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

[Francesco Valla <francesco@valla.it>]

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.
> > +            maxItems: 1
> > +
> > +        additionalProperties:
> > +          type: object
> > +          $ref: /schemas/virtio/virtio-device.yaml
> > +          maxItems: 1
> > +
> > +        required:
> > +          - reg
> > +
> > +    additionalProperties: false
> > +
> > +    required:
> > +      - '#address-cells'
> > +      - '#size-cells'
> > +
> > +additionalProperties: true
> > +
> > +examples:
> > +  - |
> > +    remoteproc-cm33 {
> > +      virtio {
> > +          #address-cells = <1>;
> > +          #size-cells = <0>;
> > +
> > +          vdev@0 {
> > +              reg = <0>;
> > +
> 
> Do we need the 'reg' since we already have vdev@X?  I'll let the DT people
> provide their input on this.
>

AFAIK yes, because the rproc_get_vdev_fwnode() helpers search for indexed
child nodes using the 'reg' property, not the node name. This I believe
is the preferred way of doing things.

> > +              gpio {
> > +                  compatible = "virtio,device29";
> > +
> > +                  gpio-controller;
> > +                  #gpio-cells = <2>;
> > +              };
> > +          };
> > +
> > +          vdev@1 {
> > +              reg = <1>;
> > +
> > +              i2c {
> > +                  compatible = "virtio,device22";
> > +
> > +                  #address-cells = <1>;
> > +                  #size-cells = <0>;
> > +
> > +                  eeprom@50 {
> > +                      compatible = "atmel,24c1025";
> > +                      reg = <0x50>;
> > +                  };
> 
> The previous patch introduced bindings for virtio SPI while the above two are
> for GPIO and I2c, which is very confusing.  I suggest you pick one and apply
> everywhere.
>

This is because both GPIO and I2C bindings are already defined - even if
not used in the devicetree files part of the kernel tree.

Moving forward, I plan to submit at least the spi-virtio bindings as a
separate patch set, as they can be used independently of this one.

> > +              };
> > +          };
> > +      };
> > +    };
> > +...
> > 
> > -- 
> > 2.55.0
> >

Regards,
Francesco