virtio: Formally reserve bits 28-31 to be 'transport' features.
We assign feature bits as required, but it makes sense to reserve some
for the particular transport, rather than the particular device.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
diff --git a/include/linux/virtio_config.h b/include/linux/virtio_config.h
index 7eb4b34..5a30cfb 100644
--- a/include/linux/virtio_config.h
+++ b/include/linux/virtio_config.h
@@ -18,6 +18,12 @@
/* We've given up on this device. */
#define VIRTIO_CONFIG_S_FAILED 0x80
+/* Some virtio feature bits (currently bits 28 through 31) are reserved for the
+ * transport being used (eg. virtio_ring), the rest are per-device feature
+ * bits. */
+#define VIRTIO_TRANSPORT_F_START 28
+#define VIRTIO_TRANSPORT_F_END 32
+
/* Do we get callbacks when the ring is completely used, even if we've
* suppressed them? */
#define VIRTIO_F_NOTIFY_ON_EMPTY 24