On Friday 30 January 2009 09:35:07 Alex Williamson wrote:

+static bool virtnet_send_command(struct virtnet_info *vi, u8 class, u8 cmd,
+				 void *data, unsigned int len)
+{
+	struct scatterlist sg[3];
+	struct virtio_net_ctrl_hdr ctrl;
+	virtio_net_ctrl_ack status;
+	unsigned int tmp;
+	int i = 0;
+
+	if (!virtio_has_feature(vi->vdev, VIRTIO_NET_F_CTRL_VQ))
+		return false;
+
+	sg_init_table(sg, len ? 3 : 2);

I'd test data rather than len here.

+	sg_set_buf(&sg[i++], &ctrl, sizeof(ctrl));
+	if (len)
+		sg_set_buf(&sg[i++], data, len);
+	sg_set_buf(&sg[i], &status, sizeof(status));
+
+	ctrl.class = class;
+	ctrl.cmd = cmd;
+
+	status = ~0;
+
+	if (vi->cvq->vq_ops->add_buf(vi->cvq, sg, i, 1, vi) != 0)
+		BUG();

Hmm, I prefer initialize buffer, then set sg to refer to it.  Seems to make
more sense to me.

+	while (!vi->cvq->vq_ops->get_buf(vi->cvq, &tmp))
+		cpu_relax();

This probably deserves a comment about why it's OK to spin here.

+	return status == VIRTIO_NET_OK ? true : false;

Or "return status == VIRTIO_NET_OK;" ?

See what I mean about nit-picking?
Rusty.