Re: [RFC PATCH 0/5] gpio: add PMIO support to gpio-mmio

[Jose Javier Rodriguez Barbarin <dev-josejavier.rodriguez@duagon.com>]

On Thu, Apr 09, 2026 at 10:14:17AM +0200, Linus Walleij wrote:
> Hi Jose,
> 
> thanks for your proposal!!

You are welcome :)

> 
> I'm very happy to see some traction on this. I add WBG to CC because he
> wrote so many port-mapped drivers that I think he'll be thrilled to make
> use of this as well.

I was a bit worried about if my approach was correct or not, so I'm really
glad to hear such positive feedback.

> 
> On Tue, Apr 7, 2026 at 8:49 PM Jose Javier Rodriguez Barbarin
> <dev-josejavier.rodriguez@duagon.com> wrote:
> 
> > This series is an RFC for adding port-mapped I/O (PMIO) support to
> > gpio-mmio.
> (...)
> > In particular, feedback would be appreciated on:
> > - whether extending gpio_generic_chip_config is the right direction;
> 
> Pointed out on the patch that you can just create a
> gpio_generic_port_chip_config
> or something like that, it's only used at config time (usually locally
> in probe()) resulting in a transient stack allocation anyway.
> 
> Also that makes it easier to see what's going on.

Seems interesting.

As you pointed out, creating the new gpio_generic_port_chip_config would
need more refactoring to adapt the new structure. I'm OK with that so I'm
working on it. I will include those changes on v2.

> 
> > - whether introducing a common MMIO/PMIO register descriptor is
> >   acceptable;
> > - whether PMIO support should instead be implemented differently in
> >   gpio-mmio.
> 
> The main feedback I have is to use a union between port and
> MMIO address instead of a struct with both.
> 
> It makes it clear that we only ever use one of them and saves
> some memory, especially since we use several instances of
> it per generic chip later in the code.
> 

Annotated. I will include the union on v2.

> Yours,
> Linus Walleij

Thanks for your review and for your comments/suggestions. I really
appreciate that.

Regards,

Javier R.