On Wed, Feb 25, 2026 at 05:54:00PM +0000, Shenwei Wang wrote:
>
>
> > -----Original Message-----
> > From: Bjorn Andersson <[email protected]>
> > Sent: Wednesday, February 25, 2026 9:53 AM
> > To: Shenwei Wang <[email protected]>
> > Cc: Andrew Lunn <[email protected]>; Mathieu Poirier
> > <[email protected]>; Arnaud POULIQUEN
> > <[email protected]>; Linus Walleij <[email protected]>; Bartosz
> > Golaszewski <[email protected]>; Jonathan Corbet <[email protected]>; Rob Herring
> > <[email protected]>; Krzysztof Kozlowski <[email protected]>; Conor Dooley
> > <[email protected]>; Frank Li <[email protected]>; Sascha Hauer
> > <[email protected]>; Shuah Khan <[email protected]>; linux-
> > [email protected]; [email protected];
> > [email protected];
> > Pengutronix Kernel Team <[email protected]>; Fabio Estevam
> > <[email protected]>; Peng Fan <[email protected]>;
> > [email protected]; [email protected];
> > [email protected]; [email protected]; dl-linux-imx
> > <linux-
> > [email protected]>; Bartosz Golaszewski <[email protected]>
> > Subject: [EXT] Re: [PATCH v8 3/4] gpio: rpmsg: add generic rpmsg GPIO driver
> > On Tue, Feb 24, 2026 at 10:43:06PM +0000, Shenwei Wang wrote:
> > >
> > >
> > > > -----Original Message-----
> > > > From: Andrew Lunn <[email protected]>
> > > > Sent: Tuesday, February 24, 2026 4:15 PM
> > > > To: Shenwei Wang <[email protected]>
> > > > Cc: Mathieu Poirier <[email protected]>; Bjorn Andersson
> > > > <[email protected]>; Arnaud POULIQUEN
> > > > <[email protected]>; Linus Walleij <[email protected]>;
> > > > Bartosz Golaszewski <[email protected]>; Jonathan Corbet
> > > > <[email protected]>; Rob Herring <[email protected]>; Krzysztof Kozlowski
> > > > <[email protected]>; Conor Dooley <[email protected]>; Frank Li
> > > > <[email protected]>; Sascha Hauer <[email protected]>; Shuah
> > > > Khan <[email protected]>; linux- [email protected];
> > > > [email protected]; [email protected]; Pengutronix
> > > > Kernel Team <[email protected]>; Fabio Estevam
> > > > <[email protected]>; Peng Fan <[email protected]>;
> > > > [email protected]; [email protected];
> > > > [email protected]; [email protected];
> > > > dl-linux-imx <linux- [email protected]>; Bartosz Golaszewski
> > > > <[email protected]>
> > > > Subject: [EXT] Re: [PATCH v8 3/4] gpio: rpmsg: add generic rpmsg
> > > > GPIO driver
> > > > > Please explain how you would design your generic rpmsg-gpio driver
> > > > > which is derived From gpio-virtio?
> > > >
> > > > We have already seen the virtio commands are pretty much identical
> > > > to what i suggested.
> > > >
> > > > You could just replace virtqueue_add_sgs() with rpmsg_sendto() and
> > > > reimplement
> > > > virtio_gpio_request_vq() to be the callback registered with
> > rpmsg_create_ept().
> > > > The rest of basic GPIO handling should not need any changes at all.
> > > >
> > >
> > > Creating endpoints and calling rpmsg_sendto() is only a small part of
> > > the picture. You also need to manage the service announcement from the
> > > remote side and handle asynchronous notification messages. That entire
> > > flow is already implemented in the existing virtio_rpmsg_bus driver.
> > > Re‑implementing those pieces just to mimic gpio‑virtio over RPMSG would
> > essentially mean reinventing the wheel without any real benefit.
> > >
> >
> > I can absolutely see a benefit to this, there are multiple different rpmsg
> > backends
> > supported in Linux, so a gpio-rpmsg driver could be used by any one of them.
> >
> > I don't see this to be a case of "reinventing the wheel". Instead we copy
> > what
> > looks to be a very functional wheel and make it fit rpmsg.
> > This will result in some "duplication", but rpmsg already provide the life
> > cycle
> > management and has a clean send/callback interface, so there shouldn't be
> > any
> > inventing...
> >
>
> Interesting — could you walk me through how you’d structure the driver with
> the new
> proposal? I’d like to see how you would layer it conceptually.
>
> The current RPMSG solution:
>
> On Remoteprc On Linux
> GPIOs -> RPMSG -> VIRTIO == VIRTIO -> RPMSG -> GPIO-RPMSG drivers
>
> The VIRTIO solution:
>
> On Remoteprc On Linux
> GPIO -> VIRTIO == VIRTIO -> GPIO-VIRTIO driver
>
> Your proposal:
>
> On Remoteprc On Linux
> GPIOs -> RPMSG -> VIRTIO == VIRTIO -> ???
What I'm suggesting is the following:
GPIOs -> RPMSG -> VIRTIO == VIRTIO -> RPMSG -> GPIO-RPMSG
^ ^
\-----+------------------------------/
|
|
With this interface on being directly derived from the existing protocol
(and likely the implementation as well) using gpio-virtio.
You can have multiple "GPIOs" (presumably a "bank" each) instances and
that will be reflected in having multiple "GPIO-RPMSG" instances.
I haven't made any attempts at implementing this, but it looks very
similar to gpio-virtio in concept and it looks very similar to the
exiting RPMSG tty in the sense of being a generic implementation.
To reach something functional on the Linux side it seems to be a matter
of taking the gpio-virtio driver, register a rpmsg_driver instead,
change _virtio_gpio_req() to use rpmsg_send(), and perform the actions
of virtio_gpio_event_vq() in the rpmsg_driver callback function.
Regards,
Bjorn
>
> Thanks,
> Shenwei
>
> > Similarly, I'm guessing that there's a firmware-side implementation of
> > virtio-gpio
> > in Zephyr, it should be straightforward to transplant this to the rpmsg
> > interface.
> >
> > Regards,
> > Bjorn
> >
> > > Thanks,
> > > Shenwei
> > >
> > > > Interrupt support does however need some changes. The
> > > > virtio_gpio_request_vq() replacement would need to see if the
> > > > received message indicates an interrupt and call the equivalent of
> > > > virtio_gpio_event_vq(), since rpmsg does not have a separate mechanism
> > > > to
> > deliver interrupts, unlike rpmsg.
> > > >
> > > > At a guess, 90% of the code would stay the same?
> > > >
> > > > Andrew
