Re: [PATCH v8 3/4] gpio: rpmsg: add generic rpmsg GPIO driver

[Mathieu Poirier]

On Tue, 24 Feb 2026 at 15:32, Shenwei Wang <shenwei.wang@xxxxxxx> wrote:
>
>
>
> > -----Original Message-----
> > From: Andrew Lunn <andrew@xxxxxxx>
> > Sent: Tuesday, February 24, 2026 4:23 PM
> > To: Shenwei Wang <shenwei.wang@xxxxxxx>
> > Cc: Arnaud POULIQUEN <arnaud.pouliquen@xxxxxxxxxxx>; Linus Walleij
> > <linusw@xxxxxxxxxx>; Bartosz Golaszewski <brgl@xxxxxxxxxx>; Jonathan Corbet
> > <corbet@xxxxxxx>; Rob Herring <robh@xxxxxxxxxx>; Krzysztof Kozlowski
> > <krzk+dt@xxxxxxxxxx>; Conor Dooley <conor+dt@xxxxxxxxxx>; Bjorn Andersson
> > <andersson@xxxxxxxxxx>; Mathieu Poirier <mathieu.poirier@xxxxxxxxxx>; Frank Li
> > <frank.li@xxxxxxx>; Sascha Hauer <s.hauer@xxxxxxxxxxxxxx>; Shuah Khan
> > <skhan@xxxxxxxxxxxxxxxxxxx>; linux-gpio@xxxxxxxxxxxxxxx; linux-
> > doc@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; Pengutronix Kernel Team
> > <kernel@xxxxxxxxxxxxxx>; Fabio Estevam <festevam@xxxxxxxxx>; Peng Fan
> > <peng.fan@xxxxxxx>; devicetree@xxxxxxxxxxxxxxx; linux-
> > remoteproc@xxxxxxxxxxxxxxx; imx@xxxxxxxxxxxxxxx; linux-arm-
> > kernel@xxxxxxxxxxxxxxxxxxx; dl-linux-imx <linux-imx@xxxxxxx>; Bartosz
> > Golaszewski <brgl@xxxxxxxx>
> > Subject: Re: [EXT] Re: [PATCH v8 3/4] gpio: rpmsg: add generic rpmsg GPIO driver
> >
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> >
> >
> > > > > + remote_cm33{
> > > > > +     rpmsg {
> > > > > +        rpmsg-io-channel {
> > > > > +          #address-cells = <1>;
> > > > > +          #size-cells = <0>;
> > > > > +
> > > > > +          gpio@0 {
> > > > > +            compatible = "rpmsg-gpio";
> > > > > +            reg = <0>;
> > > > > +            gpio-controller;
> > > > > +            #gpio-cells = <2>;
> > > > > +            #interrupt-cells = <2>;
> > > > > +            interrupt-controller;
> > > > > +          };
> > > > > +          gpio@1 {
> > > > > +            compatible = "rpmsg-gpio";
> > > > > +            reg = <1>;
> > > > > +            gpio-controller;
> > > > > +            #gpio-cells = <2>;
> > > > > +            #interrupt-cells = <2>;
> > > > > +            interrupt-controller;
> > > > > +          };
> >
> > > Then how would you distinguish gpio@0 from gpio@1 on the CM33 RPMSG bus
> > in the example above?
> > > They are running on the same transport.
> >
> > Doesn't reg indicate the channel number? gpio@0 is on rpmsg channel 0. gpio@1
> > is on channel 1? The reg value gets filled into struct rpmsg_channel_info when
> > the endpoints are created?
>
> There is only a single RPMSG channel for the CM33 remoteproc in this example-its name
> is "rpmsg-io-channel". As I mentioned above, both gpio@0 and gpio@1 run over this same transport.
> The transport here is the RPMSG channel, so multiple GPIO controllers share that channel.
>

That is one of my main problem with this proposal - multiplexing
several GPIO controllers over the same RPMSG channel adds complexity.
RPMSG can already handle multiplexing via channels, use one RPMSG
channel per GPIO controller.

> Thanks,
> Shenwei
>
> >
> >    Andrew
>