On Mon, Jul 19, 2021 at 12:34 PM Viresh Kumar [off-list ref] wrote:

On 14-07-21, 23:07, Arnd Bergmann wrote:

quoted

On Wed, Jul 14, 2021 at 5:43 PM Rob Herring [off-list ref] wrote:

quoted

I guess it comes down to is 'virtio,mmio' providing a bus or is it
just a device? I guess a bus (so 2 nodes) does make sense here.
'virtio,mmio' defines how you access/discover the virtio queues (the
bus) and the functional device (i2c, gpio, iommu, etc.) is accessed
via the virtio queues.

It's not really a bus since there is only ever one device behind it.
A better analogy would be your 'serdev' framework: You could
have a 8250 or a pl011 uart, and behind that have a mouse, GPS
receiver or bluetooth dongle.

In Documentation/devicetree/bindings/serial/serial.yaml, you also
have two nodes for a single device, so we could follow that
example.

So two device nodes is final then ? Pretty much like how this patchset did it
already ? I need to get rid of reg thing and use "virtio,DID" though.

Let's give Rob another day to reply here. I think two nodes is easier
to get working than one node, even when we continue supporting the
current iommu binding that relies on a single node, but we could make
it work either way if necessary.

       Arnd