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

Michael S. Tsirkin
2009-05-13T07:20:22Z

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;
}

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MST