Re: [RFC PATCH 16/27] virtio: Expose virtqueue_alloc_element

[Stefan Hajnoczi]

On Wed, Dec 09, 2020 at 07:46:49PM +0100, Eugenio Perez Martin wrote:
> On Tue, Dec 8, 2020 at 9:26 AM Stefan Hajnoczi <stefanha@gmail.com> wrote:
> >
> > On Fri, Nov 20, 2020 at 07:50:54PM +0100, Eugenio Pérez wrote:
> > > Specify VirtQueueElement * as return type makes no harm at this moment.
> >
> > The reason for the void * return type is that C implicitly converts void
> > pointers to pointers of any type. The function takes a size_t sz
> > argument so it can allocate a object of user-defined size. The idea is
> > that the user's struct embeds a VirtQueueElement field. Changing the
> > return type to VirtQueueElement * means that callers may need to
> > explicitly cast to the user's struct type.
> >
> > It's a question of coding style but I think the void * return type
> > communicates what is going on better than VirtQueueElement *.
> 
> Right, what I meant with that is that nobody uses that feature, but I
> just re-check and I saw that contrib/vhost-user-blk actually uses it
> (not checked for more uses). I think it is better just to drop this
> commit.

contrib/vhost-user-blk doesn't use hw/virtio/virtio.c. The code is
similar and copy-pasted, but you are free to change this file without
affecting vontrib/vhost-user-blk :).

I still think it's clearer to make it obvious that this function
allocates an object of generic type or at least the change is purely a
question of style and probably not worth making.

Stefan

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