On Tue, Mar 09, 2021 at 05:38:44PM -0400, Jason Gunthorpe wrote:

The pattern also makes it clear that vfio_register_group_dev() must be
last in the sequence, as once it is called the core code can immediately
start calling ops. The init/register gap is provided to allow for the
driver to do setup before ops can be called and thus avoid races.

Yes, APIs that init and register together are generatelly a rather
bad idea.

Reviewed-by: Christoph Hellwig <hch@lst.de>