[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 at nxp.com> wrote:
>
>
>
> > -----Original Message-----
> > From: Andrew Lunn <andrew at lunn.ch>
> > Sent: Tuesday, February 24, 2026 4:23 PM
> > To: Shenwei Wang <shenwei.wang at nxp.com>
> > Cc: Arnaud POULIQUEN <arnaud.pouliquen at foss.st.com>; Linus Walleij
> > <linusw at kernel.org>; Bartosz Golaszewski <brgl at kernel.org>; Jonathan Corbet
> > <corbet at lwn.net>; Rob Herring <robh at kernel.org>; Krzysztof Kozlowski
> > <krzk+dt at kernel.org>; Conor Dooley <conor+dt at kernel.org>; Bjorn Andersson
> > <andersson at kernel.org>; Mathieu Poirier <mathieu.poirier at linaro.org>; Frank Li
> > <frank.li at nxp.com>; Sascha Hauer <s.hauer at pengutronix.de>; Shuah Khan
> > <skhan at linuxfoundation.org>; linux-gpio at vger.kernel.org; linux-
> > doc at vger.kernel.org; linux-kernel at vger.kernel.org; Pengutronix Kernel Team
> > <kernel at pengutronix.de>; Fabio Estevam <festevam at gmail.com>; Peng Fan
> > <peng.fan at nxp.com>; devicetree at vger.kernel.org; linux-
> > remoteproc at vger.kernel.org; imx at lists.linux.dev; linux-arm-
> > kernel at lists.infradead.org; dl-linux-imx <linux-imx at nxp.com>; Bartosz
> > Golaszewski <brgl at bgdev.pl>
> > 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 at 0 {
> > > > > +            compatible = "rpmsg-gpio";
> > > > > +            reg = <0>;
> > > > > +            gpio-controller;
> > > > > +            #gpio-cells = <2>;
> > > > > +            #interrupt-cells = <2>;
> > > > > +            interrupt-controller;
> > > > > +          };
> > > > > +          gpio at 1 {
> > > > > +            compatible = "rpmsg-gpio";
> > > > > +            reg = <1>;
> > > > > +            gpio-controller;
> > > > > +            #gpio-cells = <2>;
> > > > > +            #interrupt-cells = <2>;
> > > > > +            interrupt-controller;
> > > > > +          };
> >
> > > Then how would you distinguish gpio at 0 from gpio at 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 at 0 is on rpmsg channel 0. gpio at 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 at 0 and gpio at 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
>