Re: [PATCH RFC 0/9] gpio: improve support for shared GPIOs

[Linus Walleij <linus.walleij@linaro.org>]

Replying to self so Bartosz don't have to tell me off...

On Wed, Oct 1, 2025 at 10:49 AM Linus Walleij <linus.walleij@linaro.org> wrote:

> and every GPIO access on every system will be proxied
> and then this better be fast.

What about I read the code before I talk :/

Inspecting patch 4/9 it is clear that only GPIOs that actually
need to be proxied are proxied.

> Two things come to mind, and I bet you have thought of
> them already:
>
> 1. Footprint: all systems using regulators will now have
>    to compile in all this code as well.

This still holds. It could be a concern if it's a lot of code.

> 2. Performance, I didn't quite get it if every GPIO on the
>   system will be proxied through a layer of indirection
>   if you select HAVE_SHARED_GPIOS
>   but that would not be good, since some users are in
>   fastpath such as IRQ handlers, and the old way of
>   sharing GPIOs would just affect pins that are actually
>   shared.

It is clear from patch 4/9 that this only affects GPIOs
that are actually shared, and those tend to not be
performance-critical so this concern is moot.

Yours,
Linus Walleij