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

Avi Kivity
2009-05-13T07:28:02Z

Michael S. Tsirkin wrote:
> 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;
> }
>

Much saner.

--
Do not meddle in the internals of kernels, for they are subtle and quick to panic.