Re: [PATCH v2 1/1] gpiolib: of: add gpio-line node support

[Bartosz Golaszewski]

On Mon, 16 Feb 2026 22:20:10 +0100, James Hilliard
<james.hilliard1@xxxxxxxxx> said:
> On Mon, Feb 16, 2026 at 4:38 AM Bartosz Golaszewski <brgl@xxxxxxxxxx> wrote:
>>
>> On Sat, 14 Feb 2026 22:32:37 +0100, James Hilliard
>> <james.hilliard1@xxxxxxxxx> said:
>> > Allow GPIO controller child nodes marked with "gpio-line" to
>> > configure direction/flags at probe time without hogging the line.
>> >
>> > Teach OF gpiochip scanning and OF dynamic reconfiguration handlers to
>> > process gpio-line nodes in addition to gpio-hog nodes.
>> >
>> > Also parse "gpio-line-name" and apply it to desc->name. For gpio-hog
>> > nodes, keep "line-name" semantics as the hog consumer label.
>> >
>>
>> One important thing that's missing from this commit description is: what is
>> the use-case and why do you need this.
>
> Added some more use-case details in v3:
> https://lore.kernel.org/all/20260216211021.3019827-1-james.hilliard1@xxxxxxxxx/
>
> In my case I'm setting up the GPIO line initial state and names for
> userspace consumers mostly. I want to be able to configure the
> individual line names from a combination of the dts file and multiple
> dtso files for the same gpiochip along with setting up an initial state
> before userspace consumers operate on the lines.
>
>> The DT binding patch should be sent together with this in a single series. It
>> should also be documented in the relevant .rst file.
>
> Which file would that be?
>

Documentation/driver-api/gpio/board.rst would fit best.

> I had previously added docs to gpio.txt but was told here to just
> drop the docs:
> https://lore.kernel.org/all/b851bfd4-3c35-489f-a32d-dcd7a37ca99a@xxxxxxxxxx/
>

There's a difference between device-tree bindings (formal, machine-readable
definition of the firmware ABI) under Documentation/devicetree/bindings/ and
documentation for humans residing elsewhere in Documentation/. Make sure to
not confuse the two. I would expect both to be supplied with such a change.

>> I suppose it's another shot at defining what we previously called
>> "initial-line-state", "default-line-state", etc. What happens when someone
>> requests the line, reconfigures it and then releases it?
>
> This should just provide an initial configuration, subsequent consumers
> would override whatever is set here AFAIU.
>

Yeah, that's what I was afraid of. This is not hardware description, this is
user-convencience and as such I don't think it has place in DT bindings and -
by extension - in DTS.

I'm afraid I don't have good alternatives to offer, solving this has been
attempted several times in the past without success. Even gpio-hog would likely
not get past DT maintainer review these days but it's ABI now so will stay
supported.

How early do you need to set these settings?

Bartosz

>> This should also not be OF-specific but rather a GPIOLIB-wide switch.
>
> Like this?:
> https://lore.kernel.org/all/20260216211021.3019827-1-james.hilliard1@xxxxxxxxx/
>
>>
>> Bartosz
>