Re: [PATCH v5 1/5] dt-bindings: remoteproc: imx_rproc: Add "rpmsg" subnode support

[Shenwei Wang]

> -----Original Message-----
> From: Rob Herring <robh@xxxxxxxxxx>
> Sent: Wednesday, November 12, 2025 6:53 AM
> To: Shenwei Wang <shenwei.wang@xxxxxxx>
> Cc: Bjorn Andersson <andersson@xxxxxxxxxx>; Mathieu Poirier
> <mathieu.poirier@xxxxxxxxxx>; Krzysztof Kozlowski <krzk+dt@xxxxxxxxxx>; Conor
> Dooley <conor+dt@xxxxxxxxxx>; Shawn Guo <shawnguo@xxxxxxxxxx>; Sascha
> Hauer <s.hauer@xxxxxxxxxxxxxx>; Jonathan Corbet <corbet@xxxxxxx>; Linus
> Walleij <linus.walleij@xxxxxxxxxx>; Bartosz Golaszewski <brgl@xxxxxxxx>;
> Pengutronix Kernel Team <kernel@xxxxxxxxxxxxxx>; Fabio Estevam
> <festevam@xxxxxxxxx>; Peng Fan <peng.fan@xxxxxxx>; linux-
> remoteproc@xxxxxxxxxxxxxxx; devicetree@xxxxxxxxxxxxxxx; imx@xxxxxxxxxxxxxxx;
> linux-arm-kernel@xxxxxxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; linux-
> doc@xxxxxxxxxxxxxxx; dl-linux-imx <linux-imx@xxxxxxx>
> Subject: [EXT] Re: [PATCH v5 1/5] dt-bindings: remoteproc: imx_rproc: Add
> "rpmsg" subnode support
> > +        patternProperties:
> > +          "gpio@[0-9a-f]+$":
> > +            type: object
> > +            unevaluatedProperties: false
> > +            properties:
> > +              compatible:
> > +                enum:
> > +                  - fsl,imx-rpmsg-gpio
> > +
> > +              reg:
> > +                maxItems: 1
> 
> I still don't understand what the numbers for 'reg' mean here. You explained it
> and I still don't understand. In any case, it needs to be explained in the schema.
> 
> For example, why do GPIO and I2C each have their own number space?
> 

Hi Rob,

The reg property represents the index of the GPIO controllers. Since the driver manages controllers 
on a remote system, this index tells the remote system which controller to operate.

For example, if the remote system has four GPIO controllers but only allocates two (indices 0 and 2) 
to Linux, the DTS might look like this:

          gpio@0 {
            compatible = "fsl,imx-rpmsg-gpio";
            reg = <0>;
          };

          gpio@2 {
            compatible = "fsl,imx-rpmsg-gpio";
            reg = <2>;
          }

Similarly, I²C numbers are mapped to their corresponding remote controllers in the same way. That's why
each has their own number space.

Thanks,
Shenwei

> > +
> > +              "#gpio-cells":
> > +                const: 2
> > +
> > +              gpio-controller: true