Re: [PATCH v4 00/17] Add VFIO mediated device support and DEV-MSI support for the idxd driver

[Dan Williams]

On Mon, Nov 2, 2020 at 10:26 AM Jason Gunthorpe <jgg@xxxxxxxxxx> wrote:
>
> On Mon, Nov 02, 2020 at 11:18:33AM -0700, Dave Jiang wrote:
> >
> >
> > On 11/2/2020 10:19 AM, Jason Gunthorpe wrote:
> > > On Mon, Nov 02, 2020 at 08:20:43AM -0800, Raj, Ashok wrote:
> > > > Creating these private interfaces for intra-module are just 1-1 and not
> > > > general purpose and every accelerator needs to create these instances.
> > >
> > > This is where we are going, auxillary bus should be merged soon which
> > > is specifically to connect these kinds of devices across subsystems
> >
> > I think this resolves the aux device probe/remove issue via a common bus.
> > But it does not help with the mdev device needing a lot of the device
> > handling calls from the parent driver as it share the same handling as the
> > parent device.
>
> The intention of auxiliary bus is that the two parts will tightly
> couple across some exported function interface.
>
> > My plan is to export all the needed call via EXPORT_SYMBOL_NS() so
> > the calls can be shared in its own namespace between the modules. Do
> > you have any objection with that?
>
> I think you will be the first to use the namespace stuff for this, it
> seems like a good idea and others should probably do so as well.

I was thinking either EXPORT_SYMBOL_NS, or auxiliary bus, because you
should be able to export an ops structure with all the necessary
callbacks. Aux bus seems cleaner because the lifetime rules and
ownership concerns are clearer.