virtio_pci_modern: support devices with no config

Virtio 1.0 spec lists device config as optional.
Set get/set callbacks to NULL. Drivers can check that
and fail gracefully.

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

diff --git a/drivers/virtio/virtio_pci_modern.c b/drivers/virtio/virtio_pci_modern.c
index 0e54cc8..68ebc20 100644 (file)
--- a/drivers/virtio/virtio_pci_modern.c
+++ b/drivers/virtio/virtio_pci_modern.c
@@ -422,6 +422,21 @@ static void del_vq(struct virtio_pci_vq_info *info)
        free_pages_exact(info->queue, vring_pci_size(info->num));
 }
 
+static const struct virtio_config_ops virtio_pci_config_nodev_ops = {
+       .get            = NULL,
+       .set            = NULL,
+       .generation     = vp_generation,
+       .get_status     = vp_get_status,
+       .set_status     = vp_set_status,
+       .reset          = vp_reset,
+       .find_vqs       = vp_modern_find_vqs,
+       .del_vqs        = vp_del_vqs,
+       .get_features   = vp_get_features,
+       .finalize_features = vp_finalize_features,
+       .bus_name       = vp_bus_name,
+       .set_vq_affinity = vp_set_vq_affinity,
+};
+
 static const struct virtio_config_ops virtio_pci_config_ops = {
        .get            = vp_get,
        .set            = vp_set,
@@ -652,9 +667,11 @@ int virtio_pci_modern_probe(struct virtio_pci_device *vp_dev)
                                                &vp_dev->device_len);
                if (!vp_dev->device)
                        goto err_map_device;
-       }
 
-       vp_dev->vdev.config = &virtio_pci_config_ops;
+               vp_dev->vdev.config = &virtio_pci_config_ops;
+       } else {
+               vp_dev->vdev.config = &virtio_pci_config_nodev_ops;
+       }
 
        vp_dev->config_vector = vp_config_vector;
        vp_dev->setup_vq = setup_vq;