Re: [PATCH 1/3] virtio: find_vqs/del_vqs virtio operations

["Michael S. Tsirkin" <mst@redhat.com>]

On Wed, May 13, 2009 at 10:47:08AM +0930, Rusty Russell wrote:
> On Wed, 13 May 2009 01:03:30 am Michael S. Tsirkin wrote:
> > On Wed, May 13, 2009 at 12:00:02AM +0930, Rusty Russell wrote
> > > and perhaps consider
> > > varargs for the callbacks (or would that be too horrible at the
> > > implementation end?)
> > >
> > > Thanks,
> > > Rusty.
> >
> > Ugh ... I think it will be. And AFAIK gcc generates a lot of code
> > for varargs - not something we want to do in each interrupt handler.
> 
> Err, no I mean for find_vqs:  eg.
> 	(block device)
> 	err = vdev->config->find_vqs(vdev, 1, &vblk->vq, blk_done);
> 
> 	(net device)
> 	err = vdev->config->find_vqs(vdev, 3, vqs, skb_recv_done, skb_xmit_done, NULL);
> 
> A bit neater for for the single-queue case.
> 
> Cheers,
> Rusty.

Oh. I see. But it becomes messy now that we also need to pass in the
names, and we lose type safety.
Let's just add a helper function for the single vq case?

static inline struct virtqueue *virtio_find_vq(struct virtio_devide *vdev,
					       vq_callback_t *c, const char *n)
{
	vq_callback_t *callbacks[] = { c };
	const char *names[] = { n };
	struct virtqueue *vq;
	int err = vdev->config->find_vqs(vdev, 1, &vq, callbacks, names);
	if (err < 0)
		return ERR_PTR(err);
	return vq;
}


-- 
MST