Re: [PATCH 0/4] gpio: mxc: silence warning about GPIO base being statically allocated

[Bartosz Golaszewski <brgl@xxxxxxxx>]

On Tue, Jan 21, 2025 at 11:37 AM Ahmad Fatoum <a.fatoum@xxxxxxxxxxxxxx> wrote:
>
> Hello Bartosz,
>
> On 15.01.25 17:52, Bartosz Golaszewski wrote:
> >
> > I recently wrote a user-space compatibility layer for sysfs[1]. While
> > right now it doesn't support static base numbers, I'm very open to
> > adding it except that I wasn't sure how to approach it.
> >
> > Is this of any use to you and could it help you switch to libgpiod
> > without changing your user-space set-up (given the support for static
> > GPIO numbering)?
>
> If the goal is to have a drop-in replacement for sysfs outside
> of the kernel, I think it needs to maintain the same numbering.
>
> I am not sure I see myself using it, because the new projects are using
> libgpiod from the get-go. My issue is not with removal of sysfs, but with
> user hostile deprecation approaches.
>
> > If so, how would you like to see this implemented? A
> > config file at /etc that would list chip labels and their desired GPIO
> > base?
>
> Many GPIOs tend to not have labels. I think the mapping config file
> should rather map GPIO controllers to a base address. The same thing the
> kernel is currently doing. This assumes the numbering of the built-in
> GPIO controllers is deterministic, e.g. by consulting /aliases. I haven't
> checked, but I hope this is already the case.

Well, they will have labels, it's just that the label will be
something like "6e80000.gpio" which can very well be mapped onto a
predefined GPIO range.

The file could look like:

/etc/gpio-static-base.conf

```
6e80000.gpio 12
foobar 340
```

Where the first column is the label and the second the static base
that must be less than 512 - ngpio.

Bart