[resend/standalone PATCH v4] Add auxiliary bus support

[Jason Gunthorpe]

On Mon, Jan 04, 2021 at 07:12:47PM -0800, Dan Williams wrote:

> I get that, but I'm fearing a gigantic bus_ops structure that has
> narrow helpers like ->gpio_count() that mean nothing to the many other
> clients of the bus. Maybe I'm overestimating the pressure there will
> be to widen the ops structure at the bus level.

If we want a 'universal device' then that stuff must live
someplace.. Open coding the dispatch as is today is also not the end
of the world, just seeing that is just usually a sign something is not
ideal with the object model.

Jason