[PATCH] mmc: core: Initial support for SD express card/host

[Christoph Hellwig]

On Fri, Jul 24, 2020 at 03:35:47PM +0200, Arnd Bergmann wrote:
> Starting simple is generally a good idea, yes.
> 
> It would be good to have feedback from the nvme driver maintainers.
> 
> One way I can see the handshake working would be to have
> an sdexpress class_driver that provides interfaces for both mmc
> and nvme to link against. The mmc core can then create a
> class device when it finds an sd-express device and that
> class device contains a simple state machine that keeps track of
> what either side think is going on, possibly also providing
> a way to perform callbacks between the two sides.

None of this is in scope for the NVMe spec, so I don't really want
to deal with it in the NVMe driver in any way.  Given that a SD
express card just turns into a normal PCIe link if you really want
to check that something probed I think you'd want to track if any
PCIe driver is bound to the device.  Or just wait and see if we really
need anything after all.