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

[Shenwei Wang]

> -----Original Message-----
> From: Andrew Lunn <andrew at lunn.ch>
> Sent: Tuesday, February 24, 2026 4:15 PM
> To: Shenwei Wang <shenwei.wang at nxp.com>
> Cc: Mathieu Poirier <mathieu.poirier at linaro.org>; Bjorn Andersson
> <andersson at kernel.org>; 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>; 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: [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.

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