[PATCH RFT 2/6] gpio: mmio: get chip label and GPIO base from device properties

[Bartosz Golaszewski]

On Wed, Jun 25, 2025 at 10:54 AM Krzysztof Kozlowski <krzk at kernel.org> wrote:
>
> On 25/06/2025 09:35, Bartosz Golaszewski wrote:
> > On Tue, 24 Jun 2025 at 21:44, Linus Walleij <linus.walleij at linaro.org> wrote:
> >>
> >> On Tue, Jun 24, 2025 at 3:19 PM Bartosz Golaszewski <brgl at bgdev.pl> wrote:
> >>
> >>> From: Bartosz Golaszewski <bartosz.golaszewski at linaro.org>
> >>>
> >>> Ahead of removing struct bgpio_pdata support from the gpio-mmio generic
> >>> module, let's add support for getting the relevant values from generic
> >>> device properties. "label" is a semi-standardized property in some GPIO
> >>> drivers so let's go with it. There's no standard "base" property, so
> >>> let's use the name "gpio-mmio,base" to tie it to this driver
> >>> specifically. The number of GPIOs will be retrieved using
> >>> gpiochip_get_ngpios() so there's no need to look it up in the software
> >>> node.
> >>>
> >>> Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski at linaro.org>
> >>
> >> This works for me.
> >> I wouldn't be stoked to see device trees abusing the "gpio-mmio,base"
> >> property all of a sudden just because it now exists as a device
> >> property though... I kind of wish we had a way to opt out of exposing
> >> this to all the sub-property paths. But it seems tiresome, so:
> >>
> >> Reviewed-by: Linus Walleij <linus.walleij at linaro.org>
> >>
> >> Yours,
> >> Linus Walleij
> >
> > That's not a problem - this property is not in any DT bindings and as
> > such is not an allowed property in DT sources. For out-of-tree DTs? We
> > don't care about those.
> That's not true, we do care about implied ABI. Try changing/breaking
> this later, when users complain their out of tree DTS is affected, and
> explaining this all to Greg.
>

Wait, seriously? I thought that the upstream bindings are the source
of truth for device-tree sources...

> Rob was/is working on tools checking this for such implied ABI, I think.
> For of_xxx() calls it is obvious, for device_xxx() or fwnode_xxx() it is
> not, therefore please add a comment that this is not allowed to be used
> by Devicetree platforms (or that this is only for
> ACPI/platform_data/whatever). I don't have any other guideline/solution
> other than a comment.
>

Ok.

Bart