Re: [PATCH 02/10] vfio: Split creation of a vfio_device into init and register ops

[Jason Gunthorpe <jgg@nvidia.com>]

On Fri, Mar 12, 2021 at 01:04:29PM +0000, Liu, Yi L wrote:
> Hi Jason,
> 
> > From: Jason Gunthorpe <jgg@nvidia.com>
> > Sent: Wednesday, March 10, 2021 5:39 AM
> > 
> [...]
> > diff --git a/include/linux/vfio.h b/include/linux/vfio.h
> > index b7e18bde5aa8b3..ad8b579d67d34a 100644
> > +++ b/include/linux/vfio.h
> > @@ -15,6 +15,18 @@
> >  #include <linux/poll.h>
> >  #include <uapi/linux/vfio.h>
> > 
> > +struct vfio_device {
> > +	struct device *dev;
> > +	const struct vfio_device_ops *ops;
> > +	struct vfio_group *group;
> > +
> > +	/* Members below here are private, not for driver use */
> > +	refcount_t refcount;
> > +	struct completion comp;
> > +	struct list_head group_next;
> > +	void *device_data;
> 
> A dumb question. If these fields are not supposed to be used by
> "external modules" like vfio_pci driver, how about defining a private
> struct vfio_dev_prive within vfio.c and embed here?

This is rarely done, there should be a good reason to do it, as making
a private structure in a container_of system requires another memory
allocation.

'struct device' has this for instance, look at the 'p' member.

In this case I can't see much value

Jason