Re: [PATCH RFC 08/12] dt-bindings: remoteproc: add remoteproc-virtio

[Francesco Valla <francesco@valla.it>]

Hello Rob,

On Wed, Oct 07, 2026 at 08:42:06AM -0500, Rob Herring wrote:
> On Tue, Oct 06, 2026 at 06:51:52PM -0600, Mathieu Poirier wrote:
> > On Tue, 6 Oct 2026 at 12:39, Rob Herring <robh@kernel.org> wrote:
> > >
> > > On Tue, Sep 22, 2026 at 09:44:20PM +0200, Francesco Valla wrote:
> > > > On Tue, Sep 22, 2026 at 09:40:31AM -0600, Mathieu Poirier wrote:
> > > > > On Wed, Sep 16, 2026 at 11:10:53PM +0200, Francesco Valla wrote:
> > > > > > Add a new binding to describe remoteproc-provided virtio devices; while
> > > > > > these are discovered through a resource table parsed by the remoteproc
> > > > > > infrastructure at runtime, their description can be needed to probe
> > > > > > non-discoverable buses (such as I2C) or to link consumers and suppliers.
> > > > > >
> > > > > > Each vdev is described by a dedicated "group" node, which then includes
> > > > > > a virtio-device node, which binding is already existent and used by
> > > > > > virtio-mmio. Each vdev shall be stattically linked to a "group" node
> > > > > > using its index inside the resource table as the reg property of the
> > > > > > node; this permits to have multiple instances of the same type of
> > > > > > device.
> > > > > >
> > > > > > The binding is intended to be generic and adopted by any remoteproc
> > > > > > provider.
> > > > > >
> > > > > > Signed-off-by: Francesco Valla <francesco@valla.it>
> > > > > > ---
> > > > > >  .../bindings/remoteproc/remoteproc-virtio.yaml     | 89 ++++++++++++++++++++++
> > > > > >  1 file changed, 89 insertions(+)
> > > > > >
> > > > > > diff --git a/Documentation/devicetree/bindings/remoteproc/remoteproc-virtio.yaml b/Documentation/devicetree/bindings/remoteproc/remoteproc-virtio.yaml
> > > > > > new file mode 100644
> > > > > > index 000000000000..c4a0d84b1460
> > > > > > --- /dev/null
> > > > > > +++ b/Documentation/devicetree/bindings/remoteproc/remoteproc-virtio.yaml
> > > > > > @@ -0,0 +1,89 @@
> > > > > > +# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
> > > > > > +%YAML 1.2
> > > > > > +---
> > > > > > +$id: http://devicetree.org/schemas/remoteproc/remoteproc-virtio.yaml#
> > > > > > +$schema: http://devicetree.org/meta-schemas/core.yaml#
> > > > > > +
> > > > > > +title: Virtio devices over remoteproc
> > > > > > +
> > > > > > +description: |
> > > > > > +  Virtio devices ("vdevs") can be exposed using the remoteproc infrastructure
> > > > > > +  and its resource table. For some of them, a device tree node might be needed
> > > > > > +  to describe remote undiscoverable hardware and/or connect consumers and
> > > > > > +  providers.
> > > > > > +
> > > > > > +maintainers:
> > > > > > +  - Francesco Valla <francesco@valla.it>
> > > > > > +
> > > > > > +properties:
> > > > > > +  virtio:
> > > > > > +    description: Contains a group of Virtio devices exposed by the remoteproc.
> > > > > > +
> > > > > > +    properties:
> > > > > > +      '#address-cells':
> > > > > > +        const: 1
> > > > > > +
> > > > > > +      '#size-cells':
> > > > > > +        const: 0
> > > > > > +
> > > > > > +    patternProperties:
> > > > > > +      "^vdev@[0-9a-f]+$":
> > > > > > +        type: object
> > > > > > +
> > > > > > +        properties:
> > > > > > +          reg:
> > > > > > +            description: Virtio device index inside the resource table.
> > >
> > 
> > There are 2 configurations we need to account for: (1) each device
> > located behind the remote processor gets its own set of virtqueues and
> > adheres to the virtio specifications.  This is the configuration
> > targeted by this thread.  The other configuration (2), discussed in
> > the other thread, involves virtio piggy-backed over RPMSG.  The hope
> > is to represent both configurations using the same bindings.  For (1),
> > virtio devices will be advertised in the resource table and for (2),
> > virtio devices will be announced via the existing remoteproc namespace
> > service.
> > 
> > > Who/what defines the resource table?
> > 
> > The resource table is part of the firmware image and is parsed by the
> > remoteproc core.  For (1), as presented in this set, "reg" links the
> > entry in the resource table with the device definition in the DT.  For
> > (2), the definition is also a device index, but said index is
> > communicated to the remoteproc core using a namespace announcement
> > rather than the resource table.
> > 
> > I hope to establish bindings for configuration (1) and merge that work
> > first.  Once that is done we can extend it to cover (2).
> 
> "Defined by firmware" is all I needed. Please make sure the binding 
> patches include this information or I'll forget and just ask again.
>

I'll include this detail in the next version of the bindings; I'm always
working on .rst documentation to add to the next version of the patchset.

> Rob

Regards,
Francesco