Re: [PATCH vhost v9 3/6] virtio: find_vqs: pass struct instead of multi parameters

["Michael S. Tsirkin" <mst@redhat.com>]

On Thu, Jun 20, 2024 at 05:20:49PM +0800, Xuan Zhuo wrote:
> On Thu, 20 Jun 2024 05:14:24 -0400, "Michael S. Tsirkin" <mst@redhat.com> wrote:
> > On Thu, Jun 20, 2024 at 05:00:49PM +0800, Xuan Zhuo wrote:
> > > > > @@ -226,21 +248,37 @@ struct virtqueue *virtio_find_single_vq(struct virtio_device *vdev,
> > > > >
> > > > >  static inline
> > > > >  int virtio_find_vqs(struct virtio_device *vdev, unsigned nvqs,
> > > > > -			struct virtqueue *vqs[], vq_callback_t *callbacks[],
> > > > > -			const char * const names[],
> > > > > -			struct irq_affinity *desc)
> > > > > +		    struct virtqueue *vqs[], vq_callback_t *callbacks[],
> > > > > +		    const char * const names[],
> > > > > +		    struct irq_affinity *desc)
> > > > >  {
> > > > > -	return vdev->config->find_vqs(vdev, nvqs, vqs, callbacks, names, NULL, desc);
> > > > > +	struct virtio_vq_config cfg = {};
> > > > > +
> > > > > +	cfg.nvqs = nvqs;
> > > > > +	cfg.vqs = vqs;
> > > > > +	cfg.callbacks = callbacks;
> > > > > +	cfg.names = (const char **)names;
> > > >
> > > >
> > > > Casting const away? Not safe.
> > >
> > >
> > >
> > > Because the vp_modern_create_avq() use the "const char *names[]",
> > > and the virtio_uml.c changes the name in the subsequent commit, so
> > > change the "names" inside the virtio_vq_config from "const char *const
> > > *names" to "const char **names".
> >
> > I'm not sure I understand which commit you mean,
> > and this kind of change needs to be documented, but it does not matter.
> > Don't cast away const.
> 
> 
> Do you mean change the virtio_find_vqs(), from
> const char * const names[] to const char *names[].
> 
> And update the caller?
> 
> If we do not cast the const, we need to update all the caller to remove the
> const.
> 
> Right?
> 
> Thanks.


Just do not split the patchset at a boundary that makes you do that.
If you are passing in an array from a const section then it
has to be const and attempts to change it are a bad idea.


> >
> > --
> > MST
> >