(struct soc_camera_device *icd)
 	if (ici->icd)
 		return -EBUSY;
 
-	if (ici->ops->clock_start) {
 	ret = ici->ops->clock_start(ici);
 	if (ret < 0)
 		return ret;
-	}
 
+	if (ici->ops->add) {
 		ret = ici->ops->add(icd);
 		if (ret < 0)
 			goto eadd;
+	}
 
 	ici->icd = icd;
 
 	return 0;
 
 eadd:
-	if (ici->ops->clock_stop)
 	ici->ops->clock_stop(ici);
 	return ret;
 }
@@ -539,8 +538,8 @@ static void soc_camera_remove_device(struct soc_camera_device *icd)
 	if (WARN_ON(icd != ici->icd))
 		return;
 
+	if (ici->ops->remove)
 		ici->ops->remove(icd);
-	if (ici->ops->clock_stop)
 	ici->ops->clock_stop(ici);
 	ici->icd = NULL;
 }
@@ -1383,8 +1382,8 @@ int soc_camera_host_register(struct soc_camera_host *ici)
 	    ((!ici->ops->init_videobuf ||
 	      !ici->ops->reqbufs) &&
 	     !ici->ops->init_videobuf2) ||
-	    !ici->ops->add ||
-	    !ici->ops->remove ||
+	    !ici->ops->clock_start ||
+	    !ici->ops->clock_stop ||
 	    !ici->ops->poll ||
 	    !ici->v4l2_dev.dev)
 		return -EINVAL;