linux-kernel - Re: [PATCH v5 1/5] dt-bindings: remoteproc: imx

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Message-ID:
 <PAXPR04MB918521F7ABFB880CD1F6B1F889CCA@PAXPR04MB9185.eurprd04.prod.outlook.com>
Date: Wed, 12 Nov 2025 15:36:19 +0000
From: Shenwei Wang <shenwei.wang@....com>
To: Rob Herring <robh@...nel.org>
CC: Bjorn Andersson <andersson@...nel.org>, Mathieu Poirier
	<mathieu.poirier@...aro.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor
 Dooley <conor+dt@...nel.org>, Shawn Guo <shawnguo@...nel.org>, Sascha Hauer
	<s.hauer@...gutronix.de>, Jonathan Corbet <corbet@....net>, Linus Walleij
	<linus.walleij@...aro.org>, Bartosz Golaszewski <brgl@...ev.pl>, Pengutronix
 Kernel Team <kernel@...gutronix.de>, Fabio Estevam <festevam@...il.com>, Peng
 Fan <peng.fan@....com>, "linux-remoteproc@...r.kernel.org"
	<linux-remoteproc@...r.kernel.org>, "devicetree@...r.kernel.org"
	<devicetree@...r.kernel.org>, "imx@...ts.linux.dev" <imx@...ts.linux.dev>,
	"linux-arm-kernel@...ts.infradead.org"
	<linux-arm-kernel@...ts.infradead.org>, "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>, "linux-doc@...r.kernel.org"
	<linux-doc@...r.kernel.org>, dl-linux-imx <linux-imx@....com>
Subject: Re: [PATCH v5 1/5] dt-bindings: remoteproc: imx_rproc: Add "rpmsg"
 subnode support



> -----Original Message-----
> From: Rob Herring <robh@...nel.org>
> Sent: Wednesday, November 12, 2025 6:53 AM
> To: Shenwei Wang <shenwei.wang@....com>
> Cc: Bjorn Andersson <andersson@...nel.org>; Mathieu Poirier
> <mathieu.poirier@...aro.org>; Krzysztof Kozlowski <krzk+dt@...nel.org>; Conor
> Dooley <conor+dt@...nel.org>; Shawn Guo <shawnguo@...nel.org>; Sascha
> Hauer <s.hauer@...gutronix.de>; Jonathan Corbet <corbet@....net>; Linus
> Walleij <linus.walleij@...aro.org>; Bartosz Golaszewski <brgl@...ev.pl>;
> Pengutronix Kernel Team <kernel@...gutronix.de>; Fabio Estevam
> <festevam@...il.com>; Peng Fan <peng.fan@....com>; linux-
> remoteproc@...r.kernel.org; devicetree@...r.kernel.org; imx@...ts.linux.dev;
> linux-arm-kernel@...ts.infradead.org; linux-kernel@...r.kernel.org; linux-
> doc@...r.kernel.org; dl-linux-imx <linux-imx@....com>
> 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