Re: [RFC PATCH 1/2] vfio-mdev: Wire in a request handler for mdev parent

[Cornelia Huck <cohuck@redhat.com>]

On Thu, 19 Nov 2020 16:56:11 +0100
Halil Pasic <pasic@linux.ibm.com> wrote:

> On Thu, 19 Nov 2020 12:30:26 +0100
> Cornelia Huck <cohuck@redhat.com> wrote:
> 
> > > +static void vfio_mdev_request(void *device_data, unsigned int count)
> > > +{
> > > +	struct mdev_device *mdev = device_data;
> > > +	struct mdev_parent *parent = mdev->parent;
> > > +
> > > +	if (unlikely(!parent->ops->request))    
> > 
> > Hm. Do you think that all drivers should implement a ->request()
> > callback?  
> 
> @Tony: What do you think, does vfio_ap need something like this?
> 
> BTW how is this supposed to work in a setup where the one parent
> has may children (like vfio_ap or the gpu slice and dice usecases).

I'd think that the driver would either keep some kind of reference
counting (do something when the last child is gone), notifies all
other children as well, or leaves the decision to userspace. Probably
highly depends on the driver.

> 
> After giving this some thought I'm under the impression, I don't
> get the full picture yet.
> 
> Regards,
> Halil
>