Re: [PATCH v2] gpiolib: Disallow identical line names in the same chip

[Andy Shevchenko <andy.shevchenko@xxxxxxxxx>]

On Wed, Jan 6, 2021 at 12:09 PM Bartosz Golaszewski
<bgolaszewski@xxxxxxxxxxxx> wrote:
> On Wed, Jan 6, 2021 at 12:24 AM Linus Walleij <linus.walleij@xxxxxxxxxx> wrote:
> > On Tue, Jan 5, 2021 at 6:28 PM Andy Shevchenko
> > <andy.shevchenko@xxxxxxxxx> wrote:
> > > On Tue, Jan 5, 2021 at 10:31 AM Linus Walleij <linus.walleij@xxxxxxxxxx> wrote:
> > > > We need to make this namespace hierarchical: at least do not
> > > > allow two lines on the same chip to have the same name, this
> > > > is just too much flexibility. If we name a line on a chip,
> > > > name it uniquely on that chip.
> > > >
> > > > This does not affect device tree and other gpiochips that
> > > > get named from device properties: the uniqueness
> > > > per-chip however affect all hotplugged devices such as
> > > > GPIO expanders on USB.
> > >
> > > ...
> > >
> > > > [Dropped warning for globally unique]
> > >
> > > > + * - Allow names to not be globally unique but warn about it.
> > >
> > > Is the second part of this sentence still ture?
> > > Maybe I missed a warning we are talking about here?
> >
> > Oops old text, Bartosz if this looks OK otherwise can you fix
> > this when applying? (Just delete that line.)

> I can do it alright. But in the context of user-space I think this
> doesn't really change anything. DT users still can use non-unique
> names and libgpiod still has to account for that if the API is to be
> considered correct. Is this change really useful?

IMHO it is useful and the earliest we do the better.

> How does it affect
> ACPI users that already define non-unique names?

I suppose that in ACPI we don't have many users that do it on their
own (for IoT Intel platforms GPIO expanders have unique names).
Also see above. I prefer to have a bug report with a clear source of
the issue (like a table that the user can't / won't change which
predates the date of kernel release with a patch.

+cc: to the user who lately was active in the area.

Flavio, perhaps one more rule to the gpio-line-names property has to
be added into documentation (Bart, same to DT docs?):
 - names inside one chip must be unique

-- 
With Best Regards,
Andy Shevchenko