On Fri, Nov 29, 2013 at 08:52:23PM +0100, Antonios Motakis wrote:
> diff --git a/hw/virtio/vhost-backend.c b/hw/virtio/vhost-backend.c
> index 05de174..80defe4 100644
> --- a/hw/virtio/vhost-backend.c
> +++ b/hw/virtio/vhost-backend.c
> @@ -25,9 +25,18 @@ static int vhost_kernel_call(struct vhost_dev *dev,
> unsigned long int request,
>
> int vhost_call(struct vhost_dev *dev, unsigned long int request, void *arg)
> {
> - int result;
> + int result = -1;
>
> - result = vhost_kernel_call(dev, request, arg);
> + switch (dev->backend_type) {
> + case VHOST_BACKEND_TYPE_KERNEL:
> + result = vhost_kernel_call(dev, request, arg);
> + break;
> + case VHOST_BACKEND_TYPE_USER:
> + fprintf(stderr, "vhost-user not implemented\n");
> + break;
> + default:
> + fprintf(stderr, "Unknown vhost backend type\n");
> + }
The switch statement approach gets messy fast when local variables are
needed inside some case labels. It also makes it hard to conditionally
compile features without using #ifdef.
Perhaps instead a VhostOps struct could be used:
/* Vhost backends implement this interface */
typedef struct {
int vhost_call(struct vhost_dev *dev,
unsigned long int request,
void *arg);
...
} VhostOps;
const VhostOps vhost_kernel_ops = {
...
};
const VhostOps vhost_user_opts = {
...
};
ret = dev->vhost_ops->vhost_call(dev, request, arg);
Something along those lines. It keeps the different backend
implementations separate (they can live in separate files and be
conditional in Makefile.objs).
