Re: [RFC PATCH 0/6] virtio: Add support for Virtio message transport

[Viresh Kumar]

Hi Rob,

On 30-07-25, 08:39, Rob Herring wrote:
> On Wed, Jul 30, 2025 at 4:29 AM Viresh Kumar <viresh.kumar@xxxxxxxxxx> wrote:
> > ### Memory Mapping and Reserved Memory Usage
> >
> > The first two patches enhance the reserved-memory subsystem to support attaching
> > struct device`s that do not originate from DT nodes — essential for virtual or
> > dynamically discovered devices like the FF-A or loopback buses.
> 
> We support creating devices from reserved-memory nodes.

I didn't know about this.

> Just add a
> compatible which you should do anyways because node names are not
> supposed to be that specific or an ABI.

Yeah, I already knew that the node-names thing isn't going to fly as
you and Krzysztof rightly pointed out. I just wanted inputs from you
guys and so did that as a first implementation to get the discussion
started.

I tried something like this now:

      reserved-memory {
        #address-cells = <2>;
        #size-cells   = <2>;
        ranges;

        rmem@100000000 {
          compatible = "restricted-dma-pool", "virtio-msg,loopback";
          reg = <0x00000001 0x00000000  0x0 0x00400000>; /* 4 MiB */
        };
      };

and this works fine. I am adding two compatibles for virtio-msg:
"virtio-msg,loopback" and "virtio-msg,ffa". Yes I will properly
document them in the next version.

With this, we don't need the 2nd patch anymore:
  of: reserved-memory: Add of_reserved_mem_lookup_by_name

but still need the 1st one:
  of: reserved-memory: Add reserved_mem_device_init()

Thanks.

-- 
viresh