virtio: feature bit manipulation helpers

Add virtio_{add,clear}_feature helper functions for manipulating a
feature bits variable. This has some benefits over open coding:
- add check that the bit is in a sane range
- make it obvious at a glance what is going on
- have a central point to change when we want to extend feature bits

Convert existing code manipulating features to use the new helpers.

Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

1 files changed, 12 insertions, 0 deletions

diff --git a/include/hw/virtio/virtio.h b/include/hw/virtio/virtio.h
index d1b416b..85e72d6 100644
--- a/include/hw/virtio/virtio.h
+++ b/include/hw/virtio/virtio.h
@@ -219,6 +219,18 @@ void virtio_queue_set_host_notifier_fd_handler(VirtQueue *vq, bool assign,
 void virtio_queue_notify_vq(VirtQueue *vq);
 void virtio_irq(VirtQueue *vq);
 
+static inline void virtio_add_feature(uint32_t *features, unsigned int fbit)
+{
+    assert(fbit < 32);
+    *features |= (1 << fbit);
+}
+
+static inline void virtio_clear_feature(uint32_t *features, unsigned int fbit)
+{
+    assert(fbit < 32);
+    *features &= ~(1 << fbit);
+}
+
 static inline bool virtio_is_big_endian(VirtIODevice *vdev)
 {
     assert(vdev->device_endian != VIRTIO_DEVICE_ENDIAN_UNKNOWN);