[RFC v2 6/9] virtio-bus: introduce queue_enabled method

[Cindy Lu <lulu@redhat.com>]

From: Jason Wang <jasowang@redhat.com>

This patch introduces queue_enabled() method which allows the
transport to implement its own way to report whether or not a queue is
enabled.

Signed-off-by: Jason Wang <jasowang@redhat.com>
---
 hw/virtio/virtio.c             | 6 ++++++
 include/hw/virtio/virtio-bus.h | 4 ++++
 2 files changed, 10 insertions(+)

diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
index 04716b5f6c..09732a8836 100644
--- a/hw/virtio/virtio.c
+++ b/hw/virtio/virtio.c
@@ -3169,6 +3169,12 @@ hwaddr virtio_queue_get_desc_addr(VirtIODevice *vdev, int n)
 
 bool virtio_queue_enabled(VirtIODevice *vdev, int n)
 {
+    BusState *qbus = qdev_get_parent_bus(DEVICE(vdev));
+    VirtioBusClass *k = VIRTIO_BUS_GET_CLASS(qbus);
+
+    if (k->queue_enabled)
+        return k->queue_enabled(qbus->parent, n);
+
     return virtio_queue_get_desc_addr(vdev, n) != 0;
 }
 
diff --git a/include/hw/virtio/virtio-bus.h b/include/hw/virtio/virtio-bus.h
index 38c9399cd4..0f6f215925 100644
--- a/include/hw/virtio/virtio-bus.h
+++ b/include/hw/virtio/virtio-bus.h
@@ -83,6 +83,10 @@ typedef struct VirtioBusClass {
      */
     int (*ioeventfd_assign)(DeviceState *d, EventNotifier *notifier,
                             int n, bool assign);
+    /*
+     * Whether queue number n is enabled.
+     */
+    bool (*queue_enabled)(DeviceState *d, int n);
     /*
      * Does the transport have variable vring alignment?
      * (ie can it ever call virtio_queue_set_align()?)
-- 
2.21.1