From mboxrd@z Thu Jan  1 00:00:00 1970
From: Avi Kivity <avi@redhat.com>
Subject: Re: [PATCH 1/3] virtio: find_vqs/del_vqs virtio operations
Date: Wed, 13 May 2009 10:26:45 +0300
Message-ID: <4A0A7635.6090107@redhat.com>
References: <cover.1242080138.git.mst@redhat.com> <200905130000.03032.rusty@rustcorp.com.au> <20090512153330.GB26883@redhat.com> <200905131047.09416.rusty@rustcorp.com.au> <20090513071834.GC31139@redhat.com>
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Cc: Rusty Russell <rusty@rustcorp.com.au>,
	Christian Borntraeger <borntraeger@de.ibm.com>,
	virtualization@lists.linux-foundation.org,
	Anthony Liguori <anthony@codemonkey.ws>, kvm@vger.kernel.org,
	Carsten Otte <cotte@de.ibm.com>
To: "Michael S. Tsirkin" <mst@redhat.com>
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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.