remoteproc: Further extend the vdev life cycle

Tie the vdev (and hence vring) life cycle to the resource parsing and
resource cleanup operations, allowing us to safely register and
unregister virtio devices on the go.
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>

drivers/remoteproc/remoteproc_core.c

@@ -377,6 +377,9 @@ static int rproc_handle_vdev(struct rproc *rproc, struct fw_rsc_vdev *rsc,
 			goto unwind_vring_allocations;
 	}
 
+	/* track the rvdevs list reference */
+	kref_get(&rvdev->refcount);
+
 	list_add_tail(&rvdev->node, &rproc->rvdevs);
 
 	/* it is now safe to add the virtio device */
@@ -839,8 +842,10 @@ static void rproc_resource_cleanup(struct rproc *rproc)
 	}
 
 	/* clean up remote vdev entries */
-	list_for_each_entry_safe(rvdev, rvtmp, &rproc->rvdevs, node)
+	list_for_each_entry_safe(rvdev, rvtmp, &rproc->rvdevs, node) {
 		rproc_remove_virtio_dev(rvdev);
+		kref_put(&rvdev->refcount, rproc_vdev_release);
+	}
 }
 
 /*