virtqueue_drain
while ((req = virtqueue_drain(vq, &last)) != NULL) {
while ((buf = virtqueue_drain(vq, &last)) != NULL)
while ((control = virtqueue_drain(vq, &last)) != NULL)
while ((m = virtqueue_drain(vq, &last)) != NULL) {
while ((txhdr = virtqueue_drain(vq, &last)) != NULL) {
while (virtqueue_drain(vq, &last) != NULL)
while ((req = virtqueue_drain(vq, &last)) != NULL)
void *virtqueue_drain(struct virtqueue *vq, int *last);