linux-kernel - Re: [PATCH v4 1/2] gpio: gpio-mlxbf3: Add gpio driver support

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Date:   Thu, 23 Feb 2023 21:58:40 +0200
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     Asmaa Mnebhi <asmaa@...dia.com>
Cc:     "linus.walleij@...aro.org" <linus.walleij@...aro.org>,
        "bgolaszewski@...libre.com" <bgolaszewski@...libre.com>,
        "linux-gpio@...r.kernel.org" <linux-gpio@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-acpi@...r.kernel.org" <linux-acpi@...r.kernel.org>
Subject: Re: [PATCH v4 1/2] gpio: gpio-mlxbf3: Add gpio driver support

On Thu, Feb 23, 2023 at 9:08 PM Asmaa Mnebhi <asmaa@...dia.com> wrote:
>
> > > > +       npins = MLXBF3_GPIO_MAX_PINS_PER_BLOCK;
> > > > +       device_property_read_u32(dev, "npins", &npins);
> > >
> > > I don't see DT bindings for this property (being added in this series). Is it
> > already established one?
> > >
> > > Ah that’s my bad. The property should be called "ngpios" like in the DT
> > documentation. Will fix.
> >
> > And why do you need it? What's a corner case that the GPIO library doesn't
> > handle yet?
>
> We have 2 gpiochips, gpiochip 0 supports 32 gpio pins and gpiochip 1 supports only 24 pins.
> If I remove the logic from gpio-mlxbf3.c, the gpiolib.c logic will correctly set the ngpios = 32 for gpiochip 0 but will wrongly set ngpios=32 for gpiogchip 1:

So, either you need to have two entries in DT per chip or ngpios should be 56.

-- 
With Best Regards,
Andy Shevchenko