Re: [PATCH v3 1/2] vfio/pci: Have all VFIO PCI drivers store the vfio_pci_core_device in drvdata

[Jason Gunthorpe <jgg@nvidia.com>]

On Thu, May 05, 2022 at 12:54:09PM -0600, Alex Williamson wrote:
> > > I'd also rather see the variant driver fail to register with the core
> > > than to see a failure opening the device an arbitrary time later.  
> > 
> > It still permits a driver to be wrong, eg all the drivers are like
> > this today:
> > 
> > 	ret = vfio_pci_core_register_device(&hisi_acc_vdev->core_device);
> > 	if (ret)
> > 		goto out_free;
> > 	dev_set_drvdata(&pdev->dev, &hisi_acc_vdev->core_device);
> > 
> > So a WARN_ON inside register_device will not catch the mistake, as
> > this is the common pattern it isn't as helpful.
> 
> In the above case the WARN_ON would trigger because drvdata isn't set
> to the core device for the registration call.  Yes, a driver could
> still set drvdata after the registration call, but then they get to
> explain why they set drvdata twice and thought they could get away with
> changing it after the core made pretty clear that it wants a specific
> thing there.  Thanks,

I'm OK with this idea, it is not quite a nice to set the drvdata in
the middle of the probe function, but it does work here.

I'll fix it

Jason