Re: [EXT] Re: [PATCH v13 3/4] gpio: rpmsg: add generic rpmsg GPIO driver

[Padhi, Beleswar]

On 4/28/2026 8:13 PM, Shenwei Wang wrote:
> > -----Original Message-----
> > From: Beleswar Prasad Padhi <b-padhi@xxxxxx>
> > Sent: Tuesday, April 28, 2026 2:25 AM
> > To: Shenwei Wang <shenwei.wang@xxxxxxx>; 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>
> > Cc: 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>; Andrew Lunn <andrew@xxxxxxx>
> > Subject: [EXT] Re: [PATCH v13 3/4] gpio: rpmsg: add generic rpmsg GPIO driver
> > On 28/04/26 00:53, Shenwei Wang wrote:
> > [...]
> >
> > > > > +     void *channel_devices[MAX_PORT_PER_CHANNEL];
> > > > So this is technically a rpmsg endpoint (struct rpmsg_endpoint)
> > > > without naming it "endpoint". Every rpmsg endpoint has a reference to
> > > > its parent rpmsg channel (struct rpmsg_device) which represents the
> > > > same information here. So we should use the framework standard here.
> > > Yes, agree to use "endpoint_devices".
> >
> > I did not mean to say to just change the variable name from "channel_devices" to
> > "endpoint_devices". Infact you would not need to have this field & struct
> > anymore.
> >
> > Pseudo-code:
> > 1. Add a 'struct rpmsg_endpoint *ept' field to struct rpmsg_gpio_port
> >      to maintain the ept to port idx map.
> >
> > 2. Call port->ept = rpmsg_create_ept(rpdev,
> >                                                              rpmsg_gpio_channel_callback,
> >                                                              port, {rpdev.id.name,
> >                                                              RPMSG_ADDR_ANY,
> >                                                              RPMSG_ADDR_ANY})
> >      from rpmsg_gpiochip_register().
> On the Linux side, we invoke rpmsg_create_ept. What is expected from the remote system in this case?


Nothing extra in my opinion. rpmsg_create_ept() just creates a dynamic
local endpoint address for Linux's usage. The firmware just has to make
sure to reply to the same endpoint address where it received the
message. This should already be in place IMO, because currently you are
sending all messages in the default endpoint (rpdev->ept) which is also
dynamic[1] and is created when the channel is created. And you receive
the responses correctly. (Unless you have hard-coded the default ept
address in the firmware)

[1]: 
https://github.com/torvalds/linux/blob/master/drivers/rpmsg/rpmsg_core.c#L480
(chinfo.src is RPMSG_ADDR_ANY)

Thanks,
Beleswar

> If the remote side does not need any extra support, this would be an excellent solution.
>
> Thanks,
> Shenwei
>
> > 3. Send msgs from local ept in rpmsg_gpio_send_message() by:
> >      rpmsg_send(port->ept, msg, sizeof(*msg));
> >
> > 4. Get the port info in rpmsg_gpio_channel_callback() by:
> >      struct rpmsg_gpio_port *port = priv;
> >
> > Which also eliminates the need for struct rpdev_drvdata as you can just do
> > rpmsg_get_rproc_node_name(rpdev) from rpmsg_gpiochip_register().