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

On Tue, 24 Feb 2026 at 15:32, Shenwei Wang [off-list ref] wrote:

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-----Original Message-----
From: Andrew Lunn <andrew@lunn.ch>
Sent: Tuesday, February 24, 2026 4:23 PM
To: Shenwei Wang <shenwei.wang@nxp.com>
Cc: Arnaud POULIQUEN <arnaud.pouliquen@foss.st.com>; Linus Walleij
[off-list ref]; Bartosz Golaszewski [off-list ref]; Jonathan Corbet
[off-list ref]; Rob Herring [off-list ref]; Krzysztof Kozlowski
[off-list ref]; Conor Dooley [off-list ref]; Bjorn Andersson
[off-list ref]; Mathieu Poirier [off-list ref]; Frank Li
[off-list ref]; Sascha Hauer [off-list ref]; Shuah Khan
[off-list ref]; linux-gpio@vger.kernel.org; linux-
doc@vger.kernel.org; linux-kernel@vger.kernel.org; Pengutronix Kernel Team
[off-list ref]; Fabio Estevam [off-list ref]; Peng Fan
[off-list ref]; devicetree@vger.kernel.org; linux-
remoteproc@vger.kernel.org; imx@lists.linux.dev; linux-arm-
kernel@lists.infradead.org; dl-linux-imx [off-list ref]; Bartosz
Golaszewski [off-list ref]
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;
+          };

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Then how would you distinguish gpio@0 from gpio@1 on the CM33 RPMSG bus

in the example above?

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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

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   Andrew